30 entries found for : sfn2014
Nair DV, Al-Badri MM, Peng H, Schenkman N, Pacheco-Quinto J, Eckman CB, Iacono D, Eckman EA (2014) Chronic oxotremorine treatment ameliorates depressive phenotype in a rodent model of Alzheimer’s disease. Neuroscience 2014 Abstracts 670.03. Society for Neuroscience, Washington, DC.
Summary: Alzheimer’s disease (AD) is a progressive neurodegenerative condition that is characterized by changes to brain structure and function. It is estimated that depression and other neuropsychiatric symptoms occur in up to 90% of AD patients, yet the neurobiological basis of these symptoms and their influence on the clinical course of AD remain unclear. Using a rat model of AD-like basal forebrain cholinergic cell loss, our lab has previously shown that central administration of a muscarinic receptor agonist, oxotremorine, for 4 weeks could induce hippocampal neurogenesis and reverse the spatial working memory deficit triggered by cholinergic denervation. Preliminary experiments conducted with this model in our lab also revealed a depressive phenotype emerging between 11 and 15 weeks after cholinergic denervation. The depressive phenotype was detected using a sucrose consumption test and further confirmed by forced swim test. The goal of the present study was to determine whether effects of chronic oxotremorine treatment could ameliorate the depressive phenotype observed after selective cholinergic cell loss in the basal forebrain. Adult female Sprague Dawley rats were injected intracerebroventricularly (icv) with the immunotoxin 192-IgG-saporin (SAP), to induce AD-like basal forebrain cholinergic cell loss. After a 5 week recovery period, the rats then received 8 weeks of icv infusion of either oxotremorine or vehicle (saline) via osmotic minipump. Behavioral testing to assess the depressive phenotype was carried out using the sucrose consumption test every 2 weeks during oxotremorine treatment. The phenotype was further confirmed by forced swim test. Biochemical analysis of a range of markers including tryptophan hydroxylase, the rate limiting enzyme for synthesis of serotonin, was performed after extraction of the brains following the behavioral tests. Results of these experiments demonstrate that oxotremorine treatment prevents the development of the depressive phenotype in SAP-lesioned rats. A number of oxotremorine-treated rats showed increases in tryptophan hydroxylase, suggesting a possible mechanism for the improved behavioral phenotype Based on these data, we propose that 192-IgG saporin lesioned rats may be an effective model for studying the pathophysiology and therapeutic modulation of age- and neurodegeneration-related neuropsychiatric symptoms such as depression.
Related Products: 192-IgG-SAP (Cat. #IT-01)
Phillips K, Kucinski A, Albin R, Sarter M (2014) Impairments in gait, posture and complex movement control in rats modeling the multi-system, cholinergic-dopaminergic losses in PD. Neuroscience 2014 Abstracts 692.21. Society for Neuroscience, Washington, DC.
Summary: In addition to striatal dopamine loss, degeneration of cholinergic neurons in the basal forebrain (BF) and the brainstem pedunculopontine nucleus (PPN) were documented in patients with Parkinson’s disease (PD). Loss of cholinergic projections to cortical, thalamic and midbrain regions have been associated with impairments in gait and postural control and a propensity for falls. We previously demonstrated that loss of cortical cholinergic inputs and the resulting impairments in attentional control ‘unmask’ gait and postural risk factors and thus yielded falls in rats with striatal dopamine loss (Kucinski et al., 2013). For this research we developed a new behavior task for the assessment of gait, postural control, and fall propensity (Michigan Complex Motor Control Task; MCMCT). Here, to determine the contributions of the PPN cholinergic projection system to complex movement control, we also lesioned the cholinergic pars compacta (posterior) division of the PPN by infusing anti-ChAT saporin-coupled immunotoxin. Rats received these lesions either in combination with BF cholinergic (192-IgG-saporin) or dorsomedial striatal dopamine loss (6-OHDA), or all three lesions together (“triples”). MCMCT performance by triples was characterized by more falls than in rats with just PPN lesions, PPN plus striatal dopamine loss, or rats with loss of both BF and PPN cholinergic neurons. High fall rates in triples persisted throughout the 20-day MCMCT testing sequence, indicating that daily practice did not improve the interactions between loss of attentional control and gait and postural deficits that underlie falls. Interestingly, combined loss of BF and PPN cholinergic neurons increased falls relative to controls and single lesions, suggesting that ascending cholinergic PPN loss sufficiently dysregulates striatal dopamine input for BF cholinergic cell loss to ‘unmask’ the impact of the former on striatal dysfunction. Finally, PPN cholinergic cell loss resulted in ballistic postural (recovery) movements and slip-triggered switches to asymmetrical gait. Such behavior was previously observed in rats after electrolytic lesions of the PPN region, considered a model of “Parkinsonian festination” (Cheng et al., 1981) and it may assist in maintaining balance by stabilizing the center of gravity. Collectively, our findings support the hypothesis that PPN cholinergic projections contribute to the mediation of gait symmetry and postural control, and when lesioned in combination with forebrain cholinergic and dopaminergic system, results in profound impairments in the control of complex movements. This research was supported by the Michael J. Fox Foundation.
Related Products: Anti-ChAT-SAP (Cat. #IT-42)
ATS Poster of the Year Winner. Read the featured article in Targeting Trends.
The role of the basal forebrain cholinergic neurons in cued extinction memory
Schreiber WB, Keller S, Knox D (2014) The role of the basal forebrain cholinergic neurons in cued extinction memory. Neuroscience 2014 Abstracts 748.01. Society for Neuroscience, Washington, DC.
Summary: Fear extinction learning and memory requires inhibition of neural activity in amygdala (AMY) nuclei driven by neural substrates in the ventromedial prefrontal cortex (vmPFC), resulting in the behavioral phenotype of a decreased fear response (e.g. low levels of conditioned freezing). Fear extinction memory retrieval is sensitive to contextual feature manipulations, rendering extinction memory retrieval sensitive to hippocampal (HIPP) input to the AMY. Function of the vmPFC and HIPP requires cholinergic innervation from basal forebrain cholinergic neurons (BFCNs), including neurons in the nucleus basalis (NB), horizontal diagonal band of Broca (hDBB), vertical diagonal band of Broca (vDBB), and medial septum (MS). Given the importance of the vmPFC and HIPP for extinction memory, we hypothesized that intact BFCNs would be critical for extinction memory. We found that complete BFCN lesions using 192 IgG-saporin disrupted acquisition of cued fear extinction memory (Experiment 1). Follow-up studies examining more restrictive cholinergic lesions of the MS/vDBB (Experiment 2) or the NB/hDBB (Experiment 3) suggest these two clusters of BFCNs may differentially modulate acquisition and retention of cued extinction memory. The overall results of this study suggest that BFCNs are a component of the fear extinction circuit and a potential target for the pharmacological treatment of psychological disorders thought to stem from extinction memory deficits (e.g. PTSD).
Related Products: 192-IgG-SAP (Cat. #IT-01)
Köppen JR, Stuebing SS, Sieg M, Blackwell AA, Blankenship P, Grisley ED, Cheatwood JL, Wallace DG (2014) Is selective hippocampal cholinergic deafferentation sufficient to produce temporally graded retrograde amnesia?. Neuroscience 2014 Abstracts 749.20. Society for Neuroscience, Washington, DC.
