Plasma vasopressin (AVP) and oxytocin (OT) levels are decreased in mammals after alcohol ingestion. We have discovered, using electrophysiological and biochemical techniques that ethanol inhibits the release of these peptides from the rat neurohypophysis, as well as from isolated neurohypophysial nerve terminals. The inhibition of release appears to result from a reduction in calcium currents in the terminals. In this proposal, we will use a number of approaches to characterize the sensitive calcium channel. First, we will use pharmacological tools and single channel recording to describe a number of identifying characteristics of the channel, and to determine the mechanisms by which this calcium channel is affected by EtOH. Second, we will use a combined immunochemical and electrophysiological approach to determine whether AVP and OT terminals contain the same Ca channel population, and whether the mechanisms of EtOH inhibition of release is the same for the two terminal types. We have found that EtOH augments rather than inhibits release in certain lines of rat. We will examine whether this is the consequence of different calcium channel populations in terminals from the different lines. Finally, we will inject mRNA from different brain regions into Xenopus oocytes, in the hopes of determining whether the sensitive channel found in the terminals is unique to these peptidergic neurons, or is found in other brain regions as well. We will also use the oocyte expression system to examine the expression of channels from mRNA derived from the different rat lines, which will help us to understand whether the differences seen in the different lines reflect differences in the channel protein, or differences in posttranslational processing or membrane environment.
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