Chemical sympathectomy and diurnal fluctuations of noradrenaline calorigenic action in the rat

In the rat, in which a diurnal fluctuation of the sensitivity to noradrenaline was previously found, the effect of injected 6-hydroxydopamine (6-OHDA) was investigated. The heat production and catecholamines contents in the interscapular brown adipose tissue, heart and adrenals were measured. Chemical sympathectomy induces a disappearance of diurnal fluctuation in the sensitivity to injected noradrenaline. In these animals a lower capacity for heat production was found. However, a significant calorigenic effect of injected noradrenaline in 6-OHDA-treated animals was still present. In sympathectomized animals a depletion of noradrenaline from interscapular brown adipose tissue and the heart was observed. Besides, a change in adrenaline/noradrenaline ratio was found in the adrenals.     

Alteration of antioxidant status following sympathectomy: Differential effects of modified plasma levels of adrenaline and noradrenaline

The influence of altered levels of endogenous catecholamines following adrenalectomy or 6-hydroxydopamine (6-OH) treatment (alone or in combination) on enzymatic (glutathione reductase, catalase, glutathione peroxidase and Cu,Zn superoxide dismutase) and non-enzymatic (glutathione) antioxidant components of heart, liver, kidney, lung and erythrocytes in male Wistar rats was investigated. Functional antioxidant status was assessed in terms of susceptibility to t-butylhydroperoxide-induced sulfhydryl group oxidation (an indirect measure of glutathione depletion) and lipid peroxidation, as measured by thiobarbituric acid-reactive substance (TBARS) formation. Reduced levels of adrenaline and noradrenaline resulted from adrenalectomy and 6-OH treatment, respectively, while a combination of these treatments led to a reduction in the levels of both catecholamines. Adrenalectomy was associated with alterations in glutathione reductase activity in the heart and liver (increased). 6-OH treatment alone produced an elevation in glutathione reductase activity only in the heart. In adrenalectomized animals, 6-OH treatment produced no further increases in glutathione reductase activities of heart or liver. In lung, however, the combination of adrenalectomy and 6-OH treatment caused an elevation in both glutathione peroxidase and glutathione reductase activities. Glutathione levels of liver alone were elevated following adrenalectomy, while those of erythrocytes and liver (but not other tissues investigated) were increased by the combination of adrenalectomy and 6-OH treatment. The kidney was relatively resistant to the effects of sympathectomy and showed no changes in any of the antioxidant components measured. Adrenalectomy alone or in combination with 6-OH produced an increase in susceptibility to peroxide-induced sulfhydryl group oxidation only in the heart. 6-OH treatment caused a reduction in peroxide-induced TBARS formation only in the kidney. Both adrenalectomy and the combination of adrenalectomy and 6-OH treatment were associated with reduced TBARS formation in the liver, lung and kidney, but not heart. Results from this study demonstrate that the effects of sympathectomy on antioxidant status vary among tissues. Differences between adrenalectomy and 6-OH treatment on antioxidant components are suggestive of differential actions of adrenaline and noradrenaline on tissue antioxidant status which may have important implications under conditions associated with elevations in levels of these catecholamines including chronic stress and myocardial infarction.     

Epinephrine and dopamine colocalization with norepinephrine in various peripheral tissues: guanethidine effects

Chemical sympathectomy with guanethidine (Gnt) selectively destroys the postganglionic noradrenergic neurons, whereas dopaminergic fibers and nonneural catecholamine-secreting cells are spared. As a result, the relative proportions of norepinephrine (NE), epinephrine (E), and dopamine (DA) in tissues can be differentially affected. This study was done to show the possible differences in the relative amount of catecholamines in some organs and tissues that might indicate the nature of the secretory cells from which they originate. The contents of NE, E, and DA were assessed in rats neonatally treated with Gnt. Gnt-treated rats showed significantly lower levels of NE (P < 0.01) in all tissues except the adrenal gland and paraganglia. Epinephrine was present in all tissues with mean levels below 25 ng/g, with the exception of the adrenal gland (700 microg/gland) and paraganglia (100 ng/g). Only the heart showed lower values in Gnt-treated rats. Mean DA levels were also very high in paraganglia (530 ng/g). In the Gnt-treated rats, DA levels fell practically to zero except in the duodenum, mesentery, and adrenal, whereas there were high levels in the paraganglia, which were significantly different from controls. The results suggest that the three catecholamines are contained mainly in noradrenergic sympathetic fibers of muscle, white adipose tissue, heart, liver, pancreas, and spleen. The duodenum and mesentery may have dopaminergic fibers or E- and DA-containing nonneural cells. Hepatic-vagus paraganglia contain all the catecholamines in relatively high amounts in nonneural cells, and Gnt treatment raises DA levels without affecting the other amines.     

