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The calcium dependence of electrical and mechanical responses of the odontophore protractor muscle of Busycon canaliculatum. A sucrose-gap study of calcium antagonist action.

Huddart, H. and Nelson, I. D. and Brooks, D. D. and Hill, R. B. (1992) The calcium dependence of electrical and mechanical responses of the odontophore protractor muscle of Busycon canaliculatum. A sucrose-gap study of calcium antagonist action. Comparative Biochemistry and Physiology Part A: Physiology, 102 (2). pp. 299-305.

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Abstract

1. 1. Exposures for 30 min to Ca-free salines irreversibly inhibited responses of the odontophore protractor (OP) muscles of Busycon canaliculatum to ACh and high K+ salines. Under continuous field stimulation, Ca-free salines extinguished the responses within 3 min and recovery on Ca readmission was only partial. 2. 2. Nifedipine converted normally smooth ACh-induced depolarizations into oscillatory events generating small twitch-like contractions. 3. 3. Nifedipine converted normally tonic high K+ responses into depolarizations with fast spike-like action potentials generating fast twitches. The low K+induced action potentials and fast twitches of this muscle were greatly enhanced by nifedipine. Nifedipine induced rapid transient inward current pulses accompanying this twitch activity. 4. 4. Co2+, Cd2+ and Gd3+ all inhibited the ACh and K+ responses of the OP muscle but Gd3+ was the most consistent and potent inhibitor of these responses. 5. 5. Gd3+ did not affect K+- or ACh-induced depolarization levels but eliminated spike-like action potentials and the twitches they generated. 6. 6. When the muscle membranes were depolarized with increasing K+ subsequent ACh responses were inhibited and eventually eliminated at about −41 mV, indicating that the ACh receptor here showed voltage inactivation. 7. 7. Although dependent upon an influx of[Ca]0 for CIRC to effect EC coupling, this Ca appears to enter the cells by a mechanism unlike that of mammalian smooth muscle. The cellular Ca pool appears to be independently but not synergistically accessed by ACh and K+ in the induction of contractile responses.

Item Type: Article
Journal or Publication Title: Comparative Biochemistry and Physiology Part A: Physiology
Subjects: G Geography. Anthropology. Recreation > GE Environmental Sciences
Departments: Faculty of Arts & Social Sciences > Politics & International Relations (Merged into PPR 2010-08-01)
Faculty of Science and Technology > Lancaster Environment Centre
ID Code: 22780
Deposited By: ep_ss_importer
Deposited On: 09 Jan 2009 11:24
Refereed?: No
Published?: Published
Last Modified: 26 Jul 2012 16:06
Identification Number:
URI: http://eprints.lancs.ac.uk/id/eprint/22780

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