caa a22 4500 465826253 CHVBK 20180323112150.0 cr unu---uuuuu 170327e19901101xx s 000 0 eng 10.1007/BF00691718 doi (NATIONALLICENCE)springer-10.1007/BF00691718 Unusual responses of proboscis muscles of Busycon canaliculatum to some calcium antagonist agents [Elektronische Daten] [H. Huddart, D. Brooks, R. Lennard, R. Hill] Summary: K- and ACh-induced responses of the radular sac, odontophore retractor, and radular retractor muscles ofBusycon canaliculatum were found to be strongly dependent upon [Ca]0. Diltiazem had strong positive inotropic and chronotropic actions on fast twitch activity in the odontophore retractor and radular protractor muscles. K-induced tonic force in these muscles was partly inhibited by diltiazem but only at very high concentrations. ACh responses in all muscles were eliminated by diltiazem. Nifedipine enhanced fast twitches and tonic force in response to high K, and induced persistent spontaneous fast twitch discharges. Nifedipine inhibited ACh-induced tonic force, but induced rhythmic bursts of fast twitches persisting long after nifedipine washout. Verapamil strongly inhibited K- and ACh-induced tonic force in all three muscles at high concentration, but stimulated fast twitch responses and converted ACh contractures into fast twitch activity. Sucrose gap studies showed that nifedipine and diltiazem reduced K- and ACh-induced tension and depolarization. Paradoxically, verapamil reduced K- and ACh-induced tension but significantly enhanced their induced depolarizations. Diltiazem, nifedipine and verapamil did not act like slow Ca channel antagonists in these muscles. This may reflect differences in channel structure between molluscs and mammals, or differences in the cellular calcium release pathways operated by such channels in molluscan and mammalian muscle. These ‘Ca-ant-agonists' appeared to act as agonists of fast twitch activity in these muscles and antagonists of the ACh-induced calcium release pathway for tonic force development. Springer-Verlag, 1990 Busycon canaliculatum nationallicence Proboscis muscles nationallicence Calcium antagonists nationallicence ACh responses nationallicence High K responses nationallicence Huddart H. Department of Zoology, The University of Rhode Island, Biological Science Building, 02881, Kingston, Rhode Island, USA aut Brooks D. Department of Zoology, The University of Rhode Island, Biological Science Building, 02881, Kingston, Rhode Island, USA aut Lennard R. Department of Zoology, The University of Rhode Island, Biological Science Building, 02881, Kingston, Rhode Island, USA aut Hill R. Department of Zoology, The University of Rhode Island, Biological Science Building, 02881, Kingston, Rhode Island, USA aut Journal of Comparative Physiology B Springer-Verlag 159/6(1990-11-01), 727-738 0174-1578 159:6<727 1990 159 360 https://doi.org/10.1007/BF00691718 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00691718 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Huddart H. Department of Zoology, The University of Rhode Island, Biological Science Building, 02881, Kingston, Rhode Island, USA aut NATIONALLICENCE 700 1- Brooks D. Department of Zoology, The University of Rhode Island, Biological Science Building, 02881, Kingston, Rhode Island, USA aut NATIONALLICENCE 700 1- Lennard R. Department of Zoology, The University of Rhode Island, Biological Science Building, 02881, Kingston, Rhode Island, USA aut NATIONALLICENCE 700 1- Hill R. Department of Zoology, The University of Rhode Island, Biological Science Building, 02881, Kingston, Rhode Island, USA aut NATIONALLICENCE 773 0- Journal of Comparative Physiology B Springer-Verlag 159/6(1990-11-01), 727-738 0174-1578 159:6<727 1990 159 360 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer