CIRCLING BEHAVIOR INDUCED BY APOMORPHINE AFTER LESIONS OF THE HABENULA

Apomorphine, 2 mg/kg (s.c.) produced significant contralateral turning in rats with unilateral radiofrequency lesions of the habenula nucleu s over a test period of 60 min when tested at post-surgery days 3, 7, and 14. Levels of contralateral circling were not significantly increa sed when the animals were tested on days 21 and 28, although a contral ateral bias was still observed. Rotation induced by apomorphine was co mpletely blocked by the administration of haloperidol (0.3 mg/kg i.p.) , and there was no behavioural asymmetry in lesioned animals following administration of saline or a high dose of haloperidol (2 mg/kg i.p.) . These results indicate that unilateral habenula lesions lead to imba lance of dopaminergic activity, which is expressed as contralateral ci rcling when the animal is challenged with apomorphine.