Summary: Dementia of the Alzheimer’s type (DAT) is a neurodegenerative disorder marked by degeneration of basal forebrain structures and is associated with significant mnemonic deficits. The current study used a rat string-pulling task to evaluate whether selective cholinergic deafferentation of the hippocampus is sufficient to produce temporally graded retrograde amnesia. Female rats were pre-trained to pull strings to obtain reinforcement (cashew). Subsequently, rats were trained to discriminate between two scented strings. One scented string was consistently reinforced (+A), while the other scented string was never reinforced (B). After rats met criterion, they either waited two weeks (recent) or six weeks (remote) prior to receiving a sham surgery or infusion of 192-IgG-Saporin into the medial septum. Two weeks later rats were given four days of reversal training during which they experienced the same scented strings; however, the cashew was at the end of the string that was not previously reinforced. Following reversal training, rats were trained on a novel discrimination (+C/D). The results of the current study are consistent with selective cholinergic deafferentation of the hippocampus being sufficient to produce retrograde amnesia that was not temporally graded. First, all rats met criterion in a similar number of days. Rats receiving infusion of 192-IgG-Saporin into the medial septum had a higher number of correct responses during reversal training, relative to sham rats; however, no group differences were observed between recent and remote groups. Next, there were no group differences in the ability to learn a new discrimination. Finally, no group differences we observed in the latency to approach and pull up the string. The results were not caused by deficits in motivation or motor function, but they do reflect impairments in mnemonic function. The current study provides a novel behavioral assessment technique that models the retrograde amnesia characteristics observed in DAT.
Related Products: 192-IgG-SAP (Cat. #IT-01)
Van Kampen JM, Kay DG, Maelicke A (2014) The galantamine prodrug, Memogain®, reverses deficits in hippocampal neurogenesis associated with the loss of basal forebrain cholinergic neurons. Neuroscience 2014 Abstracts 789.21. Society for Neuroscience, Washington, DC.
Summary: Loss of basal forebrain cholinergic innervation of the hippocampus and severe neuronal loss within the hippocampal CA1 region are early hallmarks of Alzheimer's disease (AD), and are strongly correlated with cognitive status. This loss of cholinergic innervation is a key factor underlying alterations in hippocampal neurogenesis, which are also characteristic of AD. We have previously reported the effects of various cholinergic compounds on hippocampal neurogenesis indicating that acetylcholine serves as a potent neurogenic regulator. Memogain® (GLN 1062) is an inactive galantamine pro-drug with 15 fold higher brain availability than galantamine. It is designed to provide improved blood brain barrier penetration, greater potency, and fewer side effects than the cholinesterase inhibitors currently used for the treatment of Alzheimer's dementia. This would serve both to promote patient adherence and permit the use of higher doses. Galantamine is unique among the cholinesterase inhibitors in that it also has allosteric actions at α-7 nicotinic receptors, activation of which has been linked to both disease-modifying and cognitive enhancing effects, as well as effects on hippocampal cell proliferation. Here, we describe the neurogenic actions of Memogain® in a rodent model of cholinergic depletion. Infusion of the immunotoxin, 192IgG saporin (SAP), used to induce selective basal forebrain cholinergic cell loss reminiscent of that found in AD, resulted in a pronounced loss of basal forebrain cholinergic neurons and hippocampal ChAT fiber density. Consistent with earlier reports, SAP-lesioned animals had significantly fewer BrdU+ and PCNA+ cells in both the dentate gyrus and CA1 region of the hippocampus, when compared to sham-operated control animals. These animals also displayed significant impairments in spatial working memory, as assessed by a T-maze and the radial arm maze. By contrast, animals treated with Memogain® displayed a restoration of hippocampal cell proliferation, increased neuronal cell counts, normalized neuronal migration, and improvements in cognitive function. Thus, the beneficial effects of Memogain® may extend beyond acute cognitive enhancement, to include disease modification through support of hippocampal neurogenesis.
Related Products: 192-IgG-SAP (Cat. #IT-01)
The effects of targeted intracerebral saporin injection on recovery from stroke
Becker A, Goldberg M (2014) The effects of targeted intracerebral saporin injection on recovery from stroke. Neuroscience 2014 Abstracts 800.09. Society for Neuroscience, Washington, DC.
Summary: It is well known that the diffuse neuromodulatory systems of the brain play a role in cortical plasticity that may extend to cortical reorganization after brain injury. The basal forebrain cholinergic system in particular is necessary for both cortical plasticity and behavioral recovery from cortical electrolytic lesions. The role of the cholinergic system in recovery from stroke has never been directly investigated. In this experiment, we asked the question: is the basal forebrain cholinergic system in the mouse necessary for behavioral recovery from stroke? To answer this question, we administered intracerebral injections of the selective immunotoxin mu p75-saporin bilaterally to the cholinergic nucleus basalis in young adult mice. Using choline acetyltransferase immunohisochemistry, cresyl violet staining, and fluoro-jade B staining we discovered a dose at which these injections eliminate local cholinergic neurons while leaving other cell types and cholinergic cells outside the nucleus basalis unharmed. We report the effects of these injections on behavioral recovery from a subsequently induced photothrombotic cortical ischemic stroke.
Related Products: mu p75-SAP (Cat. #IT-16)
Contribution of hindbrain catecholamine neurons to orexin-induced feeding
Li A-J, Wang Q, Davis H, Ritter S (2014) Contribution of hindbrain catecholamine neurons to orexin-induced feeding. Neuroscience 2014 Abstracts 834.08. Society for Neuroscience, Washington, DC.
Summary: Both lateral hypothalamic orexinergic neurons and hindbrain catecholaminergic neurons contribute to feeding behavior. In addition, both phenotypes are widely distributed in the brain and their terminal sites are in many cases overlapping. In the hindbrain, both orexin receptor subtypes (OX1R and OX2R) have been found in close proximity to dopamine-β-hydroxylase (DBH)-expressing cell bodies, raising the question of whether orexin stimulates feeding by activating catecholamine neurons. We tested this hypothesis in the present study. First, we implanted rats with fourth ventricular (4V) cannulas and tested feeding in response to 4V injection of orexin (0.5 nmol). Orexin stimulated feeding in rats, and this stimulation was abolished in rats given paraventricular hypothalamic injections of the retrogradely-transported immunotoxin, anti-DBH-saporin, which targets and destroys DBH-expressing neurons. We then examined hindbrain c-Fos expression in normal rats in response to 4V injection of the same orexin dose that stimulated food intake. Using multiple immunofluorescent labels and confocal microscopy we found that most of the orexin-induced c-Fos-immunoreactive (-ir) neurons in the dorsomedial and ventrolateral medulla were DBH-ir and, moreover, that orexin-ir varicosities were situated in close proximity to the Fos-expressing DBH-ir soma. Together these results suggest that orexin stimulates feeding, at least in part, by activating hindbrain catecholamine neurons.
Related Products: Anti-DBH-SAP (Cat. #IT-03)
Patrone LA, Biancardi V, Bicego KC, Gargaglioni LH (2014) Medullary catecholaminergic (CA) neurons modulate hypoxic ventilatory response in neonatal rats (P7-8). Neuroscience 2014 Abstracts 643.10. Society for Neuroscience, Washington, DC.
Summary: It is known that catecholaminergic (CA) neurons are involved in autonomic and respiratory regulation during low O2 conditions in adult mammals. We evaluated the participation of medullary CA neurons of male and female neonatal rats (P7-8) in mediating the hypoxic ventilatory response (HVR) by specifically lesioning them with antidopamine beta-hydroxylase-saporin (DBH-SAP, 42ng / 100nL) injected into the 4th ventricle. We also quantified rates of O2 consumption (VO2) of control and lesioned neonates (P7-8) exposed to hypoxia. Minute ventilation (VE) of neonates was recorded by pressure-plethysmography from the body chamber during normoxia and hypoxia (10% O2), and the VO2 measurement by open flow respirometry. The mammalian HVR typically results in increased VE upon exposure to acute hypoxia. HVR was significantly reduced in male and female lesioned neonatal rats by about 23 and 15%, respectively, (male- control group: 137.3±7.9 (% of baseline) vs. lesioned group: 105.3±2.4 (% of baseline), p<0.01; female- control group: 127.0±3.0 (% of baseline) vs. lesioned group: 108.6±1.7 (% of baseline) p<0.02). The VO2 was decreased in the lesioned newborns, but only the lesioned male group was significantly lower (control group: 76.8±12.14 (% of baseline) vs. lesioned group: 45.3±13.3 (% of baseline) p<0.03). These results suggest that catecholaminergic neurons, specifically from medullary nuclei, exert an excitatory modulation of O2 chemosensitivity in neonatal rats.
