Olanzapine differentially affects 5-HT2A and 2C receptor mRNA expression in the rat brain

This study examined regional changes in rat brain mRNA levels encoding 5-HT2A and 5-HT2C receptors following chronic olanzapine treatment. The immediate effect (2 h after the last treatment) was a down-regulation of 5-HT2A receptor mRNA expression, predominantly in the hypothalamus, limbic system and striatum, while a rebound effect was observed 48 h later. 5-HT2C receptor mRNA expressions were decreased in the substantia nigra. Correlations between 5-HT2A receptor mRNA expression and total food intake, weight gain and energy efficiency were observed.