Changes in nitric oxide in heart of intact and sympathectomized rats of different age

Nitric oxide production in heart tissues of rats of different age in the norm and after pharmacological sympathectomy was studied by electron spin resonance spin-trapping. Rats at the age of 14, 21, 70, and 100 days were used in the experiment. The concentration of nitric oxide produced in rat heart tissues proved to considerably decrease during ontogeny. Pharmacological sympathectomy notably decreased nitric oxide production in the heart in 14-and 21-day-old rats: the nitric oxide concentration in the spin trap as well as the level of R and T conformers of hemoglobin nitrosyl complexes decreased. In 70-day-old rats, pharmacological sympathectomy had no notable effect on the level of nitric oxide-containing paramagnetic complexes.     

Cardiovascular, metabolic and endocrine effects of chemical sympathectomy and of adrenal demedullation in fetal sheep

A procedure in fetal sheep for causing peripheral sympathectomy by regular intravascular guanethidine sulphate administration and for causing adrenal demedullation by intragland injection of acid formalin is reported. Demedullation substantially removed adrenaline from the fetal circulation, but has a small effect only on noradrenaline. Plasma noradrenaline levels were depressed by 50% when demedullated fetuses were also subject to peripheral sympathectomy by guanethidine sulphate treatment. This provides some evidence that the paraganglia in the sheep fetus contributes to resting plasma catecholamines. Furthermore the ability of adrenal demedullation to increase markedly this pool of extra-adrenal chromaffin tissue indicates that in the fetus adrenal activity regulates the growth of these para-aortic bodies. In response to sympathectomy plasma vasopressin concentrations rose substantially, whilst adrenal demedullation caused a small rise. Demedullation and sympathectomy depressed fetal plasma glucose and elevated plasma cortisol. In both sympathectomised and adrenal demedullated fetuses resting heart rate and blood pressure was not depressed. However in those with a depleted peripheral nervous system periods of cardiovascular instability were apparent after 2-3 days of treatment with guanethidine sulphate. Hence there were regular episodes where fetal blood pressure and heart rate fell sharply followed 60-90s later by very large increases in blood pressure sustained for up to 10 min and associated with substantial production of plasma vasopressin and catecholamines. These results show that fine cardiovascular control in the fetus requires an intact sympathetic system as the endocrine system is too slow responding to effectively maintain reflex vascular control.     

Effects of clinical death and pre-administered inderal on adrenoreactivity of the heart in post-resuscitation period

Acute lethal blood loss followed by resuscitation was found to decrease noradrenaline and increase epinephrine levels in heart muscle in experiments on mongrel male rats which significantly increase heart beta-adreno-receptors sensitivity to exogenous noradrenaline. Preliminary inderal injection prevents excessive heart beta-adreno-receptors stimulation by catecholamines, considerably reduces post-resuscitation rhythmic disturbances and prevents ventricular fibrillation which significantly decreases early post-resuscitation lethality.     

Differential Effects of Chemical Sympathectomy on Expression and Activity of Tyrosine Hydroxylase and Levels of Catecholamines and DOPA in Peripheral Tissues of Rats