Related Products: Anti-DBH-SAP (Cat. #IT-03)
The role of the supramammillary area in spatial learning and memory
Shim H, Park H-J, Lee H, Shim I (2014) The role of the supramammillary area in spatial learning and memory. Neuroscience 2014 Abstracts 652.05. Society for Neuroscience, Washington, DC.
Summary: The supramammillary area (SuM) of the hypothalamus, although small in size, has wide spread connection with numerous brain structures. It is known that the SuM can control the frequency of the hippocampal theta rhythm, which plays a role in the cognitive functions of the hippocampal formation. In order to examine the role of the specific cells of the SuM in learning and memory, selective cholinergic neurotoxic or excitotoxic lesioned rats of the SuM were tested for spatial memory on the Morris water maze (MWM) test. After the behavior tests, the expression of acetylcholine esterase (AChE) in the hippocampus was studied using the immunohistochemistry. In the MWM test, both lesion of the SuM with 192 IgG-saporin and ibotenic acid produced the impairment of spatial learning and memory. In the immunohistochemistry, the SuM-lesioned rat model by selective cholinergic neurotoxin showed decrease in the AChE expression in the hippocampal CA3. These findings suggest that cholinergic cells of the SuM area play a critical role in the process of consolidation of memory.
Related Products: 192-IgG-SAP (Cat. #IT-01)
Hulsey D, Hays S, Khodaparast, N, Casavant R, Ruiz A, Das P, Nutting E, Carrier X, Iyengar M, Quareshi I, Sultana S, Rennaker R, Kilgard M (2014) Vagus nerve stimulation dependent enhancement of cortical plasticity requires cholinergic innervation of the cortex. Neuroscience 2014 Abstracts 542.20. Society for Neuroscience, Washington, DC.
Summary: Primary motor cortex (M1) transiently reorganizes in response to motor skill learning. Pairing forelimb movements with Vagus Nerve Stimulation (VNS) drives enhanced and robust analogous plasticity within M1. These changes occur outside of the typical period for motor plasticity and are independent of new skill learning. The mechanism by which VNS enhances M1 plasticity is not well understood. Skill learning and the associated cortical plasticity is dependent on cholinergic innervation of the cortex. VNS may enhance plasticity by engaging neuromodulatory systems necessary for plasticity. We hypothesize that cholinergic innervation of M1 is necessary for motor plasticity associated with VNS pairing. To test this hypothesis, we trained female Sprague Dawley rats on a skilled lever pressing task emphasizing use of the proximal forelimb. After task acquisition, one group of rats received a lesion to the cholinergic neurons of the basal forebrain using 192-IgG-Saporin, while another group received a control injection. All subjects also received a VNS cuff implant during the surgery. After one week of recovery, all subjects receive VNS paired to successful task performances for five days. Intracortical microstimulation was performed to derive M1 maps of each group 24 hours after their final VNS paired session. Subjects with an intact cholinergic system show significant expansion of proximal forelimb representation over naïve animals within the cortex. Subjects without cholinergic innervation of the cortex show no difference in M1 organization when compared to naïve animals. We conclude that cholinergic innervation is necessary for the effects of VNS on motor plasticity.
Related Products: 192-IgG-SAP (Cat. #IT-01)
Fraley GS (2014) Immunolesions of melanopsin receptive neurons in the adult Pekin drake attenuates the hormonal reproductive axis. Neuroscience 2014 Abstracts 543.01. Society for Neuroscience, Washington, DC.
Summary: Several light sensitive receptors have been described in the avian brain that are thought to regulate the reproductive axis independently from the eyes and pineal gland. Recently, my lab has described the presence of three of these photoneuroendocrine systems in the Pekin duck: opsin, opsin 5, and melanopsin. I set out to test the hypothesis that melanopsin receptive neurons are necessary to maintain seasonal reproductive status in the Pekin drake. To accomplish this, 50-week-old Pekin drakes were housed in the aviary at Hope College under long day length (18 hrs lights on) conditions in floor pens (5 drakes per pen). To specifically lesion melanopsin-receptive neurons, drakes were anethestized (8 mg/kg Propofol, IV), given analgesics (2 mg/kg ketfen, SC) skin incised and a trephine hole drilled 10 mm caudal to bony orbits and 1 mm to the left of midline. A 33 gauge stainless steel needle attached to a Hamilton syringe was lowered stereotactically 3.5 mm ventral to dura into the lateral ventricle. Three microliters of an anti-melanopsin-saporin conjugate (MSAP, 100 ng/ul) was injected into the lateral ventricle (n = 10). Control drakes were injected with 3 ul of equimolar unconjugated anti-melanopsin and saporin (SAP, n = 10). The incision was closed with VetBond, and the drakes returned to the aviary after complete recovery from anesthesia. After 4 weeks, birds were euthanized (400 mg/kg FatalPlus, IP) and body weight measured, and brains, pituitaries, and testes collected and stored for analyses. MSAP-treated drakes had significantly (p < 0.001) reduced relative teste weights compared to SAP controls. qRT-PCR analyses (n = 5 per treatment) of anterior pituitary showed a significant reduction (p < 0.001) in both LH-beta and FSH mRNA’s. Immunoctyochemical analyses (n = 5 per treatment) showed a significant reduction in melanopsin and GnRH-immunoreactivities. These data underscore the importance of the photoneuroendocrine system in maintaining the reproductive axis in seasonally breeding birds.
Related Products: Melanopsin-SAP (Cat. #IT-44)
Involvement of kndy neurons in luteinizing hormone surges induced by steroids
Helena CV, Toporikova N, Kalil B, Stathopoulos AM, Anselmo-Franci JA, Bertram R (2014) Involvement of kndy neurons in luteinizing hormone surges induced by steroids. Neuroscience 2014 Abstracts 543.11. Society for Neuroscience, Washington, DC.
Summary: A subset of hypothalamic arcuate neurons that coexpress kisspeptin, neurokinin B and dynorphin (KNDy neurons) has been postulated to be critical for puberty onset and regulation of luteinizing hormone (LH) secretion. A method for targeted ablation of KNDy neurons was recently developed using the molecular neurotoxin saporin conjugated to the selective NK3R agonist [MePhe7]Neurokinin B (Nk3-SAP). Ovariectomized rats were microinjected bilaterally into the arcuate nucleus with Blank-SAP or Nk3-SAP. One set of rats was transcardiacally perfused 1, 2 or 3 weeks after the injections and immunocytochemistry for kisspeptin was performed in the arcuate nucleus region. The number of KNDy neurons was significantly decreased after 1 week of the toxin injection, however maximal fiber ablation was only achieved 3 weeks after the microinjections. Another group of rats was treated with oil (OVO), estradiol (OVE) or estradiol plus progesterone (OVEP). One week later, rats had their jugular vein cannulated and blood samples were taken at 10am and hourly from 3 until 6pm. Selective ablation of KNDy neurons of OVO rats significantly reduced basal LH levels at all time points studied. Basal LH levels in OVE and OVEP animals did not differ between groups, yet KNDy ablation increased peak LH levels in the afternoon of OVE and OVEP rats. A third group of OVE animals was microinjected with norbinaltorphimine (nor-BNI), a kappa opioid receptor antagonist, directly into the anteroventral periventricular nucleus (AVPV) one hour before the expected LH surge. The blockage of dynorphin receptors intra-AVPV significantly increased the LH surge, similar to the effect of KNDy ablation in OVE rats. Our results suggest that KNDy neurons provide inhibition to AVPV kisspeptin neurons through dynorphin and thus regulate the size of the LH surge induced by estradiol or estradiol plus progesterone.
