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Calcium channel blockers apparently decrease noradrenaline release from nerve-skin terminals in Caudiverbera
B Norris1, J Concha, G Contreras
1Department of Physiology, Faculty of Biological Sciences, University of Concepción, Chile.
Abstract:
1. The effects of three calcium channel blockers, verapamil, diltiazem and nifedipine were examined on the response of the skin neuroepithelial synapse of the toad Caudiverbera caudiverbera to electrical stimulation. 2. The stimulus induced a significant rise in potential difference (PD) and short-circuit current (SCC). The three calcium antagonists reduced the responses in a dose-dependent manner. The greatest reduction was induced by verapamil followed by diltiazem and nifedipine. 3. Amiloride treatment did not affect the responses to electrical stimulation, indicating that the response to nerve stimulation is not due to current flowing through sodium channels. 4. When the preparation was blocked by either of the three antagonists, the skin response to noradrenaline was not affected. 5. It may be concluded that verapamil, diltiazem or nifedipine reduce the release of noradrenaline at the neuroepithelial synapse of C. caudiverbera.