Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C1323099 (sympathomimetic)
 2,957 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Tha alpha-sympathomimetic agonists, clonidine, naphazoline, methoxamine, oxymetazoline and phenylephrine were used to further characterize the alpha-adrenoceptors mediating the positive inotropic effect in the isolated papillary muscle of the rabbit heart. The maximal inotropic effects of these amines were compared with the effect of isoprenaline and it was examined whether or not these amines compete for alpha-adrenoceptors. On the papillary muscle stimulated at 0.5 Hz, phenylephrine showed a high affinity (pD2 value=6.13) and produced the most pronounced intrinsic activity of the alpha-sympathomimetic amines. Therefore, the intrinsic activity of phenylephrine, in the presence of prindolol (3 X 10(-8) M), was used for comparison with those of the other alpha-agonists. Clonidine caused a positive inotropic effect: the intrinsic activity amounted to 0.32 of that of phenylephrine; the affinity was the highest among the amines tested (pD2 value=6.46); its effect was inhibited by 10(-6) M phentolamine. The affinity and the intrinsic activity of naphazoline were slightly lower than those of clonidine. Methoxamine showed a relatively high intrinsic activity (0.56) but the lowest affinity (4.68). Oxymetazoline did not cause any positive inotropic effect. Clonidine, naphazoline and oxymetazoline antagonized the positive inotropic effect of phenylephrine, mediated via the alpha-adrenocaptors in the presence of 3 X 10(-8) M prindolol, in a competitive manner. This observation suggests that these alpha-sympathomimetic amines compete with phenylephrine for the same receptor site. Thus the present results provide additional evidence for alpha-adrenoceptors mediating the positive inotropic actions of sympathomimetic amines in the rabbit papillary muscle.
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PMID:alpha-Adrenoceptors in the ventricular myocardium: clonidine, naphazoline and methoxamine as partial alpha-agonists exerting a competitive dualism in action to phenylephrine. 0 87

Clonidine, xylometazoline and naphazoline given ip cause a transition from sniffing to licking or gnawing stereotypy induced by amphetamine or apomorphine. Methoxamine, phenylephrine and in a lesser degree noradrenaline (all given ivc) inhibit licking and gnawing stereotyped behavior. Biochemical results correlate with the depressant action of clonidine and naphazoline on central noradrenergic neurotransmission and also with the stimulant action of methoxamine and phenylephrine on noradrenergic system. The both groups of alpha-adrenergic agonists seem to modify both the central dopaminergic and noradrenergic system activity in the same direction. It is suggested that this action can play a role in observed modification by alpha-sympathomimetic drugs of responses to dopamine agonists. However, the influence of alpha-sympathomimetics on other brain systems must be also taken into consideration.
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PMID:The effect of alpha-adrenergic receptor stimulant drugs on amphetamine or apomorphine-induced stereotypy in rats. 3 70

1 The effects of stimulating sympathetic or non-adrenergic non-cholinergic (NANC) nerves or of the addition of noradrenaline (NA) or isoprenaline (Iso) were investigated on carbachol-induced tone and on contractions produced by acetylcholine (ACh) and by pelvic nerve stimulation, in the rabbit rectococcygeus muscle.2 Each procedure reduced carbachol-induced tone; sympathetic and NANC nerve stimulation were equipotent but both were less effective than sympathomimetic drugs, of which Iso was the better. Both Iso and NA, but not sympathetic nerve stimulation, inhibited the contractions produced by pelvic nerve stimulation in a concentration-dependent manner. Against ACh-induced contractions, only Iso was effective. The effects of NANC nerve stimulation on the motor responses to pelvic nerve stimulation or to ACh were not investigated.3 The inhibitory effects of sympathetic nerve stimulation, of Iso and of NA were reduced by propranolol (3 x 10(-6) M) but unaffected by phentolamine (3 x 10(-5) M).4 In the presence of high (45 mM) concentrations of KCl, Iso and NA produced a concentration-dependent inhibition of tone that was antagonized by propranolol (3 x 10(-6) M).5 Methoxamine (4 x 10(-7) to 4 x 10(-5) M) and phenylephrine (5 x 10(-7) to 5 x 10(-5) M) which interact mainly with alpha(1)-adrenoceptors, produced only small, transient reductions in carbachol-induced tone which were subject to tachyphylaxis, unlike those produced by Iso and NA. These inhibitory effects were antagonized by phentolamine (3 x 10(-6) M) or azapetine (3 x 10(-6) M).6 Phenylephrine (5 x 10(-4) M) and high doses (3 x 10(-5) M or greater) of NA enhanced the contractile response to pelvic nerve stimulation and, on occasion, produced muscle contraction. These effects were antagonized by phentolamine (3 x 10(-6) M).7 These results suggest that inhibition of the rectococcygeus, a muscle which has no intramural nerve plexus, can be inhibited by stimulation of extrinsic NANC nerves, the transmitter for which is unknown and by sympathetic nerve stimulation via alpha- and beta-adrenoceptors located postsynaptically on the muscle. Excitatory alpha-adrenoceptors may also be present.
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PMID:The response of the rabbit rectococcygeus muscle to stimulation of extrinsic inhibitory nerves and to sympathomimetic drugs. 728 2

Insertion of Silastic rods containing the directly acting sympathomimetic drug, methoxamine, adjacent to the epididymis of rats caused a temporary reduction in fertility with no loss of ability to mate. This effect lasted up to 3 weeks. At the time of the maximal antifertility action (3-7 days after insertion), the number of spermatozoa in the ejaculate fell to almost zero, and there was a reduction in the total number of spermatozoa in the epididymis resulting from a significant drop in the number present in the cauda. Methoxamine also caused immotility and decapitation of the remaining epididymal spermatozoa. The indirectly acting sympathomimetics, tyramine and norephedrine, did not affect fertility. It is postulated that methoxamine acts to induce infertility principally by bringing about a reduction of sperm numbers in the ejaculate. This could have been produced either by a failure of the vas and cauda to contract normally at copulation or because the sperm store in the cauda had fallen below a critical threshold level.
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PMID:Effect of local application of sympathomimetic drugs to the epididymis on fertility in rats. 735 77