Differential response of dopamine neurons to α-melanotropin and analogues in relation to their endocrine and behavioral potency

Abstract

Functional changes in DA neurons of male rats were assessed by microfluorimetry. The tuberoinfundibular DA neurons which control MSH secretion, were most affected by α-MSH and its typical C-terminal active site (in α-MSH 11–13); the response persisted after hypophysectomy. The nigral DA neurons were most sensitive to a behaviorally more potent compound, 4-Met (O 2), 8-D-Lys, 9-Phe-ACTH 4–9. They responded to ACTH 4–10 as well as α-MSH 11–13. Differences between sexes and the effect of hypophysectomy point to interactions with other hormone axes in the case of the nigral system. The results indicate a differential responsiveness of the DA neuron groups which appears to be linked with endocrine and behavioral functions.