Recent evidence suggests that catecholamines inhibit insulin release by stimulating a2-adrenoreceptors in P-cells of the pancreatic islets. In the present study, iv injections of 0.1 and 0.3 mg/kg of yohimbine, an a2-adrenoreceptor antagonist, resulted in increased plasma insulin and decreased plasma glucose concentrations in the dog. The use of a2-adrenoreceptor antagonists may be of value in non-insulin-dependent diabetic patients by counteracting the inhibitory influence of endogenous catecholamines. o

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This study was carried out to determine whether yohimbine antagonizes the retrograde flow of spermatozoa into the urinary bladder of dogs caused by xylazine. Adult dogs were assigned to one of four groups of six dogs each and treated as follows: saline control, xylazine (2.2 mg/kg, i.m.), yohimbine (0.2 mg/kg, i.m.), yohimbine/xylazine (yohimbine, 0.2 mg/kg, i.m., followed 10 min later by xylazine, 2.2 mg/kg, i.m.). Pre- and post-treatment urine were collected by cystocentesis from all dogs. The mean (+/- SD) adjusted total number of spermatozoa in the post-treatment urine of xylazine-treated dogs (141.02 +/- 136.75 x 10(6)) was 15 times higher (P < 0.05) than the number in the post-treatment urine of control dogs (9.16 +/- 20.26 x 10(6), 1763 times higher (P < 0.05) than the number in the urine of yohimbine-treated dogs (0.08 +/- 0.20 x 10(6), and 56 times higher (P < 0.05) than the total number in the post-treatment urine of yohimbine/xylazine-treated dogs (2.54 +/- 4.54 x 10(6)). These results confirm that xylazine induces a significant (P = 0.007) displacement of spermatozoa into the urinary bladder of dogs and demonstrate that pre-treatment with yohimbine prevents this effect.

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