Related Products: NKB-SAP (Cat. #IT-63)
Properties of recombinant isolectin B4 (IB4): Binding and immunostaining
Kohls MD, Lappi DA, Ancheta LR (2014) Properties of recombinant isolectin B4 (IB4): Binding and immunostaining. Neuroscience 2014 Abstracts 627.07. Society for Neuroscience, Washington, DC.
Summary: Isolectin B4 (IB4) is a protein found in the seeds of Griffonia simplicifolia, a woody climbing shrub native to western and central Africa. Although initially used as an identifier and agglutination agent for B-type red blood cells, it has since become widely used in the neurosciences as a neuronal tracer, for labeling specific populations in the spinal cord, and as a targeting moiety for delivering toxins to specific cells. Recent developments in response to competition from the nutritional supplement industry have reduced the available supply of seeds from which the native protein is purified. In order to create a consistent supply of pure and active IB4 we have determined the full nucleotide sequence of the IB4 gene, cloned it from Griffonia genomic DNA, and expressed recombinant IB4 in E. coli. The recombinant IB4 (rIB4) was purified and tested in several activity assays against the native protein. A fusion protein of rIB4 and GFP was created to demonstrate the use of this protein in immunostaining. Griffonia also contains isolectin A that agglutinates A-type red blood cells - the A and B lectins form tetramers with varying subunit combinations. These tetramers are potential sources of contamination in preparations of the native protein. rIB4 is completely free of any A lectin contamination. The rIB4 is highly pure, and has identical activity to the native protein.
Related Products: IB4-SAP (Cat. #IT-10)
Cholinergic regulation of aromatase in brain
Li J, Nelson D, Gibbs R (2014) Cholinergic regulation of aromatase in brain. Neuroscience 2014 Abstracts 640.10. Society for Neuroscience, Washington, DC.
Summary: Our goal is to understand mechanisms by which estrogens can influence brain function and cognition. Estrogens have been shown to influence neuronal plasticity and cognitive performance. Recent studies suggest that, in some cases, local estrogen synthesis can have a greater impact on neuronal survival and plasticity than systemic estrogen administration. Cholinergic projections also have a significant impact on neuronal plasticity in the brain, and recent studies demonstrate critical links between effects of estrogens and effects mediated by cholinergic inputs. In this project we are investigating whether aromatase expression and activity in specific regions of the adult brain are regulated by cholinergic activity. In one experiment, ovariectomized (OVX) rats were treated with the cholinesterase inhibitors donepezil (3 mg/Kg) or galantamine (5 mg/Kg) daily for one week prior to tissue collection. In a second experiment, OVX rats received intraseptal infusions of 192IgG-saporin (SAP) to selectively destroy cholinergic inputs to the hippocampus. Tissues were collected two weeks following the infusions. Different groups of rats were used to evaluate effects on aromatase mRNA and aromatase activity. Effects on aromatase mRNA were evaluated using qRT-PCR. Effects on aromatase activity were evaluated using a novel microsomal assay in which brain tissue microsomes were extracted and activity was measured in vitro by measuring conversion of testosterone to estradiol. Results show an increase in aromatase mRNA in the preoptic area following treatment with galantamine, but no effect in the hippocampus, frontal cortex, or amygdala. Galantamine also produced an increase in aromatase activity in the amygdala, but no significant effect in other brain regions. Donepezil had no significant effects on either aromatase mRNA or activity. Effects of the cholinergic lesions are still being evaluated; however, preliminary results suggest no significant effect on relative levels of aromatase mRNA in the hippocampus. These results indicate that cholinergic manipulations can affect aromatase expression and activity in specific regions of the brain such as the preoptic area and amygdala, with little or no effect in the hippocampus and frontal cortex. This could have important implications for the effects of cholinergic and anticholinergic medications on local estrogen production in the brain.
Related Products: 192-IgG-SAP (Cat. #IT-01)
Llorente A, Gonzalez De San Roman E, Moreno M, Manuel I, Giralt M, Rodriguez R (2014) Activity mediated by neurolipid (CB1 and LPA1) and neuropeptide (GAL1) receptors in a rat model with cholinergic basal forebrain lesion. Neuroscience 2014 Abstracts 307.25. Society for Neuroscience, Washington, DC.
Summary: The cholinergic basal forebrain neurons (CBFN) which innervate cortical, hippocampal and amygdaloid areas, control learning and memory processes and are damaged in Alzheimer´s disease. An intraparenquimal injection of the 192IgG-saporin (SAP) immunotoxin, specifically eliminates CBFN. The present study examined the activity of endocannabinoid (CB1), lysophosphatidic acid (LPA1), galanin (GAL1) and muscarinic (MR) receptors, measuring Gi/o protein activation by [35S]GTPγS autoradiography in rats after the selective cholinergic basal forebrain lesion. CB1 immunoreactivity (CB1-ir) was also analyzed in the SAP administration area. We observed a high CB1-ir in the basal forebrain of the lesioned rats. The autoradiographic assays revealed that WIN55,212-2 (10 μM) evoked stimulation (CB1 activity) was increased in lateral olfactory tract (data expressed in % stimulation over basal; CSF vs SAP; 55 ± 11% vs 128 ± 13%, p<0.05) and in entorhinal cortex (156 ± 17% vs 277 ± 30%, p<0.01), but decreased in hippocampal dentate gyrus (299 ± 37% vs 166 ± 21%, p<0.05) and in medial amygdala (116 ± 20% vs 50 ± 7%, p<0.05). LPA (10 μM) induced stimulation (LPA1 activity) showed an increase in the internal capsule (60 ± 10% vs 137 ± 19%, p<0.01). The MR activity that was measured using carbachol (100 μM) was increased in hippocampal dentate gyrus (27 ± 6% vs 62 ± 7%, p<0.05) and in entorhinal cortex (55 ± 10% vs 94 ± 11%, p<0.05) but decreased in the nucleus basalis of Meynert (nbM) (46 ± 10% vs 15 ± 6%, p<0.05). Finally, there was an increased stimulation (GAL1 activity) of galanin (1 μM) in the nbM (45 ± 13% vs 80 ± 12%, p<0.05). The CB1-ir and GAL1 activity was increased in the lesioned area where the cholinergic neurotransmission was impaired, indicating a possible neuroprotective action on the surviving CBFN.
Related Products: 192-IgG-SAP (Cat. #IT-01)
Development of morphine analgesic tolerance is modulated by spinal P2X7 receptors
Leduc-Pessah HL, Weilinger N, Fan C, Thompson R, Trang T (2014) Development of morphine analgesic tolerance is modulated by spinal P2X7 receptors. Neuroscience 2014 Abstracts 327.08. Society for Neuroscience, Washington, DC.
Summary: Growing evidence suggests that microglia, which are immune cells in the central nervous system, are causally involved in the development of opioid analgesic tolerance. Here, we investigated the importance of spinal microglial ATP-gated P2X7 receptors (P2X7Rs) in morphine tolerance. In adult male Sprague Dawley rats, we found that seven days of systemic morphine treatment resulted in a progressive decline in morphine anti-nociception and a loss in analgesic potency, the two key features of analgesic tolerance. The development of morphine tolerance correlated with an increase in spinal Iba-1 expression, a marker indicative of microglial activation. To assess whether spinal microglia are required for morphine tolerance, we depleted microglia in the spinal cord of morphine treated rats using intrathecal injections of a saporin-conjugated antibody to Mac1 (Mac1-saporin). We found that Mac1-saporin attenuated the decline in morphine anti-nociception in rats that received chronic morphine treatment. In contrast, intervention with Mac1-saporin failed to restore morphine analgesia in rats with established tolerance. Thus, spinal microglia are causally involved in the development, but they are not required for the ongoing expression, of morphine tolerance. In addition, we found that P2X7R protein expression was markedly increased in the spinal cord of morphine tolerant animals. Pharmacological blockade of P2X7Rs with the selective antagonist A740003 attenuated the development of tolerance but did not reverse established tolerance. In BV2 microglial cells, repeated morphine treatment increased total P2X7R protein expression, an effect recapitulated by the mu-opioid receptor agonist DAMGO, and suppressed by the mu-receptor antagonist, CTAP. The morphine-induced increase in P2X7R protein expression was concomitant with a potentiation of BzATP evoked P2X7R calcium responses and inward current. Collectively, our findings suggest that spinal microglia are causally involved in the development, but not expression, of morphine analgesic tolerance. We also determined that the expression and function of P2X7R in microglia are critically modulated by mu-opioid receptors.
