37 entries

Role of the septohippocampal GABAergic system in spatial orientation

Koppen JR, Winter SS, Cheatwood JL, Wallace DG (2010) Role of the septohippocampal GABAergic system in spatial orientation. Neuroscience 2010 Abstracts 806.16/KKK21. Society for Neuroscience, San Diego, CA.

Summary: Spatial orientation depends on the integrity of multiple neural systems. For example, during the progression of Alzheimer’s Disease, degeneration of the basal forebrain is associated with cognitive impairments including episodes of wandering. The medial septum projects both cholinergic and GABAergic fibers into the hippocampus. Research and therapies have typically focused on enhancing function of the cholinergic component; however, the GABAergic component has also been shown to contribute to hippocampal function. Previous attempts to characterize the role of the GABAergic system in spatial orientation involved non-selective lesion techniques in combination with the water maze task have failed to characterize the nature of the deficit mediating the impaired performance. Development of GAT1-Saporin immunotoxin provides a novel tool to selectively destroy GABAergic neurons in the medial septum. The current study examined the effects of injecting GAT1-Saporin or saline (sham lesion) into the medial septum on spatial orientation using the food-hoarding paradigm. The food-hoarding paradigm involves training rats to search for food pellets on a large circular table and carrying the food pellet directly to a visible refuge. Three probes dissociate the use of environmental and self-movement cues: 1) Hidden probe involved placing the refuge below the surface of the table, limiting rats to use distal environmental or self-movement cues to locate the refuge; 2) Dark Probe involved using the hidden refuge with the room lights off, limiting rats to use self-movement cues to locate the refuge; 3) New probe involved placing the hidden refuge on the opposite side of table, placing environmental and self-movement cues in conflict. Both sham and GAT1-Saporin rats were accurate in returning to the refuge during the Hidden probe. Only sham rats were accurate in carrying food to the refuge during the Dark probe. During the New probe, both groups initially carried the food pellet to the former refuge location. Although sham rats consistently carried the food pellet to the new refuge location after their initial error, GAT1-Saporin rats continued to perseverate to the former refuge location. The current study demonstrates a role for the septohippocampal GABAergic system in spatial orientation related to processing self-movement cues.

Related Products: GAT1-SAP (Cat. #IT-32)

Evidence that focal hippocampal interneuron loss disrupts theta-rhythm activity in dorsal CA1

Rossi CA, Lehmkhule MJ, Kesner RP, Dudek FE (2010) Evidence that focal hippocampal interneuron loss disrupts theta-rhythm activity in dorsal CA1. Neuroscience 2010 Abstracts 811.1/LLL64. Society for Neuroscience, San Diego, CA.

Summary: Hippocampal theta activity (6-12 Hz) is an oscillatory local field potential that is thought to play a critical role in the encoding and storage of new information. As a hypothetical mechanism for theta rhythm generation, interneurons have been proposed to appropriately time the GABAergic inhibition of principal cells, as a means of organizing the theta pattern; however, little experimental work has been done to test this hypothesis directly. The current study aims to test in a relatively direct manner the hypothesis that interneurons synchronize the activity of pyramidal cells into theta-band oscillations. In the current study, SSP-saporin (a selective interneuron-targeting neurotoxic lesioning agent) was infused into six sites located in dorsal CA1 in order to create an interneuron-only lesion confined to that area. Animals were also implanted with chronic field potential recording electrodes aimed at areas CA1, CA3, and dentate gyrus. All animals were then monitored, using video and EEG recordings, 24 h per day for the next 7 to 10 days. In addition, EEG was recorded while animals were allowed to explore a novel open field for 30 min in order to create a situation where theta rhythm activity is highly likely to occur. Local field potentials from animals that received SSP-Saporin injections into the dorsal CA1 area revealed attenuation of theta rhythm activity in the lesioned area. Recordings from controls, however, showed a robust peak of activity in the theta frequency band, similar to what has been traditionally described in the hippocampus of naive rats. Together, these results suggest that local elimination of interneurons disrupts local theta rhythm without induction of seizure activity. These experiments provide evidence concerning the possible organizational role of GABAergic interneurons in theta rhythm, an important component of normal hippocampal function.

