Isoproterenol increases the phosphorylation of the synapsins and increases synaptic transmission in dentate gyrus, but not in area CA1, of the hippocampus

✍ Scribed by Karen D. Parfitt; A. Van Doze; Daniel V. Madison; Michael D. Browning

• Publisher: John Wiley and Sons
• Year: 1992
• Tongue: English
• Weight: 812 KB
• Volume: 2
• Category: Article
• ISSN: 1050-9631
• DOI: 10.1002/hipo.450020108

✦ Synopsis

Previous studies have shown that either norepinephrine (NE) or isoproterenol (ISO) enhances the slope of the field excitatory postsynaptic potential (EPSP) in the dentate gyrus of the rat hippocampal formation. In contrast, NE and I S 0 cause no increase in excitatory transmission in area CAI of the hippocampus. The molecular mechanism underlying this brain region-specific increase in synaptic transmission is not known. The phosphorylation of synapsin I and synapsin 11, two homologous presynaptic vesicle-associated proteins, is thought to promote neurotransmitter release. The authors have observed previously NEand ISO-enhanced phosphorylation of synapsins I and I1 in the dentate gyrus. The purpose of this study was to determine whether ISO-stimulated phosphorylation also occurs in the CAI, where IS0 has no effect on excitatory neurotransmission. These studies were correlated with electrophysiological studies in in vitro hippocampal slices. Superfusion of slices with IS0 resulted in an increase in EPSP slope in the dentate but not in area CAI. The enhanced dentate EPSP returned to baseline levels within 30 minutes of washout of the drug. Isoproterenol produced corresponding increases in the phosphorylation of the synapsins in dentate slices but had no effect on these proteins in CAI slices. Moreover, in dentate slices exposed to a 30-minute wash following incubation with ISO, phasphorylation of the synapsins returned to control levels. This close temporal and brain regional correlation between I S 0 stimulation of both synapsin phosphorylation and synaptic transmission suggests that the synapsin proteins may play a role in the synaptic potentiation produced by I S 0 in the dentate.