Effects of beta-endorphin and dynorphin A on cholinergic neurotransmission in canine airway smooth muscle.
To determine the effects of the opioid peptides, beta-endorphin and dynorphin A, on airway smooth muscle function and its possible modulation by tissue peptidases, we studied canine bronchial segments under isometric conditions in vitro. Addition of beta-endorphin or dynorphin A did not alter the resting tension. However, beta-endorphin (10(-6) M) but not dynorphin A decreased the contractile responses to electrical field stimulation (EFS, 0.5-40 Hz). This effect was dose-dependent and reversed by naloxone. In contrast, acetylcholine-induced contractions were not affected by these opioids. The beta-endorphin-induced inhibition of the contractile responses to EFS was not augmented by peptidase inhibitors such as thiorphan, captopril, bestatin and leupeptin. These results suggest that beta-endorphin prejunctionally inhibits parasympathetic muscle contraction, and that endogenous peptidases do not play a modulatory role in this effect of beta-endorphin.
Horii
S
S
First Department of Medicine, Tokyo Women's Medical College, Japan.
Tamaoki
J
J
Kanemura
T
T
Yamawaki
I
I
Takizawa
T
T
D000818:Animals; D001980:Bronchi / Q000187:drug effects / Q000294:innervation; D002216:Captopril / Q000494:pharmacology; D004285:Dogs; D004399:Dynorphins / Q000494:pharmacology*; D004558:Electric Stimulation; D066298:In Vitro Techniques; D007537:Isometric Contraction; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects* / Q000294:innervation; D009270:Naloxone / Q000494:pharmacology; D010275:Parasympathetic Nervous System / Q000187:drug effects*; D011480:Protease Inhibitors / Q000494:pharmacology; D009435:Synaptic Transmission / Q000187:drug effects*; D015244:Thiorphan / Q000494:pharmacology; D001615:beta-Endorphin / Q000494:pharmacology*
D011480:Protease Inhibitors; D009270:Naloxone; D001615:beta-Endorphin; D004399:Dynorphins; D002216:Captopril; D015244:Thiorphan