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PubMed1985

Influence of subdiaphragmatic vagotomy and brown fat sympathectomy on thermogenesis in rats.

Infusion of rats with insulin (8 U/day via implanted minipump) for 7 days caused a 22% rise in resting oxygen consumption, which was inhibited by acute injection of the beta-adrenergic antagonist propranolol. Insulin treatment produced significant increases in brown fat mass, protein content, and total thermogenic activity (assessed from binding of guanosine diphosphate to isolated brown fat mitochondria), but these responses were inhibited by prior surgical sympathectomy of the tissue. Animals subjected to subdiaphragmatic vagotomy gained more weight than pair-fed, sham-operated controls and showed reductions in total energy expenditure, the acute thermogenic response to a meal and brown adipose tissue activity. Daily injections of insulin (1 U/day) prevented all of these effects of vagotomy. These data demonstrate that the changes in brown fat activity induced by exogenous insulin are mediated by the sympathetic nervous system and that the depressed thermogenesis and brown fat activity associated with vagotomy appear to be due to a relative insulin deficiency and can be reversed by treatment with the hormone.

Adipose Tissue, Brown↗
PubMed1984

Responses of SHR to combinations of chemical sympathectomy, adrenal demedullation, and training.

The single and combined influences of exercise training, chemical sympathectomy (SYMX), and surgical adrenal demedullation (D) were examined in four separate spontaneously hypertensive rat (SHR) groups. SYMX was accomplished by subcutaneous injections of antinerve growth factor (ANGF) over a 5-day period after birth followed by 20 separate injections of guanethidine sulfate during a 27-day period. Measurements of urine, plasma, or tissue levels of catecholamines indicated that these experimental procedures were effective. The animals were exercise trained (T) for 10 wk or longer at 40-60% of their VO2max capacity, and all T groups exhibited longer run times or higher muscle cytochrome oxidase activity; however, only the SHR + T subgroup had a significantly higher VO2max value than its control (NT). Training lowered resting systolic blood pressure (SBP) in the SHR subgroup but normalization of SBP occurred only with SYMX. Interestingly, only the SYMX + T subgroup with intact adrenal glands also had lower SBP values than the NT. The SHR + T and SYMX + T subgroups but not the SYMX + D + T had less cardiac acceleration after ip injections of atropine than their controls. Heavier heart weights were observed only in the SHR + T subgroup; SYMX was associated with lighter heart weights regardless of whether the rats had been T or D. These collective findings demonstrated again the importance of the sympathetic nervous system to an exercise response, suggesting that an intact adrenal medulla was essential for SHR groups to achieve many of the adaptations associated with training.

Adrenal Medulla↗
PubMed1989

Chronic whole body sympathectomy fails to protect ischemic rabbit hearts.

We determined whether chronic chemical sympathetic denervation could protect the rabbit heart against ischemia. Rabbits received 10 mg/kg 6-hydroxydopamine (6-HD) twice during the first week, then 100 mg.kg-1.wk-1 for the following 7 wk. After this interval the rabbits were anesthetized, the chests were opened, and in each a coronary branch was occluded for 45 min followed by reperfusion for 3 h. Collateral flow was determined with radioactive microspheres during coronary occlusion. Flow to the ischemic myocardium of the 6-HD group (0.06 +/- 0.03 ml.min-1.g-1) was not significantly different from that in the control group (0.04 +/- 0.02 ml.min-1.g-1). Infarct size was determined with triphenyltetrazolium chloride staining. Average infarct size calculated as a percentage of risk zone was similar in the 6-HD and control groups (59 +/- 15 and 60 +/- 12%, respectively). We conclude that chronic chemical sympathectomy does not induce collateral growth in the rabbit heart. Furthermore, endogenous catecholamines do not contribute to injury in the ischemic rabbit heart.

Animals↗
PubMed1991

Sympathectomy stimulates capillary but not precapillary growth in hypertrophic hearts.

