Effects of the atypical antidopaminergic drug, metoclopramide and the selective antimuscarinic drug, pirenzepine on neurotransmission

Abstract

Metoclopramide is equipotent to chlorpromazine in a number of biochemical and behavioural tests which measure antidopaminergic effects. In spite of the extensive use of metoclopramide for gastrointestinal disturbances and as an antiemetic, it is not usually prescribed for psychiatric indications. The present study, using neuroendocrine and receptor technics, shows that in addition to its antidopaminergic effects metoclopramide has atypical effects on neurotransmission. Thus, metoclopramide increases growth hormone secretion which is usually decreased by neuroleptic drugs, and also tends to increase plasma noradrenaline levels. The discrepancies between the receptor affinities of benzamides in vitro and their effects in vivo are also discussed, as well as the selective antimuscarinic action of pirenzepine on metoclopramide-induced hormonal effects.

Key Words:

• etoclopramide
• Neurotransmission
• Pirenzepine