Activation of orexin-1 receptors in the amygdala enhances feeding in the diet-induced obesity rats: Blockade with μ-opioid antagonist.

Obesity has become a global problem due to its sharply increased prevalence and associated complications. Orexin and opioid signaling can regulate feeding behavior and represent potential therapeutic targets for obesity. In the present experiment, we sought to ascertain the effects of orexin-A and μ-opioid signaling regulation in the basomedial amygdala (BMA) on feeding and investigate the physiology of gastric distension (GD)-responsive neurons in a diet-induced obesity (DIO) and diet-induced obesity resistance (DR) rat model. Intra-BMA infusions of orexin-A increased the firing of BMA GD neurons and increased food intake, and that these effects could be abolished by pretreatment with the orexin-1 receptor (OX-1R) antagonist SB334867, these effects could also be somewhat attenuated by co-administration of naloxone. In the DIO and DR rats, mRNA expression of OX-1R and μ-opioid receptors were increased in the BMA. Our results strongly suggest that orexin-A and opioid signaling in the BMA play a major role in regulating GD neuronal excitability and feeding behavior in obesity.