Different effects of reducing agents on ω-conotoxin GVIA inhibition of [³H]-acetylcholine release from rat cortical slices and guinea-pig myenteric plexus

Abstract

1. The effect of reducing reagents on ω-conotoxin GVIA (ω-CgTX) inhibition of the release of [³H]-acetylcholine ([³H]-ACh) induced by tityustoxin, K⁺ 50 mM and electrical stimulation was investigated in rat brain cortical slices.

2. In cortical slices the inhibition of tityustoxin or electrically-stimulated [³H]-ACh release by ω-CgTX was dramatically increased by reducing reagents ascorbate or β-mercaptoethanol. Dehydroascorbic acid did not substitute for ascorbate

3. Depolarization induced by K⁺ 50 mM caused [³H]-ACh release from cortical slices which was not inhibited by ω-CgTX, even in the presence of ascorbate.

4. In the guinea-pig myenteric plexus, ω-CgTX inhibition of the tityustoxin induced release of [³H]-ACh was independent of ascorbate.

5. It is suggested that N-type-like calcium channels in guinea-pig myenteric plexus may have pharmacological/biochemical diversity from similar channels of rat cerebral cortex.

Full Text

The Full Text of this article is available as a PDF (453.3 KB).