Tyrosine hydroxylase (TH) mRNA and activity and concentrations of 3,4-dihydroxyphenylalanine (DOPA) and catecholamines were examined as markers of sympathetic innervation and catecholamine synthesis in peripheral tissues of sympathectomized and intact rats. Chemical sympathectomy with 6-hydroxydopamine (6-OHDA) markedly decreased norepinephrine and to a generally lesser extent TH activities and dopamine in most peripheral tissues (stomach, lung, testis, duodenum, pancreas, salivary gland, spleen, heart, kidney, thymus). Superior cervical ganglia, adrenals and descending aorta were unaffected and vas deferens showed a large 92% decrease in norepinephrine, but only a small 38% decrease in TH activity after 6-OHDA. Presence of chromaffin cells or neuronal cell bodies in these latter tissues, indicated by consistent expression of TH mRNA, explained the relative resistance of these tissues to 6-OHDA. Stomach also showed consistent expression of TH mRNA before, but not after 6-OHDA, suggesting that catecholamine synthesizing cells in gastric tissue are sensitive to the toxic effects of 6-OHDA. Tissue concentrations of DOPA were mainly unaffected by 6-OHDA, indicating that much of the DOPA in peripheral tissues is synthesized independently of local TH or sympathetic innervation. The differential effects of chemical sympathectomy on tissue catecholamines, DOPA, TH mRNA and TH activity demonstrate that these variables are not simple markers of sympathetic innervation or catecholamine synthesis. Other factors, including presence of neuronal cell bodies, parenchymal chromaffin cells, non-neuronal sites of catecholamine synthesis and alternative sources of tissue DOPA, must also be considered when tissue catecholamines, DOPA and TH are examined as markers of sympathetic innervation and local catecholamine synthesis.     

Effect of sympathectomy and demedullation on increased myenteric and dorsal vagal complex Fos-like immunoreactivity by cholecystokinin-8

Chemical sympathectomy with daily, intraperitoneal (IP) injections of guanethidine sulfate to adult rats, attenuated myenteric, but not dorsal vagal complex (DVC) Fos-like immunoreactivity (Fos-LI) by cholecystokinin-8 (CCK). This technique destroys only 60-70% of the sympathetic neurons, and spares the hormonal source of catecholamines, the adrenal medulla. The goal of the current study is to evaluate the effect of complete sympathectomy or destroying 100% of the sympathetic neurons by injecting guanethidine to 1-day-old pups (40 mg/kg daily for 5 weeks), and surgically removing the adrenal medulla. In the DVC, demedullation and sympathectomy-demedullation increased Fos-LI by CCK in the area postrema and nucleus of the solitary tract, but sympathectomy-demedullation increased it only in the area postrema. In the myenteric plexus, sympathectomy increased this response in the duodenum, and demedullation increased it in the duodenum and jejunum. On the other hand, sympathectomy-demedullation attenuated myenteric Fos-LI in the jejunum. These results indicate that catecholamines may play an inhibitory role on the activation of the DVC neurons by CCK. In the myenteric neurons, however, catecholamines may have both inhibitory and excitatory roles depending on the level of the intestine e.g., duodenum vs. jejunum. This may also indicate that CCK activates the enteric neurons by different mechanisms or through different pathways.     

Effects of dosed sympathectomy on the development of adaptation-compensation reaction of C-cells of the thyroid gland and chromaffin cells of the adrenal glands in young rats

Using radioimmunological, morphometrical, electron microscopic and luminescent methods, comparative analysis of thyroid C-cells and adrenal chromaffin cells has been carried out at guanethidine sympathectomy in young rats. Significant decrease of functional activity of C-cells with concomitant hyperplasia of C-cells population under blockade of sympathetic influences has been revealed. Compared to C-cells, adrenal chromaffinocytes of sympathectomized rats possess higher degree of structural-functional mobilization and are characterized by intensive secretion of catecholamines directed at restoration of tissue neurotransmitter deficit.     

Dopamine and norepinephrine in the alimentary tract changes after chemical sympathectomy and surgical vagotomy

