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PubMed1979

Disappearance and recovery of catecholamine innervation in brain regions of adult goldfish following 6-hydroxydopamine treatment.

The effect of 6-OHDA treatment on catecholamine innervation was studied in the cerebellum, optic tectum and lobus vagi of the goldfish. Catecholamine terminals completely disappeared in less than two weeks after intraventricular injection of 10 microgram 6-OHDA. In periods comprised between 40 days and 4 months after drug injection, catecholamine terminals reappeared to a different degree. The cerebellum showed the highest recovery and, as far as the valvula cerebelli was concerned, also over-innervation. The remarkable power to restore catecholamine innervation led to a distribution of reappearing terminals similar to that of normal animals in the different layers of the three structures examined.

Animals↗
PubMed1984

Involvement of Na influx in acetylcholine receptor mediated secretion of catecholamines from cultured bovine adrenal medulla cells.

The role of sodium (Na) in stimulus-secretion coupling of adrenal medulla was investigated in primary culture of bovine adrenal medulla cells. In Na-free medium, the secretion of catecholamines and influx of 45Ca induced by carbachol were decreased to 30% and 18% of control responses, respectively. Carbachol induced secretion of catecholamines and influx of 45Ca were not inhibited by tetrodotoxin, a highly selective blocker of voltage dependent Na-channels. Carbachol caused a rapid influx of 22Na which was inhibited by hexamethonium but not by tetrodotoxin. Nicotine but not muscarine could be a substitute for carbachol and caused catecholamine secretion, 45Ca influx 22Na influx. Veratridine caused continuous secretion of catecholamines and influxes of 45Ca and 22Na which were blocked by tetrodotoxin. These results indicate that in cultured bovine adrenal medulla cells, stimulation of nicotinic receptor causes the influx of Na through receptor-mediated Na-channels but not through voltage-dependent Na-channels, and that influxed Na may facilitate the influx of Ca which triggers the secretory process. The sodium ion seems to be involved in the stimulus-secretion coupling evoked by physiological secretagogue in adrenal medulla.

Adrenal Medulla↗
PubMed1984

Absence of catecholamine uptake mechanism in the isolated perfused adrenal gland of the rat.

The left adrenal gland of the rat was perfused in vitro via the adrenal vein with Krebs-bicarbonate solution to study accumulation of exogenous catecholamines and secretion of endogenous norepinephrine and epinephrine by exposing the gland to various sympathomimetic agents. Perfusions with high concentrations of norepinephrine for 30 min did not result in its accumulation over the endogenous norepinephrine content. High concentrations of dopamine, norepinephrine and phenylephrine failed to displace significant quantities of endogenous catecholamines in the perfusate over those secreted spontaneously. Agents known to release norepinephrine from sympathetic nerves, such as tyramine and ephedrine, were ineffective in causing secretion of catecholamines from the rat adrenal gland. We have concluded that chromaffin cells of the isolated rat adrenal gland do not exhibit an efficient uptake system across their membrane for transporting catecholamines.

Absorption↗
PubMed1992

Catecholamine histofluorescence depletion in the infarcted brain parenchyma but not in the adventitia of the occluded cerebral arteries in rats.

The effect of acute cerebral ischemia on the catecholamine-containing nerve fibers in the brain parenchyma and in the adventitia of the cerebral arteries was studied in the rat. Unilateral cerebral ischemia was produced with an intraluminal thread technique which does not damage the adventitia of cerebral arteries. One to three days after surgery the ischemic damage of the brain was consistently observed in the territory of the middle cerebral artery of the operated side. Depletion of catecholamine histofluorescence was observed in the infarcted brain parenchyma. However, in the adventitia of the middle cerebral arteries of the operated side, catecholamine histofluorescence remained intact. No detectable changes in fluorescence were observed in the brain parenchyma or adventitia of the cerebral arteries in the contralateral side. The results indicate that the perivascular catecholamine-containing nerve fibers are not impaired by the intraluminal occlusion of the cerebral artery in the early stage of ischemia.

Animals↗
PubMed1979

Anti-microtubular agents as inhibitors of desensitization to catecholamine stimulation of adenylate cyclase in Ehrlich ascites tumor cells.

