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At least 19 recordsLinked to original sources
PubMedDate not supplied

Comparative circulating serum levels of mepivacaine with levo-nordefrin and lidocaine with epinephrien.

Expected blood levels of common local anesthetics have been reported for numerous types of injections. Comparative levels of mepivacaine and lidocaine after dental injection have been only partially evaluated. A study was designed to compare the circulating serum level of 36 mgs. of mepivacaine with 1:20,000 levonordefrin (M) and 36 mgs. of lidocaine with 1:100,000 epinephrine (L) in 1.8 cc dental cartridges after standardized's bilateral maxillary infiltrations. Each of five subjects received 1.8 cc of (L) to the left maxillary second bicuspid and 1.8 cc of (M) to the right maxillary second bicuspid at a rate of one cc per minute. The serum was sampled before the injections and at 5, 15, 30, 60, 90, 120 and 240 minute intervals after the injections and analyzed by gas liquid chromatography. The results indicated that the serum level of (M) peaked at 30 minutes, 0.37 μg/ml of serum and (L) had peaks at 15 and 30 minutes, 0.22 μg/ml of serum. This difference was statistically significant, (p <.01) at all times sampled with (M) always resulting in a higher serum level. Serum levels persisted throughout the four hour test period.

Adult↗
PubMed1986

Liquid chromatographic separation of enantiomers of adrenergic agonists.

Many established and experimental adrenergic agonists are derivatives of 2-aminoethanol with a phenol or catechol moiety in the 1-position. There is considerable interest in the stereochemical aspects of the actions of such chiral drugs. Surprisingly, however, little has been published on the chromatographic separation of the enantiomers of these compounds, and what has been published involved nearly exclusively capillary gas-liquid chromatography. In this report, the resolution of the racemates of ten adrenergic agents using reversed-phase liquid chromatography is described. The procedure is based on derivatizing the racemic mixture of each agent with the chiral reagent 2,3,4,6-tetra-O-acetyl-beta-D-glucopyranosyl isothiocyanate, followed by separation of the resulting diastereomers on octadecylsilane columns using methanol-aqueous ammonium acetate mixtures as mobile phase. Detection was at 254 nm. The separation of the enantiomers of norphenylephrine and of octopamine was less than complete; the resolution of the other agents, i.e., synephrine, N-ethylnorphenylephrine, p-hydroxyephedrine, p-hydroxynorephedrine, metanephrine, normetanephrine, isoproterenol, and nordefrin, was complete. The derivative of (-)-isoproterenol eluted before that of its antipode. The procedure may be applicable to other similar agents.

Adrenergic Agonists↗
PubMed1992

Anticoccidial activities of 7-bromo-N-(2-imidazolidinylidene)-1H-indazol-6-amine and other alpha 2 adrenergic agonists.

Activity against the coccidial pathogen Eimeria tenella in chickens has been discovered among alpha 2 adrenergic agonists. The clonidine analog 7-bromo-N-(2-imidazolidinylidene)-1H-indazol-6-amine was active in feed at 7.5 ppm, a concentration similar to the use levels of potent commercial agents, e.g., maduramicin. Additional alpha 2 agonists were also found to have anticoccidial activity, for example, the catecholamine nordefrin, which is chemically unrelated to clonidine. However, alpha 1 agonists and alpha antagonists were inactive. These observations imply that anticoccidial effects reflect involvement of a receptor with the characteristics of the vertebrate alpha 2 adrenoceptor. alpha 2 agonists that permeate the blood-brain barrier (like clonidine) inhibit feed intake at efficacious levels, whereas those that are restricted to the peripheral compartment (such as catecholamines) do not inhibit feed intake as much. Hence, anticoccidial efficacy may be a peripheral adrenergic effect whereas depression of feed intake is likely centrally mediated.

Adrenergic alpha-Agonists↗
PubMed1978

Characterization of the monoaminergic innervation of immature rat neocortex: a histofluorescence analysis.

