SOCS-3 expression in leptin-sensitive neurons of the hypothalamus of fed and fasted rats

Treatment of rodents with exogenous leptin increases SOCS-3 mRNA levels in the arcuate nucleus (ARC) and dorsomedial nucleus (DMN) of the hypothalamus. To determine if SOCS-3 gene activity in the hypothalamus could be influenced by changes in physiological levels of circulating leptin, we performed in situ hybridization (ISH) and immunostaining for SOCS-3 expression in fed vs. fasted (48 h) rats. The ARC and DMN were the only regions of the diencephalon that showed SOCS-3 ISH and the autoradiographic ISH signal for SOCS-3 mRNA was visibly less in the ARC and DMN of fasted rats. The ISH signal for SOCS-3 mRNA was decreased 70% in the ARC and 90% in the DMN (to background levels) when animals were fasted ( P