Long-term lithium treatment in rats attenuates m-chlorophenylpiperazine-induced decreases in food intake but not locomotor activity.

Administration of various doses of m-chlorophenylpiperazine (m-CPP, a 5-HT agonist) to rats produced dose-related decreases in food intake and locomotor activity. Long-term (21-25 days) but not short-term (3-7 days) lithium treatment attenuated m-CPP-induced decreases in food intake. However, neither short-term nor long-term lithium treatment had any significant effect on m-CPP-induced decreases in locomotor activity. These findings suggest development of functional subsensitivity of 5-HT1B receptors mediating decreases in food intake and provide further evidence that m-CPP's effects on food intake are mediated by different mechanisms from those regulating locomotor activity.