Adenylate cyclase activity of the homogenate of Ehrlich ascites tumor cells pretreated with catecholamine at 37 degrees C was not stimulated by the addition of the same catecholamine, whereas that of the cells without the pretreatment was stimulated. Such a desensitization was induced hardly at all when the pretreatment was performed at low temperature. The desensitization of adenylate cyclase activity to catecholamine stimulation was prevented by pre-pretreatment of the cells with colchicine prior to the catecholamine pretreatment. The effect of colchicine was dependent on the period of the treatment and concentration of colchicine. Vinblastine had a similar effect, whereas cytochalasin B was without effect. Thus, involvement of microtubules was suggested in the desensitization of the membrane-associated enzyme to external stimulation.

Adenylyl Cyclases↗
PubMed1980

Regulation of catecholamine-responsive adenylate cyclase activity in rat reticulocyte membranes by endogenous factors: general characteristics and resolution into protein and nucleotide components.

A 100 000 X g soluble, supernatant fraction obtained from the hemolysate of rat reticulocytes was studied for its effect upon catecholamine-sensitive adenylate cyclase activity in reticulocyte membranes. The supernatant material, devoid of adenylate cyclase activity itself, amplified isoproterenol-dependent activity in responsive membranes and was an essential requirement for the expression of hormone sensitivity in membranes rendered unresponsive to isoproterenol alone. The increment in catecholamine-associated activity conferred upon reticulocyte membranes by the supernatant material was beta-adrenergic because it did not affect basal or fluoride-related activity and was completely inhibited by propranolol. Guanine nucleotides were present in the supernatant but could account for only a fraction of the total activity because the supernatant was able to cause greater stimulation than maximal concentrations of GTP and when specified concentrations of exogenous GTP were compared with equivalent nucleotide concentrations in the supernatant, the supernatant always led to greater activity. The supernatant was resolved into protein-and nucleotide-containing components by ion-exchange chromatography. Each component was approximately one-half as active in amplifying catecholamine-dependent adenylate cyclase as the unresolved, crude supernatant material. The activity eluted in the first peak of the DEAE chromatogram was resistant to alkaline phosphatase, sensitive to trypsin, not dialyzable and contained no detectable concentrations of GTP or GDP. In contrast, the activity eluted the second peak of the DEAE chromatogram was sensitive to alkaline phophatase, resistant to trypsin, completely dialyzable and contained both GTP (30 microM) and GDP (10 microM) in significant concentrations. Neither the crude supernatant nor its two active components affected the binding of [125I]-iodohydroxybenzylpindolol to reticulocyte membranes. These observations establish in rat reticulocytes the presence of protein and guanine nucleotide constituents which have independent influences upon the catecholamine-responsive adenylate cyclase of reticulocyte membranes.

Adenylyl Cyclases↗
PubMed1980

Use of cell fusion techniques to probe the mechanism of catecholamine-induced desensitization of adenylate cyclase in frog erythrocytes.

The catecholamine-sensitive adenylate cyclase system appears to be comprised of at least three components; the beta-adrenergic receptor (R component), the catalytic unit of adenylate cyclase (C component) and a nucleotide regulatory protein (N component), responsible for mediating the effects of guanine nucleotides on the system. Cell fusion techniques were used to investigate the role of these three components in the process of homologous desensitization in the frog erythrocyte. Dicyclohexylcarbodiimide (DCCD) was used to inhibit beta-receptor function in one population of frog erythrocytes, whilst phenyl glyoxal was employed to inactivate the N and C components in a second population of frog erythrocytes. Using Sendai virus to fuse the two types of modified cell, heterologous beta-adrenergic receptor-adenylate cyclase systems were constructed which contained components from each cell type. When beta receptors from cells previously desensitized to catecholamines were coupled to N-C components derived from fresh erythrocytes, the resulting hybrid exhibited a densitized response to isoproterenol. By contrast, when beta-adrenergic receptors from fresh cells were coupled to N-C components derived from desensitized erythrocytes, no decreased responsiveness to isoproterenol was apparent in the hybrid. That this resensitization was the result of the addition of fresh beta-adrenergic receptors was demonstrated in a control experiment. Frog erythrocytes were desensitized simultaneously to catecholamines and prostaglandin E1 and modified with DCCD which inactivates the beta-adrenergic receptor but not the prostaglandin receptor. When fresh beta-adrenergic receptors were supplied by cell fusion to these doubly desensitized erythrocytes, only the beta-adrenergic response was restored to control levels. The response to prostaglandin remained desensitized in the hybrids, indicating that the observed resensitization of catecholamine-stimulated adenylate cyclase activity was specific and was due to the addition of fresh beta-adrenergic receptors. These data suggest that in the frog erythrocyte, homologous desensitization is primarily the result of receptor-related alterations.

