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PubMed1994

Role of the sympathetic nervous system in hypertension and benign prostatic hyperplasia.

Hypertension and benign prostatic hyperplasia (BPH) have a number of features in common. For example, both occur with increasing frequency in the elderly, and both are a major source of health expenditure worldwide. However, the most striking feature linking hypertension and BPH is the aetiological role of the sympathetic nervous system. Sympathetic tone mediated by the alpha-receptor is vital in the control of blood pressure. By selectively inhibiting the alpha 1-adrenoceptors in the vasculature, thereby inhibiting the response to epinephrine and norepinephrine and thus reducing peripheral resistance, selective alpha 1-inhibitors such as doxazosin produce a physiological reduction in blood pressure. Receptors of the alpha 1 subtype are also found in the prostate, the urethra and bladder neck. Doxazosin, by reducing the tone of the prostatic smooth muscle, has the potential to improve urinary flow rate, as well as the obstructive and irritative symptoms characteristic of BPH.

Adrenergic alpha-Antagonists↗
PubMed1996

Increased activation of sympathetic nervous system and endothelin by mental stress in normotensive offspring of hypertensive parents.

BACKGROUND: The pathogenesis of essential hypertension is still uncertain, but genetic factors and the sympathetic nervous system are likely to be involved. Sympathetic nerve activity and hormonal circulatory control mechanisms, however, are affected by blood pressure itself. Hence, early functional changes are best investigated in normotensive subjects at risk to develop hypertension, such as normotensive offspring of hypertensive parents. METHODS AND RESULTS: Muscle sympathetic nerve activity (MSA) was measured in the peroneal nerve of 10 normotensive offspring of parents with essential hypertension and 8 offspring of normotensive parents. Measurements were performed under resting conditions, during a 10-minute period of hypoxia (12.5% O2/87.5% N2) and during a 3-minute mental stress test. The tests were separated by a 30-minute resting period. Plasma samples for determination of norepinephrine and endothelin were collected before and after the tests. Baseline values of MSA were comparable in offspring of hypertensive and normotensive parents. During hypoxia, MSA, heart rate, and norepinephrine and endothelin plasma levels increased in offspring of hypertensive and normotensive parents to a comparable degree, whereas no significant changes in blood pressure and plasma norepinephrine levels were observed in either group. During mental stress, MSA and plasma norepinephrine and endothelin increased only in offspring of hypertensive parents (P < .001 to .01). In parallel, blood pressure increased significantly only in offspring of hypertensive parents (P < .001 to .05) but heart rate increased in both groups (P < .001 to .05). CONCLUSIONS: The activity of the sympathetic nervous system and plasma norepinephrine and endothelin levels are increased during mental stress only in offspring of hypertensive parents, whereas the response to hypoxia was similar in offspring of hypertensive and normotensive parents, suggesting a genetically determined abnormal regulation of the sympathetic nervous system to certain stressful stimuli in offspring of hypertensive parents. This may play a role in the pathogenesis of essential hypertension.

Adult↗
PubMed1992

Obesity, the sympathetic nervous system, and essential hypertension.

There is ample evidence that the sympathetic nervous system is important in the etiology of essential hypertension. Plasma catecholamines such as norepinephrine and epinephrine are the most common indexes of sympathetic function used in studies of essential hypertension. Plasma norepinephrine is higher in young essential hypertensive patients than in normotensive subjects. Other methods to examine sympathetic activity, such as blood pressure response to sympatholytic agents, measurement of regional sympathetic activity, vascular reactivity to sympathetic agonists, power spectral analysis, and microneurography, have all provided further evidence for enhanced sympathetic activity in essential hypertension, especially in younger subjects. Certain groups that make up a substantial part of the essential hypertensive population, such as obese subjects, have heightened sympathetic activity that could contribute to hypertension. Plasma norepinephrine levels are significantly higher in obese compared with nonobese subjects, and the remarkable fall in blood pressure with weight loss in obese subjects is correlated with reductions in plasma norepinephrine. Antihypertensive agents have variable effects on sympathetic activity; some agents (diuretics and direct vasodilators) have elevating effects, some agents (centrally acting agents and alpha-antagonists) have lowering effects, and others (converting enzyme inhibitors, calcium blockers, and beta-blockers) have mixed effects. Tailoring therapy toward agents that reduce sympathetic activity for specific groups perceived as having neurogenic hypertension, such as obese subjects, is a goal yet to be attained.

