Conditioned release of neurotransmitters as measured by microdialysis.

The purpose of this research was to measure conditioned release of neurotransmitters in vivo and to study their role as neuromodulators in neural circuits controlling food intake. 1. Extracellular serotonin (5HT) was measured in the hypothalamus during (a) injection of the anorectic drug d-fenfluramine, (b) a normal meal and (c) during the taste of a flavor that previously had been paired with nausea. All these situations increased 5HT, suggesting it plays a role in suppression of food intake. 2. Extracellular dopamine (DA) in the nucleus accumbens (NAC) was released (a) during eating and (b) by a conditioned taste associated with intragastric infusion of carbohydrate, but (c) DA decreased in response to a taste that had been paired with nausea. Thus some DA projections to the NAC may modulate circuits that reinforce eating safe food. Drugs that release DA mimic, in part, this safe food effect.(ABSTRACT TRUNCATED AT 250 WORDS)