Related Products: Mac-1-SAP rat (Cat. #IT-33)
Correlation between hemodynamics and neuronal activity during altered brain states
Lecrux C, Sandoe C, Neupane S, Kropf P, Toussay X, Tong X-K, Shmuel A, Hamel E (2014) Correlation between hemodynamics and neuronal activity during altered brain states. Neuroscience 2014 Abstracts 352.03. Society for Neuroscience, Washington, DC.
Summary: Introduction: Changes in neuronal activity are spatially and temporally replicated by concurrent alterations in cerebral blood flow (CBF) under physiological conditions, a phenomenon known as neurovascular coupling (NVC) which forms the basis of several brain imaging techniques. However, virtually nothing is known about NVC under conditions of altered brain states. Using the whisker-to-barrel pathway, we tested whether the coupling between neuronal activity and cerebral perfusion would be affected by changes in cortical states triggered by varying acetylcholine (ACh) tone. Methods: Sensory stimulation was induced in rats by mechanical whisker stimulation. In the barrel cortex, CBF was measured by laser-Doppler flowmetry and somatosensory evoked potentials (SEPs) were recorded with a multichannel electrode. Activated neurons were identified by double-immunohistochemistry for c-Fos and markers of pyramidal cells or GABA interneurons. ACh tone was increased pharmacologically (physostigmine 0.1mg/kg, subcutaneous; linopirdine, 10mg/kg, intraperitoneal) or through basal forebrain (BF) electrical stimulation. ACh tone was decreased using a selective cholinotoxin (saporin, 4mg/2mL, icv). Under enhanced ACh tone, muscarinic (scopolamine, 0.1mg/kg, intravenous) or central nicotinic (chlorisondamine dichloride, 12mg/5mL, icv) receptors were selectively blocked. Results: Whisker-evoked CBF responses were altered by changes in ACh tone induced by linopirdine (+31±4%, p<0.001), physostigmine (+40±8%, p<0.01), BF stimulation (+52±18%, p<0.05) or saporin (-41%, p<0.001) compared to their respective controls. These changes reflected alterations in the activity or extent, but not in the identity, of the neuronal network of cortical pyramidal cells and specific GABA interneurons selectively recruited by whisker stimulation. Under enhanced or decreased ACh tone, whisker-evoked CBF responses accurately mirrored changes in neuronal activity, and correlated with corresponding changes in the amplitude of the SEPs in cortical layers II/III and IV. Moreover, a positive correlation was observed between hemodynamic changes and band-limited power in the high gamma band in cortical layers II/III. The enhanced CBF response under high ACh tone required muscarinic ACh receptor activation. Conclusions: Changes in neuronal and vascular signals upon sensory stimulation remain tightly correlated under enhanced or reduced ACh tone, and reflect altered activity of the neuronal network selectively recruited by sensory stimulation. These subtle changes are reliably captured by superficial hemodynamic signals.
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Johnson CS, Watts AG (2014) Hindbrain catecholaminergic projections to the paraventricular nucleus are required for activation of glutamatergic terminals by glycemic challenges. Neuroscience 2014 Abstracts 452.13. Society for Neuroscience, Washington, DC.
Summary: Hindbrain catecholaminergic inputs to the paraventricular nucleus of the hypothalamus (PVH) are necessary for the full response of neuroendocrine neurons to glycemic challenges. The drive provided to the neuroendocrine neurons by ascending catecholaminergic afferents also appears to require a glutamatergic component, as direct norepinephrine stimulation of the peri-PVH region results in a significant increase in glutamatergic excitatory postsynaptic potentials. To determine if these hindbrain catecholaminergic afferents are required to increase the excitatory synaptic drive to neuroendocrine neurons in the medial parvocellular region (mp) of the PVH, we have developed an immunocytochemical (ICC) method to assess if appositions alter their activity in response to a stimulus. This method relies on detecting the increased phosphorylation states of two key intracellular signaling intermediaries, ERK and synapsin I (Syn I), that occur as terminals become activated. Adult male Sprague-Dawley rats received central injections of the immunotoxin saporin conjugated with a dopamine-β-hydroxylase antibody, aimed at the PVH, to ablate catecholaminergic projections from the hindbrain. Rats were then fitted with jugular catheters and administered 2U/kg/ml insulin or 250 mg/kg 2-deoxy-glucose. Following perfusion, coronal sections were cut through the PVH and run for ICC using antibodies against Vesicular Glutamate Transporter 2 (VGluT2), phospho-ERK, and phospho-Syn I. Confocal Z-stacked images through the PVH were acquired, and analysis of 3D images was performed using Volocity software to assess colocalization of VGluT2 with phospho-ERK & phospho-Syn I in terminals within the PVHmp. The mean Pearson’s Colocalization Coefficient was compared across groups. With a glycemic challenge, animals with intact catecholaminergic projections showed an increased numbers of appositions exhibiting colocalization of VGluT2 with the phosphorylated signaling molecules compared to controls. Animals without hindbrain catecholaminergic projections, however, had significantly fewer colocalized appositions. This suggests that catecholaminergic inputs from the hindbrain to the PVH are necessary for the glutamatergic excitation to the neuroendocrine neurons in the medial parvocellular region of the PVH in response to a glycemic stressor, as demonstrated through changes in appositional activity levels.
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Konsman J, Chaskiel L, Bristow A, Dantzer R (2014) Interleukin-1 receptor-expressing cells in the arcuate hypothalamus mediate peripheral interleukin-1-induced hypophagia. Neuroscience 2014 Abstracts 453.13. Society for Neuroscience, Washington, DC.
Summary: Although the reduction in food intake observed in acute infectious and inflammatory diseases has been proposed to represent a regulated adaptive response, the underlying mechanisms remain incompletely understood. Our previous work has shown that the pro-inflammatory cytokine interleukin-1 (IL-1) can act in the brain to alter behavior during peripheral inflammation. The arcuate nucleus of the rat hypothalamus plays a pivotal role in the regulation of food intake and expresses the signaling interleukin-1 receptor (IL-1R1) (Ericsson et al., J. Comp. Neurol., 1995). However, lesioning of the neuropeptide Y(NPY)- and proopiomelancortin(POMC)-expressing neurons, the two major neuronal populations in the arcuate nucleus regulating food intake, does not attenuate the reduction of food intake after peripheral interleukin-1 administration (Reyes & Sawchenko, J. Neurosci., 2002). Besides neurons, venules and glia constitute the main nervous cell types expressing the signaling interleukin-1 receptor. Moreover, glial cells, and in particular tanycytes in the arcuate nucleus, have been proposed to play a role in the regulation of food intake (Bolborea & Dale, Trends Neurosci., 2013). In the present work, we set out ) to determine if IL1-R1-expressing cells in the hypothalamus mediate reduced food intake in response to peripheral IL-1 administration, and 2) if so, to identify the cell types involved. Cells expressing IL-1R1 were killed by infusion of IL-1 coupled to the intracellular toxin saporin (IL-1-SAP) into the arcuate hypothalamus. Control infusions consisted of uncoupled IL-1 and saporin and PBS. At least one week later rats were injected intraperitoneally with IL1. Intra-arcuate IL-1-SAP attenuated the reduction in food intake after peripheral administration of IL-1, indicating that arcuate cells mediate IL-1-induced hypophagia. Post mortem histochemical analyses of brain sections of the same animals revealed that intra-arcuate IL-1-SAP reduced the number of NPY-neurons, without affecting the number of POMC-neurons or the surface covered by tanycytes. Taken together, these findings indicate that IL-1R-bearing NPY neurons in the arcuate nucleus take part in the reduction of food intake after peripheral IL-1 administration and suggest that hypophagia observed in infectious and inflammatory diseases reflects, at least in part, a regulated response.
