sfn2004

Saenz C, Dominguez R, de Lacalle S (2004) Estrogen supports structural plasticity of the basal forebrain cholinergic system in vivo. Neuroscience 2004 Abstracts 72.11. Society for Neuroscience, San Diego, CA.

Summary: It is known that estrogen (E2) modulates the structural plasticity of a variety of neurons, involving the activation of second messenger systems. We have previously described a strong E2-induced outgrowth in cholinergic neurons in vitro, and in the present study we follow up those results and examine E2’s ability to enhance cholinergic arborization in vivo, under several conditions. Twenty F344 female rats were used, 10 of them gonadectomized. All the rats received a unilateral lesion (200 nl of 192 IgG-saporin) into the left HDB, and a month later were randomly assigned to receive E2 or placebo via s.c. pellets for 60 days, at which point the rats were sacrificed, the brains prepared for histology and series of sections stained with an antibody against p75NTR. Sections were carefully matched across individuals, 10 neurons selected from both lesioned and intact HDB, and photographed. Neurons were chosen from the same area in all cases, located in the periphery of the HDB, where the neuritic arborization could be easily identified. Image analysis was performed using Metamorph software, on a predetermined set of parameters. Each image was the result of a stack of photographs taken at 2 µm intervals through the depth of the section. We compared mean neurite number per neuron and total neurite length per neuron, and found that in the healthy cholinergic neurons (control side), E2 contributed to a significant increase in neurite length and number. By contrast, no effect was found on cholinergic neurons from the lesioned side, showing that E2 cannot reverse the neuronal degeneration induced by the immunotoxin. These results are important in that they provide additional support to the hypothesis that E2 may be beneficial in preventing cholinergic degeneration, but no longer useful once neuronal damage has occurred.

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

Hawkes CA, Kar S (2004) Loss of basal forebrain cholinergic neurons by 192 igG-Saporin induces increased IGF-II/M6P receptor expression in select brain areas. Neuroscience 2004 Abstracts 92.1. Society for Neuroscience, San Diego, CA.

Summary: Alzheimer’s disease (AD) is characterized neuropathologically by the presence of extracellular amyloid plaques, intracellular neurofibrillary tangles and neuronal loss in selected brain areas, including basal forebrain cholinergic neurons, which project to the hippocampus and neocortex. Increasing evidence supports a role of the endosomal-lysosomal (EL) system in the pathophysiology of AD. A key component of the EL system is the insulin-like growth factor-II/mannose-6-phosphate (IGF-II/M6P) receptor, a single transmembrane domain glycoprotein which functions in the intracellular trafficking of lysosomal enzymes, and in the internalization of extracellular IGF-II and M6P-containing ligands. However, very little is known about the functional significance of this receptor in the brain. We examined expression of the IGF-II/M6P receptor and other markers of the EL system, at different time points following bilateral i.c.v. injection of 192 IgG-saporin. 192 IgG-saporin produced an almost complete loss of ChAT-positive neurons in the basal forebrain, as well as fibers in the hippocampus and frontal cortex, while striatal cholinergic neurons were unaffected. Western blotting and immunocytochemistry results indicate an upregulation of IGF-II/M6P receptor levels in the septum and frontal cortex. A modest increase was also observed in cathepsin D levels. The level of other EL markers, such as Rab5 and LAMP1, showed varied temporal and spatial changes. These results suggest that brain areas innervated by basal forebrain neurons, respond differently to the loss of cholinergic input and that elements of the EL system may be involved in cholinergic degeneration/compensatory responses of surviving neurons.

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

Kar S, Hawkes C, Jhamandas JH (2004) Selective loss of basal forebrain cholinergic neurons by 192 IgG-saporin induces activation of glycogen synthase kinase-3β activity. Neuroscience 2004 Abstracts 92.2. Society for Neuroscience, San Diego, CA.

Summary: Glycogen synthase kinase-3β (GSK-3β) is a multifunctional enzyme involved in a variety of biological events including development, glucose metabolism and cell death. Its activity is negatively regulated by phosphorylation of Ser9 and upregulated by Tyr216 phosphorylation. Activation of GSK-3β induces apoptosis in a variety of cultured neurons and the inhibitory control of its activity by Akt kinase is one of the best characterized cell survival signaling pathways. In the present study, the cholinergic immunotoxin 192-IgG saporin was used to address the potential role of GSK-3β in the degeneration of the basal forebrain cholinergic neurons which are preferentially vulnerable in Alzheimer’s disease (AD) brain. Our results show that GSK-3β colocalizes with a subset of the forebrain cholinergic neurons and that loss of these neurons is accompanied by a transient decrease in phospho-Akt and phospho-Ser9 GSK-3β levels in the basal forebrain, hippocampus and the cortex. Neither total Akt, GSK-3β, nor phospho-Tyr216 GSK-3β levels were significantly altered in the aforesaid brain regions of treated animals. These results provide the very first evidence that increased GSK-3β activity is associated with in vivo degeneration of the forebrain cholinergic neurons and thus may be involved in the loss of these neurons as observed in AD brains.