Related Products: SSP-SAP (Cat. #IT-11)

Do GAT1-saporin lesions of the medial septum damage GABAergic afferents to the medial septum?

Gielow M, Roland J, Servatius, RJ Pang KCH (2010) Do GAT1-saporin lesions of the medial septum damage GABAergic afferents to the medial septum?. Neuroscience 2010 Abstracts 811.3/LLL66. Society for Neuroscience, San Diego, CA.

Summary: 192-IgG saporin is an antibody directed to the p75 receptor conjugated to the ribosomal-inactivating compound saporin. 192-IgG saporin has been widely used to selectively ablate cholinergic cells of the basal forebrain. Cholinergic lesions are typically made by injections of 192-IgG saporin at the soma in basal forebrain nuclei. However, 192-IgG saporin is also effective in damaging specific cholinergic projections by administration of the toxin in the axon terminal region. Recently, GAT1-saporin has been developed as a tool to selectively damage cells expressing the GABA transporter GAT1. GAT1-saporin combines an antibody to the GABA transporter GAT1 with saporin. GAT1 transporters are primarily localized to neurons and GAT1-saporin has been shown to selectively damage GABAergic neurons in the BNST and medial septum. Given the similarity to 192-IgG saporin, a major question is whether GAT1-saporin is effective in damaging GABAergic afferents to the area of administration. Our previous studies found that GAT1-saporin administered to the medial septum / diagonal band of Broca (MSDB) damages GABAergic septohippocampal neurons and impaired performance on delayed match to position tasks. While it seems likely that damage of GABAergic MSDB neurons is responsible for these behavioral impairments, one cannot rule out the possibility that destruction of GABAergic afferents to the MSDB may also contribute. Therefore, the present study was undertaken to determine whether GAT1-saporin lesions of the MSDB damage the GABAergic hippocamposeptal projection. Male Sprague Dawley rats received both fluorogold and either GAT1-saporin or vehicle in medial septum. Immunocytochemistry for choline acetyltransferase and parvalbumin confirmed the extent of the lesion. The majority of hippocamposeptal GABAergic neurons contain the neuropeptide somatostatin. Quantification of double-labeled hippocampal fluorogold-positive cell bodies with anti-somatostatin immunofluorescence was performed using unbiased stereology. Preliminary data suggest that GABAergic hippocamposeptal neurons are intact. These results will be important in understanding the damage produced by GAT1-saporin.

Related Products: GAT1-SAP (Cat. #IT-32)

The effects of a combination of antioxidants and essential fatty acids as treatment for Alzheimer’s disease in the mu-p75 saporin-injected model

Matchynski JJ, Lowrance SA, Rossignol J, Dekorver NW, Puckett ND, Pappas CA, Trainor KJ, Delongchamp JL, Radwan J, Heldt JC, Dey ND, Dunbar GL (2010) The effects of a combination of antioxidants and essential fatty acids as treatment for Alzheimer’s disease in the mu-p75 saporin-injected model. Neuroscience 2010 Abstracts 856.15/I21. Society for Neuroscience, San Diego, CA.

Summary: Alzheimer’s disease (AD) is a progressive neurodegenerative disorder that is marked by a progressive loss of memory and affects over five million people nationwide (Alzheimer’s Association, 2010). It is characterized by an increase in oxidative stress, amyloid plaques, neurofibrillary tangles, and the loss of cholinergic neurons. Mice injected with the ribosome deactivating protein, mu-p75 saporin, model the deficits in memory, loss of cholinergic neurons, and increased oxidative stress observed in AD. The current study aimed to decrease the deficits observed in the saporin mouse model using a combination of antioxidants from tart cherries and essential fatty acids, Cerise© total body rhythm (TBR). Mice dosed with TBR or methylcellulose were given bilateral ventricular injections of phosphate buffer saline or saporin. Memory and motor functioning were then measured in a series of behavioural tests. Results indicate that TBR decreased the memory deficits observed in object recognition, place recognition, and Morris-water-maze tasks, as well as the inflammatory response and loss of cholinergic neurons in the medial septum. The findings suggest that TBR could provide an effective, adjunctive treatment that may delay the onset or decrease the severity of AD.