In the neocortex of 6-day-old rat, abundant axon terminals which exhibit specific catecholamine fluorescence are found in all regions and throughout all cortical layers. The overall density of axons in 6-day-old cortex is similar to the density in the adult cortex. In immature cortex, there are two distinct fluorescent plexuses, both presumably noradrenergic, one in the molecular layer and another in the lower half of the cortex. The superficial plexus is composed primarily of horizontal fibers, and the deep plexus of a dense feltwork of obliquely oriented fibers suggestive of a terminal field. The cortical plate itself is traversed by a few vertical processes. Following lesions of the midbrain tegmentum no fluorescent axons are seen in cortex, providing evidence that the fluorescent axons in cortex arise from brain stem neurons. The deep and superficial plexuses can be differentially visualized depending on the histochemical techniques employed and on pharmacological treatment, such as loading with a monoamine congener. Both deep and superficial axons are shown to contain endogenous catecholamines but those fibers in the deep plexus are filled to far less than their maximum capacity. The pharmaco-histochemical differences between axons in the two plexuses suggest that there may exist two distinct catecholaminergic projections to lateral neocortex. The demonstration of an extensive cortical monoamine innervation early in ontogeny supports the possibility that monoamine neurons play an important role in information processing and/or developmental interactions in the immature brain.

Age Factors↗
PubMed1987

Rapid and reversible desensitisation of vascular and platelet alpha 2 adrenoceptors.

The effects of intravenous infusion with the alpha2 adrenoceptor selective agonist alpha methylnoradrenaline on pressor responses to alpha adrenoceptor agonists, alpha2 adrenoceptor mediated platelet aggregation and adenylate cyclase were examined in conscious rabbits. Pressor responses to alpha methylnoradrenaline but not phenylephrine were decreased in a dose dependent manner during methylnoradrenaline infusion at all times examined. Recovery of these responses after stopping infusion was dependent on both the dose infused and the duration of the infusion. Alpha methylnoradrenaline infusion resulted in a dose and time dependent decrease in the pro-aggregatory response of platelet to adrenaline without any significant change in the response to ADP or in the number of [3H]yohimbine binding sites. The ability of PGE1 to stimulate adenylate cyclase was not influenced by alpha methylnoradrenaline infusions. However, reversal of this stimulation by adrenaline was decreased by relatively long (30 min) infusions of the highest dose of alpha methylnoradrenaline examined. It is concluded that alpha methylnoradrenaline infusions resulted in desensitisation of all the alpha2 adrenoceptor mediated responses examined. However the time course for the desensitisation apparently differed according to the response examined.

Adrenergic alpha-Agonists↗
PubMed1977

A catecholaminergic neuron connecting the first two optic neuropiles (lamina ganglionaris and medulla externa) of the crayfish pacifastacus leniusculus.

The crustacean optic neuropiles, the lamina ganglionaris and especially the medulla externa, show a specific pattern of green fluorescence with the fluorescence histochemical method of Falck-Hillarp. Normally, only the terminals and the cell bodies fluoresce, but in reserpine-treated animals exogenous catecholamines are taken up by the whole adrenergic neuron and are thus visualized as a whole. Incubating crayfish optic neuropiles in dopamine or alpha-methylnoradrenaline after reserpine treatment demonstrated a tangential neuron connecting the lamina and the medulla externa. The morphology of this tangential neuron differs from the two types of tangential neurons, Tan1 and Tan2, previously characterized with Golgi techniques. The catecholaminergic neuron thus constitutes, a third tangential neuron type.

Animals↗
PubMed1975

Brain tissue transplanted to the anterior chamber of the eye: 3. Substitution of lacking central noradrenaline input by host iris sympathetic fibers in the isolated cerebral cortex developed in oculo.

Fetal parietal cerebral cortex was homologously transplanted to the anterior chambers of the eyes of adult rats. The transplants got vascularized, proliferated, as measured by in vivo stereoscopic inspections, and differentiated into brain tissue similar to cortex cerebri in situ and survived for long times, greater than 41/2 months. Fibers from the intact sympathetic adrenergic ground plexus of the iris were able to innervate the transplants in an organotypic way regarding fluorescence morphology, pattern of distribution of the nerve terminals and, to a certain extent, density of innervation, the only variable parameter being density of innervation. Thus, in unpretreated or MAO inhibited transplants only rather few to scattered terminals could be found, while after preincubation in 10(-5)M alpha-methyl-noradrenaline the number of visible terminals was normal or slightly less than normal, as compared to cortex cerebri in situ. When superior cervical ganglia (SCG) were transplanted together with fetal cortex tissue to sympathetically denervated eyes the ingrowth in the cortex tissue was similar to that after single cortex transplantation combined with 5 day old SCG, while a marked hyperinnervation was encountered when combined with adult SCG. It is concluded that the developing cortex cerebri, deprived of its normal CNS source of adrenergic nerves, is able to receive sympathetic adrenergic nerves from the iris in an organotypic way upon transplantation to the anterior chamber of the eye.

