The interaction of enkephalins with substance P on vascular smooth muscle.
Interactions between SP and the enkephalins have bben reported in the CNS, and the possibility of a more peripheral site of interaction has now been investigated. SP (10(-6) - 10(-4) g/ml) induced dose-related contractions of the rabbit isolated aorta, which were resistant to alpha-adrenoceptor blockade (phentolamine, 5 x 10(-6) g/ml). Neither met- nor leu-enkephalin had any intrinsic action on the aorta, but met-enkephalin at 5 x 10(-6) g/ml significantly inhibited responses to SP but not to NE. Morphine (5 x 10(-6) g/ml) potentiated responses to NE, but had no significant effect on responses to SP. It is apparent that SP and met-enkephalin act on a common receptor on vascular smooth muscle, that met-enkephalin has no intrinsic action on this receptor, and that the receptor is morphine-insensitive.
D000818:Animals; D001011:Aorta / Q000187:drug effects; D004347:Drug Interactions; D004723:Endorphins / Q000494:pharmacology*; D004745:Enkephalins / Q000494:pharmacology*; D005260:Female; D066298:In Vitro Techniques; D009020:Morphine / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects*; D009126:Muscle Relaxation / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects*; D009638:Norepinephrine / Q000494:pharmacology; D011817:Rabbits; D013373:Substance P / Q000494:pharmacology*
D004723:Endorphins; D004745:Enkephalins; D013373:Substance P; D009020:Morphine; D009638:Norepinephrine