Adenylyl Cyclases↗
PubMed1987

Involvement of central alpha-pressor and beta-depressor adrenoceptors in the cardiovascular response to intracerebroventricular catecholamines in the rat.

Microinjections of catecholamines were performed into the lateral ventricle of anesthetized and unanesthetized rats and the blood pressure effects recorded prior to or after the administration of pharmacological antagonists. Injections of 20-100 micrograms normetanephrine (alpha-agonist) produced only pressor responses in both groups of animals. Injections of 10-20 micrograms of norepinephrine (preferentially an alpha-agonist) produced mainly pressor in awake and only depressor responses in anesthetized animals, whereas injections of 10-20 micrograms of epinephrine (preferentially a beta-agonist) produced only depressor responses in both groups of animals. Intracerebroventricular pretreatment with the beta-blocker propranolol (40-100 micrograms) blocked the depressor responses to the catecholamines or even reverted them into clear pressor response. Pretreatment with the alpha-blocker phentolamine (100 micrograms) reduced the pressor effects induced by the intraventricular injection of catecholamines. The existence of central alpha-pressor and beta-depressor mechanisms mediating the blood pressure responses to the intracerebroventricular administration of catecholamines is proposed.

Animals↗
PubMed1982

Catecholamines in head and body blood of eels and rats.

1. When compared with other vertebrates, the circulating titers of norepinephrine and epinephrine of the yellow eel are very low. 2. The ratio of the catecholamine titers in the eel differs from that reported for other vertebrates. 3. Following decapitation, the titers of the catecholamines are higher in head blood than in body blood of both unanesthetized and anesthetized eels. In decapitated rats, only the dopamine titer is higher in head blood. 4. As in the lamprey, agitation stress causes a drop of circulating catecholamines. However, other forms of stress cause the expected increase. 5. It appears that many data on catecholamines in both brain and circulation of vertebrates in general have been influenced by stress effects.

Animals↗
PubMed1983

Localization of substance P- and enkephalin-like immunoreactivity in relation to catecholamine-containing cell bodies in the cat dorsolateral pontine tegmentum: an immunofluorescence study.

The distribution of tyrosine hydroxylase-, substance P- and enkephalin-immunoreactive neurons in the cat dorsolateral pons was studied using the indirect immunofluorescence method of Coons. To allow for the visualization of substance P- and enkephalin-immunoreactive cell bodies, colchicine was injected either in the ventricular space or in the cerebral tissue. The distribution of the tyrosine hydroxylase-immunoreactive cell bodies corresponded with the well-known distribution of catecholamine cells in this area of the brain. The observation of adjacent sections treated separately with tyrosine hydroxylase- and enkephalin-antiserum revealed that most catecholaminergic cells contain enkephalin-immunoreactivity. In addition to this catecholamine-enkephalin cell population, a moderate number of substance P-immunoreactive cell bodies was found in dorsolateral pons. The peribrachial nuclei were found to be densely supplied with substance P- and enkephalin-immunoreactive fibers, whereas the medial subdivisions, which contain the majority of the catecholamine cells in the dorsolateral pons, display a moderate number of immunoreactive fibers. These results are suggestive of interactions between peptide-containing and catecholaminergic neurons and also between-peptide-containing and non-catecholamine-containing neurons in the cat dorsolateral pons.

Animals↗
PubMed1986

Contrasting monoamine oxidase activity and tyramine induced catecholamine release in PC12 and chromaffin cells.

