Sucrose rich diet modifies thermogenic response to injection of muscimol into the posterior hypothalamus in the rat.

The firing rate of the nerves innervating interscapular brown adipose tissue, temperatures of colon and interscapular brown adipose tissue, heart rate and oxygen consumption were monitored in urethane-anaesthetized male Sprague-Dawley rats fed with a sucrose rich diet. These variables were measured for 40 min before (baseline values) and 40 min after a 56 ng muscimol injection into the posterior hypothalamus. The same variables were monitored in other rats fed with a laboratory standard diet. Saline was injected into the posterior hypothalamus of control rats fed with sucrose or standard diet. Muscimol injection induced a decrease in firing rate, interscapular brown adipose tissue and colonic temperatures and oxygen consumption. This reduction was more evident in the rat fed with a sucrose rich diet than animals fed with standard diet. The kind of diet did not modify the decrease in heart rate induced by muscimol. These findings suggest that a sucrose rich diet modifies GABA-ergic responses to muscimol injection into the posterior hypothalamus.