Papaverine-insensitive and papaverine-sensitive drug-induced contractions of chick smooth muscle.
The mechanisms by which acetylcholine (ACh) and noradrenaline (NA) induce muscle contraction were examined in the chick expansor secundariorum muscle in early life, because responsiveness to ACh disappeared and responsiveness to NA persisted during development. ACh-induced contractions decreased with lowered temperature, while NA-induced contractions increased between 30 and 20 degrees C. Papaverine depressed and antagonized NA-induced contractions, but did not depress ACh-induced contractions. The second application of ACh in Ca2+-free solution produced a negligible contraction. In contrast, even the third application of NA in Ca2+-free solution still evoked a contraction of more than 50% of the response in normal solution. These results suggest that the pathway from cholinergic receptor activation to contraction is mainly mediated through a papaverine-insensitive and external Ca2+-dependent process, whereas the pathway from adrenergic receptor activation to contraction is mainly mediated through a papaverine-sensitive and external Ca2+-independent process.
D000818:Animals; D002118:Calcium / Q000502:physiology; D002645:Chickens; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects*; D010208:Papaverine / Q000494:pharmacology*; D011941:Receptors, Adrenergic / Q000187:drug effects; D011950:Receptors, Cholinergic / Q000187:drug effects; D013696:Temperature
D011941:Receptors, Adrenergic; D011950:Receptors, Cholinergic; D010208:Papaverine; D002118:Calcium