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Kruashvili L, Mepharishvili M, Dashniani M, Burjanadze M, Demurishvili M (2014) Spatial long-term memory and modulation of NMDA receptor subunit expression in medial septal immunolesioned rats. Neuroscience 2014 Abstracts 463.19. Society for Neuroscience, Washington, DC.
Summary: The present study was designed to investigate the effect of selective immunolesions of cholinergic and GABA-ergic SH projection neurons (using 192 IgG-saporin and GAT-1 saporin, respectively) on spatial memory assessed in water maze and the N-methyl-D-aspartate (NMDA) receptor GluN2B subunit expression in the rat hippocampus. We used water maze training protocol with eight training trials. One day after training, probe test with the platform removed was performed to examine long-term spatial memory retrieval. We found that immunolesion of medial septal cholinergic neurons did not affect spatial learning as exhibited by a decreased latency to find the hidden platform across the eight training trials. In contrast, rats with immunolesions of medial septal GABAergic neurons did not show a decreased latency across training trials in water maze. Trained control rats spent significantly longer than chance (15 s) performances such as swimming time in test sector (where the hidden platform was located). Moreover, they spent significantly longer in test sector than in the opposite sector, confirming the establishment of long-term memory. In contrast, the preference for test sector was abolished in medial septal immunolesioned rats. Because Saporin treated rats learned the location of the hidden platform during training, the results suggest that saporin treated rats could not remember the training a day later. We found that the expression level of NR2B subunit of NMDA receptor in the hippocampus was decreased significantly in the GAT-1 treated group compared with the control and saporin treated groups. In conclusion, our findings suggest that immunolesion of medial septal GABAergic neurons can interrupt hippocampus[[unable to display character: ‐]]dependent spatial learning, possibly through modulation of NMDA receptor subunit expression in the hippocampus. Moreover, our finding that selective lesions of medial septal cholinergic neurons affects probe-test performance but not spatial learning, suggests that septohippocampal cholinergic projections are involved specifically in the consolidation or retrieval, but not in the acquisition of long-term spatial memory.
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Tiwari D, Haynes J, Short J, Pouton C (2014) Investigating the potential of stem cell based therapy in an immunotoxin mouse model of Alzheimer’s disease. Neuroscience 2014 Abstracts 295.14. Society for Neuroscience, Washington, DC.
Summary: Purpose: To characterize a dual reporter embryonic stem (ES) cell line and validate an immunotoxin mouse model of Alzheimer’s disease for future transplantation experiments. Methods: A dual (mcherry and Lhx8+) reporter ES cell line was derived from E14Tg2a mouse ES cells assessed for differentiation capability and characterized using immunocytochemistry. For the immunotoxin model, 6-8 weeks C57BL/6 male mice (n = 12) were treated with bilateral intracerebroventricular injections of saline or mu-p75-saporin toxin (0.4µg/µl/mouse) to cause cholinergic neuronal lesions. Mice were cognitively assessed using a novel water maze (WM) protocol and novel object recognition (NOR) paradigm. Immunohistochemistry was performed to detect toxin dependent neuronal loss. Results: A significant difference in learning the WM task was observed during cued and spatial trials, with toxin-treated mice showing longer latency to platform than controls (two way ANOVA; p<0.01). Also performance during probe trial was significantly reduced in treated mice (t-test; p<0.05), indicating memory loss by toxin. No memory impairment was detected using the NOR test. Immunohistochemistry for choline acetyltransferase (ChAT) confirmed a significant loss (p<0.001; t test) of cholinergic neurons in the medial septum. These data indicate that the model is appropriate for future transplantation studies. FACS analysis of reporter cell line showed a small population of Lhx8+ cells at day 6 and 10 of differentiation. Immunocytochemistry for ChAT on day 18 cells revealed few cholinergic positives neurons as compared to wild type controls. Conclusion: Literature suggests a possible role of Lhx8 in cholinergic development and these cells are being further investigated by transplantation.
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Manuel I, Llorente A, Gonzalez de San Roman E, Merino L, Giralt M, Rodriguez-Puertas R (2014) Memory and cholinergic impairment using a new approach of bilateral lesion of rat cholinergic basal forebrain. Neuroscience 2014 Abstracts 134.02. Society for Neuroscience, Washington, DC.
Summary: The cholinergic basal forebrain neurons (CBFN), which innervate cortical, hippocampal and amygdaloid areas control learning and memory processes and are damaged in Alzheimer´s disease (AD). The aim of the present study was to characterize the model of selective induced CBFN death in the nucleus basalis of Meynert (nbM) of adult Sprague-Dawley rats by intraparenquimal injection of the specific CBFN immunotoxin 192IgG-saporin (SAP) (n=11; 1μl/side [135ng/μl]). Learning and memory behavior was evaluated with the passive avoidance (PA) test. The CBFN density and the presence of glial cells were evaluated by immunofluorescence (P75NTR, Neu-N, GFAP, Iba-1). The AChE activity and AChE+ neuron density were analyzed by staining reaction. A significant decrease in CBFN (P75NTR -ir) density was observed in SAP treated rats (-82,7% vs aCSF, p<0,001). We found that cognitive impairment in the PA test and the reduction in the CBFN density in nbM correlated with each other (P75NTR+-ir vs PA, r2=0,51, p<0,05). Similar results were obtained for the reduction in AChE staining in cortical areas (entorhinal cortex: r2=0,55, p<0,01), hippocampus (CA3 pyramidal: r2=0,49, p<0,01) and amygdala (anterior: r2=0,43, p<0,01). Immunofluorescence studies showed a high density of activated microglia (Iba-1-ir) and an abscence of astrocytes (GFAP-ir) in the SAP administration area. Moreover, using MALDI-IMS assay, some lipid species were modified around the lesion area in SAP treated rats. The obtained data on the above described model of CBFN death, mimics the cognitive and cholinergic system impairment described in AD patients.
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Akiyama T, Tominaga M, Davoodi A, Nagamine M, Takamori K, Carstens MI, Carstens E (2014) Spinal antinociceptive effect of gastrin releasing peptide (GRP) via GABAergic inhibitory interneurons expressing the GRP receptor (GRPR). Neuroscience 2014 Abstracts 158.02. Society for Neuroscience, Washington, DC.
