Interleukin-1α injection into ventromedial hypothalamic nucleus of normal rats depresses food intake and increases release of dopamine and serotonin

A microdialysis injector probe administered IL-1 alpha into ventromedial hypothalamus (VMN) and concurrently measured release of dopamine (DA), DOPAC, 5-HT, and 5-HIAA. After baseline dialyses, six rats received 2-ng IL-1 alpha and six rats received vehicle (1 mu l saline) into VMN. Sixty minutes later, food was provided for 40 min while VMN monoamines were measured every 20 min. Vehicle had no significant effect on monoamines, their metabolites, or food intake. Food intake was significantly lower in IL-1 alpha rats vs, controls (p < 0.01). Baseline levels of VMN monoamines (pg/10 mu l dialysate) in IL-1 alpha and vehicle groups were similar. DA and 5-HT rose immediately on injecting IL-1 alpha and remained higher (p < 0.05) than basal during the first 60 min and 40 min sampling period, respectively. Levels of 5-HIAA also increased (p < 0.01). Eating decreased VMN DA in controls, and decreased VMN DOPAC in IL-1 alpha-treated rats. During eating, VMN 5-HT in control rats significantly increased while increasing VMN 5-HIAA occurred in IL-1 alpha rats. Findings show that an IL-1 alpha pathophysiological dose injected into the VMN was associated with anorexia and significantly increased dopaminergic and serotonergic activities and suggest that enhanced VMN DA and 5-HT activities may be part of an IL-1 alpha-initiated cascade involved in IL-1 alpha-associated anorexia. (C) 1998 Elsevier Science Inc.