Peripheral alpha 2 adrenoceptor stimulation contributes to the sympatholytic effect of guanfacine in humans.

摘要: Guanfacine 3 mg was infused into six volunteers over 1 h on two occasions to investigate whether its sympatholytic effect is centrally or peripherally mediated. On one occasion, the central effects of guanfacine were blocked by prior administration idazoxan 0.2 mg/kg i.v. (45 min preguanfacine); alpha 2-blockade confirmed inhibition guanfacine-induced rise in plasma growth hormone. Rapid disappearance from circulation prevented antagonism peripheral 2 receptor (confirmed suppression insulin both occasions). Idazoxan elevated noradrenaline concentration 0.26 +/- 0.018 ng/ml; however, caused a similar (approximately 30%) reduction after and vehicle. systolic diastolic blood pressure, but no change observed either occasion. Thus, appears be mediated not due baroreceptor activation. This consistent with stimulation presynaptic receptors.