Summary: GRPR-expressing dorsal horn neurons signal itch. We investigated a role for such neurons in modulating the spinal neurotransmission of mechanical and heat pain in mice. In behavioral studies, we measured heat and mechanical paw withdrawal thresholds using Hargreaves and von Frey assays, respectively. Mice received intrathecal (it) administration of one of following (5 µL volume); bombesin (6.2 pmol), GRP (0.1 nmol), and GRPR antagonists RC-3095 (0.03 nmol) and BW2258U89 (1.5 nmol). It administration of bombesin or GRP significantly reduced both heat and mechanical withdrawal thresholds with a maximal effect 10 min post-administration. In contrast, it administration of RC-3095 and BW2258U89 significantly increased both heat and mechanical withdrawal thresholds with a maximal effect 10 min post-administration. Mice treated with it bombesin-saporin to ablate GRPR-expressing spinal neurons exhibited reduced heat and mechanical withdrawal thresholds. It GRP failed to elicit heat and mechanical hyperalgesia in these mice. In electrophysiological recordings from superficial lumbar dorsal horn neurons, either bombesin or RC-3095 was spinally applied during responses elicited by noxious mechanical or heat stimulation of the cutaneous receptive field on the hindpaw. Bombesin increased both noxious mechanical- and heat-evoked activity in bombesin-sensitive neurons, while RC-3095 decreased noxious heat-evoked activity. In bombesin-insensitive neurons, bombesin decreased both noxious mechanical- and heat-evoked activity, while RC-3095 increased both. We additionally employed a double-label strategy to investigate if GRPR-expressing dorsal horn neurons coexpressed GABA, a molecular marker of inhibitory interneurons. Approximately 10% of GRPR-positive neurons were immunopositive for GABA. These results indicate that a subset of GRPR-expressing neurons function as interneurons in a circuit that suppresses nociceptive transmission in the dorsal horn. Noxious mechanical and heat stimuli activate GRPR-expressing dorsal horn neurons. A GABAergic subset of these may serve as inhibitory interneurons that contribute to inhibition of spinal neurons signaling heat and mechanical pain. Alternatively, GRPR-expressing neurons may drive other subsets of inhibitory interneurons. The antinociceptive circuit described here can be activated by pruritogens. We propose that the relative activity in antinociceptive and antipruritic circuits within the dorsal horn modulates itch- and pain-signaling ascending neurons to result in the perception of itch or pain.
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C1 neurons excite A5 noradrenergic neurons during hypoxia condition
Borella TL, Takakura AC, Moreira TS (2014) C1 neurons excite A5 noradrenergic neurons during hypoxia condition. Neuroscience 2014 Abstracts 168.07. Society for Neuroscience, Washington, DC.
Summary: C1 neurons activate sympathetic tone and stimulate the hypothalamic-pituitary-adrenal axis in circumstances such as pain, hypoxia or hypotension. They also innervate pontine noradrenergic cells group, including the locus coeruleus (LC) and the ventrolateral pontine catecholaminergic region (A5). Activation of C1 neurons reportedly inhibits pontine neurons; however, because these neurons are glutamatergic and have excitatory effects elsewhere, we re-examined the effect of C1 activation on pontine noradrenergic neurons (A5) using a more selective method. We examined the neuronal effects of destroying C1 catecholaminergic neurons with unilateral injection of the immunotoxin anti-dopamine beta-hydroxylase-saporin (anti-DβH-Sap) into the A5 region during hypoxic condition. Bilateral injections of anti-DβH-Sap into A5 destroyed tyrosine hydroxylase (TH) neurons but spared facial motoneurons and serotonergic neurons within the ventrolateral medulla. Hypoxia (8% O2 - 3 hours) induced a robust increase in Fos expression within the catecholaminergic C1 region of the ventrolateral medulla. On the lesioned side, Fos expression was significantly reduced (53.4 ± 17.6 vs. control: 129.8 ± 22.3 neurons) within the C1 region after hypoxia challenge. Residual Fos expression seen in lesioned side in response to hypoxia provides a basis for probing additional circuits that may be recruited in hierarchical manner in response to hypoxia. In conclusion, the C1 neurons activate the ventrolateral pontine noradrenergic neurons (A5 region) possibly via the release of glutamate from monosynaptic C1 inputs.
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Anderson ML, Nokia MS, Shors TJ (2014) The role of acetylcholine in learning: Cholinergic MSDB lesions retard trace eyeblink conditioning and decrease adult neurogenesis. Neuroscience 2014 Abstracts 177.10. Society for Neuroscience, Washington, DC.
Summary: Decades ago, acetylcholine was considered intrinsic to processes related to attention and/or learning and memory. However, in the last decade or so, this relationship has been questioned and with good reason. That said, only a few studies have addressed the involvement of acetylcholine in tasks that require an animal to associate stimuli separated in time, such as trace eyeblink conditioning. Trace eyeblink conditioning is associated with hippocampal theta rhythmic activity and dependent on adult neurogenesis in the hippocampus, both of which are thought to be mediated by cholinergic activity. In the present study, 192 IgG-Saporin (SAP) was infused into the medial septum diagonal band (MSDB) complex of Sprague-Dawley rats to selectively kill cholinergic neurons bilaterally or unilaterally. Each side of the MSDB predominantly projects to the ipsilateral hippocampal formation. Animals were considered to have a bilateral lesion if the number of neurons that express choline acetyltransferase was reduced by at least 80% compared to sham animals or a unilateral lesion if the difference in the reduction between hemispheres was greater than 30%. Animals with bilateral, unilateral or sham lesions were trained with trace eyeblink conditioning at least 14 days after the SAP infusion. Animals were given 200 trials for four days for 800 trials in total. Animals with a sham lesion made more conditioned responses over all 800 trials compared to animals with bilateral and unilateral lesions. Conditioned responses increased over time in all groups. Taken together, bilateral and unilateral lesions both retard but do not drastically impair learning. In two separate experiments, the effect of bilateral and unilateral lesions on adult neurogenesis and theta rhythms was assessed. Animals were injected with 5-bromo-2’-deoxyuridine (BrdU) to label dividing cell at least 14 days after the SAP infusion. Seven days later, the number of BrdU-positive cells in the dentate gyrus of the hippocampus of animals with bilateral and unilateral lesions was reduced by ~40% in both hemispheres. Hippocampal local field potentials were recorded from another group of animals. Seven days following the SAP infusion, relative theta power was reduced in the bilateral but not unilateral group. However, by Day 14 relative theta power was similar in all three groups. This data suggests that a reduction in the number of new neurons in the hippocampus may be a contributing factor to a trace learning deficit as a result of a MSDB lesion. Moreover, disrupting septohippocampal cholinergic activity even in one hemisphere only is enough to reduce hippocampal adult neurogenesis and retard learning.
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Prefrontal cholinergic overload and attentional capacities in aging
Yegla B, Kelbaugh A, Mookhtiar A, Parikh V (2014) Prefrontal cholinergic overload and attentional capacities in aging. Neuroscience 2014 Abstracts 211.25. Society for Neuroscience, Washington, DC.
Summary: The cognitive reserve hypothesis of aging posits that brain activity attempts to cope with functional age-related changes. Individuals with lower cognitive reserve are considered more susceptible to cognitive decline and age-related pathologies. However, what neuronal mechanisms underlie cognitive reserve, and how these mechanisms provide compensation for age-related decline in attentional capacities remains unknown. The basal forebrain cortical cholinergic input system is a critical component of the brain’s attentional system. Healthy older adults show attentional load-dependent posterior-anterior shift in aging (PASA) characterized by higher activation of the prefrontal regions. However, it is not known whether prefrontal cortex (PFC)-driven cholinergic mechanisms compensate for age-related decline in attentional capacities. Here, we investigated the impact of partial cholinergic deafferentation of the PFC on attentional capacities in young and aged rats. The impact of cholinergic depletion on neuronal activation in the PFC and posterior parietal cortex (PPC) was also investigated using a semi-quantitiative c-fos immunohistochemistry procedure. Young and aged rats were trained in an operant sustained attention task (SAT) that required the animals to distinguish between signal and non-signal events to attain a reward. After attaining criterion (70% correct responses on both trial types), animals either received bilateral infusions of 192-IgG saporin or sterile saline into the PFC and the performance was monitored for 4 weeks. Aged rats required more training sessions to acquire criterion than young rats. However, post-criterion performance prior to lesion surgeries remained similar between the two age groups. Saline-infused aged rats show a greater number of c-fos expressing cells in the PFC but not PPC as compared to the young animals. Restricted loss of prefrontal cholinergic inputs produced attentional impairments in aged rats (SAT scores: 0.43±0.08 vs. 0.63±0.05 in young lesioned rats). Moreover, lesioned aged rats show reduced c-fos positive counts in the PFC as compared to aged intact rats. Collectively, these data suggest that PASA shifts and prefrontal overload foster top-down processes to maintain attentional capacities in aging. Moreover, these compensatory processes are triggered by prefrontal cholinergic inputs.
