Effects of cocaine–amphetamine regulated transcript (CART) on hormone release

Abstract

Objective: Cocaine- and amphetamine-regulated transcript (CART) is a recently described neuropeptide widely expressed in the rat brain. CART is abundant in hypothalamus nuclei controlling anterior pituitary function. In the paraventricular nucleus CART mRNA is colocalized with vasopressin and corticotrophin-releasing factor containing neurons. The data may suggest that CART plays a role in hypothalamic regulation of neuroenocrine functions. Material and methods: Male Wistar–Kyoto rats were investigated. Experiment I: CART was administered intracerebroventricularly (i.c.v.) in a dose of 0.5 μg dissolved in 5 μl vehicle. At 60, 120 min after the infusion of CART or vehicle animals were decapitated and trunk blood was collected until hormonal estimations. Experiment II: CART in a dose of 10 μg was injected intravenously (i.v.). At 60, 120, 240 min the rats were decapitated and the trunk blood was collected. Serum rLH, rFSH, rPRL, rTSH, rGH and plasma leptin, NPY concentrations were measured by RIA methods. Results: CART administered centrally (i.c.v.) simulated significantly GH release after 60 min ( p<0.05) and after 120 min ( p<0.01). CART increased also PRL after 60 min ( p<0.05). A marked increase of corticosterone level was observed at 60 and 120 min ( p<0.01, p<0.01). We did not observe significant changes in LH, FSH and TSH. We found an increase of serum leptin concentrations at 60 min after CART administration ( p<0.01). However, serum NPY levels did not change. After intravenous injection (i.v.) of CART an increase of GH was observed at 120, 240 min ( p<0.01, p<0.01, respectively). A rise in serum PRL was found at 240 min ( p<0.05). Corticosterone concentrations were enhanced at 60, 120, 240 min ( p<0.01, p<0.01, p<0.01, respectively). We did not observe significant changes in LH, FSH and TSH. Conclusions: CART may play a modulating role in the mechanism of pituitary hormone release.