Main Article Content
The roles of central catecholamines and 5-hydroxytryptamine in morphine analgesia were investigated. Drugs that are relatively selective in modifying central monoaminergic activity were used. Nociceptive response was tested by the modified hot plate method. L-Dopa and apomorphine antagonized while chlorpromazine, haloperidol, alpha-methyl-para-tyrosine, and clonidine enhanced morphine analgesia. Para-chlorophenylalanine blocked but L-tryptophan potentiated this effect of morphine. All these changes were significant. The results of the present study indicated that increased brain catecholaminergic or decreased 5-hydroxytryptaminergic activity inhibited the analgesic effect of morphine. On the contrary, decreased central catecholaminergic or increased 5-hydroxytryptaminergic activity enhanced morphine analgesia.
Upon acceptance of an article, the Pharmacological and Therapeutic Society of Thailand will have exclusive right to publish and distribute the article in all forms and media and grant rights to others. Authors have rights to use and share their own published articles.