EFFECTS OF SCH39166 AND DOMPERIDONE ON THE MEAL PATTERNING OF MALE-RATS

In male rats given free access to food (45 mg pellets) and water, ingestive behavior is structured into meals. The selective dopamine D-1 antagonist SCH39166 had little effect on total food intake, meal size, or feeding rate. However, it did produce a marked, dose-related reduction in drinking that resulted from an increase in intermeal interval with unchanged meal size. Possible peripheral and central explanations of this effect are discussed. In a second experiment, the peripheral dopamine D-2 antagonist, domperidone, was shown to have little effect on either feeding or drinking. A dose of 10 mg/kg did reduce feeding rate, but this probably represents a central effect, because doses that were only slightly higher have previously been shown to reduce stimulant-induced hyperactivity and stereotypy. These experiments confirm the functional distinction between D-1-like and D-2-like dopamine receptors in the control of ingestive behavior, with the D-1 receptor having a greater role in drinking and central D-2 receptors affecting several aspects of feeding behavior.