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 D1 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 D2 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 D1-like and D2-like dopamine receptors in the control of ingestive behavior, with the D1 receptor having a greater role in drinking and central D2 receptors affecting several aspects of feeding behavior.