Humans↗
PubMed2001

The sympathetic nervous system and long-term blood pressure regulation.

There is considerable evidence that activation of the sympathetic nervous system plays an important role in the pathogenesis of several cardiovascular diseases, including hypertension. However, the mechanisms that account for sympathetic activation and the precise mechanisms that mediate neurally induced hypertension are unclear. In large part, this is due to the difficulty in assessing sympathetic function under chronic conditions. Consequently, acute observations are often extrapolated to infer that similar neural mechanisms are operative under more longterm conditions, an unwarrantable assumption. Nonetheless, considerable theoretical and experimental evidence points to the renal sympathetic nerves as the critical link between the sympathetic nervous system and long-term arterial pressure control. Both chronic increases and decreases in renal adrenergic activity alter renal excretory function and produce sustained elevations and reductions in arterial pressure, respectively. Recent observations, including those in dogs with hemibladders and one denervated kidney, indicate that chronic suppression of renal sympathetic nerve activity and attendant natriuresis are long-term compensatory responses to excess body fluid volumes and hypertension. Furthermore, studies combining deafferentation of cardiac receptors and sinoaortic baroreceptors with the split-bladder preparation suggest that chronic renal sympathoinhibition is mediated by baroreflex mechanisms, an especially important finding given the technical limitations in determining whether baroreflexes completely reset and impact sympathetic activity in chronic hypertension. In contrast to the chronic inhibitory effects of baroreflexes on sympathetic activity, other studies indicate that angiotensin II (Ang II) has sustained renal sympathoexcitatory effects. The opposing long-term effects of baroreflexes and Ang II on renal sympathetic nerve activity support two major hypotheses for sympathetic activation in hypertension: baroreflex dysfunction and activation of the renin-angiotensin system, abnormalities often associated with clinical hypertension.

Animals↗
PubMed1992

The role of the sympathetic nervous system in promoting liver cirrhosis induced by carbon tetrachloride, using the essential hypertensive animal (SHR).

The effects of the sympathetic nervous system on liver injury induced experimentally by carbon tetrachloride (CCl4) were examined in spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rats (WKY). It was found that the SHR had an elevated catecholamine (CA) content in the adrenal gland without any treatment, and fluorescence histochemistry also revealed dense adrenergic innervations in the liver. Moreover, the SHR showed greater sensitivity to CCl4 stimulation in the sympathetic nervous system than the WKY, resulting in a decreased hepatic blood flow in the acute stage and a depleted CA in the adrenal gland, a lowered blood pressure (BP) and a released non-esterified fatty acid (NEFA) from peripheral adipose tissue in the chronic stage. Upon repetition of the CCl4 treatments twice a week for 4 weeks, the liver injury was more severe in the SHR than in the WKY. Plasma glutamate-pyruvate transaminase (GPT) activity was increased in both strains but more significantly in the SHR than in the WKY. Histological examination of the liver in the SHR showed established cirrhosis, whereas only bridging fibrosis was seen in the WKY. These results suggest that the pathogenesis of the liver damage induced by CCl4 in the SHR, is attributable to the enhanced response of the sympathetic nervous system that releases massive amounts of CA which then lead to vasoconstriction and metabolic changes that promote liver damage.

Animals↗
PubMed1985

Role of vasopressin and sympathetic nervous system during hypertonic NaCl infusion in conscious dog.

