Xylazine HCl is a strong agonist of α2-adrenoceptor [1].
Xylazine HCl has been reported to stimulate the proliferation of rat thymocytes in vivo (at doses of 2.5 mg/kg and 5 mg/kg) and in vitro (at concentration of 5 mM) [2]. In the analgesic testing, Xylazine has shown a significant prolongation of the analgesic effects in the presence of naloxine in 40 and 50 mins. In addition, Xylazine has also shown the inhibitory effect in the mouse vas deferens bioassay with the IC50 value of 18nM. Furthermore, Xylazine has displayed a potent specific [3H]-dihydromorphine binding inhibition with the IC50 value of 8μM in opiate receptor binding test [1].
References:
[1] S. BROWNING, D.LAWRENCE1, A.LIVINGSTON & B.MORRIS. Interaction of drugs active at opiate receptors and drugs active at α2-adrenoceptors on various test systems
[2] Colić M1, Cupić V, Pavicić L, Vucević D, Varagić VM. Xylazine, an alpha 2-adrenergic agonist, modulates proliferation of rat thymocytes in vivo and in vitro. Methods Find Exp Clin Pharmacol. 2000 Sep;22(7):557-62.