['Melatonin, the neurohormone for darkness, mediates photoperiod dependent changes in physiology and behavior by targeting specific membrane bound receptors (MT1 and MT2). In the present study, we investigated the impact of MT1 receptor-deficiency on feeding behavior, locomotor activity and mRNA expression levels encoding for the polypeptide Pomc and neuropeptide Y (Npy) in the hypothalamic arcuate nucleus (ARC) and the adenohypophysis (pars distalis, PD and pars intermedia, PI) in a comparison between wild-type (WT) and MT1-deficient (MT1-/-) mice.', 'The MT1-/- mice spent significantly more time in feeding than the WT-mice, while the general locomotor behavior, body weight and the total amount of food consumed did not differ between both genotypes. The nocturnal expression levels of Pomc in ARC and PD were significantly higher in WT as compared to MT1-/- mice and exogenous melatonin administered during the light phase stimulated Pomc expression in WT mice only. No differences were found between WT and MT1-/- mice with regard to Pomc expression levels in the PI.'] Does melatonin Receptor 1-Deficiency affect Feeding Dynamics and Pro-Opiomelanocortin Expression in the Arcuate Nucleus and Pituitary of Mice?