Benzodiazepine antagonist Ro 15-1788 counteracts the prolactin-lowering effects of other benzodiazepines in rats.

A number of centrally active benzodiazepines lowered baseline serum prolactin concentrations after oral administration to male rats. The increase of circulating prolactin levels elicited by oral administration of various neuroleptic agents was also reduced by prior or simultaneous oral administration of several benzodiazepines in a dose-dependent manner. Since both effects were prevented by simultaneous administration of the benzodiazepine antagonist Ro 15-1788 they are probably mediated by central benzodiazepine receptors which interfere with aminergic mechanisms governing serum prolactin.