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Burk JA, Otoya D, Leong C, Ng A, Kozikowski CT (2014) Assessing removal of illumination as a signal: Effects of loss of basal forebrain corticopetal cholinergic neurons. Neuroscience 2014 Abstracts 263.06. Society for Neuroscience, Washington, DC.
Summary: In the vast majority of experiments assessing visual attention in animal models, tasks are employed that require the detection of a stimulus that was previously absent. Relatively few experiments have employed procedures where the signal is the removal of a previously presented stimulus. In the present experiment, we modified a previously validated measure of a visual attention that required detection of a signal (illumination of a central panel light for 500, 100 or 25ms) from “blank” trials when the light was not illuminated. Loss of basal forebrain corticopetal cholinergic neurons has been shown to decrease signal detection in this task. We modified the task so that the central panel light was illuminated throughout the intertrial interval and a signal occurred when the light was turned off (4-s) whereas a blank trial occurred when the central panel light remained illuminated. Male FBNF1 hybrid rats were trained in this revised attention task and then assigned to receive infusions of 192IgG-saporin or saline into the basal forebrain. Rats were retrained in the task after surgery and then received one session with a houselight flashing in the back of the chamber throughout testing and a second session with the signal decreased from 4-to 2-s. During presurgical training, we observed that animals required a longer signal to maintain stable task performance when the signal involved turning off the central panel light. Surprisingly, loss of basal forebrain corticopetal cholinergic inputs was associated with higher rates of signal detection compared with sham-lesioned animals, although this effect was attenuated with subsequent training. Flashing the houselight decreased accuracy on blank trials, but did not differentially affect lesioned and sham-lesioned animals. Signal detection accuracy significantly declined in both lesioned and sham-lesioned animals when the signal duration was decreased. Collectively, these results suggest that task manipulations appear to have similar effects whether the signal involves turning the central panel light on or off. However, the neural mechanisms that are engaged during these two types of tasks appear to be different. Future work in our laboratory will explore the role of basal forebrain noncholinergic neurons in performance of a task with turning the central panel light off serves as a signal.
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Kozikowski CT, Wolfe EL, Yanev PG, Burk JA (2014) Interactions between noncholinergic basal forebrain neurons and muscarinic receptors in attentional processing. Neuroscience 2014 Abstracts 263.16. Society for Neuroscience, Washington, DC.
Summary: Numerous studies have provided evidence that basal forebrain corticopetal cholinergic neurons are critical for normal attentional performance. However, the role of noncholinergic basal forebrain neurons in attention has not been well-characterized. Moreover, evidence regarding interactions between cholinergic receptor activity and noncholinergic basal forebrain neurons remains scarce. In the present experiment, rats (n=15) were trained in a two-lever sustained attention task that required to discriminate between brief illumination of a centrally located panel light (500, 100, 25 ms) from trials when the light was not illuminated. After reaching criterion performance, rats received infusions into the basal forebrain of saline (n=7) or the immunotoxin, GAT1-saporin (n=8), to lesion noncholinergic neurons. After re-establishing performance after surgery, all rats received systemic administration of the muscarinic receptor antagonist, scopolamine (0, 0.05, 0.20 mg/kg, ip). When attentional testing resumed after surgical recovery, lesioned animals’ task performance did not significantly differ from sham-lesioned animals. However, following the highest dose of scopolamine, lesioned animals exhibited a larger decline in signal detection accuracy compared to sham-lesioned animals. Additionally, lesioned animals’ omission rate was higher during injection sessions compared to sham-lesioned animals. These results suggest that noncholinergic basal forebrain neurons are not necessary for performance in a well-trained attention task. However, loss of these neurons renders animals’ attentional performance more vulnerable to decreased cholinergic system stimulation. Finally, the lesion-induced increase in omissions may reflect a role for noncholinergic basal forebrain neurons in processes beyond attention.
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Dinh TT, Huston N, Ritter S (2014) Lesions of hindbrain catecholaminergic projections to nucleus accumbens, bed nucleus of the stria terminalis, lateral parabrachial nucleus or locus coeruleus do not impair glucoprivic feeding. Neuroscience 2014 Abstracts 256.05. Society for Neuroscience, Washington, DC.
Summary: We have shown previously that injection of the retrogradely transported immunotoxin, anti-dopamine beta-hydroxylase (DBH) saporin (DSAP), into the paraventricular nucleus of the hypothalamus (PVH) or arcuate nucleus, abolishes feeding in response to central or systemic glucoprivation. Since DSAP injection destroys DBH-expressing neurons with projections to the injection site, these results strongly implicate hindbrain catecholamine neurons as major mediators of glucoprivic feeding. In order to further define the essential circuitry underlying glucoprivic feeding, we injected DSAP into these additional sites: locus coeruleus (LC), accumbens shell (AcbSh), ventrolatersal bed nucleus of the stria terminalis (vlBNST) and lateral parabrachial nucleus (LPBN). These sites are innervated by hindbrain catecholamine neurons and some sites receive collateral innervation from PVH-projecting catecholamine neurons. Appropriate placement and volume for DSAP administration was determined by co-labeling of DBH-ir neurons with retrograde tracer injected into target sites. Lesions were confirmed by postmortem evaluation of DSAP injection site and by hindbrain catecholamine cell and terminal loss. We found that the feeding response to systemic glucoprivation was not significantly or permanently impaired by injection of DSAP into any of these sites. Based on our results to date, we tentatively conclude that direct projections from hindbrain catecholamine neurons to the LC, AcbSh, vlBNST and LPBN are not required for glucoprivic feeding. The hypothalamus appears to be the major recipient of direct innervation from catecholamine neurons required for glucoprivic feeding
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Fu R, Chen X, Zho W, Li J, Ye J-H (2014) Selective ablation of mu opioid receptor expressing gaba neurons in the rostromedial tegmental nucleus promotes ethanol intake. Neuroscience 2014 Abstracts 267.30. Society for Neuroscience, Washington, DC.
Summary: BACKGROUND AND PURPOSE The cellular mechanisms underlying the aversive effect of ethanol that limits its intake are not well understood, although recent evidence has linked aversion with synaptic inhibition of dopamine neurons in the ventral tegmental area. Emerging evidence indicates that the rostromedial tegmental nucleus (RMTg), a newly defined midbrain structure exerts a major GABAergic inhibitory control over midbrain dopamine neurons and encodes aversive stimuli. The RMTg contains mostly GABAergic neurons and with dense μ-opioid receptor (MOR) immunoreactivity. However, the role of RMTg in the regulation of ethanol intake has not been well investigated. EXPERIMENTAL APPROACH We compared voluntary ethanol intake and locomotion in rats with intra-RMTg infusion of dermorphin-saporin or blank saporin. Dermorphin-saporin is a neurotoxin, which could selectively lesion MOR-expressing neurons. We measured ethanol intake in rats given intermittent access to ethanol (20% vol/vol) using a two bottle choice paradigm. We euthanized the rats, dissected their brains and analyzed the glutamic acid decarboxylase67 (GAD67) and MOR protein expression and immunoreactivity immediately following the behavioral test. KEY RESULTS In rats that received intra-RMTg injection of dermorphin-saporin, we observed a robust increase in the intake of and the preference to ethanol, and in the locomotor activity; but a significantly reduced GAD67 and MOR protein expression, as well as a massive loss of neurons with GAD67 and MOR immunoreactivity within the RMTg. We observed no such changes in rats that received injection of blank saporin or saline. Together, These findings indicate that MOR-expressing GABA neurons in the RMTg play a crucial role in the regulation of ethanol consumption, implicating the dysfunction of these neurons likely play a critical role in the pathogenesis of alcoholism, and that these neurons should represent an appropriate target for the development of therapeutic strategies against alcohol use disorders.
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