Related Products: mu p75-SAP (Cat. #IT-16)

Molsidomine promotes the recovery of cognitive deficit induced by 192 IgG saporin in rats

Hernandez MA, Hernández-Melesio M, Gonzalez-Ezquivel D, Quevedo-Corona L, Jiménez-Cataño M, Santoyo-Pérez M, Rios-Castañeda C, Pérez-Severiano F (2010) Molsidomine promotes the recovery of cognitive deficit induced by 192 IgG saporin in rats. Neuroscience 2010 Abstracts 856.27/I33. Society for Neuroscience, San Diego, CA.

Summary: The NO donor molsidomine (MOLS) has been used as a pharmacological tool in order to antagonize the cognitive deficit associated to cholinergic hypofunction produced by scopolamine. However, the participation of NO in the recovery of cholinergic deficit due to the administration of the cholinergic immunotoxin, 192 IgG saporin (SAP) has not been analyzed. The aim of the present study was to determine the effect of MOLS to counteract the cognitive deficits induced by cholinergic denervation in the object recognition task. Male Wistar rats were divided in the follow experimental groups according to the intraseptal administration of SAP and its vehicle PBS, and the injection (i.p) of the NO donor molsidomine and its vehicle saline: SAP (0.22 µg), PBS (0.1M pH 7.4), molsidomine (4mg/kg), SAP/molsidomine. The single dose of MOLS used in this study antagonized the cognitive failure related to SAP administration and increased the exploration time of novel object. We conclude that MOLS promote the acquisition of recognition memory in the model of cholinergic denervation associated to 192 IgG SAP and further immunohistological studies are being carried out in order to demonstrate that nitric oxide could have an effect over the cholinergic functionality.

Related Products: 192-IgG-SAP (Cat. #IT-01)

Leptin-saporin lesions of the arcuate nucleus induce an arrhythmic circadian feeding pattern

Wiater MF, Oostrom M, Barfield R, Dinh TT, Li A-J, Ritter S (2010) Leptin-saporin lesions of the arcuate nucleus induce an arrhythmic circadian feeding pattern. Neuroscience 2010 Abstracts 733.6. Society for Neuroscience, San Diego, CA.

Summary: The endogenous circadian rhythm of feeding is incompletely understood. The leptin sensitive network within the arcuate nucleus (Arc) of the hypothalamus is important for the control of feeding. Genetic deletion of leptin or leptin receptors results in profound obesity, hyperphagia, and the loss of day/night differences in food intake. Because the Arc is critically involved in control of food intake and contains leptin receptors, we hypothesized that the Arc plays an important role in maintenance of feeding rhythms. To examine this hypothesis, we injected a newly developed targeted toxin, leptin conjugated to saporin (LSAP), into the Arc to lesion leptin receptor-expressing neurons in the vicinity of the injection. Controls were injected saporin conjugated to a peptide with no known action or receptor (blank-saporin, BSAP). We expected the Arc LSAP would disrupt the circadian rhythm of food intake, as seen in rats with genetic deletion of leptin or its receptor. Eating rhythms were monitored continuously (each minute) over a 60-day period using BioDAQ (Research Diets) automated meal monitoring equipment. Data were analyzed for circadian rhythm using ClockLab (ActiMetrics) software. Eatograms (food intake in actogram format), showing eating times and durations comparable to actograms used for wheel-running activity, and Chi-square periodograms were generated. Feeding was monitored in light:dark, dark:dark, or light:light conditions. The LSAP injection caused profound hyperphagia, weight gain and disrupted circadian feeding patterns. Although LSAP rats remained sensitive to light and dark under certain circumstances and were capable of an apparent rhythm during light:dark conditions, feeding was arrhythmic by all measures when photic cues were removed (i.e., in dark:dark and light:light conditions). At the end of experimentation, lesions were analyzed using immunohistochemistry to detect agouti gene related protein (AGRP) and α-melanocortin stimulating hormone (α-MSH) neurons, both known to express leptin receptors. Cell bodies positive for these peptides were greatly diminished in the Arc. Results indicate that the Arc contributes importantly to the expression of circadian rhythms of food intake.