Animals↗
PubMed1979

Absence of indoleamine-accumulating neurons in the retina of humans and cynomolgus monkeys.

Indoleamine-accumulating neurons have previously been detected in cats, rabbits, goldfish, chicken, pigeons, and Cebus monkeys, and were therefore also looked for in humans and in Old World monkey. Cynomolgus irus. The monkey eyes were injected intravitreally with 50 microgram 5,6-dihydroxytryptamine, 5 microgram alpha-methylnoradrenaline, or both drugs simultaneously. The human retinas were incubated in either drug. Previous observations on the distribution of dopaminergic neurons were confirmed in the two species, but no indoleamine-accumulating neurons were detected. The result emphasizes the similarity between human and Old World monkey retinas and contrasts them with the retina of the New World monkeys.

5,6-Dihydroxytryptamine↗
PubMed1989

Estimation of pA2 values at presynaptic alpha 2-autoreceptors in rabbit and rat brain cortex in the absence of autoinhibition.

An attempt was made to determine pA2 values of antagonists at the presynaptic, release-inhibiting alpha 2-autoreceptors of rabbit and rat brain cortex under conditions when there was very little released noradrenaline in the autoreceptor biophase and, hence, pA2 values were not distorted by endogenous autoinhibition. Cortex slices were preincubated with 3H-noradrenaline and then superfused and stimulated by trains of 4 pulses delivered at 100 Hz or, in a few cases, by trains of 36 pulses at 3 Hz. The alpha-adrenoceptor agonists clonidine, noradrenaline, and alpha-methylnoradrenaline concentration-dependently decreased the stimulation-evoked overflow of tritium. The alpha-adrenoceptor antagonists yohimbine, rauwolscine and idazoxan did not increase the overflow of tritium elicited by 4 pulses/100 Hz in rabbit brain slices and increased it only slightly in rat brain slices. In contrast, the antagonists increased markedly the overflow at 36 pulses/3 Hz. All antagonists caused parallel shifts to the right of the concentration-response curves of clonidine, noradrenaline, and alpha-methylnoradrenaline. pA2 values were calculated either from linear regression of log [agonist concentration ratio - 1] on log [antagonist concentration] or from sigmoid curve fitting. The slopes of the linear regression lines were close to unity, and the pA2 values calculated by the two methods agreed well. There was no consistent preferential antagonism of any antagonist to any agonist. pA2 values determined with stimulation by 4 pulses/100 Hz were by 0.53-0.80 log units higher than those determined with stimulation by 36 pulses/3 Hz.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1979

Reinnervation following guanethidine-induced sympathectomy of adult rats.

The reinnervation of various tissues by autonomic neurons has been studied in adult rats which had been sympathectomized by chronic guanethidine treatment (30 or 60 mg/kg/day for 8--15 weeks). In the heart, iris, ileum, mesentery, vas deferens and epididymis, fluorescence histochemistry reveals an almost complete disappearance of adrenergic fibres which is very longlasting. Even after 63 weeks few fluorescent fibres can be seen in these tissues and the density of innervation is not increased by incubation in alpha-methylnoradrenaline. The superior cervical ganglion represents an exception; large numbers of fluorescent fibres but few fluorescent ganglion cells were apparent during recovery. Axon counts carried out by electron microscopy on the vas deferens showed that after recovery for one year the number of axons was similar to that of controls; however, the pattern of innervation was abnormal, small granular vesicles were rarely seen and there was little uptake of 5-hydroxydopamine. On the basis of this evidence and of some pharmacological data it is suggested that there is a limited reinnervation by adrenergic axons accompanied by a great increase in the number of non-adrenergic, possibly cholinergic, axons.

Animals↗
PubMed1978

Dopamine uptake in serotoninergic terminals in vitro: a valuable tool for the histochemical differentiation of catecholaminergic and serotoninergic terminals in rat cerebral structures.

