EFFECT OF MORPHINE ON WET-DOG SHAKES CAUSED BY CEREBROVENTRICULAR INJECTION OF SEROTONIN

Intraventricular administration of serotonin to rats causes 'wet-dog' shakes, a sign of morphine withdrawal. The frequency of the shakes is dose-dependent. Shaking is potentiated by pretreatment withdrawal. Shaking is potentiated by pretreatment with an inhibitor of monoamine oxidase or with 5,7-dihydroxytryptamine, and is depressed by morphine or serotonin receptor blockers. Depression of serotonin-induced shaking by morphine is reversed rapidly by naloxone. However, naloxone did not reverse the inhibition of 'wet-dog' shakes caused by serotonin receptor blockers.