PC12 (phaeochromocytoma derived) cells possess the catecholamine synthesizing enzymes as well as the ability to store and release the catecholamines in response to K+. However, their monoamine oxidase activity and catecholamine release in response to tyramine has not been examined previously. PC12 cells have monoamine oxidase activity which oxidizes type A (noradrenaline and serotonin) and type A-B (dopamine, tyramine and kynuramine) substrates, and is selectively inhibited by clorgyline (IC50 approximately 10(-6) M). In contrast, PC12 cell monoamine oxidase hardly oxidizes phenylethylamine a type B substrate, and is relatively insensitive to inhibition by the selective monoamine oxidase type B inhibitor, 1-deprenyl (IC50 approximately 10(-6) M). By the above criteria it is apparent that the monoamine oxidase in PC12 is solely type A. The kinetics of the oxidase are similar to those of monoamine oxidase type A reported in other tissues including the adrenergic neuron, having apparent Km values of 400, 280, 170 and 227 microM for noradrenaline, dopamine, serotonin and tyramine. The apparent Km value for phenylethylamine is 235 microM. On the other hand, isolated chromaffin cells have the B form of monoamine oxidase with high affinity (Km approximately 25 microM) for phenylethylamine and low affinities for noradrenaline (Km approximately 1100 microM) and adrenaline (Km approximately 1700 microM). This enzyme form is selectively inactivated by the monoamine oxidase type B inhibitor, 1-deprenyl. In similar fashion to peripheral adrenergic neurons, PC12 cells share the capacity to express a tyramine releasable pool of catecholamines, a property entirely lacking in mature cultured chromaffin cells, even though the latter cells are capable of taking up tyramine by a cocaine sensitive process.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Gland Neoplasms↗
PubMed1988

Binding of [3H]phencyclidine to adrenal medullary cells: inhibition of 22Na influx, 45Ca influx, 86Rb efflux and catecholamine secretion caused by carbachol and veratridine.

In bovine adrenal medullary cells, phencyclidine inhibited carbachol-induced influx of 22Na, 45Ca and secretion of catecholamines in a concentration-dependent manner with a similar potency (IC50 7.0 microM). Phencyclidine also suppressed veratridine-induced influx of 22Na, 45Ca and secretion of catecholamines (IC50 60.0 microM). High K-induced 45Ca influx and catecholamine secretion were not affected by phencyclidine. In the cells preloaded with 86Rb (an alternative tracer for 42K), phencyclidine inhibited the efflux of 86Rb caused by carbachol (IC50 10.0 microM) or by veratridine (IC50 56.0 microM), but had no effect on high K-induced 86Rb efflux. [3H]Phencyclidine bound specifically to adrenal medullary cells, and binding was saturable, reversible and with two different equilibrium dissociation constants (4.3 and 77.4 microM). In a competition experiment, the specific binding of [3H]phencyclidine was not inhibited by carbachol, muscarine, D-tubocurarine, hexamethonium, tetrodotoxin, veratridine and scorpion venom. The present findings suggest: (1) phencyclidine does not inhibit voltage-dependent Ca channels and Ca-dependent K channels; (2) phencyclidine binds to two populations of sites, each of which is functionally linked to nicotinic receptor-ion channel complex and to voltage-dependent Na channels, and inhibits Na influx caused by carbachol and veratridine. Inhibition of Na influx by phencyclidine leads to the reduction of Ca influx, K efflux and catecholamine secretion caused by carbachol and veratridine.

Adrenal Medulla↗
PubMed1990

The secretion of catecholamines, chromogranin A and neuropeptide Y from the adrenal medulla of the cat via the adrenolumbar vein and thoracic duct: different anatomic routes based on size.