The contribution of arginine vasopressin (AVP) and the sympathetic nervous system to the pressor response elicited by hypertonic NaCl infusion was investigated in conscious dogs with intact carotid sinus baroreceptors or in dogs subjected to chronic sinoaortic baroreceptor denervation (SAD). Infusion of 6% NaCl at 0.05 ml X kg-1 X min-1 for 60 min increased plasma osmolality an average of 12 +/- 2 mosmol/kg in both intact and SAD dogs. Arterial pressure increased 6 +/- 2 mmHg in intact animals and was normalized by subsequent administration of a specific vascular AVP antagonist. Pretreatment with the AVP antagonist did not alter resting arterial pressure but prevented the increase due to the osmotic stimulus. Pretreatment with ganglionic blockade reduced resting arterial pressure (-17 +/- 2 mmHg). Subsequent infusion of hypertonic NaCl elevated arterial pressure (21 +/- 7 mmHg) to a significantly greater level than that observed with the autonomic nervous system intact. In SAD dogs, the osmotic stimulus increased arterial pressure (16 +/- 1 mmHg) to a significantly greater extent than in intact animals. Subsequent administration of AVP antagonist normalized arterial pressure, and pretreatment with the antagonist prevented any pressor response. Pretreatment with ganglionic blockade did not alter the pressor response (15 +/- 2 mmHg) to hypertonic NaCl. Data suggest that the increase in arterial pressure due to an osmotic stimulus is due to AVP release and does not require a functional sympathetic nervous system. The response is normally buffered by arterial baroreflexes, presumably due to sympathetic withdrawal.

Animals↗
PubMed1996

Influence of insulin, sympathetic nervous system activity, and obesity on blood pressure: the Normative Aging Study.

OBJECTIVE: To examine the association of insulin and sympathetic nervous system activity with blood pressure elevation in a cross-sectional study of 752 nondiabetic male participants of the Normative Aging Study, aged 43-90 years. METHODS: Testing included a physical examination, medical history, fasting and post-carbohydrate insulin and glucose levels determinations, an anthropometric examination, and 24 h urine collection for catecholamine level determination. Total obesity was represented by body mass index, central obesity by the abdomen circumference:hip circumference ratio, and sympathetic nervous system activity by 24 h urinary excretion of norepinephrine. RESULTS: Systolic and diastolic blood pressure (SBP and DBP, respectively) were positively related to body mass index, abdomen:hip ratio, norepinephrine excretion, and insulin levels in univariate analyses. The relationship between insulin level and SBP and DBP persisted after adjustment for body mass index, abdomen:hip ratio, norepinephrine, age, smoking, physical activity level, and antihypertensive medication use. The norepinephrine level was related to SBP and DBP after adjustment for insulin level, age, smoking, physical activity level, and antihypertensive medication use, and these relationships remained marginally significant after further adjustment for body mass index and abdomen:hip ratio. In contrast, neither body mass index nor abdomen:hip ratio were related to blood pressure after adjustment for insulin level. Among participants in the lowest tertiles both of insulin and of norepinephrine levels, 10% were hypertensive, compared with 35% in the highest tertiles of these variables. In a multiple logistic regression model, insulin level, norepinephrine level, and an interaction term for insulin level with norepinephrine excretion were independent predictors of hypertension. CONCLUSIONS: The results suggest that insulin level and sympathetic nervous system activity are associated with hypertension among middle-aged and elderly men.

Adult↗
PubMed2003

Signaling via nucleotide receptors in the sympathetic nervous system.

Nucleotides have long been recognized as transmitters in the sympathetic nervous system that are involved in both ganglionic and sympatho-effector transmission. In the past 10 years, more than a dozen different receptors for nucleotides have been characterized by molecular cloning. In the same period, a number of stimulatory and inhibitory effects of nucleotides on sympathetic neurons have been identified, and the receptors and signaling cascades involved have been characterized. Within sympathetic ganglia, sympathetic neurons are excited by nucleotides via ATP-gated cation channels (P2X receptors) and via G-protein-coupled nucleotide (P2Y) receptors. At postganglionic sympathetic axons, presynaptic P2X receptors mediate a positive feedback modulation of sympatho-effector transmission, whereas presynaptic P2Y receptors predominantly mediate an autoinhibition of sympathetic transmitter release. This review summarizes the way in which signals generated via these nucleotide receptors are integrated within single sympathetic neurons to contribute to the function of the whole system. The arising knowledge permits predictions about desirable and adverse effects of drugs that bind to these receptors.

Animals↗
PubMed1989

[Sympathetic nervous system response to exercise in patients with congestive heart failure].

