mRNA expression levels of leptin-related substances can be modified in risperidone-injected rats

This study was undertaken to find an answer to the discrepancy between enhanced leptin mRNA expression level in white adipose tissue and its normal serum level in the rats given risperidone of 0.1 mg/kg/day (an equivalent dose to the standard one used for patients) for 21 consecutive days. In the white adipose tissues of rats injected with risperidone, mRNA expression levels of the genes encoding truncated a form of leptin receptor (Ob-Ra) and suppressor of cytokine signaling-3 (SOCS-3) were up-regulated; α 1c-adrenergic receptor subtype mRNA expession level was down-regulated. On the contrary, the mRNA expression levels of the genes encoding long form of leptin receptor (Ob-Rb), Ob-Ra, SOCS-3, and neuropeptides known to regulate the appetite were not altered in the hypothalamus, a target site of leptin, obtained from the rats injected with risperidone for 21 consecutive days. These data indicate the importance of the adaptation that occurred in the white adipose tissue of the rats injected with risperidone for semi-chronic duration.