Related Products: Leptin-SAP (Cat. #IT-47), Blank-SAP (Cat. #IT-21)

Krx-0501 reduces cognitive deficits in a saporin mouse model of Alzheimer’s disease

Lowrance SA, Matchynski JJ, Rossignol J, Dekorver N, Fink K, Salibi P, Dunbar GL (2010) Krx-0501 reduces cognitive deficits in a saporin mouse model of Alzheimer’s disease. Neuroscience 2010 Abstracts 856.8/I14. Society for Neuroscience, San Diego, CA.

Summary: Alzheimer’s disease (AD) is a progressive neurodegenerative disease marked by memory loss and dysfunction of cholinergic neurons. Neurotrophic factors, like nerve growth factor (NGF), have shown to improve cognitive function in AD patients. The inability of NGF to cross the blood brain barrier (BBB) and painful side effects have caused serious concerns over its future use as a treatment. Substituted pyrimidines, such as KRX-0501 (KRX; Keryx Biopharmaceuticals, New York, NY) on the other hand, readily cross the BBB and exert beneficial neurotrophic-like effects in vivo. In this study KRX was administered daily to mice that were given intra-cerebroventricular injections of mu p-75 Saporin (SAP; Advanced Targeting Systems, San Diego, CA) or vehicle (phosphate buffered saline). KRX treatment began at seven weeks of age and continued for 32 days. Doses were set at 10, 15, and 20mg/kg respectively. Animals were tested for cognitive impairment using the Morris water maze (MWM) task, object recognition (OR) and place recognition (PR) tasks while motor deficits were tested using MWM swim speed, rotarod (RR) and the open field (OF) tasks. On day 33 of KRX treatment, mice were sacrificed by transcardial perfusion. In a second experiment, mice received SAP or vehicle surgery and were sacrificed for enzyme-linked immunosorbent assay (ELISA) analysis. MWM results revealed significantly lower escape latencies of control animals relative to SAP animals. In addition mice treated with the low and middle doses of KRX displayed decreased escape latency on the MWM. In the OR task, only mice in the highest treatment group performed significantly above chance levels. No between group differences were seen in the PR task, swim speed, latency to fall from the RR, and distance travelled in the OF. Immunohistochemistry (IHC) using the glial fibrillary acidic protein antibody indicated that astrocyte activation took place primarily around the surgical injection sites. IHC labeling against choline-acetyltransferase revealed a significant decrease in cholinergic neurons of the medial septum. Finally, ELISA protein analysis of midbrain sections revealed that the KRX treatments did not increase levels of endogenous NGF. These results show that SAP injections produced a reproducible destruction of cholinergic neurons, accompanied by memory deficits in the MWM, in the absence of motoric deficits. The KRX treatment attenuated memory deficits, despite unabated cholinergic cell loss in the medial septum, and did so without affecting levels of endogenous NGF.

Related Products: mu p75-SAP (Cat. #IT-16)

Defining the role of norepinephrine in cannabinoid-induced aversion and anxiety

Carvalho AF, Van Bockstaele E (2010) Defining the role of norepinephrine in cannabinoid-induced aversion and anxiety. Neuroscience 2010 Abstracts 833.3. Society for Neuroscience, San Diego, CA.

