Naloxone reverses inhibitory effects of fatigue and of compounds not related to narcotic analgesics in the guinea-pig ileum
Van Nueten, J.M.; Janssen, P.A.; Fontaine, J.
Archives Internationales de Pharmacodynamie et de Therapie 220(2): 349-350
1976
ISSN/ISBN: 0003-9780 PMID: 952591 Document Number: 100849
Whether naloxone can affect inhibition of gastrointestinal motility caused by compounds other than narcotic analgesics was investigated. When segments of guinea pig ileum were exposed to a sustained increase in distending pressure (2 cm H2O), peristaltic activity ceased within 15-60 min; this fatigue phenomenon was reversed by naloxone, in concentrations (10-8-1.6 .times. 10-7 g/ml) which antagonized the effect of morphine (4 .times. 10-8-10-5 g/ml) and fentanyl (1.6 .times. 10-10-4 .times. 10-8 g/ml). The same concentrations of naloxone reversed the inhibitory effects on peristaltic activity of adenosine, AMP, ADP and ATP (6.3 .times. 10-7-10-5 g/ml) and reversed the inhibition caused by the neuroleptics haloperidol (1.6-6.3 .times. 10-7 g/ml) and droperidol (6.3 .times. 10-7-2.5 .times. 10-6 g/ml), by the ganglion-blocking drug hexamethonium (6.3 .times. 10-7-2.5 .times. 10-6 g/ml), the local anesthetic agent xylocaine (6.3 .times. 10-7-2.5 .times. 10-6 g/ml) and the spasmolytic drug papaverine (1.6-6.3 .times. 10-7 g/ml). Higher concentrations of the inhibitory agents studied were not antagonized. Naloxone-induced reversal of inhibition in the guinea pig ileum probably does not necessarily demonstrate that the inhibition is caused by a specific action on morphine receptors.