Pre- and postsynaptic actions of nifedipine at an identified cholinergic central synapse ofAplysia
✍ Scribed by P. Fossier; G. Baux; L. -E. Trudeau; L. Tauc
- Publisher
- Springer
- Year
- 1992
- Tongue
- English
- Weight
- 542 KB
- Volume
- 422
- Category
- Article
- ISSN
- 0031-6768
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✦ Synopsis
The effects of the dihydropyridine (DHP) Ca 2+ channel antagonist, nifedipine, were studied on the cholinergic synapse between the presynaptic neurones B4/B5 and the postsynaptic neurones B3/B6 located in the buccal ganglion of Aplysia californica. Nifedipine (10gM) decreased the presynaptic Ca 2+ current by 30~
Blockade of DHP-sensitive Ca 2+ channels, however, did not affect quantal transmitter release from the presynaptic neurones. Thus, at this synapse, DHPsensitive Ca 2+ channels appear not to be involved in acetylcholine (ACh) release. The postsynaptic response to an ionophoretic application of ACh was decreased by nifedipine, pointing to a blocking action of the drug on the postsynaptic receptor/channel complex. Nifedipine was also found to activate protein kinase C, which in turn induces an increase in the nifedipine-resistant presynaptic Ca 2+ influx and in the number of released ACh quanta. These effects of nifedipine could be prevented by a previous application of 1, 5-(isoquinolinylsulfonyl)-2-methylpiperazine (H-7), a protein kinase blocker.