Summary: In the central nervous system, cannabinoids have been shown to regulate neurotransmitter release, control the hypothalamic-pituitary-adrenal axis and impact several physiological systems, such as food intake, pain and emotion perception. Manipulation of the cannabinoid system using exogenous compounds has been explored as a potential therapeutic for several disorders; however some severe side effects have been reported. Understanding the neural circuits and neurochemical substrates impacted by cannabinoids will provide a better means of gauging their actions within the central nervous system that may contribute to the expression of unwanted side effects. Previous work from our lab had shown that the cannabinoid receptor (CBr) agonist WIN 55,212-2 is able to induce changes in noradrenergic transmission in limbic structures such as prefrontal cortex (PFC) and the nucleus accumbens (Acb). Moreover, we have previously reported that norepinephrine in the nucleus accumbens (Acb) is critical for WIN 55,212-2-induced aversion, as measured by the place conditioning paradigm. In the present study, we further explore the role of norepinephrine in cannabinoid-induced behaviors. More specifically, we investigate whether norepinephrine in the limbic forebrain of rats is important for the anxiety induced by WIN 55,212-2 (3.0 mg/kg, i.p.). Lesion of noradrenergic neurons in the Acb and bed nucleus of the stria terminalis (BNST) was achieved by the intracerebral injection of the toxin saporin conjugated with an antibody that recognizes the enzyme dopamine-beta-hydroxylase (DBH). This toxin yields a specific lesion of noradrenergic neurons. The anxiogenic effects of WIN 55,212-2 were then measured in the elevated zero maze. The results show that depletion of noradrenergic innervation of the Acb and BNST did not reduce the anxiogenic properties of WIN 55,212-2. These results, together with our previous findings, suggest that the anxiogenic and aversive properties of the CBr agonist WIN 55,212-2 are differentially regulated, with the aversive effects being dependent on noradrenergic transmission within the Acb and the anxiogenic effects being regulated by a, yet to be determined, alternative mechanism/circuit.

Related Products: Anti-DBH-SAP (Cat. #IT-03)

Patterning of somatosympathetic reflexes: Identification of distinct bulbospinal sympathoexcitatory RVLM projections by conduction velocity and catecholamine phenotype

Burke PG, Neale J, Korim WS, Mcmullan S, Pilowsky PM, Goodchild AK (2010) Patterning of somatosympathetic reflexes: Identification of distinct bulbospinal sympathoexcitatory RVLM projections by conduction velocity and catecholamine phenotype. Neuroscience 2010 Abstracts 694.11/HHH34. Society for Neuroscience, San Diego, CA.

Summary: The aim of this study was to examine the somatosympathetic reflex (SSR) response of different sympathetic nerves to identify distinct projections of presympathetic vasomotor RVLM neurons by axonal conduction and catecholamine phenotype. All experiments were conducted in urethane-anaesthetised (1.3 g/kg ip), paralysed, vagotomised and artificially ventilated Sprague Dawley rats (n = 44). First, we determined the simultaneous activity of dorsal root potentials and the splanchnic SSR to single shock sciatic nerve (SN) stimulation (single 0.2 ms pulse, 50 sweeps at 0.5-1 Hz, 1-80 V, n=4). Second, we simultaneously recorded the sympathoexcitatory response of multiple, sympathetic nerves (cervical, renal, splanchnic and lumbar) to low (A-fibre afferent; 4-10 V) and high (A- and C-fibre afferents; +40 V) SN stimulation (n=19). Third, we examined the cervical or splanchnic SSR to low intensity SN stimulation in rats following RVLM microinjection of somatostatin (SST) or muscimol (n=8). Fourth, we examined the splanchnic SSR in rats pretreated with intraspinal anti-dopamine-beta-hydroxylase-saporin (anti-DβH-SAP; 24 ng/side, n=8), a neurotoxin that depleted ~70% of catecholamine (C1) neurons in the RVLM compared to IgG-saporin control (n=5). Low intensity SN stimulation evoked biphasic responses in the renal, splanchnic and lumbar nerves but a single peak in the cervical nerve. High intensity SN stimulation evoked triphasic responses in the renal, splanchnic and lumbar nerves and a biphasic cervical response. RVLM injections of SST abolished the early peak of the cervical and splanchnic SSR. Intraspinal pretreatment with anti-DβH-SAP eliminated the late peak of the splanchnic SSR and attenuated the first peak. It is concluded that the mono- or bi-phasic SSR responses are generated by A-fibre afferent inputs driving two classes of bulbospinal sympathoexcitatory RVLM neurons with myelinated or unmyelinated axonal conduction. Secondly, unmyelinated RVLM presympathetic neurons, presumed to be all C1, innervate splanchnic, renal and lumbar SPN, whereas myelinated C1 and non-C1 neurons innervate all sympathetic outflow examined. These findings extend prior evidence that the RVLM expresses several types of phenotypically distinct descending sympathoexcitatory pathways.

