Central urocortin activation of sympathetic-regulated energy metabolism in Wistar rats.

The corticotropin-releasing hormone (CRH) system, including CRH and urocortin (UCN), is implicated in the central control of appetite and energy metabolism. Urocortin, a recently isolated neuropeptide closely related to CRH is involved in the central signaling cascade that inhibits energy intake. When administered intracerebroventricularly and intra-hypothalamically, UCN potently decreases food intake. Receptors for UCN, while widely distributed, are expressed in hypothalamic nuclei. As the hypothalamus is involved in modulating autonomic outflow, UCN may also act as a catabolic neuropeptide to facilitate energy expenditure through sympathetic-regulated thermogenesis. To test the hypothesis that UCN also enhances regulatory energy expenditure via the activation of the sympathetic nervous system, we examined whole body oxygen consumption (VO(2)) and colonic temperature in male Wistar rats in response to central UCN administration. That is, the intracerebroventricular injection of 1.0 microg of UCN in male Wistar rats (n=10) significantly increased whole body oxygen consumption compared to PBS control. In addition, colonic temperature was significantly increased (Delta0.7 +/- 0.08 degrees C) in UCN- vs. PBS-administered rats, which was prevented by pretreatment with the ganglionic blocker chlorisondamine. These studies suggest that UCN acutely increased whole body oxygen consumption and body temperature via central activation of sympathetic outflow.