Mechanism of pressor effect of 5,6-dihydroxytryptamine in pithed rats.

5,6-dihydroxytryptamine (5,6-DHT) - a neurotoxic drug causing a chemical degeneration of 5-hydroxytryptamine (5-HT) neurones in brain and to a lesser extend of peripheral adrenergic neurones-provokes a dose-dependent increase in the blood pressure of pithed rats after its intravenous injection. Although the noradrenaline content of the heart, spleen, rectum, and vas deferens is reduced by 50-68% 3 h after the i.p. injection, an indirect sympathomimetic effect does not contribute to the pressor effectof 5,6-DHT. Furthermore, 5,6-DHT does not directly interact with adrenoceptors of the cardiovascular system. The pressor effect of 5,6-DHT thus rests solely on a direct stimulation of 5-HT receptors. The following findings support these statements: [ABSTRACT FROM AUTHOR]