Cocaine- and amphetamine-regulated transcript peptide-(55-102) and thyrotropin releasing hormone inhibit hypothalamic...

Cocaine- and amphetamine-regulated transcript (CART) peptide-(55-102) and thyrotropin releasing hormone (TRH) play an anorectic role in the hypothalamus. Catecholamines are also involved in appetite control and we have previously found that leptin, an adipocyte-derived anorectic hormone, inhibits hypothalamic norepinephrine and dopamine release. We have studied the effect of CART peptide-(55-102) and TRH on basal and depolarization (K+ 15 mM)-induced norepinephrine and dopamine release from rat hypothalamic neuronal endings (synaptosomes) in vitro. We have found that basal catecholamine release was not modified; both CART peptide-(55-102) and TRH, the former with a higher sensitivity, dose-dependently inhibited depolarization-induced dopamine release, and did not affect the stimulated norepinephrine release. Considering the role played by dopamine in the central mechanisms of reward, these findings suggest that the inhibition of dopamine release could underlie the decreased appetitive behaviour induced by CART peptide-(55-102) and TRH.