[Biochemical studies on tienocarbine and related compounds]

Tienocarbine (1,9-dimethyl-7,8,9,10-tetrahydrothieno[3,2-e] pyrido[4,3-b] indole lactate) in oral doses of 10 mg X kg-1 lowers dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) in the striata of rats without influencing contents of biogenic amines; this points to a reduced dopamine (DA) turnover. This effect is still present after 28 days of daily application. At the same time the serotonin (5-HT) turnover is not influenced. Tienocarbine displaces 3H-DA and 3H-spiperone from their specific binding sites in the nucleus caudatus of calf brain. Structural variation results in preponderance of either dopamineagonistic (turnover lowered) or antagonistic (turnover increased) properties of the molecules. The whole class of compounds therefore can be considered as mixed dopamine agonists-antagonists.