Enhanced release of striatal dopamine following medial hypothalamic damage in rats

Rats given bilateral lesions of the medial hypothalamus, using either direct or radio frequency current, and killed 2 hours later showed a significant elevation in striatal concentration of homovanillic acid (HVA), while striatal dopamine (DA) was unaltered. After unilateral damage the elevated HVA was seen only in the hemisphere ipsilateral to the lesion. In rats killed 2 days after such damage, the striatal HVA did not differ from controls. The elevation of HVA, suggesting an enhanced release of striatal DA, is associated with a resistance to the cataleptic action of the DA receptor blocking agent droperidol. The present findings suggest that medial hypothalamic lesions can increase neurotransmission within brain DA neurons, and that this neurochemical event may account for at least some of the short-term behavioral effects of these lesions. The relationship of these brain events to the long-term behavioral effects of the lesion remains an important issue for future research.