A comparison of drug-induced rotation in rats lesioned in the medial forebrain bundle with 5,6-dihydroxytryptamine or 6-hydroxydopamine.

Drug-induced rotational behaviour was studied in two groups of rats with differing chemical lesion of the right medial forebrain bundle (MFB). 6-hydroxydopamine (6-OH-DA), 3.5 mug, injected in one group, induced a marked lowering of dopamine (DA) and noradrenaline (NA) in the right hemiforebrain. 5,6-Dihydroxytryptamine (5,6-HT), 10 mug, injected in a second group, produced a profound and long-lasting depletion of 5-hydroxytryptamine (5-HT) and DA, but not of NA. Rotational behaviour induced in both groups by DA receptor agonists (apomorphine, piribedil, L-DOPA, ergometrine, ergocornine, 2-bromo-alpha-ergocryptine, ergocristine, methylergometrine) and agents releasing DA (d-methamphetamine, methylphenidate) were qualitatively identical and quantitatively very similar, suggesting a minor role of 5-HT striatal terminals in these experimental conditions. LSD induced contralateral rotation by direct stimulation of the DA receptor, while L-5-hydroxy-tryptophan (L-5HTP) was inactive.