DOPAMINE IN THE LATERAL HYPOTHALAMUS MAY BE INVOLVED IN THE INHIBITION OF LOCOMOTION RELATED TO FOOD AND WATER SEEKING

Experiments were conducted in male rats to assess the motor effects of bilateral intraperifornical microinjections of sulpiride, dopamine (DA) and other drugs. Sulpiride increased locomotion of the animals in all the experiments reported here. DA (10-mu-g) administered 5 minutes before sulpiride (8-mu-g) reduced the motor stimulant effect of the neuroleptic from 1601.3 +/- 337.6 to 742.5 +/- 180.4 counts/30 min. SCH 23390 (15-mu-g), haloperidol (2.5-mu-g) and atropine (18-mu-g) did not modify the locomotion level of animals acclimated to the actimeters. After carbachol (5-mu-g) the animals attained a level of hyperactivity (1459.5 +/- 146.5 counts/30 min) similar to that induced by sulpiride (1595.7 +/- 365.7 counts/30 min) in the same experiment. In other experiments DA (10-mu-g) administered 30 min before sulpiride again blocked the effect of 8-mu-g of sulpiride, and reduced the initial hyperactivity of food-and water-deprived animals previously familarized with the actimeters (922.4 +/- 49.38 counts/15 min under saline, vs. 544 +/- 29 counts/15 min under DA). The same DA dose did not modify the initial spontaneous activity of nonfamiliarized nonfood-deprived rats (508.9 +/- 96.1 after saline vs. 520.9 +/- 47.1 after DA). These results suggest the presence of cells in the lateral hypothalamus involved in the control of locomotion. These experiments also suggest that locomotion triggered by the LH may be exploratory behavior essential to the search for water and food. As a corollary, DA in the LH appears to be involved not only in the inhibition of feeding and drinking but also in the inhibition of exploratory and food- and water-directed locomotion.