The effect of CART on pituitary hormones release from cultured pituitary cells harvested from fasted and fed ad libitum male rats

Roles of cocaine- and amphetamine-regulated transcript peptide in the rostral ventrolateral medulla in cardiovascular regulation in rats

Cocaine- and amphetamine-regulated transcript peptide (CARTp) is present in neurons and varicose fibers in the rostral ventrolateral medulla (RVLM) that is crucial in the control of cardiovascular function. Prior research indicated that intracisternal administration of CARTp evokes hypertension and accumulation of Fos in the RVLM. Despite the interaction among CARTp, cardiovascular effect, and the RVLM, no studies have directly examined whether CARTp participates in cardiovascular regulation in the RVLM. The current study directly examined the modulation of blood pressure and baroreflex sensitivity by CARTp in the RVLM in the different strain of rats. Immunohistochemical study showed that CARTp immunoreactive (CART-IR) cell bodies and varicose CART-IR fibers were observed throughout the RVLM in the SD, WKY, and SHRs. Varicose CART-IR nerve fibers were particularly abundant in the WKY and SHRs. Bilateral microinjection of CARTp (30 pmol) into the RVLM caused a significant increase in mean arterial pressure (MAP) in WKY and SHRs. Bilateral microinjection of CARTp antibody (1:5000) into the RVLM displayed a fall in the basal level of the MAP in SHRs but had no effects in WKY rats. In SD rats, bilateral microinjection of CARTp (6, 30 or 60 pmol) into the RVLM did not change the MAP but attenuated phenylephrine-induced bradycardia in a dose-dependent manner. We propose that CARTp acting in the RVLM may involvement in the cardiovascular regulation either by increases in the blood pressure or by decreases in the baroreflex sensitivity in rats. Moreover, endogenous CARTp in the RVLM is associated with the maintenance of basal blood pressure of SHRs.

Impaired hypothalamic cocaine- and amphetamine-regulated transcript expression in lateral hypothalamic area and paraventricular nuclei of dehydration-induced anorexic rats

Negative energy balance promotes physiological adaptations that ensure the survival of animals. The hypothalamic-pituitary-thyroid axis regulates basal energy expenditure and its down-regulating adaptation to negative energy balance is well described: in fasting, the serum content of thyrotrophin (TSH) and thyroid hormones (TH) decreases, enhancing the survival odds of individuals. By contrast, dehydration-induced anorexic (DIA) rats present an impaired hypothalamic-pituitary-thyroid (HPT) axis adaptation despite their negative energy balance: increased circulating TSH levels. The implication of cocaine- and amphetamine-regulated transcript (CART), an anorexic peptide, in HPT axis function impairment and food-avoidance behaviour displayed by DIA animals is unknown. Because CART is co-expressed with the peptide that regulates the HPT axis in hypophysiotrophic paraventricular nucleus (PVN) neurones (TSH-releasing hormone), we analysed CART expression and possible implications with respect to high TSH levels of DIA animals. We examined whether changes in CART expression from the lateral hypothalamic area (LHA) and arcuate nucleus (ARC) could participate in food-avoidance of DIA rats. DIA and forced-food restricted (FFR) animals reduced their body weight and food intake. FFR rats had a down-regulation of their HPT axis (reduced serum TH and TSH content), whereas DIA animals had reduced TH but increased TSH levels. CART mRNA expression in the ARC decreased similarly between experimental groups and diminished in anterior, medial PVN and in LHA of FFR animals, whereas DIA animals showed unchanged levels. This impaired CART mRNA expression in the anterior PVN and LHA could be related to the aberrant feeding behaviour of DIA rats but not to their deregulated HPT axis function.