Secretion of the adrenal medulla was stimulated in nine cats by insulin-induced hypoglycemia. Levels of catecholamines (mol. wt 153-183), neuropeptide Y (mol. wt 4254) and chromogranin A (mol. wt 48,000) were measured in concurrently collected samples of adrenolumbar venous blood and thoracic duct lymph for up to 4 h following insulin administration. Insulin-induced hypoglycemia elicited an increase in the secretion of catecholamines, which reached peak levels in the adrenolumbar venous plasma at 1.5-2 h and in the lymph at 2.5 h. Although catecholamines were the most numerous measured molecules in the lymph, levels of norepinephrine and epinephrine were 75-250-fold less than those found in the adrenolumbar venous plasma. Neuropeptide Y in the adrenolumbar venous plasma reached peak levels between 1 and 1.5 h; at this time approximately 20% of the peak venous amount was detected in the lymph. Chromogranin A was found in approximately equal amounts in both plasma and lymph; the peak level in the plasma occurred at 1.5-2 h, while that in the lymph was reached at 2-3 h. We suggest that the size of a molecule influences the route it takes following exocytosis from the chromaffin vesicle. Smaller molecules such as catecholamines may pass directly into the circulation, while larger molecules such as chromogranin A may be temporarily sequestered in the interstitial space before passing into the lymph, and hence into the circulation.

Adrenal Medulla↗
PubMed1992

Mechanism through which GABAA receptor modulates catecholamine secretion from bovine chromaffin cells.

The actions and mechanism of GABAergic modulation of catecholamine secretion from isolated bovine chromaffin cells were investigated. The GABAA receptor agonist muscimol induced a fast rise in cytosolic [Ca2+]. The mean peak increase was 290 +/- 30 nM over basal levels. The increase in cytosolic [Ca2+] was abolished in the absence of extracellular [Ca2+] and was blocked by the GABAA antagonist bicuculline and the dihydropiridine nifedipine. Muscimol also elicited the release of catecholamines and increased the bisoxonol fluorescence indicating a cell depolarization. The [Ca2+] entry was well correlated with muscimol-evoked catecholamine secretion. When cells were treated with muscimol and a second secretagogue, a biphasic behavior was revealed. Muscimol enhanced the catecholamine release evoked by low concentrations of nicotine or K+, whereas release obtained at high concentrations of nicotine or K+ was actually inhibited. When the muscimol effect on membrane potential was studied in the presence of low K+ or nicotine concentrations, an enhancement of the bisoxonol fluorescence was observed. This effect was reversed at high concentrations of both K+ and nicotine. Measurement of 36Cl- fluxes showed an increase in membrane permeability to Cl- during muscimol stimulation. The influx or efflux in Cl- was dependent on membrane potential. In normal conditions, with a K+ concentration of 5.4 mM, a Cl- efflux was observed by both radiometric techniques, with 36Cl- and by the use of the chloride-sensitive fluorescent probe 6-methoxy-N-(3-sulphopropil)quinolinium, as indicator of intracellular Cl-. At high nicotine (20 mM) or K+ concentrations (105 mM) a Cl- influx was observed using 6-methoxy-N-(3-sulphopropil)quinolinium.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Distribution of dopamine-containing neurons and fibres in the feline medulla oblongata: a comparative study using catecholamine-synthesizing enzyme and dopamine immunohistochemistry.

The distribution of dopamine-immunoreactive neurons and fibres in the feline medulla oblongata was examined by immunocytochemistry with antisera to the catecholamine-synthesizing enzymes tyrosine hydroxylase, dopamine-beta-hydroxylase and phenylethanolamine-N-methyltransferase, and with antisera to the catecholamines dopamine and L-dihydroxyphenylalanine. Neurons immunoreactive for the catecholamine-synthesizing enzymes were found in two regions of the medulla, the ventrolateral A1 region and the dorsomedial A2 region. Double-staining studies with antisera to the enzymes indicated that a population of neurons within both regions were immunoreactive for tyrosine hydroxylase but not dopamine-beta-hydroxylase or phenylethanolamine-N-methyltransferase, implying that they synthesize dopamine. Studies using the dopamine antisera demonstrated the presence of dopamine-immunoreactive neurons in both the ventrolateral and dorsomedial regions of the medulla; in the dorsomedial region, they were found in the area postrema, nucleus tractus solitarius and dorsal motor vagal nucleus, mainly at levels caudal to the obex. Dopamine-immunoreactive fibres were found in several areas of the medulla including the nucleus tractus solitarius, inferior olive, dorsal motor vagal, spinal trigeminal, hypoglossal, cuneate, gracile, and raphe nuclei. Double-staining studies with antisera to dopamine and dopamine-beta-hydroxylase revealed a population of cells immunoreactive for dopamine alone. The presence of some double-stained neurons, however, implies some cross-reactivity of the dopamine antiserum with noradrenaline or adrenaline and/or recognition of dopamine present as a metabolic intermediary in some noradrenergic neurons. No L-dihydroxyphenylalanine-immunoreactive neurons were found in the medulla, although fibres were seen. These data provide evidence for the existence of catecholamine neurons which utilize dopamine as a final synthetic product within the medulla oblongata.

