Long-term administration of m-chlorophenylpiperazine to rats does not alter functional sensitivity of either pre-synaptic or postsynaptic 5-HT1A receptors.

Administration of the selective 5-HT(1A) agonist, 8-hydroxy-2(di-n-propylamino)tetralin (8-OHDPAT ), to rats produced increases in food intake in freely fed animals and decreases in food intake in food-deprived animals. Acute pre-treatment with various doses of m-chlorophenylpiperazine (m-CPP, another 5-HT agonist) attenuated 8-OHDPAT-induced increases in food intake in the free-feeding paradigm and enhanced 8- OHDPAT-induced decreases in food intake in the food-deprived paradigm. In the two paradigms, however, neither increases nor decreases in food intake induced by 8-OHDPAT were altered in animals following long- term (21-day) treatment with m-CPP versus saline when animals were challenged with 8-OHDPAT 48 h after the last dose of m-CPP. These findings suggest that long-term m-CPP treatment does not alter the functional sensitivity of 5-HT(1A) receptors located pre-synaptically that mediate hyperphagia or 5-HT(1A) receptors located post-synaptically that mediate decreases in food intake by induction of the serotonin behavioural syndrome.