The response of the sympathetic nervous system to exercise in patients with congestive heart failure was studied in 65 patients (NYHA functional class I 28, II 23, and III 14) and 22 normal subjects (N) by submaximal treadmill testing with the modified Bruce's or Sheffield's protocols. Plasma norepinephrine (NE) and epinephrine (E) levels were also measured at rest, at the end of each stage, and immediately after and 5 min after exercise. In accordance with the severity by NYHA functional class, the exercise duration became shorter and the discontinuation of exercise with symptoms occurred more frequently. Systolic blood pressure and double products (DP) at the peak exercise were significantly lower in patients with NYHA class III. NE and increments of NE increased during exercise [peak NE (pg/ml); N: 589, I: 646, II: 1253, and III: 997] and were higher at rest, during exercise and in recovery in patients with NYHA classes II and III than in the normal subjects and NYHA class I patients. E increased gradually during exercise [peak E (pg/ml); N: 60, I: 66, II: 63, and III: 66] and there were no significant differences among the four groups. A negative correlation (r = -0.53) between the peak NE and exercise duration was observed in normal subjects, while a positive correlation (r = 0.55) was observed in patients with NYHA class II. A positive correlation (r = 0.54) between DP at the peak exercise and the peak NE was observed in patients with NYHA class I, whereas a negative correlation (r = -0.46) was observed in patients with NYHA class III. The NE response in patients with NYHA classes II and III increased significantly, suggesting compensatory activation of the sympathetic nervous system for impaired cardiac function. In conclusion, the NE response to submaximal exercise testing differs in each NYHA functional class and it might be a useful indicator to evaluate cardiac function of patients with congestive heart failure.

Aged↗
PubMed1985

Noradrenaline release and sympathetic nervous system activity.

Measurements of the plasma concentration of noradrenaline, or more specifically the rate at which noradrenaline enters plasma, provide a useful guide to sympathetic nervous system function in humans. The overall rate of release of noradrenaline to plasma gives an overview of sympathetic nervous system activity (integrated nerve firing rate), detecting generalized changes, whether occurring as a reflex response, produced by drugs, or accompanying disease processes. The pattern of sympathetic nervous activation, however, is not delineated, only the net change in neurotransmitter release. Measurement of regional rates of noradrenaline release allows the clinical assessment of organ-specific sympathetic nervous tone, and consequently more penetrating analysis of sympathetic nervous system pathophysiology in disease states. The major problem in interpreting regional noradrenaline spillover measurements lies in the difficulty in differentiating those changes in noradrenaline spillover due to altered nerve firing, from those due to extraneous factors which might also affect spillover, such as the possible influence of blood flow on noradrenaline washout.

Adrenergic Fibers↗
PubMed1999

Role of sympathetic nervous system in cyclosporine-induced rise in blood pressure.

To clarify the role of the sympathetic nervous system in the development of cyclosporine A (CsA)-induced rise in blood pressure (BP), the effects of CsA on 24-hour ambulatory BP (ABP) were studied in patients with familial amyloid polyneuropathy (FAP) who underwent a liver transplantation. On the basis of autonomic function tests, patients with absent or mild-to-moderate sympathetic damage (Group A, n=11, age 29 to 43 years, disease duration 2 to 6 years) and patients with severe sympathetic damage (Group B, n=9, age 27 to 38 years, disease duration 3 to 9 years) were identified. Both groups were followed for 1 year. The daily doses of CsA and the CsA whole blood trough levels between the groups did not differ. Pretransplantation values of daytime and nighttime ABP were, respectively, 117+/-8/76+/-7 mm Hg and 108+/-12/68+/-9 mm Hg in group A and 107+/-6/66+/-4 mm Hg (P<0.05 group A versus group B) and 102+/-6/62+/-4 mm Hg in group B. In response to CsA, BP increased in all patients, but more so in patients of group B than in patients of group A. One year after transplantation, daytime and nighttime ABP had increased by 6+/-9/3+/-11% and 12+/-10/14+/-14% in group A and by 12+/-6/13+/-10% (P<0.05) and 21+/-11/27+/-21% (P<0.01) in group B. In both groups, the increase in nighttime ABP was greater than the increase in daytime ABP, which resulted in an attenuation or, even, a reversal of the diurnal BP rhythm. Because the rise in BP was greater in patients with more advanced sympathetic dysfunction, the sympathetic nervous system appears to counteract the CsA-induced rise in BP rather than causing it. This implies involvement of factors other than sympathetic activation in the pathogenesis of CsA-induced rise in BP in patients with familial amyloid polyneuropathy.

Adult↗
PubMed2000

Sympathetic nervous system function in fibromyalgia.

