Sympathetic Nervous System Overactivity Research Articles

Effect of alcohol withdrawal on blood pressure, plasma renin activity, aldosterone, cortisol and dopamine beta-hydroxylase.

Sixty-five alcoholic patients admitted for detoxification had blood pressure, withdrawal symptoms, plasma cortisol (PC) and plasma aldosterone (PA) levels, plasma renin activity (PRA), and serum dopamine beta-hydroxylase (DBH) levels measured on the first and fourth days after admission. On the morning after admission blood pressure was elevated (greater than 140/90) in 32 patients (49%) and was 160/95 mmHg or more in 21 (32%). PRA was initially elevated in 41 patients, PA levels in 14, and 13 patients had raised PC levels. By the fourth day, blood pressure and biochemical measures had fallen significantly while urine volume and sodium output, low on admission, had increased significantly. On admission urinary metanephrine levels were raised in four out of the 31 patients who had them measured. The height of both the systolic and diastolic blood pressures was significantly related to the severity of the alcohol withdrawal symptoms. Of the biochemical parameters measured, PC level correlated with systolic but not diastolic pressure, and urinary volume was inversely correlated with the height of the diastolic pressure. No relationship was found between blood pressure and PRA or PA level. The pressor effect of alcohol withdrawal could be due to sympathetic nervous system overactivity, or possibly to hypercortisolaemia . The first hypothesis seems more likely.

Impaired insulin secretion in human diabetes mellitus. I. The effect of alpha-adrenergic inhibition

The effect of nicergoline, an alpha-adrenergic blocking drug, upon insulin response to glucose has been investigated in 8 subjects with Type II (adult-onset) diabetes mellitus with fasting hyperglycemia. All subjects had no acute insulin response to intravenous glucose (20 g) pulse (AIR=Acute Insulin Response=1±5%, mean±SEM, mean change 3–10 min, % basal). Nicergoline infusion (0.1 mg/min) resulted in both a partial restoration of AIR (43±12 %, p<0.01) and in an acceleration of glucose disappearance rate (kG before nicergoline=0.38±0.04; kG during nicergoline=0.66±0.07 %/min, p<0.05). Second phase insulin secretion was not affected by nicergoline (before nicergoline=414±89%; during nicergoline=560±108%, p=NS). The present data give further support to the concept that sympathetic nervous system overactivity plays some role in defective insulin secretion in human diabetes mellitus.

A Relaxation Technique In the Management of Hypercholesterolemia

Chronic sympathetic nervous system overactivity has been implicated as a factor capable of elevating and maintaining high serum cholesterol levels independent of dietary measures. We conducted a controlled trial to determine the effect of a relaxation technique. Transcendental Meditation, on serum cholesterol levels in hypercholesterolemic subjects. Serum cholesterol levels were measured at beginning and end of an 11-month period in 12 hypercholesterolemic subjects who regularly practiced meditation. Eleven hypercholesterolemic controls who did not practice the technique were similarly followed up for 13 months. Paired comparisons showed a significant (p less than 0.005) reduction in fasting serum cholesterol levels of those subjects who practiced meditation. These results suggest that the regular practice of a relaxation technique may contribute, most likely through a reduction in adrenergic activity, to the amelioration of hypercholesterolemia in certain subjects.

Tetanus

Tetanus is caused by the organism Clostridium tetani, which produces tetanospasmin, a neurotoxin responsible for the clinical manifestations of muscle rigidity and reflex spasms. The majority of cases follow an anaerobic wound infection associated with trauma. Incubation period is usually 3 days to 3 weeks. 75% of patients present with trismus. Reflex spasms are seen in 70% of patients and characterize the severity of the disease. Treatment involves removal of the offending organism, neutralization of free neurotoxin, controlling rigidity and reflex spasm, and minimizing complications. Diazepam may be used alone in mild cases. Severe cases require the addition of nondepolarizing neuromuscular blocking agents and mechanical ventilation. Respiratory complications occur early and require aggressive airway management. A serious, late complication is the syndrome of sympathetic nervous system overactivity that is treated with alpha and beta blockade. High mortality rates seen in the United States may be due to delays in diagnosis and lack of familiarity with treatment. The disease is preventable with adequate immunization.

