Nov 3, 1975

Relative pre- and postsynaptic potencies of alpha-adrenoceptor agonists in the rabbit pulmonary artery

Naunyn-Schmiedeberg's Archives of Pharmacology
K StarkeH D Taube


The rabbit pulmonary artery contains postsynaptic alpha-adrenoceptors which meidate smooth muscle contraction; its noradrenergic nerves contain presynaptic alpha-adrenoceptors which mediate inhibition of the release of the transmitter evoked by nerve impulses. Dose-response curves for the pre- and postsynaptic effects of eight alpha-receptor agonists were determined on superfused strips of the artery in the presence of cocaine, corticosterone and propranolo. 1. According to the concentrations which caused 20% of the maximal contraction (EC20 post), the postsynaptic rank order of potency was: adrenaline greater than noradrenaline greater than oxymetazoline greater than naphazoline greater than phenylephrine greater than tramazoline greater than alpha-methylnoradrenaline greater than methoxamine. The pA2 values of phentolamine againstoxymethazoline, phenylephrine, alpha-methylnoradrenaline and methoxamine were 7.43, 7.48, 7.59 and 7.69, respectively. 2. For the investigation of presynaptic effects, the arteries were preincubated with 3H-noradrenaline. All agonists inhibited the overflow of tritium evoked by transmural sympathetic nerve stimulation. According to the concentrations which reduced the stimulation-induced overflow by ...Continue Reading

Mentioned in this Paper

Neural Inhibition
Vasomotor System
Norepinephrine, (+, -)-Isomer
Adrenergic alpha-Agonists
Pulmonary Artery Structure
Chinchilla Rabbits
Norepinephrine Receptors

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