title: Calcium modulatory properties of O,O-diphenyl O-N-cyclooctyl phosphoramidate [corrected] isolated from Ptychodiscus brevis in rat atria and smooth muscle.
abstract: Calcium modulatory activity of a marine toxin has been studied employing in vitro preparations. The toxin induced contracture in rat diaphragm was not modified by denervation, d-tubocurarine and tetrodotoxin (TTX). In contrast, varying concentrations of calcium, EGTA and ryanodine inhibited the contracture significantly. The toxin produced a series of repeating contractions in vas deferens. Experiments with TTX, adrenoceptor blockers and other agents exclude a release of neuromediators or direct stimulation of post synaptic receptors to account for the rhythmic effect in vas deferens. The dependence of rhythmicity on external Ca2+ concentration and inhibiting effect of Mn2+, ryanodine and nifedipine indicate a direct activation of voltage-sensitive calcium channel. The toxin also evoked a similar pattern of response in paced atria mediated through Ca2+ influx.
authors.affiliation: Defence Research and Development Establishment, Gwalior.
authors.forename: P K
authors.initials: PK
authors.lastname: Mazumder
authors.forename: A K
authors.initials: AK
authors.lastname: Gupta
authors.forename: D
authors.initials: D
authors.lastname: Kumar
authors.forename: S N
authors.initials: SN
authors.lastname: Dube
mesh_terms: D000818:Animals; D016275:Atrial Function / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D003516:Cycloparaffins / Q000494:pharmacology*; D004141:Dinoflagellida / Q000737:chemistry*; D004305:Dose-Response Relationship, Drug; D008297:Male; D008387:Marine Toxins / Q000494:pharmacology*; D009119:Muscle Contraction / Q000187:drug effects*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D009943:Organophosphorus Compounds / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D014649:Vas Deferens / Q000187:drug effects / Q000502:physiology
chemical_list: D003516:Cycloparaffins; D008387:Marine Toxins; C119921:O,O-diphenyl-N-cyclooctyl phosphoramidate; D009943:Organophosphorus Compounds; D002118:Calcium