Striatal neuronal responses to scrotal temperature changes and dopaminergic drugs

Seventy-nine units in the striatal region were examined in 48 urethan-anesthetized rats. When these units were classified by their thermal responsiveness, proportions of the cold-responsive, warm-responsive, and thermally unresponsive units were 25.4, 35.4, and 39.2%, respectively, of the total units tested. Either microiontophoretically or systemically administered apomorphine (a dopamine agonist) and haloperidol (a dopamine antagonist) affected (inhibited and/or excited) most (86.5-100%) cold-responsive units. In contrast, only a small percentage of the warm-responsive (28.6-43.8%) or thermally unresponsive (0-19.2%) units were affected by both apomorphine and and haloperidol. Furthermore it was found that most (73-100%) cold-responsive units were inhibited by apomorphine but excited by haloperidol; the inhibitory responses of the unit activity induced by apomorphine were antagonized by haloperidol. The reciprocal relationships between apomorphine and haloperidol were not observed in most warm-responsive (76.2-85.7%) or thermally unresponsive (80.8-100%) units. The data demonstrate that many striatal neurons are influenced by thermal afferent activation in the scrotum. The results also provide a neuronal basis for the hypothesis that the dopaminergic receptors located in the cold-responsive neurons of the striatum have effects on metabolic heat production in rats.