Sympathetic nerves are known to influence vascular growth, but their role in coronary vascular adaptations to pressure-overload left ventricular (LV) hypertrophy is unknown. Accordingly, regional sympathectomy (SYMX) was produced by painting a ring of phenol on the posterior third of the LV in seven renal hypertensive (Page: 1 kidney, 1 wrap) and seven normotensive (sham: 1 kidney, no wrap) rabbits. Two months later, maximal myocardial blood flow (MBF) following dipyridamole-induced coronary vasodilation was determined with microspheres in the intact anterior and the sympathectomized posterior regions of conscious rabbits. Histomorphometric methods were then utilized to evaluate capillary density (CD), intercapillary distance (ICD), and volume density (VD) of subepicardial and endocardial samples of each region of perfused-fixed hearts. The Page procedure significantly increased systolic blood pressure (+29%) and LV wt/body wt (+20%) above sham rabbits. In both sham and Page groups, MBF was not significantly different between intact and sympathectomized regions within either group. SYMX did not significantly alter CD, ICD, or VD between regions in the sham animals. In contrast, SYMX significantly increased CD (+30%) and VD (+26%) and decreased ICD (-21%) in the subendocardial region of Page animals. Regional SYMX did not alter myocyte cross-sectional area in Page animals. We conclude that SYMX neither 1) significantly increases resistance vessel cross-sectional lumen area in either normal or hypertrophic hearts, nor 2) significantly influences capillary growth in normal hearts, but SYMX does 3) promote capillary growth in hearts undergoing hypertrophy in response to hypertension.

Animals↗
PubMed1993

Guanethidine chemical sympathectomy: spinal cord and sciatic nerve blood flow.

The spinal cord vasculature is innervated by noradrenergic nerve fibers, the role of which in the regulation of regional spinal cord blood flow (RSCBF) is presently unclear. We used the distribution of [14C]butanol to simultaneously measure RSCBF at seven cord levels and the regional blood flow in sciatic nerve (NBF), truncal skin, and biceps femoris muscle. The subjects were control rats and rats that had been given parenteral guanethidine sulfate for 5 wk to induce selective postganglionic "chemical sympathectomy." Flows were measured under basal conditions (group I) and immediately after an arterial hemorrhage (group II). The results indicate that RSCBF was unchanged from control after guanethidine administration in both groups; however, NBF was elevated after guanethidine by 47% in group I and by 41% in group II. We conclude that in the spinal cord as in the brain, sympathetic inflow does not appear to have an important role in the regulation of regional blood flow. Sympathetic inflow appears to partly regulate NBF, however, probably by varying vascular tone.

Animals↗
PubMed1983

Effects of guanethidine sympathectomy on ventromedial hypothalamic obesity.

Since ventromedial hypothalamic (VMH) lesions apparently produce chronic increases in parasympathetic activity and decreases in sympathetic responses, two experiments were performed to determine whether decreases in sympathetic tone alone are sufficient either to produce elements of the VMH syndrome or to potentiate the expression of the syndrome in animals with lesions. In experiment 1, rats that had been injected with guanethidine sulfate for 5 wk (40 mg X kg-1 X day-1) to produce a permanent sympathectomy (SympX) were maintained on a high-fat diet and subsequently subjected to VMH lesions. In experiment 2, adrenal-demedullated animals were treated with guanethidine for 6 wk and then subsequently underwent VMH lesions. SympX in the studies (81 and 85% depletion of superior cervical ganglia neurons, respectively) did duplicate the effects of VMH lesions on salivary gland weights. In neither experiment, however, did SympX alone or in combination with demedullation mimic the effects of VMH lesions on food intake, body weight, or body fat. Determinations of free fatty acids (FFAs) in the experiments confirmed that VMH lesions elevate basal FFA levels, but they also indicated that effective VMH lesions need not impair the FFA mobilization to 2-deoxyglucose challenges as some basomedial hypothalamic lesions do. In addition, experiment 2, which employed a prolonged period of high-fat feeding, revealed that SympX plus adrenal demedullation could potentiate (a 13% increase) the effects of VMH lesions on body weight. The results taken together do not support the conclusion that a preponderance of the VMH syndrome can be accounted for by the type of reduction in sympathetic tone produced by guanethidine.

Animals↗
PubMed1990

Effect of sympathectomy on renal and circulatory action of atrial natriuretic peptide.

Sympathetic nervous system (SNS) involvement in cardiovascular (CV) and renal actions of atrial natriuretic peptide (ANP) was examined in eight chronically instrumented rats. Responses to 90-min atriopeptin II infusion (0.03 then 0.3 micrograms.kg-1.min-1) were compared with those to sodium nitroprusside (NP; 2 + 20 micrograms.kg-1.min-1) before and after sympathectomy (SX) with 6-hydroxydopamine (6-OHDA). The NP-induced drop in blood pressure (BP) was greater after SX (-12 +/- 1% before vs. -24 +/- 2% after SX). In contrast, 6-OHDA altered (blunted) only the bradycardic response to high dose of ANP (-23 +/- 5% before vs. -3 +/- 4% after SX). The decreased BP (-18 +/- 1% before vs. -12 +/- 2% after), depressed cardiac output (CO; -29 +/- 1% before vs. -22 +/- 3% after), and elevated systemic vascular resistance (SVR; 16 +/- 2 vs. 16 +/- 6%) were unchanged (paired t test, P greater than 0.05). The high dose of ANP increased urine flow by 43.2 +/- 7.2 microliters.min-1.100 g body wt-1 and sodium excretion by 1.76 +/- 0.56 mu eq.min-1.100 g body wt-1 but had no effect after SX. These results suggest that while withdrawal of SNS activity contributes to the CO-lowering effect of ANP, it does not mediate its action to elevate SVR. Attenuation of the capacity for reflex sympathoexcitation by SX did not reveal a vasodilator action. The lack of response after SX suggests that ANP's renal excretory actions are mediated in part by withdrawal of SNS activity.