The aim of this study was to examine the distribution of dopamine and norepinephrine in the proximal alimentary tract of the rat and to assess the contributions of sympathetic and vagal fibers to the tissue concentrations of both catecholamines. Tissues were extracted in perchloric acid and the catecholamines were separated by high pressure liquid chromatography and detected electrochemically. In untreated rats (controls) both catecholamines were concentrated in the gastric muscle but norepinephrine levels were 6-8 times higher (corpus, dopamine 35 +/- 7 ng . g-1, norepinephrine 265 +/- 50 ng . g-1, mean +/- SE, n = 6). In the mucosa norepinephrine concentrations were 10-12 times higher (corpus, dopamine 12 +/- 3 ng . g-1, norepinephrine 140 +/- 26 ng . g-1). Chemical sympathectomy (6 hydroxydopamine, 100 mg . kg-1 ip 3 days) significantly reduced dopamine concentrations in muscle and norepinephrine in muscle, mucosa, pylorus and duodenum. In all tissues the effects on norepinephrine were greater. Surgical vagotomy significantly reduced dopamine concentrations in the gastric muscle, but not the mucosa. Norepinephrine concentrations in the stomach of vagotomized rats were significantly reduced only in the pylorus. Differences in the relative concentrations of dopamine and norepinephrine in gastric tissues of the normal rat and differences in the effects of sympathectomy and vagotomy suggest that dopamine and norepinephrine exist, to an extent, in separate populations of cells and that dopamine is not merely a precursor of norepinephrine. Gastric mucosal dopamine, which was mainly unaffected by either treatment, may exist in APUD cells.     

Neuropeptide tyrosine (NPY)-induced potentiation of the pressor activity of catecholamines in conscious rats

IV bolus administration of 2.5-50 micrograms NPY (0.6-12.5 nmol) to conscious rats produced a dose- and time-dependent increase in systolic and diastolic blood pressure. Following priming with 2.5 micrograms NPY, or larger doses, the subsequent administrations of noradrenaline produced pressor responses that were potentiated both in magnitude and duration. The NPY-induced potentiation of the pressor response to noradrenaline was dose-dependent and extended to the pressor action of adrenaline and angiotensin II but not to the hypotensions produced by bradykinin or isoproterenol. The potentiation was not related to the fact that multiple doses of catecholamines were repeated. Reserpine did not substantially modify the NPY-induced potentiation of the pressor activity of the catecholamines. Chemical sympathectomy following 6-hydroxydopamine caused a marked supersensitivity to the catecholamines and NPY but obliterated the NPY-induced potentiation of the pressor effect of adrenaline. Nifedipine reduced the pressor action of the catecholamines and NPY but did not attenuate the NPY-induced potentiation of the pressor action of catecholamines. It is concluded that the acute pressor effect of NPY and of the potentiation of the catecholamine pressor effects involve different mechanisms.     

Effect of sympathectomy on the heart pump function in rats during postnatal ontogenesis

The influence of guanetidine sympathectomy (30 mg/kg) on the heart pump function in rats during 3 weeks in postnatal ontogenesis has been investigated. Sympathectomy restrains age-dependent establishment of stroke volume, cardiac output and heart rate. The adaptation effects of regular physical training do not develop in the animals with sympathectomy, i.e. heart rate does not decrease and stroke volume does not increase. The initial stage of adaptation of the sympathectomized animals to physical training is accompanied by decrease in stroke volume and remarkable increase in heart rate which indicates the reduction of contractile activity in the myocardium.     

Development of the linkage of beta-adrenergic receptors to cardiac hypertrophy and heart rate control: neonatal sympathectomy with 6-hydroxydopamine

Presynaptic neural projections are thought to participate in the maturation of postsynaptic sensitivity to neurotransmitters. In the current study, we have examined the effects of sympathectomy with 6-hydroxydopamine on the ontogeny of the linkage of beta-adrenergic receptors to cardiac growth and heart rate control in the rat. Destruction of sympathetic projections at birth compromised the ability of beta-receptor stimulation to evoke cardiac hypertrophy, a defect which persisted into young adulthood. The chronotropic response to beta-receptor activation, assessed by acute challenge with a submaximally-effective dose of isoproterenol, also exhibited a slowed development, but did eventually achieve normal sensitivity. In contrast, neonatal sympathectomy had only minor effects on resting heart rate, basal heart rate (the intrinsic rate in the absence of autonomic input) or maximal heart rate; these animals also showed beta-receptor desensitization of chronotropic action in response to chronic isoproterenol treatment. Chronic isoproterenol treatment itself lowered the basal heart rate, regardless of whether animals were normal or sympathectomized. Thus, during critical developmental periods, sympathetic input to beta-receptors selectively programmes the linkage between postsynaptic receptors, tissue growth and heart rate.     

