Subdiaphragmatic vagotomy fails to inhibit intravenous leptin-induced IL-1beta expression in the hypothalamus.

Leptin is known to be an important circulating signal for regulation of food intake and body weight. Recent evidence has suggested that leptin is involved in infection and inflammation. The afferent vagus nerve is known to be an important component for transmitting peripheral immune signals to the brain, such as interleukin (IL)-1beta expression in the brain, anorexia, and fever responses. In the present study, we investigated whether intravenous leptin-induced IL-1beta expression in the hypothalamus is mediated via afferent vagus nerve. IL-1beta transcripts in the hypothalamus were significantly increased on RT-PCR assessment 1 h after the administration of leptin (1 mg/kg iv) to mice. Subdiaphragmatic vagotomy did not significantly modify intravenous leptin-induced IL-1beta expression in the hypothalamus compared with that in sham-treated mice. These data suggest that circulating leptin directly acts in the brain independently of afferent vagus nerve input originating from the subdiaphragmatic organs.