Melanin-concentrating hormone-1 receptor modulates neuroendocrine, behavioral, and corticolimbic neurochemical stress responses in mice

Repeated exposure to stressful conditions is linked to the etiology of affective disorders. The melanin-concentrating hormone-1 receptor (MCHR1) may be a novel mechanism that is involved in the modulation of stress responses and affective states. The role of MCHR1 in neuroendocrine, behavioral, and neurochemical stress, and anxiety-related responses was examined by monitoring the effects of melanin-concentrating hormone (MCH) and the selective MCHR1 antagonist, GW3430, in inbred C57B1/6NTac and MCHR1-knockout (KO) and wild-type (WT) mice. Intracerebroventricular injection of MCH increased plasma corticosterone, and produced anxiety-related responses in the elevated plus maze. The selective MCHR1 antagonist, GW3430, blocked the neuroendocrine and behavioral effects of MCH and produced anxiolytic-like effects by itself in animal models of anxiety. Moreover, KO mice had an anxiolytic-like phenotype in behavioral models of anxiety, and GW3430 had anxiolytic-like effects in WT, but not KO mice. Lastly, stressor-evoked acetylcholine release within the prefrontal cortex of inbred and WT mice, but not KO mice, was blocked by GW3430. We show that MCH elicits anxiety-like responses and that the effects of a selective MCHR1 antagonist and the phenotype of KO mice are consistent with anxiolytic-like action. Distinct behavioral, physiological, and neurochemical stress, and anxiety-related responses were selectively modulated by the MCHR1, and these actions may involve corticolimbic regulation of stress responsivity and anxiety.