Urocortin in the hypothalamic PVN increases leptin and affects uncoupling proteins-1 and -3 in rats

The hypothalamic paraventricular nucleus (PVN) plays a primary role in energy homeostasis, and urocortin (UCN) decreases feeding after injection into the PVN. Peripheral uncoupling proteins (UCPs) may influence energy metabolism. The effect of UCN administered into the PVN on UCPs is unknown. We injected PVN-cannulated rats with either UCN (200 pmol) or artificial cerebrospinal fluid (aCSF) at 0800, 2000, and again at 0800. An aCSF-injected group with food intake restricted to the level of UCN-treated animals was included to control for decreased feeding in the UCN-treated rats. Two hours after the final set of injections, rats were killed, and white adipose tissue, brown adipose tissue, and biceps femoris and acromiotrapezius muscle tissues were taken for analysis of UCP-1, -2, and -3. Trunk blood was collected for measurement of plasma leptin. Relative to food-restricted control animals, UCN in the PVN significantly increased plasma leptin and UCP-1 mRNA in brown adipose tissue and decreased UCP-3 mRNA in acromiotrapezius muscle, suggesting a role for PVN UCN in the regulation of energy balance.