Localization of a new benzamide derivative, tropapride and of 1-sulpiride, in the pituitary gland of the rat.

Localization of tropapride and 1-sulpiride in the pituitary gland of the rat has been studied. A comparison of the ratio of total radioactivity in pituitary/total radioactivity in blood after i.p. administration shows that 1-sulpiride has a greater and more persistent localization in the pituitary than tropapride. Tropapride is present in this gland at 0.16 microM concentration 1 hour after an oral dose of 0.4 mg/kg, which is the ED50 value in a test related to neuroleptic activity: the antagonism of apomorphine-induced stereotypies. 1-Sulpiride, administered orally at doses near the ED50 value in the same test, gives after 1 hour pituitary concentrations at least thousand times greater.