Synchronized release of dopamine and serotonin in the medial and lateral hypothalamus of rats

A positive linear correlation between dopamine and serotonin release was fo und in the ventromedial hypothalamus and in the lateral hypothalamic area i n fasting rats and in fed rats during intermeal intervals. Dopamine release in the ventromedial hypothalamus positively correlated with dopamine and s erotonin release in the lateral hypothalamic area, which occurred only duri ng intermeal intervals and was non-significant during the meal consumption periods or during fasting. Meal size correlated significantly only with a d ecrease in serotonin release in the lateral hypothalamic area. The study wa s designed to evaluate the relationship between dopamine and serotonin rele ase in these hypothalamic areas and their dependence on feeding status. Mic rodialysis was performed simultaneously via two probes, one in the ventrome dial hypothalamus and the other in the contralateral lateral hypothalamic a rea, of freely moving male lean Zucker rats over 24 h with preserved light and dark phase, either with ad libitum access to food and water, or when no food was available. Dopamine and serotonin concentrations were measured by highperformance liquid chromatography with electrochemical detection in 20 -min dialysis samples. Time-series analysis was applied to determine linear correlations between monoamines and in relation to food intake. Data showe d that release of dopamine and serotonin is synchronized within the ventrom edial hypothalamus and lateral hypothalamic area, particularly in the dark phase and when no food was ingested. However, synchronized release of monoa mines between these nuclei occurred only during intermeal intervals: the pe riods of satiety. These findings suggest a tight relationship between dopaminergic and seroto nergic systems of the lateral hypothalamic area and ventromedial hypothalam us, which is influenced by the feeding state and which may be involved in m aintaining the balance within and between the centers of the parasympatheti c and sympathetic nervous systems. The data also illustrate that food intak e is coupled unequivocally to the release of dopamine and serotonin in the hypothalamus, suggesting it as a mechanism of activation of postsynaptic ne urons associated with new metabolic status. (C) 2000 IBRO. Published by Els evier Science Ltd. All rights reserved.