Chronic Hindbrain Administration of Oxytocin Elicits Weight Loss in Male Diet-Induced Obese Mice.

Previous studies indicate that oxytocin (OT) administration reduces body weight in high fat diet (HFD)-induced obese (DIO) rodents through both reductions in food intake and increases in energy expenditure. We recently demonstrated that chronic hindbrain [fourth ventricular (4V)] infusions of OT evoke weight loss in DIO rats. Based on these findings, we hypothesized that chronic 4V OT would elicit weight loss in DIO mice. We assessed the effects of 4V infusions of OT (16 nmol/day) or vehicle over 28 days on body weight, food intake and body composition. OT reduced body weight by approximately 4.5±1.4% in DIO mice relative to OT pre-treatment body weight (P<0.05). These effects were associated with reduced adiposity and adipocyte size (inguinal white adipose tissue (IWAT)] (P<0.05) and attributed, in part, to reduced energy intake (P<0.05) at a dose that did not increase kaolin intake (P=NS). OT tended to increase uncoupling protein-1 expression in IWAT (0.05