An in vitro method was developed to separately visualize dopaminergic, noradrenergic and serotoninergic terminals in the cerebral, hippocampal and cerebellar cortices of the rat, by means of the glyoxylic histochemical fluorescence method. Animals were pretreated with alpha-methylparatyrosine to deplete catecholamine stores. Thin vibratome sections were made and incubated in the presence of various exogenous amines and inhibitors of the catecholaminergic and serotoninergic transport systems. Experimental conditions insuring the best specificity were determined and the validity of the combined pharmacological and histochemical approach was further tested by using animals in which the cortical dopaminergic, noradrenergic or serotoninergic innervations were destroyed. Under the experimental conditions used, norepinephrine as well as alpha-methyl-norepinephrine were taken up in only noradrenergic and dopaminergic terminals. A separate visualization of the two systems was obtained by using specific uptake inhibitors. Dopamine was taken up not only in catecholaminergic but also in serotominergic terminals. The uptake of DA in serotoninergic fibers was inhibited by a specific inhibitor of the serotoninergic transport system or by the presence of serotonine in the incubating medium. The signification and the implications of thes results are discussed.

Animals↗
PubMed1988

Both alpha- and beta-adrenoreceptors contribute to the central depressor effect of catecholamines.

We compared the effects of alpha 2- and beta-adrenoreceptor blockade on the central actions of catecholamines and metabolites of alpha-methyldihydroxyphenylalanine, epinephrine, alpha-methylnorepinephrine, and alpha-methylepinephrine were studied. I.c.v. and nucleus tractus solitarii (NTS) injections were carried out under anesthesia. Following i.c.v. injection, both epinephrine and methylepinephrine rapidly reduced blood pressure and heart rate, but the effects of methylnorepinephrine occurred somewhat later. Following microinjection into the nucleus of the solitary tract, epinephrine, methylepinephrine, and methylnorepinephrine all caused hypotension and bradycardia. The hypotensive effects of all 3 amines in the NTS were attenuated in additive fashion by yohimbine, an alpha 2 adrenoreceptor antagonist, and timolol, a beta-adrenoreceptor antagonist, whereas only yohimbine attenuated the bradycardia. The combination of yohimbine and timolol abolished the effects of the amines. These data suggest that in the NTS both alpha 2 and beta adrenoreceptor stimulation contribute to the hypotensive effects of these amines, but that only alpha 2 adrenoreceptors are principally involved in the heart rate response.

Animals↗
PubMed1990

Evidence that endogenous catecholamines are involved in alpha 2-adrenoceptor-mediated modulation of the aortic baroreceptor reflex in the nucleus tractus solitarii of the rat.

Microinjections of alpha-methylnoradrenaline and tyramine into the rat nucleus tractus solitarii (NTS) potentiated the depressor and bradycardiac responses to aortic nerve stimulation whereas yohimbine injected similarly inhibited them. NTS pretreatment with yohimbine inhibited the baroreflex potentiation effects of alpha-methylnoradrenaline and tyramine whereas intraventricular pretreatment with 6-hydroxydopamine inhibited only that of tyramine. These results provide evidence that endogenous catecholamines in the rat NTS are involved in alpha 2 adrenoceptor-mediated modulation of the aortic baroreceptor reflex.

Animals↗
PubMedDate not supplied

Effect of methyldopa treatment on peripheral sympathetic nerve function in the dog.

Administration of methyldopa (100 mg/kg, p.o. twice daily for 3 days) to mongrel dogs produced a significant decrease in the mean blood pressure (MBP) and heart rate (HR). Chronotropic responses to cardioaccelerator nerve stimulation and vasoconstrictor responses to lumbar sympathetic nerve stimulation were significantly attenuated in the treated dogs. Pressor and chronotropic responses to bilateral carotid occlusion (BCO) and tyramine were also markedly reduced following treatment with methyldopa, which is consistent with the clinical findings that chronic methyldopa treatment in hypertensive patients impairs cardiovascular reflexes. Methylnorepinephrine (MNE) was significantly less potent than norepinephrine (NE) in producing an increase in MBP or hindleg perfusion pressure, while the chronotropic and inotropic potency of MNE was about equal to NE. These results indicate that treatment with methyldopa in the dog does indeed produce an impairment of peripheral sympathetic neuronal function to certain organs and this peripheral effect of the drug may be of importance in accounting for its antihypertensive action in the dog.

Animals↗