[Modulation by endogenous opioid peptides of non-adrenergic neurotransmission in the guinea-pig taenia coli (author's transl)].
The effects of opioid peptides on th response to stimulation of adrenergic or non-adrenergic inhibitory nerve were investigated in the guinea-pig taenia coli. Leu-enkephalin, met-enkephalin, (D-ala2) met-enkephalin and beta-endorphin inhibited non-adrenergic inhibitory response, in a dose-dependent manner. (D-ala2) metenkephalin and beta-endorphin were the most potent compounds in inhibiting the elicited relaxation, having ID50 values of 1 micro M. The inhibitory actions of these opioid peptides were reversed by naloxone (1 micro M). Naloxone itself potentiated the non-adrenergic inhibitory response. On the contrary, the adrenergic inhibitory response was not affected by application of leu-enkephalin, beta-endorphin or naloxone. Using an immunohistochemical method, met-enkephalin immunoreactive nerve fibers were observed in the longitudinal muscle layer, Auerbach plexus and circular muscle layer of the taenia. From these observations, it is concluded that endogenous opioid peptides may play a regulatory role in non-adrenergic inhibitory neurotransmission but endogenous opioid peptides may play a regulatory role in non-adrenergic inhibitory neurotransmission but not in adrenergic neurotransmission.
D000818:Animals; D003106:Colon / Q000032:analysis / Q000294:innervation*; D003864:Depression, Chemical; D004723:Endorphins / Q000502:physiology*; D004745:Enkephalins / Q000032:analysis; D005455:Fluorescent Antibody Technique; D006168:Guinea Pigs; D008297:Male; D009129:Muscle Tonus / Q000187:drug effects; D009270:Naloxone / Q000494:pharmacology; D010275:Parasympathetic Nervous System / Q000502:physiology*; D013564:Sympathetic Nervous System / Q000502:physiology*; D009435:Synaptic Transmission / Q000187:drug effects*
D004723:Endorphins; D004745:Enkephalins; D009270:Naloxone