Effect of short and long-term treatment with antipsychotics on orexigenic/anorexigenic neuropeptides expression in the rat hypothalamus.

Among numerous side effects of antipsychotic drugs (neuroleptics), one of the leading problems is a significant weight gain caused by disturbances in energy homeostasis. The hypothalamus is considered an important target for neuroleptics and contains some neuronal circuits responsible for food intake regulation, so we decided to study which hypothalamic signaling pathways connected with energy balance control are modified by antipsychotic drugs of different generations. We created an expression profile of different neuropeptides after single-dose and chronic neuroleptic administration. Experiments were carried out on adult male Sprague-Dawley rats injected intraperitoneally for 1 day or for 28 days by three neuroleptics: olanzapine, chlorpromazine and haloperidol. Hypothalami were isolated in order to perform PCR reactions and also whole brains were sliced for immunohistochemical analysis. We assessed the expression of orexigenic/anorexigenic neuropeptides and their receptors--neuropeptide Y (NPY), NPY receptor type 1 (Y1R), preproorexin (PPOX), orexin A, orexin receptor type 1 (OX1R) and 2 (OX2R), nucleobindin 2 (NUCB2), nesfatin-1, proopiomelanocortin (POMC), alpha-melanotropin (α-MSH) and melanocortin receptor type 4 (MC4R)--both on the mRNA and protein levels. We have shown that antipsychotics of different generations administered chronically have the ability to upregulate PPOX, orexin A and Y1R expression with little or no effect on orexigenic receptors (OX1R, OX2R) and NPY. Interestingly, antipsychotics also increased the level of some anorexigenic factors (POMC, α-MSH and MC4R), but at the same time strongly downregulated NUCB2 and nesfatin-1 signaling--a newly discovered neuropeptide known as a food-intake inhibiting factor. Our results may contribute to a better understanding of mechanisms responsible for antipsychotics' side effects. They also underline the complex nature of interactions between classical monoamine receptors and hypothalamic peptidergic pathways, which has potential clinical applications.