Animals↗
PubMed1982

Catecholamines and serotonin in rat frontal cortex after PCPA and 6-OHDA: absolute amounts and ratios.

The catecholamines dopamine, epinephrine and norepinephrine, as well as the indoleamine serotonin were measured using radioenzymatic assays, in the frontal cortex of normal rats and of rats in which serotonin synthesis had been inhibited with p-chlorophenylalanine. Besides serotonin, norepinephrine levels were significantly reduced, thus changing the monoamine ratios. To further evaluate these changes, two models of catecholaminergic deafferentation were analyzed, i.e., the massive catecholamine depletion induced by intraventricular 6-OHDA and the more selective norepinephrine deafferentation, obtained by microinjecting 6-OHDA in the dorsal noradrenergic bundle. The results are interpreted in relation to the functional interactions between the catecholamines and between the catecholamines and serotonin.

Animals↗
PubMed1982

Acetylcholinesterase in pontomedullary catecholamine neurons of the adult albino rat.

This study investigated the cholinesterasic reactivity of catecholamine neurons in the rat hindbrain with the aid of a two-step histochemical procedure. First, catecholamine cells were visualized by their formaldehyde/glutaraldehyde induced specific histofluorescence and then poststained in the same tissue with a thiocholine technique for acetylcholinesterase (AChE). Processing the vibratome-sectioned tissue in phosphate buffer subsequent to initial aldehyde fixation permitted satisfactory preservation of both amine fluorophores and esterasic reactivity. Our results, in both randomly sampled and serially sectioned material, unequivocally establish the presence of AChE in all pontomedullary cell groups emitting catecholamine fluorescence, the majority of which are known to consist of noradrenaline perikarya. Hence in contrast to previous reports the occurrence of AChE in central noradrenaline neurons appears to be generalized. The intensity of histofluorescence and esterasic staining were uncorrelated in most regions. It remains for future study to determine whether AChE in brain catecholamine neurons indicates their cholinoceptivity or subserves the catabolism of other neuromediators such as substance P.

Acetylcholinesterase↗
PubMed1989

Inhibition of ischemia-induced brain catecholamine alterations by clonidine.

The effect of clonidine, an alpha 2-agonist, on ischemia-induced alterations in brain catecholamine and metabolite levels was studied in Mongolian gerbils subjected to 180 min of unilateral cerebral ischemia. The gerbils were randomly assigned to four treatment groups: sham-operated or unilateral carotid lesion; each pretreated with clonidine 0.4 mg/kg IP, or untreated. All animals were neurologically assessed and categorized as asymptomatic, neurological deficit or seizure activity at the time of sacrifice. Hemispheric levels of noradrenaline (NA), dopamine (DA), homovanillic acid (HVA), and 3,4-dihydroxyphenylacetic acid (DOPAC) were measured using high pressure liquid chromatography with electrochemical detection. No changes from control were found in animals that remained asymptomatic regardless of treatment. In untreated gerbils that exhibited neurological deficits, marked reductions in both NA and DA and increases in HVA occurred in the ischemic hemisphere. These alterations were greater in gerbils that developed seizures during the observation period. Ischemic animals pretreated with clonidine did not show any significant alterations in catecholamine or metabolite levels from clonidine-treated, sham-operated controls in spite of the presence of neurological deficits. Although significant reductions in NA and DA still occurred in pretreated animals that developed seizures, the changes were markedly less than in untreated gerbils. These results indicate that alpha 2-adrenoceptor stimulation is an effective approach for inhibition of ischemia-induced brain catecholamine alterations, and thus may provide a useful method for assessing the role of catecholamine release in the production of acute ischemic neuronal damage.

3,4-Dihydroxyphenylacetic Acid↗