Xylazine-induced diuresis in rats is attenuated by κ-opioid receptor and α2-adrenoceptor antagonists.

Xylazine is an α2 adrenoceptor agonist approved for use in veterinary medicine as an analgesic and sedative. However, the recent use of xylazine as adulterant with opioids has created a public health emergency due to an increased number of addiction-related deaths and adverse effects. As a result, xylazine's pharmacological profile has been revisited, and it has been found to act as a full agonist at κ-opioid receptors. Because increased urine output is a well-established effect of κ-opioid receptor agonists, we determined if κ-opioid receptors are involved in xylazine-induced diuresis. Adult male Sprague-Dawley rats were used. A dose-response curve was first established through systemic administration of xylazine. Rats were injected with xylazine (1.25, 2.5, or 5 mg/kg) or saline and then placed into metabolic cages for 2 h for urine collection. Xylazine doses of 2.5 and 5 mg/kg significantly increased urine output compared to saline-injected rats, indicating that xylazine caused diuresis. Next, rats were pretreated with saline; a κ-opioid receptor antagonist, 5'-guanidinonaltrindole (5'-GNTI) (0.01-0.1 mg/kg); or an α2-adrenoceptor antagonist, yohimbine (0.3-1 mg/kg). Thirty minutes later, rats were injected with saline or a fixed dose of xylazine (2.5 mg/kg) and urine was collected for 2 h. Pretreatment with either 5'-GNTI or yohimbine significantly decreased xylazine-induced diuresis. Our findings suggest that xylazine-induced diuresis is mediated by both κ-opioid receptors and α2-adrenoceptors, highlighting the importance of considering κ-opioid receptor activation when evaluating in vivo pharmacological effects of xylazine.