Analgesic effects of 3-methoxybenzamide in rats

The i.p. injection of 3-methoxybenzamide (3-MBA) in rats produces a dose-related elevation of the threshold for response to a painful stimulus. Metoclopramide, also a substituted benzamide, has analgesic activity that is attenuated by bromocriptine, a dopamine receptor agonist, and by the narcotic antagonist, naloxone, suggesting involvement of dopamine and opiate receptors in the action of this drug. The involvement of these receptors in the analgesic action of 3-MBA has been examined using L-dopa and naloxone. Neither significantly altered the analgesic action. Although the results are preliminary, the analgesic action of 3-MBA would not seem to occur via opiate or dopamine receptors.