Changes in Cholinergic but Not in GABAergic Markers in Amygdala, Piriform Cortex, and Nucleus Basalis of the Rat Brain Following Systemic Administration of Kainic Acid

Three days after systemic administration of kainic acid (15 mg/kg, s.c.), selected cholinergic markers (choline acetyltransferase, acetylcholinesterase, muscarinic acetylcholine receptor, and high-affinity choline uptake) and GABAergic parameters [benzodiazepine and gamma-aminobutyric acid (GABA) receptors] were studied in the frontal and piriform cortex, dorsal hippocampus, amygdaloid complex, and nucleus basalis. Kainic acid treatment resulted in a significant reduction of choline acetyltransferase activity in the piriform cortex (by 20%), amygdala (by 19%), and nucleus basalis (by 31%) in comparison with vehicle-injected control rats. A lower activity of acetylcholinesterase was also determined in the piriform cortex following parenteral kainic acid administration. [3H]Quinuclidinyl benzilate binding to muscarinic acetylcholine receptors was significantly decreased in the piriform cortex (by 33%), amygdala (by 39%), and nucleus basalis (by 33%) in the group treated with kainic acid, whereas such binding in the hippocampus and frontal cortex was not affected by kainic acid. Sodium-dependent high-affinity choline uptake into cholinergic nerve terminals was decreased in the piriform cortex (by 25%) and amygdala (by 24%) after kainic acid treatment. In contrast, [3H]flunitrazepam binding to benzodiazepine receptors and [3H]muscimol binding to GABA receptors were not affected 3 days after parenteral kainic acid application in any of the brain regions studied. The data indicate that kainic acid-induced limbic seizures result in a loss of cholinergic cells in the nucleus basalis that is paralleled by degeneration of cholinergic fibers and cholinoceptive structures in the piriform cortex and amygdala, a finding emphasizing the important role of cholinergic mechanisms in generating and/or maintaining seizure activity.     

Time Course of Brain Neuronal Degeneration and Heat Shock Protein (72) Expression Following Neck Tourniquet-Induced Cerebral Ischemia in the Rat

1. The present study was designed to examine the regional expression of HSP72/73 protein after a 7.5-min period of cerebral ischemia and to compare the distribution of HSP neurons with the localization of irreversible neuronal degeneration as analyzed by silver impregnation technique.2. During 6–24 hr after cerebral ischemia clear-cut neuronal argyrophilia developed in several brain regions including the hippocampal hilus, nucleus reticularis thalami, and colliculi inferiores. With the exception of the hippocampal hilus, the structures which showed silver impregnability were HSP72 negative at 6–24 hr.3. Despite the clear HSP72 expression seen in hippocampal CA1 neurons, a significant loss of these neurons was seen at 7 days after ischemia.4. These data show that in some structures the presence of HSP72 is indicative of higher resistance of these neurons to ischemia-induced degeneration, however, the process of delayed neuronal degeneration appears to be independent of the accelerated synthesis of HSP72 seen during the early period of reflow.     

Analysis of Gene Expression Following Sciatic Nerve Crush and Spinal Cord Hemisection in the Mouse by Microarray Expression Profiling

1. The responses of periphery (PNS) and central nervous systems (CNS) towards nerve injury are different: while injured mammalian periphery nerons can successfully undergo regeneration, axons in the central nervous system are usually not able to regenerate.2. In the present study, the genes which were differentially expressed in the PNS and CNS following nerve injury were identified and compared by microarray profiling techniques.3. Sciatic nerve crush and hemisection of the spinal cord of adult mice were used as the models for nerve injury in PNS and CNS respectively.4. It was found that of all the genes examined, 14% (80/588) showed changes in expression following either PNS or CNS injury, and only 3% (18/588) showed changes in both types of injuries.5. Among all the differentially expressed genes, only 8% (6/80) exhibited similar changes in gene expression (either up- or down-regulation) following injury in both PNS and CNS nerve injuries.6. Our results indicated that microarray expression profiling is an efficient and useful method to identify genes that are involved in the regeneration process following nerve injuries, and several genes which are differentially expressed in the PNS and/or CNS following nerve injuries were identified in the present study.     

Heterogeneous Expression of the Polysialyltransferases ST8Sia II and ST8Sia IV During Postnatal Rat Brain Development

Abstract: Polysialic acid on the neural cell adhesion molecule is developmentally regulated and has been implicated in the plasticity of cell-cell interactions. The sialyltransferases ST8Sia II and ST8Sia IV are able to catalyze the synthesis of polysialic acid. This study compares the expression of ST8Sia II and ST8Sia IV mRNA during postnatal rat brain development. Northern blot analysis indicated a substantial down-regulation of ST8Sia II from high expression at postnatal day 2 to almost undetectable levels at the age of 6 months. In contrast, the decline of ST8Sia IV content was moderate. In the mature brain, ST8Sia IV is the predominant polysialyltransferase. In situ hybridization of selected brain regions at postnatal days 2, 11, and 21 confirmed the decline of ST8Sia II level in isocortex, hippocampus, and cerebellum. ST8Sia II was not detectable at any time point in the subependymal layer and the layers of the olfactory bulb. Persistent ST8Sia IV expression was localized in the subependymal layer, the glomerular layer of the olfactory bulb, and the granule cell layer of the dentate gyrus and in some widely dispersed cells of the isocortex. The distinct expression patterns of ST8Sia II and ST8Sia IV suggest their differential regulation. As discussed with regard to the persistent polysialic acid expression, ST8Sia IV should receive particular attention in the mature brain.     

Acute and Chronic Ethanol Consumption Effects on the Immunolabeling of Gq/11α Subunit Protein and Phospholipase C Isozymes in the Rat Brain

Abstract: The goal of this investigation was to examine whether postreceptor sites [G_q/11 protein and phospholipase C (PLC) isozymes] of the phosphoinositide signal transduction system are involved in neuroadaptational mechanisms in the brain during chronic ethanol consumption. It was observed that acute ethanol treatment has no effect on the immunolabeling of PLC-β₁, -γ₁, and -δ₁ and the α subunit of G_q/11 protein in the rat cortex as determined by western blotting using specific monoclonal antibodies. On the other hand, chronic ethanol consumption (15 days) resulted in a significant decrease in the immunolabeling of PLC-β₁, whereas under identical conditions, the immunolabeling of PLC-γ₁ and -δ₁ isozymes was not significantly altered. The decreased immunolabeling of PLC-β₁ during chronic ethanol consumption was not altered by 24 h of withdrawal after 15 days of ethanol consumption. The immunolabeling of the α subunit of G_q/11 protein was significantly decreased after 15 days of ethanol consumption but had returned to normal levels after 24 h of ethanol withdrawal. Also, chronic ethanol treatment resulted in a significant decrease in phosphatidylinositol 4,5-bisphosphate-specific PLC activity, which remained the same after 24 h of ethanol withdrawal. These results suggest that decreased PLC activity during ethanol consumption and its withdrawal may be due to decreased protein levels of the G_q/11 protein-coupled PLC-β₁ isozyme but not the PLC-γ₁ or -δ₁ isozyme in the rat cortex. It is possible that changes in the protein levels of the G_q/11 protein-coupled PLC-β₁ isozyme and in PLC activity in the brain may be involved in the cellular adaptation to chronic ethanol exposure.