We have studied the effects of naloxone on acetylcholine and noradrenaline release in the guinea-pig isolated distal colon, and have assessed the effect of naloxone on electrically-induced contraction of the longitudinal muscle and non-adrenergic, non-cholinergic (NANC) relaxations of the circular muscle coat. Naloxone dose-dependently increased resting and electrically-evoked acetylcholine release and electrically-evoked noradrenaline release. Naloxone was more potent in increasing resting acetylcholine release in colonic specimens obtained after chronic sympathetic denervation. Naloxone (1 mum) did not affect electrically-induced contractions of the longitudinal muscle, while it enhanced NANC relaxations of the circular muscle. The effects observed with naloxone in the present experiments suggest that opioid pathways exert a tonic restraint on neurotransmission in the guinea-pig colon. After suppression of the adrenergic inhibitory tone, the functional relevance of opioid pathways seems to be increased.
|Data di pubblicazione:||1993|
|Titolo:||Opioid pathways exert a tonic restraint in the guinea pig isolated colon. Changes after chronic sympathetic denervation.|
|Rivista:||JOURNAL OF PHARMACY AND PHARMACOLOGY|
|Codice identificativo ISI:||WOS:A1993LN64200020|
|Codice identificativo Scopus:||2-s2.0-0027236782|
|Appare nelle tipologie:||Articolo su Rivista|