The short chain sugar acid, 2-buten-4-olide, activates oxytocin-secreting neurons but not arginine vasopressin-secreting neurons in the hypothalamus of rats

The effects of intraperitoneal (i.p.) administration of 2-buten-4-olide (2-B4O), an endogenous sugar acid, on the hypothalamo-neurohypophyseal system were examined in rats. Plasma oxytocin (OXT) levels were significantly increased 15-60 min after i.p. administration of 2-B4O (100 mg/kg), whereas plasma arginine vasopressin (AVP) did not change. Dual immunostaining revealed that Fos-like immunoreactivity (LI) was predominantly observed in OXT-secreting neurons in the paraventricular (PVN) and the supraoptic nuclei (SON) 120 min after i.p. administration of 2-B4O. In addition, many Fos-LI neurons were observed in the nucleus of the tractus solitarius (NTS) after i.p. administration of 2-B4O. These results suggest that a peripherally administered high dose of 2-B4O activates OXT-secreting neurons in the hypothalamus through activation of NTS neurons, possibly as a result of a stress response.