Related Products: Anti-DBH-SAP (Cat. #IT-03), Mouse IgG-SAP (Cat. #IT-18)

Donepezil enhances effects of estradiol on DMP acquisition in rats with partial loss of septal cholinergic neurons

Gibbs RB, Chipman AM, Nelson D (2010) Donepezil enhances effects of estradiol on DMP acquisition in rats with partial loss of septal cholinergic neurons. Neuroscience 2010 Abstracts 710.23/NNN23. Society for Neuroscience, San Diego, CA.

Summary: We hypothesize that effects of estradiol on cognitive performance decrease in association with decreased basal forebrain cholinergic function, and that this accounts for the loss of estradiol effect with age and time post-menopause. In the present study, we tested the feasibility of using donepezil, a cholinesterase inhibitor commonly used to treat Alzheimer’s disease, to enhance beneficial effects of estradiol on cognitive performance in rats with septal cholinergic lesions. Young adult, ovariectomized rats received intraseptal injections of 192IgG-saporin or vehicle. Two weeks later, rats started receiving daily injections of donepezil (Don, 5 mg/Kg/day, i.p.) or vehicle. A week later, rats received either silastic capsules containing 17ß-estradiol (E) or empty capsules, implanted s.c. Rats were then trained on a delayed matching-to-position (DMP) T-maze task. Upon completion, brains were collected and sections through the medial septum were processed for detection of choline acetyltransferase (ChAT). The severity of the cholinergic lesions was ranked on a 5-point scale by estimating the loss of ChAT-positive cells in the septum. Eighty-one rats completed the study. Lesions produced a decline in performance that correlated with the severity of cholinergic cell loss (F[4,76]=10.0, p<0.0001). In rats with >50% loss of septal cholinergic neurons, treating with E and/or Don had no significant effect on the rate of DMP acquisition (F[3,36]=0.90, p=0.45). In rats with <50% loss of septal cholinergic neurons, treating with the combination of Don+E significantly increased the rate of acquisition relative to controls (p<0.05 by Tukey test), and reduced deficits associated with increasing the intertrial delay (F[9, 111]=2.30, p=0.02 for Delay x Tx interaction). Treating with Don or E alone had no significant effect, although E alone produced a strong trend toward improvement. Cholinergic lesions also increased the likelihood that rats would adopt a persistent turn χ2=13.3, p=0.0003), and treatment with Don+E reduced this effect (χ2=8.8, p=0.03). These findings demonstrate that cholinergic dysfunction produces a learning impairment as well as a loss of estrogen effect on cognitive performance which can be attenuated by treating with a cholinesterase inhibitor. The findings also indicate a critical threshold for cholinergic function below which combined therapy is not effective. We propose that combining donepezil with estrogen therapy in postmenopausal women may offer significant cognitive benefits, particularly in relatively healthy older women showing early signs of cognitive impairment or Alzheimer’s disease.

Related Products: 192-IgG-SAP (Cat. #IT-01)

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