Central catecholamine depletion inhibits peripheral lymphocyte responsiveness in spleen and blood

Experimental and clinical evidence has demonstrated extensive communication between the CNS and the immune system. To analyse the role of central catecholamines in modulating peripheral immune functions, we injected the neurotoxin 6-hydroxydopamine (6-OHDA) i.c.v. in rats. This treatment significantly reduced brain catecholamine content 2, 4 and 7 days after injection, and in the periphery splenic catecholamine levels were reduced 4 days after treatment. Central catecholamine depletion induced an inhibition of splenic and blood lymphocyte proliferation and splenic cytokine production and expression (interleukin-2 and interferon-gamma) 7 days after injection. In addition, central treatment with 6-OHDA reduced the percentage of spleen and peripheral blood natural killer (CD161 +) cells, and T-cytotoxic (CD8 +) cells in peripheral blood. The reduction in splenocyte proliferation was not associated with a glucocorticoid alteration but was completely abolished by prior peripheral sympathectomy. These data demonstrate a crucial role of central and peripheral catecholamines in modulating immune function.     

Effect of chemical sympathectomy on the development of DOCA-salt hypertension in rats

Structurally based resistance and vascular reactivity of the posterior body to noradrenaline were studied in normotensive rats and rats with DOCA-salt hypertension. The hypertension was induced in rats with intact sympathetic nervous system and in rats subjected to neonatal sympathectomy with guanethidine. During the prehypertensive stage, vascular sensitivity of the smooth muscles to noradrenaline was enhanced, with structural lesions being observed only in steady hypertension. Elevation of arterial pressure was accompanied by an increased vascular response to the stimulation of the sympathetic nerves. Sympathectomy prevented arterial pressure elevation and structural alterations in the vessels.     

An improved glyoxylic acid technique for the histochemical localization of catecholamines in brown adipose tissue

Summary A glyoxylic acid method using cryostat sections to demonstrate catecholaminergic fibres of the central nervous system was modified to show the extent of the adrenergic innervation in rat brown adipose tissue. It revealed prominent interlacing fluorescent parenchymal fibres surrounding individual adipocytes. The density of this network of fine fibres was not evident using earlier techniques. The new method also confirmed the dense networks of adrenergic fibres associated with arterial vessels. Its specificity was verified by simultaneously performing radioenzymatic determinations of tissue catecholamine levels and histochemical studies of brown adipose tissue from normal and sympathectomized rats. Chemical sympathectomy with 6-hydroxydopamine resulted in a pronounced decrease in brown adipose tissue and heart catecholamine (noradrenalin and dopamine) levels. Significantly, in brown adipose tissue of sympathectomized animals no fluorescence could be detected in terminal nerves of either the parenchyma or those of vascular smooth muscles. Nevertheless, some intense fluorescence was seen in axon bundles. The findings suggest that catecholamines of the parenchymal innervation form a larger proportion of the total catecholamine content of brown adipose tissue than was previously believed, provide stronger support for direct control of the function of multilocular adipocytes, and also confirm unpublished data reporting considerable dopamine content in brown adipose tissue.     

Chemical sympathectomy alters food intake and thermogenic responses to catecholamines in rats

It has been suggested that the sympathetic nervous system contributes to the short-term control of feeding. The adrenergic innervation of some splanchnic organs seems to be especially involved in such processes, since catecholamines reduce feeding only when injected intraperitoneally or intraportally. In this work, the effects of neonatal sympathetic denervation with guanethidine (Gnt) upon food intake were assessed in adult rats. Gnt-treated male rats had lower body weight gain. The hypophagic response to intraperitoneal (ip) norepinephrine was 70% higher in Gnt-treated animals as compared to controls (P < 0.05); that of epinephrine (E) by 33% (P < 0.05) and that of isoproterenol was not significantly modified. As in normal rats, the hypophagic effect was much stronger after ip than after intramuscular (im) administration (P < 0.05). On the other hand, resting oxygen consumption (VO2) was consistently lower in denervated animals. Ip E administration did not modify VO2, while im E caused increased motor activity and VO2 (P < 0.05). In contrast to control rats, the respiratory exchange ratio in ad libitum fed Gnt rats did not decrease after Ip E administration, suggesting a lack of effect upon lipid mobilization. The lower rate of body weight gain induced by neonatal Gnt sympathectomy might be due to lower daily food intake possibly related, in part, to the sensitization of the alpha-adrenergic porto-hepatic response to endogenous catecholamines. Compared with controls, Gnt-treated rats also showed a limited thermogenic capacity not related to feeding, and a greater degree of carbohydrate oxidation, possibly due to a defect in E-induced lipolysis, which is beta-adrenergic.     