This review focuses on studies of the sympathetic nervous system in fibromyalgia (FM). First, a brief review of the sympathetic system, and its relationship to the human stress response, is outlined. Then various studies of functional assessment of sympathetic function in FM are highlighted. Certain methods of assessment (eg, heart rate variability, biochemical, and psychophysical responses to various stressors) that we believe to be of specific importance for future research are discussed in greater detail. Finally, findings on autonomic function in related disorders--specifically, chronic fatigue syndrome, irritable bowel syndrome, and migraine--will be briefly presented.

Female↗
PubMed2003

The role of renal sympathetic nervous system in the pathogenesis of ischemic acute renal failure.

We investigated the role of renal sympathetic nervous system in the progression of ischemia/reperfusion-induced acute renal failure in rats. Acute renal failure was induced by clamping the left renal artery and vein for 45 min followed by reperfusion, 2 weeks after the contralateral nephrectomy. Renal venous plasma norepinephrine concentrations markedly and significantly increased immediately after reperfusion, thereafter, the increased level declined but remained higher even at 24 h after reperfusion. Renal sympathetic nerve activity was significantly augmented during the renal ischemia. Renal denervation or the administration of pentolinium, a ganglion blocking agent, (5 mg/kg i.v.) at 5 min before ischemia attenuated the ischemia/reperfusion-induced renal dysfunction and histological damage, such as proteinaceous casts in tubuli and tubular necrosis. The elevation of renal venous norepinephrine levels after reperfusion was suppressed by renal denervation or pentolinium treatment. Thus, a surgical or pharmacological blockade of renal sympathetic nerve prevents the progression of ischemia/reperfusion-induced acute renal failure, thereby suggesting that renal sympathetic nervous system plays an important role in the development of the ischemic acute renal failure.

Acute Kidney Injury↗
PubMed1977

[Double controlled regulation of renin release by the sympathetic nervous system. Stimulation via beta receptors and inhibition via alpha receptors].

The beta-sympathomimetic amine isoprenaline increases the plasma renin concentration by a stimulation of beta-receptors which control renin release. Isoprenaline also lowers systemic blood pressure and causes a reflex-mediated activation of the sympathetic nervous system. In these investigations it has been tested to see whether the catecholamines released by this activation modulate renin release by stimulation of certain alpha-receptors. Pretreatment of rats with reserpine or with the ganglionic blocking agent Trimethidinium enhanced the increase in plasma renin concentration induced by isoprenaline. So did pretreatment with the irreversible alpha-receptor antagonist phenoxybenzamine. Renal denervation also increased the effect of isoprenaline on plasma renin concentration. It is concluded that catecholamines released from the sympathetic nervous system can decrease renin secretion by an activation of certain alpha-receptors. The sympathetic nervous system may thus exert control of renin release by beta-receptors which stimulate and by alpha-receptors which diminish renin secretion.

Animals↗
PubMed1985

Glucose and FFA kinetics in sepsis: role of glucagon and sympathetic nervous system activity.

We have assessed the role of glucagon and sympathetic nervous system (SNS) activity on glucose and palmitate kinetics and oxidation in the conscious dog infused with live Escherichia coli bacteria by means of the simultaneous primed constant infusion of [1,2-13C]palmitate and [U-14C]-glucose. The basal rate of glucose production in septic dogs and controls was similar. However, when the glucagon concentration was selectively decreased in the septic animals by the appropriate infusion of somatostatin (S), insulin (I), and glucagon (G), the rate of glucose production decreased significantly, whereas in control animals S + I + G infusion had no effect on glucose kinetics. When alpha- and beta-adrenergic blockade was added to the infusion, the rate of glucose production decreased further and hypoglycemia developed in the septic dogs, whereas in the controls both glucose production and concentration increased. The basal rate of appearance of palmitate was increased in the septic dogs (P less than 0.01). S + I + G had no effect on palmitate appearance in either group, and sympathetic blockade caused a significant decrease in palmitate appearance in both groups of dogs. The rates of oxidation of both glucose and palmitate was related directly to their availability in plasma. Thus, in sepsis, glucagon and SNS activity play important roles in the mobilization of glucose and palmitate into the plasma and therefore in the overall state of energy metabolism.

Animals↗