Effect of xylazine hydrochloride on canine splenic weight: an index of vascular capacity.

Splenic weight, an index of changes in vascular capacity, was used to assess the effects of xylazine hydrochloride in anesthetized dogs. Intravenous xylazine (0.01, 0.1, and 1 mg/kg) produced dose-dependent decreases in vascular capacity as assessed by decreases in splenic weight which were significant (P less than 0.05) at the 1 mg/kg dose. Phenoxybenzamine, an alpha-adrenergic receptor blocking drug, prevented the splenic contractile response to xylazine. Propranolol, a beta-adrenergic receptor blocking drug, did not alter the splenic contractile response to xylazine. Intravenous xylazine (0.1 and 1 mg/kg) produced significant (P less than 0.05) decreases in heart rate, splenic arterial flow, and systolic, mean, and diastolic blood pressures. Central venous pressure increased significantly (P less than 0.05) in dogs given the 1 mg/kg dose.