Procaine injection into the paraventricular nucleus reduces sympathetic and thermogenic activation induced by frontal cortex stimulation in the rat

These experiments were designed to test the effect of procaine injection in to the paraventricular nucleus on the sympathetic and thermogenic changes i nduced by frontal cortex stimulation, Oxygen consumption, firing rate of th e sympathetic nerves to interscapular brown adipose tissue (IBAT), along wi th IBAT and colonic temperatures (T-IBAT and T-C) were monitored in fasted male Sprague-Dawley rats before and 25 min after an electrical stimulation of the frontal cortex. The same variables were monitored in rats with admin istration of procaine into the paraventricular nucleus. The results show th at cortical stimulation raises oxygen consumption, sympathetic neuron firin g rates, T-IBAT, and T-C, This increase is reduced by procaine injection. T hese findings suggest that the paraventricular nucleus plays a key role in the sympathetic and thermogenic changes induced by cortical stimulation. (C ) 1999 Elsevier Science Inc.