Animals↗
PubMed1995

Chemical sympathectomy and maternal separation affect neonatal stress responses and adrenal sensitivity to ACTH.

The participation of sympathetic adrenal innervation in the control of the neonatal adrenocortical system and in changes in adrenal sensitivity after maternal separation for 24 h was tested in 10- and 23-day-old pups. Chemical sympathectomy by guanethidine (20 mg/kg body wt) decreased basal and stimulated corticosterone compound B (B) secretion without affecting adrenocorticotropic hormone (ACTH) release, abolished the enhanced adrenal sensitivity to ACTH induced by maternal separation in 10-day-old pups, but did not modify adrenal sensitivity following ether stress in 23-day-old pups. Guanethidine treatment did not affect body and adrenal weight or adrenal choline acetyltransferase activity, but it increased tyrosine hydroxylase activity at both ages. Both chronic guanethidine treatment and acute corticotropin-releasing factor immunoneutralization reduced plasma B levels after maternal separation without affecting plasma ACTH levels. Maternal separation in 10-day-old pups enhanced basal and stimulated ACTH and B secretion after exposure to ether vapors and insulin-induced hypoglycemia (IIH). In nonseparated pups, IIH did not stimulate ACTH secretion and caused small increases in B secretion; however, the enhanced response of separated pups to IIH was due to the effects of intraperitoneal injection.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Glands↗
PubMed1991

Influences of chemical sympathectomy and simulated weightlessness on male and female rats.

Maximum oxygen consumption (VO2max) has been shown to be reduced after periods of simulated weightlessness. To assess the role of the sympathetic nervous system in these reductions, Sprague-Dawley rats were either chemically sympathectomized (SYMX) or injected with saline (SHAM) and assigned to head-down suspension (HDS), horizontal restraint with the hindlimbs weight bearing (HWB), or cage-control (CC) conditions. VO2max, run time (RT), and mechanical efficiency (ME) were measured before suspension and on days 7 and 14. Male and female SHAM HDS groups exhibited reduced measures of VO2max (12-13%) after 7 and 14 days, and this decrease was attenuated in the SYMX and HWB rats. HDS resulted in a significant reduction in RT (9-15%) in both the male and female rats, and ME was significantly reduced after HDS in male and female SYMX and male SHAM rats (23-33%) but not in the female SHAM rats. Lesser reductions in ME were observed in the HWB rats. HDS and HWB were associated with lower body, fat-free, and fat masses, which were similar in male and female rats as well as for the SHAM and SYMX conditions. In a related HDS experiment with normal rats, plasma norepinephrine and epinephrine were increased by 53 and 42% after 7 days, but only epinephrine returned to baseline after 14 days. It was concluded that chemical sympathectomy and/or a weight-bearing stimulus will attenuate the loss in VO2max associated with simulated weightlessness in rats despite similar changes in body mass and composition. The mechanism(s) remains unclear at this time.

Adrenal Glands↗
PubMed1996

Sympathectomy induces adrenergic excitability of cutaneous C-fiber nociceptors.

1. The effects of ipsilateral removal of the superior cervical ganglion on the subsequent responsiveness of C-fiber polymodal nociceptors (CPMs) of the ear to close-arterial injections of norepinephrine (NE) were evaluated in adult, anesthetized rabbits. 2. In normal unanesthetized rabbits, the two ears were usually at the same temperature. Immediately after the ganglionectomy, the ipsilateral ear was warmer; however, at the time of electrophysiological recordings (4-23 days) the majority of animals had the ipsilateral ear cooler by > or = 1 degree C, suggestive of denervation supersensitivity. 3. NE (50 ng) did not activate any CPMs (n = 28) from intact animals. 4. Seven of 22 CPMs recorded from sympathectomized ears were activated by NE (50 ng). The responses varied considerably but typically consisted of 2-4 impulses in the 60 s after the NE injection. In some instances, repetitive activity continued for many minutes. Such prolonged discharge differs from the adrenergic responses seen after partial nerve damage. 5. The induction of adrenergic excitability in CPMs by sympathectomy is suggested to be a counterpart to postsympathectomy neuralgia in human beings and a possible part of the mechanism leading to sympathetically related pain states.

