Feeding and hypothalamic stimulation increase dopamine turnover in the accumbens

The hypothesis that the dopaminergic system plays a role in feeding behavior was tested in three experiments. First, microdialysis was performed in the nucleus accumbens (NAC) at 20 min intervals during free feeding in rats at 80% of normal body weight. Extracellular concentration of dopamine (DA), dihydroxyphenylacetic acid (DOPAC), and homovanillic acid (HVA) increased significantly during eating indicating an increase in DA turnover. Second, microdialysis samples were collected from the NAC during bar pressing with a) a signal light on and food available, b) the light on but no food available, c) neither light nor food. Only when food was available did extracellular DA, DOPAC and HVA increase significantly. This increase in DA turnover occurred in the accumbens but not in the ventral striatum. Third, electrical stimulation of the perifornical lateral hypothalamus (LH) that was capable of inducing feeding increased extracellular DA, DOPAC and HVA in the NAC. This occurred whether the animal had food to eat or not. The effect of LH stimulation on DA turnover resembled the effects of free feeding and operant feeding in Experiments 1 and 2. Perifornical LH stimulation did not increase dopamine turnover in the ventral striatum. The results show that perifornical LH stimulation activates the mesolimbic dopamine system and that dopamine release in the accumbens is involved in feeding. The increase in dopamine turnover outlasted the consummatory act. This suggests that accumbens dopamine may be related to sensory input, feeding reflexes, food reward or memory processes and not just to the consummatory act itself.