Pre- and postsynaptic effects of yohimbine stereoisomers on noradrenergic transmission in the pulmonary artery of the rabbit

An examination of 5‐hydroxytryptamine receptors in human saphenous vein

“…Docherty & Hyland, 1985b). The pA2 of 6.36 obtained for yohimbine in the absence of cocaine is similar to the pA2 of 6.56 obtained at a1-adrenoceptors in the rabbit pulmonary artery (Weitzell et al, 1979). Muller-Schweinitzer (1984), also using the human isolated saphenous vein, found that yohimbine was approximately 60 times less potent against 5-HT than against NA.…”

Separation of adrenergic and non‐adrenergic contractions to field stimulation in the rat vas deferens

“…In trains of stimuli In the absence of postjunctional blockade: rauwolscine, a 'selective' M2-adrenoceptor antagonist (Weitzell, et al., 1979), increased the height of responses to trains at 1-10 Hz. However, the increases were small and the effect was best characterized as a change in the time course; the peak was achieved more slowly, but was of longer duration, than the control 'twitch' (Figure 7b).…”

“…The response to a single supramaximal stimulus (0.5 ms) consists of two consecutive components, Is and IIs, but their proportions differ in the two portions ( Figure. 'Adrenergic' blockade In either portion, Is was resistant but IIs was susceptible to corynanthine, a stereoisomer of yohimbine which is a preferential xl-adrenoceptor antagonist (Weitzell, Tanaka & Starke, 1979;McGrath, 1981).…”

Evidence for neuro‐effector transmission through postjunctional α2‐adrenoceptors in human saphenous vein

“…In a previous study, we obtained results in rabbit portal vein which could best be explained in terms of a mixed population of a,-and M2-receptors mediating stimulation-evoked contraction (Docherty & Starke, 1982); however, that demonstration required the elimination of ml-mediated contractions by use of the irreversible antagonist phenoxybenzamine. In this present study, we have examined the a-receptors involved in contractions evoked by nerve stimulation in human saphenous vein employing the selective alantagonist prazosin (Cambridge et al, 1977) and the selective m2-antagonist yohimbine (Weitzell et al, 1979).…”