Evidence for neuro-effector transmission through postjunctional alpha 2-adrenoceptors in human saphenous vein.
The effects of the alpha 1-adrenoceptor antagonist prazosin and the alpha 2-adrenoceptor antagonist yohimbine were examined against stimulation-evoked contractions in human isolated saphenous veins. The concentration of yohimbine producing 30% inhibition of stimulation-evoked contractions (IC30) was 13.2 nM, whereas the IC30 of prazosin was greater than 250 nM. The inhibition of stimulation-evoked contractions by yohimbine was not prejunctionally mediated since yohimbine (0.01-0.1 microM) significantly potentiated the stimulation-evoked overflow of tritium in tissues pre-incubated with [3H]-noradrenaline. The high potency of yohimbine and the low potency of prazosin indicate that neuro-effector transmission in human saphenous vein is mediated predominantly by postjunctional alpha 2-adrenoceptors.
Docherty
J R
JR
Hyland
L
L
D000328:Adult; D004558:Electric Stimulation; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D009451:Neuroeffector Junction / Q000187:drug effects*; D011224:Prazosin / Q000494:pharmacology; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects*; D012501:Saphenous Vein / Q000187:drug effects; D009435:Synaptic Transmission / Q000187:drug effects*; D015016:Yohimbine / Q000494:pharmacology
D011942:Receptors, Adrenergic, alpha; D015016:Yohimbine; D011224:Prazosin