Receptor-operated calcium-channels in isolated rabbit jejunum.
Calcium channels were studied in isolated spontaneously rhythmic rabbit jejunum using the muscarinic agonist carbachol as stimulant. Carbachol failed to produce the characteristic phasic and tonic components of smooth muscle contractions. A variety of chemically distinct calcium antagonists, viz. bepridil, diltiazem, isradipine (PN 200-110), nifedipine, and verapamil, non-competitively inhibited the contractions. Diltiazem was most potent (-logIC50 = 8.30) and bepridil least potent (-logIC50 = 6.19) in inhibiting the contractions. The findings conclude with the presence of pharmacologically distinct receptor-operated calcium-channels, besides the potential-dependent calcium-channels, in the rabbit jejunum.
Sen
A P
AP
Department of Pharmaceutics, Banaras Hindu University, Varanasi, India.
Bhattacharya
S K
SK
Ramarao
P
P
D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology*; D002217:Carbachol / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D066298:In Vitro Techniques; D007583:Jejunum / Q000502:physiology; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D009130:Muscle, Smooth / Q000502:physiology*; D011817:Rabbits
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D002217:Carbachol