Studies of neurotransmitter release in the pathogenesis of hypertension.

Studies using a sensitive radioenzymatic assay for plasma noradrenaline suggest there is a selective overactivity of the sympathetic nervous system in essential hypertension. Methodology which allows the study of local sympathetic turnover in CNS nuclei and peripheral blood vessels is described. This approach has been used to study the non-innervated sympathetic turnover phaeochromocytoma. It is suggested that studies of local regulatory mechanism in neurotransmitter release are required to give a greater understanding of the central and peripheral role of the sympathetic nervous system in the pathogenesis of hypertension.

High-renin essential hypertension: adrenergic cardiovascular correlates.

1. Patients with mild essential hypertension and elevated plasma renin activity, when compared with normal subjects and hypertensive subjects with normal plasma renin, demonstrated features of sympathetic nervous cardiovascular excitation, accompanied by a raised plasma noradrenaline concentration. 2. An elevated heart rate at rest, shortened cardiac pre-ejection period, and greater heart rate reduction with acute beta-adrenoreceptor blockade (intravenous propranolol) in high-renin essential hypertension were indicative of adrenergic cardiac excitation. An elevated total of peripheral vascular resistance at rest and a greater fall in peripheral resistance with alpha-adrenoreceptor blockade (intravenous phentolamine) suggested the existence of a neurogenic increase in arteriolar resistance. 3. Blood pressure was normalized by 'total' autonomic blockade (atropine plus propranolol plus phentolamine) in the hypertensive subjects with elevated plasma renin activity. 4. These findings suggest that in mild high-renin essential hypertension increased adrenergic drive to the heart and resistance vessels exists. The elevation of blood pressure is sustained predominantly by neurogenic mechanisms. The high plasma renin activity is seen as an expression of sympathetic nervous system overactivity.

Catecholamine levels in tricyclic antidepressant self-poisoning.

Summary: In a consecutive series of 208 patients with tricyclic antidepressant self - poisoni ng, urinary catec holami ne excretion was measured, and the catecholamine level compared with that in ten patients having taken an overdose of other drugs. In both patient groups the electrocardiograph was monitored continuously for a minimum of 48 hours to detect cardiac arrhythmias. Urinary noradrenaline excretion was elevated during the first 24 hours after tricyclic antidepressant self-poisoning, to! a level 2-3 times that found in the other overdose group, but was normal by the third day. Cardiac tach ya rr h yt hmias developed i n four of the patients with antidepressant overdosage. The findings support the concept that sympathetic nervous system overactivity underlies the cardiac tachyarrhythmias which commonly accompany self-poisoning with this class of drugs.

PARTIAL LIPODYSTROPHY

Six children with partial lipodystrophy have been studied. Oral glucose tolerance was not grossly impaired but fasting serum insulin (19.4,±6.3μUml) was higher than normal, and hyperinsulinaemia after oral glucose (maximum 250μUml) was present in 3/6 children. Plasma growth hormone was normal; serum cortisol was low in 1/6 children. Fasting serum cholesterol, triglyceride, and plasma non-esterified fatty acids were normal. Fatty acid composition of adipose tissue triglyceride from non-dystrophic areas in 3/3 children showed an increased proportion of palmitoleic acid (8.8, 10.0, 11.0%) compared with normal (5.8 ± 1.5%). Plasma post-heparin lipolytic activity was normal in 3/4 children. Sweat production and sodium concentration did not differ between lipodystrophic and normal areas in 2/2 patients. Treatment with propranalol, in an attempt to inhibit sympathetic mediated lipolysis, had no beneficial effect in 2/2 children over a 4-6 month period. The results suggest that increased insulin resistance is present at an early stage of the disease, but do not provide evidence for sympathetic nervous system overactivity.