Effect of testosterone and 6-hydroxydopamine treatment on the metabolism of catecholamine and 5-hydroxytryptamine in methylcholanthrene-induced prostate carcinoma of rats.

The precursors tyrosine and tryptophan as well as the synthesizing and deaminating enzymes of catecholamines have been identified in methylcholanthrene-induced prostatic carcinoma of rats. Tyrosine hydroxylase, monoamine oxidase, catechol O-methyltransferase, dopamine, 5-hydroxytryptamine, and 5-hydroxyindoleacetic acid seemed to be neoplastic in origin, since electron microscopic studies failed to reveal the presence of any neuronal elements in this squamous epithelial cell carcinoma. Castration of rats significantly reduced the activity of tyrosine hydroxylase and the levels of tyrosine, dopamine, tryptophan, 5-hydroxytryptamine, and 5-hydroxyindoleacetic acid in prostate tumors. The changes appeared to be androgen specific since reintroduction of testosterone restored several of these biochemical parameters virtually to control limits. Chemical sympathectomy induced by 6-hydroxydopamine failed to alter monoamine metabolism; however, the prostatic tumor grown in 6-hydroxydopamine-treated rats showed significantly (32%) less necrosis than those grown in normal animals.     

Rat heart GDNF: effect of chemical sympathectomy

Developmental studies indicate a role for GDNF in survival of motor, autonomic, and sensory neurons. However, no study attempted to demonstrate its participation in autonomic nerve regeneration. In this work, chemical sympathectomy by 6-hydroxydopamine provided the model for assessing heart GDNF expression during denervation and axonal regrowth. A glyoxylic acid-based histochemical technique evaluated the noradrenergic innervation. ELISA determined GDNF levels after concentrating heart homogenates. Light and ultrastructural in situ hybridization and immunocytochemistry were used for identifying cells expressing GDNF mRNA and protein. In control rats, the GDNF cardiac levels were significantly higher in 37-day-old animals in comparison with those aging 60 days. In sympathectomized rats, GDNF cardiac levels were significantly higher 7 days after sympathectomy and dropped to control levels at day 30. GDNF mRNA was expressed in atrial and ventricular myocytes from normal and sympathectomized rats. GDNF immunoreactivity occurred on atrial granules and quantitative analysis in electron micrographs confirmed ELISA-obtained data. In ventricular myocytes gold particles occurred sparsely. These findings constitute the first evidence for GDNF synthesis by cardiomyocytes and postulate a role for this factor soon after cardiac sympathetic denervation, probably in nerve regeneration. In atrial myocytes, GDNF is probably secreted by regulated pathway.     

Histochemical evidence of chemical sympathectomy by guanethidine in newborn rats

Synopsis Guanethidine is known to cause a loss of catecholamines from sympathetically innervated tissues and sympathetic ganglia in adult animals but its effect on newborn animals has not been examined.Newborn rats were injected daily with guanethidine (20 mg/kg body weight) for 8 days. They were killed when 1 month-old along with untreated litter mate controls. Catecholamines were demonstrated in the iris, in the pineal body and in sympathetic ganglia, using the formaldehyde-induced fluorescence method.In the guanethidine-treated rats there was a complete loss of fluorescent nerve fibres from the pineal body and an almost complete loss of similar fibres from the iris. The sympathetic ganglia were reduced to less than 10% of the control ganglia, and the number of nerve cell bodies per unit area was decreased in the ganglion remnants.It is concluded that guanethidine causes, in newborn rats, an irreversible destruction of most sympathetic neurons, i.e. a chemical sympathectomy closely resembling that obtainable in newborn animals by injections of 6-hydroxydopamine or antiserum to nerve growth factor.