L-THREONINE INJECTION INTO PPC MODIFIES FOOD-INTAKE, LATERAL HYPOTHALAMIC ACTIVITY, AND SYMPATHETIC DISCHARGE

Food intake and the firing rate of lateral hypothalamic neurons and ne rves innervating interscapular brown adipose tissue (IBAT), along with IBAT and colonic temperatures, were monitored in male Sprague-Dawley rats fed a threonine-free diet. These variables were measured before a nd after a bilateral injection of L-threonine (2 nmol into each side) into the prepiriform cortex (PPC). The same variables were also monito red in 1) rats fed a threonine-free diet and injected with saline, 2) animals fed a standard diet and injected with L-threonine, and 3) rats fed a standard diet and injected with saline. The results showed that injection of L-threonine into PPC increases food intake and firing ra te of lateral hypothalamic neurons, whereas it decreases the sympathet ic discharge and body temperature in animals fed a threonine-free diet . No changes were found in the animals fed a standard diet. These find ings suggest a correlation between 1) threonine level in the PPC and 2 ) lateral hypothalamic activity and sympathetic discharge to IBAT.