Adrenergic Fibers↗
PubMedDate not supplied

Effects of chemical sympathectomy on angiotensin II-induced neointimal growth in the balloon-injured rat carotid artery.

To investigate the role of the sympathetic nervous system in angiotensin II (AngII)-stimulated medial and neointimal smooth muscle cell (SMC) replication, we sympathectomized rats with 6-hydroxydopamine (6-OHDA) in which the left carotid artery was injured by a balloon catheter. Balloon injury is associated with a loss of specific [3H]-prazosin binding. AngII (250 ng/kg/min), infused 2 weeks after balloon injury of the rat left carotid artery, increased systolic blood pressure by approximately 70 mm Hg. There was no effect of 6-OHDA on this pressor response. AngII increased the cumulative 5-bromo-2'-deoxyuridine (BrdU) labeling fraction (LF) in the uninjured right carotid media and the injured left carotid neointima as compared to controls (5.7+/-1.6% vs. 0.4+/-0.1%, p<0.05; 10.6+/-0.9% vs. 5.0+/-0.8%, p<0.05, respectively). 6-OHDA decreased the AngII-induced increase in LF in the media of the uninjured right carotid artery (AngII/6-OHDA 0.9+/-0.2% vs. AngII 5.7+/-1.6%, p < 0.05). 6-OHDA did not decrease the AngII-induced increase in LF in both the injured left carotid media and neointima at 4 weeks after balloon injury. The effects of chemical sympathectomy were comparable with those obtained 12 weeks after balloon injury. Thus, the data show that the sympathetic nervous system mediates the AngII-induced increase in SMC DNA synthesis, but only in the uninjured carotid media. This indicates a differential regulation of AngII-induced SMC replication in injured and uninjured vessels.

Angiotensin II↗
PubMed1976

Effect of chemical sympathectomy and pinealectomy upon gonads of voles (Microtus agrestis) exposed to short photoperiod.

Day length or photoperiod is an important determinant of seasonal breeding or sexual maturation in the vole (Microtus agrestis). Exposure of voles to short (6 h) photoperiods slows gonadal development or causes active gonads to regress. Abolishing pineal activity either by chemical sympathectomy, using 6-hydroxydopamine (6-OHDA), or by surgical pinealectomy, prevents this inhibiting or regressing effect of shor photo period upon gonads. Thus, the pineal gland appears to play a part in the measurement of day length by voles and in the physiological causation of their seasonal breeding.

Animals↗
PubMed1981

Evidence for increased protein synthesis in myocardial microvessels after chronic sympathectomy in the dog.

Using histochemical methods, evidence of increased protein synthesis was observed in microvessels (diameter less than 100 micrometers) from dog hearts which had been sympathectomized 2 weeks earlier when compared to controls. Such evidence consisted of increased staining intensity for the enzyme glucose-6-phosphate dehydrogenase and for the nucleic acids RNA and DNA. Increases in reaction intensities were noted in approximately 30% of the microvessels examined from the sympathectomized hearts, and may imply a vascular proliferation in these hearts. However, since no increase in capillary density was observed in sympathectomized hearts, a vascular proliferation, if it occurred, may have been involved in development of the coronary collateral circulation. These data support previous results indicating that collateral resistances are reduced following chronic cardiac sympathectomy while resistance of the coronary vascular bed itself is not altered.

Animals↗
PubMed1984

Effect of guanethidine-induced sympathectomy on osteoblastic activity in the rat femur evaluated by 3H-proline autoradiography.

Osteoblastic activity in the rat femur was assessed following sympathectomy by injections of guanethidine sulfate from birth to 14 days of age. At ages 30, 45 and 90 days, osteogenesis was monitored by quantitative autoradiography using 3H-proline. Grain counts over periosteal osteoblasts of the femoral diaphysis showed a significant reduction in the uptake of 3H-proline in sympathectomized rats. The results indicate that the sympathetic innervation of bone influences osteoblastic activity and provide support for a role of the autonomic nervous system in the regulation of bone formation.

Aging↗
PubMed1986

Fiber composition of the recurrent laryngeal nerve after experimental vagotomy and sympathectomy. A qualitative study by light and electron microscopy.

