title: Differential effects of nifedipine on nerve-mediated and noradrenaline-evoked contractions of rat anococcygeus muscle.
abstract: In rat anococcygeus muscle the inhibitory effect of nifedipine (0.01, 0.1, 1.0 and 10 microM) was determined on adrenergic twitches in response to electrical field stimulation (trains of 4 pulses, 0.1 ms pulse duration, 10 Hz) and on twitch-matching contractions evoked by noradrenaline. Nifedipine concentration-dependently reduced the neurogenic twitch with an IC50 of 0.083 microM. Nifedipine reduced the noradrenaline-evoked contraction to a markedly lesser degree (IC50 > 10 microM). The difference in the magnitude of inhibition of electrically evoked twitch and twitch-matching noradrenaline-evoked contraction was statistically significant at every concentration of nifedipine. It is concluded that inhibition of the twitch by nifedipine involves some other mechanism(s) in addition to its Ca2+ channel blocking property in smooth muscle.
authors.affiliation: Department of Pharmacological Sciences, Medical School, University of Newcastle upon Tyne, UK.
authors.forename: M M
authors.initials: MM
authors.lastname: Iravani
authors.forename: M A
authors.initials: MA
authors.lastname: Zar
mesh_terms: D000818:Animals; D015220:Calcium Channels / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects* / Q000294:innervation / Q000502:physiology; D009543:Nifedipine / Q000494:pharmacology*; D009638:Norepinephrine / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar
chemical_list: D015220:Calcium Channels; D009543:Nifedipine; D009638:Norepinephrine