Some effects of propranolol on the cardiovascular responses of the monkey to simulated subarachnoid haemorrhage.

in the experimental animal) ,z These may vary greatly in eharaoter and them have been changes consisterlt with increased activity of the sympathetic nervous system. Structural changes in the myoeardium have been described that could be produc ~d by a period of sympathetic nervous system overactivity ~ and increased tissue catecholamine levels have been measured following subaraehnoid haemorrhage and other forms of stimulation of the brain in the laboratory animals. 4 The importance of the cateeholamines is also suggested by the abolition of eneephalogenic cardhe arrhythmias in dogs following treatment with reserpine, s The portion of sympathetic nervous activity mediated by B-receptor stimulation has received some a~ention, not only because of the intrinsic interest in the mechanism of these arrhythmias, but because of the effect of rapid arrythmias on cardiac out-put and the possible reduction of cerebral blood flow. Accordingly it seemed of interest to study the effects of the prior administration of propranolol on such changes in cardiac rhythm and cerebral blood Bow as might occur following simulated subarachnoid haemorrhage in the monkey. METHOD Rhesus monkeys were sedated with intraperitoneal sodium pentobarbital 50 mg/kg body weight and the trachea was intubated. Anaesthesia was maintained with a mixture containing thirty per cent of oxygen in nitrous oxide. The animals were paralyzed with d-tubocurarine, artificially ventilated with a Harvard variable phase ventilator and then surgical preparations were made for measurements of cerebral blood flow, intracranial pressure, and systemic arterial pressure. During this period fluid balance was maintained, blood gases were measured at regular intervals, and normal body temperature was maintained. Four to six hours later, at which time cerebral blood flow was stable and a multichannel Grass encephalograph indicated brain activity consistent with light nitrous oxide anaesthesia, arrangements were made to simuhte a subaraehnoid haemorrhage. This was done by inserting a needle through a hole in the midline of the skull at a point 0.5 cm cephalad to the nasion and manipulatSng its tip alone the floor of the anterior fossa to a point about 0.75 cm anterior to the tubereulum sellae so that it lay in the

Post-traumatic Vascular Disorders and Upper Extremity Sympathectomy

Summary Post-traumatic vascular disorders may result from injuries to the small or large arteries of the upper extremity or may develop secondarily to nonvascular trauma with the vascular changes mediated through an overactive sympathetic nervous system. Arteriographic studies are of great value in delineating the nature and extent of the arterial involvement. Direct brachial puncture is an effective method of outlining the arteries of the forearm and hand but fails to provide information concerning the subclavian and axillary arteries. A preferred method is that of Seldinger wherein the catheter is introduced into the femoral artery and passed to the proximal subclavian artery of the involved extremity. Therapeutic techniques include physiotherapy for the shoulder-hand syndrome with sympathectomy reserved for those who respond poorly to conservative efforts to control an overactive sympathetic nervous system. Direct arterial reconstruction for lesions of the palmar arches and digital arteries is often successful. Favorable and unfavorable aspects of the four operative approaches to the upper thoracic sympathetic trunk are discussed with the conclusion that the transaxillary and anterolateral thoracic approaches are the safest and most satisfactory.

Role of autonomic nervous system in maintenance of cerebral and renal hypertension.

The blood pressure responses to various drugs were investigated in renal hypertensive, cerebral hypertensive and normotensive rabbits. Hexamethonium bromide and Dibenamine reduced the blood pressures of renal and cerebral hypertensives. Effects in the normal were insignificant. The cerebral hypertensive's blood pressure was slightly affected by benzodioxane. Blood pressure was not reduced at all in the other groups. Blood pressure of the renal hypertensive rabbit was greatly reduced by Veriloid and dihydroergocornine. Blood pressures of cerebral and normal animals were affected to a lesser degree. The results suggest that maintenance of hypertension in the cerebral hypertensive rabbit depends on an overactive sympathetic nervous system, possibly due to the release of medullary pressor centers from inhibitory impulses originating in higher centers; whereas, the maintenance of hypertension in the renal hypertensive rabbit may be attributed to an increased reactivity of the peripheral vasculature to a normal sympathetic tone.