A qualitative study of the nerve fiber composition of the recurrent laryngeal nerve of the rat was performed by light and electron microscopy. Various surgical denervation procedures were employed to determine the origin of the variously sized myelinated fibers and the unmyelinated axons present within the nerve. After extracranial vagotomy all myelinated fibers degenerated, whereas some unmyelinated axons remained intact. Intracranial vagotomy on the other hand revealed that about 70% of the small (1.5-4.0 micron) myelinated fibers were unaffected, as were many unmyelinated axons. After sympathectomy, both kinds degenerated but normal unmyelinated axons could be found. Thus, the majority of the small myelinated fibers are afferent sensory fibers whose cell bodies are located in the vagal ganglia at the base of the skull. The medium and large myelinated fibers represent efferent neurons originating from the brain stem. The unmyelinated fibers emanate from at least three different sites, viz. the brain stem, the sensory vagal ganglia and finally the ganglia of the cervical sympathetic nerve trunk.

Animals↗
PubMed1979

The cochlear blood flow in relation to noise and cervical sympathectomy.

The effect of noise and unilateral transection of the cervical sympathetic trunk on cochlear blood flow was studied in anesthetized cats. The sound pressure level was 100 dB and the exposure time 6 min. Neither noise nor sympathectomy were found to affect the blood flow.

Acidosis, Respiratory↗
PubMed1990

Sympathectomy fails to reveal prominent vasodilation by atrial natriuretic factor.

Reflex activation of the sympathetic nervous system may conceal direct vasodilatory actions of atrial natriuretic factor and mediate atrial natriuretic factor-induced increases in total peripheral resistance. We determined whether peripheral sympathectomy would enhance the hypotensive actions of atrial natriuretic factor and convert the increase in total peripheral resistance to peripheral vasodilation. Sympathectomized rats studied included 1) conscious rats treated with 6-hydroxydopamine alone (partially sympathectomized) and 2) conscious anephric rats sympathectomized with adrenal demedullation and 6-hydroxydopamine (totally sympathectomized), with vascular tone returned to levels of sham-operated (control) rats with norepinephrine infusion. Sympathectomized rats and appropriate control rats received rat atrial natriuretic factor infusion (0.5 microgram/kg/min) or vehicle for 1 hour. Atrial natriuretic factor infusion lowered mean arterial pressure and increased hematocrit in control rats but not in partially sympathectomized rats. Changes in cardiac output and total peripheral resistance were not significantly different between control and partially sympathectomized rats. In totally sympathectomized rats, atrial natriuretic factor lowered mean arterial pressure more than in control rats; changes in cardiac output were nearly identical in both groups, but there were no changes in total peripheral resistance from control levels in the totally sympathectomized group. Changes in plasma volume and central venous pressure were similar in totally sympathectomized rats and control rats. These findings suggest that reflex sympathetic activity largely mediated atrial natriuretic factor-induced increases in total peripheral resistance but failed to reveal an atrial natriuretic factor-mediated sustained vasodilation in the absence of sympathetic reflexes. Furthermore, atrial natriuretic factor decreased cardiac output, central venous pressure, and plasma volume independent of the sympathetic nervous system.

Adrenal Medulla↗
PubMed1997

Effect of sympathectomy on mechanical properties of common carotid and femoral arteries.

Sympathetic stimulation is accompanied by a reduction of arterial distensibility, but whether and to what extent elastic and muscle-type arterial mechanics is under tonic sympathetic restraint is not known. We addressed this issue by measuring, in the anesthetized rat, the diameters of the common carotid and femoral arteries with an echo-Doppler device (NIUS 01). Blood pressure was measured by a catheter inserted contralaterally and symmetrically to the vessel where the diameter was measured. Arterial distensibility over the systolic-diastolic pressure range was calculated according to the Langewouters formula. Data were collected in 10 intact (vehicle pretreatment) and 9 sympathectomized (6-hydroxydopamine pretreatment) 3-month-old Wistar-Kyoto rats. Compared with the intact animals, sympathectomized rats showed a marked increase in arterial distensibility over the entire systolic-diastolic pressure range. When quantified by the area under the distensibility-pressure curve, the increase was 59% and 62% for the common carotid and femoral arteries, respectively (P<.01 for both). In the femoral but not in the common carotid artery, sympathectomy was accompanied also by an increase in arterial diameter (+18%, P<.05 versus intact). Therefore, in the anesthetized normotensive rat, sympathetic activity exerts a tonic restraint on large-artery distensibility. This restraint is pronounced in elastic vessels and even more pronounced in muscle-type vessels.

Animals↗