Comparative distribution of cocaine- and amphetamine-regulated transcript (CART) in the hypothalamus of the capuchin monkey (Cebus apella) and the common marmoset (Callithrix jacchus)

Abstract

Cocaine- and amphetamine-regulated transcript (CART) is widely distributed in the brain of many species. In the hypothalamus, CART neurotransmission has been implicated in diverse functions including energy balance, stress response, and temperature and endocrine regulation. Although some studies have been performed in primates, very little is known about the distribution of CART neurons in New World monkeys. New World monkeys are good models for systems neuroscience, as some species have evolved several behavioral and anatomical characteristics shared with humans, including diurnal and social habits, intense maternal care, complex manipulative abilities and well-developed frontal cortices. In the present study, we assessed the distribution of CART mRNA and peptide in the hypothalamus of the capuchin monkey (Cebus apella) and the common marmoset (Callithrix jacchus). We found that the distribution of hypothalamic CART neurons in these monkeys is similar to what has been described for rodents and humans, but some relevant differences were noticed. Only in capuchin monkeys CART neurons were observed in the suprachiasmatic and the intercalatus nuclei, whereas only in marmoset CART neurons were observed in the dorsal anterior nucleus. We also found that the only in marmoset displayed CART neurons in the periventricular preoptic nucleus and in an area seemingly comprising the premammillary nucleus. These hypothalamic sites are both well defined in rodents but poorly defined in humans. Our findings indicate that CART expression in hypothalamic neurons is conserved across species but the identified differences suggest that CART is also involved in the control of species-specific related functions.