The Effects of p-TA and p-OA on Noradrenergic Mechanisms of the Rat Vas Deferens
In the prostatic portion of the vas deferens the noradrenaline (NA) which is released by nerve stimulation modulates the twitch responses elicited by the motor neurotransmitter. These modulatory effects are mediated by activation of inhibitory presynaptic α2 adrenoceptors, inhibitory postsynaptic β2 adrenoceptors and excitatory postsynaptic α1 adrenoceptors (Ambache et al., 1972; von Euler and Hedqvist, 1975; MacDonald and McGrath, 1980). The aim of this study was to investigate the effects of two sympathomimetic amines, p-tyramine (p-TA) and p-octopamine (p-OA) on the twitch responses of the prostatic portion of the rat vas deferens and to compare their effects with those of NA. p-Tyramine is an indirectly acting amine which produces its effects by releasing NA (Burn and Rand, 1958); in addition it was suggested that in some peripheral tissues this amine activates the adrenoceptors directly (Krishnamurty and Grollman, 1972; Morcillo et al., 1984). p-Octopamine is an amine of mixed action with both direct and indirect effects (Trendelenburg et. al., 1962; Celuch and Juorio, 1987).
KeywordsHPLC Cocaine Noradrenaline Deuterium Reserpine
Unable to display preview. Download preview PDF.
- Celuch S.M. and Juorio A.V. (1987) Effects of deuterium substitution on the chronotropic responses to some sympathomimetic amines in the isolated rat atria. Naunyn Schmied. Arch. Pharmacol, (in press).Google Scholar
- Illes P. and Dorge L. (1985) Mechanism of α2-adrenergic inhibition of neuroeffector transmission in the mouse vas deferens. Naunyn Schmied. Arch. Pharmacol. 328, 241–247.Google Scholar
- Krishnamurty U.S.R. and Grollman A. (1972) Contractile response of rat aorta to norepinephrine and tyramine. J. Pharm. Pharmacol. 182, 264–272.Google Scholar
- Trendelenburg U., Muskus A., Fleming W.W. and Gomez Alonso de la Sierra B. (1962) Effect of cocaine, denervation and decentralization on the response of the nictitating membrane to various sympathomimetic amines. J. Pharmacol, exp. Ther. 138, 181–193.Google Scholar