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

Kolasa K, Parsons D, Conger K, Harrell LE (2004) Neurotrophic modulation of cholinergic denervation and hippocampal sympathetic ingrowth following immunolesioning with 192 IgG-saporin. Neuroscience 2004 Abstracts 92.9. Society for Neuroscience, San Diego, CA.

Summary: Injection of specific cholinotoxin, 192 IgG-saporin into the medial septum (MS)of rat induces not only a selective cholinergic denervation of hippocampus (CD),but an ingrowth of peripheral sympathetic fibers, originating from the superior cervical ganglion,into the hippocampus (HSI).A similar process,in which sympathetic noradrenergic axons invade hippocampus,may also occur in Alzheimer’s disease(AD). The severity of cognitive decline in AD patients has been linked to multiple factors including cholinergic and neurotrophic factors and their receptors, which undergo selective alterations throughout the progression of AD.It is known that the sites of neurotrophin synthesis in the septo-hippocampal system are predominantly hippocampal neurons. By using 192 IgG-saporin we have been able to mimic some of the cardinal features of AD e.x.cholinergic denervation and hippocampal sympathetic ingrowth and study their effect on growth factors in dorsal hippocampus. Thus,12 weeks after injection of 192 IgG-saporin we measured neurotrophic protein and mRNA expression using Western blot and RT-PCR techniques,respectively. Choline acetyltransferase activity(ChAT)and norepinephrine(NE) concentration was also detected.There was no change in NGF,BDNF,NT3,GDNF mRNA expression,but we have found significant decrease in 240 bp and increase in 328 bp of persephin mRNA expression in CD, and “normalization” in HSI group. No significant alteration was found in NGF and persephin protein expression, but significant decrease in mature form of BDNF protein expression was found in CD, with “normalization”in HSI group.Results of the study suggest that growth factors are affected by cholinergic denervation and may play an important role in regulation and development of HSI,which might be a beneficial phenomenon for restoration of at least some cognitive function.

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

Milstein JA, Lehmann O, Theobald DEH, Dalley JW, Robbins TW (2004) Role of noradrenergic mechanisms in sustained attention, impulse control, and effects of methylphenidate in rats: Possible relevance to ADHD. Neuroscience 2004 Abstracts 123.6. Society for Neuroscience, San Diego, CA.

Summary: There has been renewed interest in noradrenergic (NA) modulation of sustained attention and impulse control both clinically, with the approval of the SNRI atomoxetine for the treatment of attention deficit hyperactivity disorder, as well as preclinically, in the mediation of the psychomotor effects of stimulants, where blockade of α1 adrenoreceptors counteracts the locomotor stimulant effects of d-amphetamine. The current study examines the role of NA in the modulation of sustained attention and impulse control using the 5-choice serial reaction time task (5CSRT) in rats. Experiment 1 examined the systemic antagonism of methylphenidate (MP)-induced impulsivity with either prazosin, an α1 adrenoreceptor antagonist, which antagonises the locomotor activating effects of amphetamine, or propranolol, a general β-adrenoreceptor blocker. Prazosin partially attenuated the MP-mediated increase in premature responding, but also caused generalised motor slowing, increasing both correct latency as well as latency to collect food reward. Propranolol completely abolished MP-induced impulsivity. This effect was centrally rather than peripherally mediated, as nadolol, a peripheral β-blocker failed to affect MP-induced premature responding. Other experiments examined the comparative effects of selective dopaminergic or serotonergic receptor blockade. A second experiment investigated the effects of selective anti-DBH saporin-induced prefrontal NA depletion. Animals with prefrontal depletions were unimpaired on the baseline version of the 5CSRT. However, they appeared to be slightly impaired under high event rate conditions. Effects of selective prefrontal NA depletion on MP-induced behavioural changes will also be examined. Taken together, these studies provide evidence for a role of noradrenaline in impulse control and the effects of MP.

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