We studied the influence of obesity caused by lethal yellow (AY) mutation in the agouti gene, short photoperiod (4/20 h light/darkness), and combination of these factors on depressive-like behavior in the forced swimming test and expression of genes encoding proinflammatory cytokines in the hypothalamus of heterozygous male C57Bl/6-AY/a mice and their wild-type littermate controls (C57Bl/6-a/a). It was shown that AY mutation as well as short photoperiod increased depressive-like behavior in mice. No effect of the interaction of AY mutation and photoperiod on immobility in the forced swimming test was revealed. In wild-type mice, increased depressive-like behavior caused by short photoperiod was accompanied by enhanced expression of Tnf gene. Exposure to short daylight increased the expression of Nos2.
Keywords: cytokines; forced swimming test; hypothalamus; lethal yellow mutation; photoperiod.