Abstract
Leptin receptors (Ob‐Rb) are located in the nucleus tractus solitarii (NTS). Leptin into the NTS decreases food intake and body weight. We have demonstrated that intra‐arcuate leptin increases sympathetic nerve activity (SNA) to brown adipose tissue (BAT) and kidney. We tested the hypothesis that activation of leptin receptors in the NTS affects SNA. In anesthetized Sprague‐Dawley rats, we microinjected leptin 0.25 or 0.5 ug or saline 50 nl into the commissural NTS while recording simultaneously SNA to BAT and kidney. Localization of the site of injection was confirmed in each experiment. Microinjection of leptin into the commissural NTS produced a dose‐related increase in renal SNA (+93 +/− 32% with 0.5 ug, P=0.04 vs. saline), but did not increase SNA to BAT (−17+/− 9%). Cooling of the rats increased SNA to BAT demonstrating the responsiveness of BAT SNA in our preparation. NTS leptin did not increase SNA in Zucker obese rats with mutations in the Ob‐Rb indicating that the increase in renal SNA in the Sprague Dawley rats is receptor mediated. Leptin injection into the rostral NTS did not affect BAT or renal SNA. In conclusion, microinjection of leptin into the commissural NTS increases SNA to kidney but not to BAT. This occurs through an Ob‐Rb mediated mechanism. Leptin produces a different pattern of sympathetic responses when administered into the NTS than it does into the arcuate nucleus.
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