Hypothalamic control of accumbens dopamine: a system for feeding reinforcement
1996
Hoebel, B.G. | Rada, P. | Mark, G.P. | Parada, M. | Puig de Parada, M. | Pothos, E. | Hernandez, L.
Results from this laboratory are reviewed that suggest identified neurotransmitter systems in the hypothalamus can reinforce feeding behavior in part by controlling dopamine release in the nucleus accumbens. Six findings are presented: 1) When mildly food-deprived rats performed an instrumental response for food pellets, dopamine was released in the accumbens and prefrontal cortex; 2) Conditioned taste stimuli excited or inhibited dopamine release in the accumbens depending on the meaning for the animal; 3) Basal extracellular dopamine in the accumbens was low in underweight rats; 4) Galanin in the hypothalamus that stimulated feeding activated a system for dopamine release in the accumbens; 5) Hypothalamic dopamine inhibited accumbens dopamine, as judged from the actions of local sulpiride, which blocked hypothalamic dopamine receptors and activated a circuit that released dopamine in the accumbens; and 6) Rats self-injected hypothalamic sulpiride. The results imply that when galanin or sulpiride causes an animal to eat, it also causes dopamine release in an accumbens system that reinforces ongoing operant behavior; thus it reinforces eating. If the food provides nutrition, as opposed to illness, then the flavor becomes a conditioned stimulus that can release dopamine in the accumbens and theoretically reinforce ingestion of that flavor in the future. It is speculated that animals will work to raise extracellular dopamine in the accumbens by ingesting appropriate flavors and eating, especially if they are underweight when their nucleus accumbens dopamine is low.
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