Effects of Yohimbine and Desipramine on Adrenal Catecholamine Release in Response to Splanchnic Nerve Stimulation in Anesthetized Dogs

Abstract

The effects of yohimbine and desipramine on adrenal catecholamine (CA) release in response to splanchnic nerve stimulation (SNS) were examined in anesthetized dogs. SNS at 1 and 3Hz produced frequency-dependent increases in epinephrine (EPI) and norepinephrine (NE) output determined from adrenal venous blood. Yohimbine (30 and 100μg/kg, i.v.), a selective α₂-adrenoceptor antagonist, enhanced the SNS-induced increases in both EPI and NE output. Desipramine (100 and 300μg/kg, i.v.), an amine pump inhibitor, enhanced the SNS-induced increases in NE output, whereas no enhancement of EPI output was produced. After desipramine treatment, yohimbine further enhanced the SNS-induced increases in EPI and NE output. After yohimbine treatment, desipramine further enhanced the SNS-induced increase in NE output. These results suggest that the release of adrenal CA in response to SNS is inhibited by α₂-adrenoceptors, and that released NE, rather than EPI, is predominantly taken up into the dog adrenal medullary cells.