Activation Of Sympathoadrenal System Research Articles

Sympathoadrenal system activity at birth: integration of postnatal adaptation.

In this article we have reviewed available information characterizing an increase in SAS activity at birth, in the so-called "catecholamine surge." Also, we have described the sources of circulating CA in the sheep fetus at birth and reviewed recent data on the significance of the CA surge at birth with regard to vital events of postnatal metabolic and cardiovascular adaptations. The results available to date suggest a unique, early neonatal dependence on circulating catecholamines for maintenance of physiologic homeostasis. The duration of this dependence and the ability of newborn animals or humans to sustain such high circulating catecholamine levels is not known. Further studies will clarify the relative importance of circulating and neuronally released CA in these adaptive events in various organ systems and test the applicability of a wide variety of adrenergic agents for therapeutic intervention.

Captopril: clinical pharmacology and benefit-to-risk ratio in hypertension and congestive heart failure.

Captopril, a competitive antagonist of angiotensin converting enzyme, has been marketed in the United States for the treatment of resistant hypertension. Despite extensive study, its exact mechanism of action remains unclear; decreased renin-angiotensin-aldosterone and sympathoadrenal system activity as well as increased bradykinin and prostaglandin E and F activity have been postulated. The drug decreases peripheral vascular resistance. Controlled trials in resistant hypertension of various etiologies and chronic congestive heart failure have demonstrated sustained effectiveness and therapeutic benefits. Side effects include skin rash, loss of taste, proteinuria, and leukopenia; higher doses and concomitant renal dysfunction appear to be predisposing factors. The benefit-to-risk ratio for captopril clearly justifies its use in resistant cases of hypertension and congestive heart failure, but further experience is needed to evaluate its use in milder forms of these diseases.

Influence of neurotropic drugs on neurogenic damages of internal organs induced by stress

Summary Drugs which promote restoration of sympatho-adrenal system activity and of sympathetic mediators, normalize the energy resources in tissues. Key enzyme synthesis of metabolic processes can be used not only for preventing but also for pharmacotherapy of diseases of internal organs where the nervous factor is the most significant.

The action of angiotensin II on the baroreflex response of the conscious ewe and the conscious fetus.

1. In conscious non-pregnant and pregnant ewes and in chronic fetal lamb preparations, the beat by beat relationship between pulse interval and systolic pressure was studied during acute elevations in arterial pressure induced by phenylephrine. Baroreflex sensitivity, which was defined as the slope of the pressure-pulse interval relationship when phenylephrine was used to raise pressure, was abolished by atropine and increased by propranolol. Baroreflex sensitivity was less in pregnant ewes and in foetal lambs compared with non-pregnant ewes. 2. These findings suggest that the vagus nerve is responsible for the reflex bradycardia that occurs in the foetus and the ewe when arterial pressure is increased. 3. In both fetal and adult sheep, actue hypertension due to I.V. injection of angiotensin II was not associated with a consistent and progressive bradycardia, such as was seen with acute hypertension caused by phenylephrine. Angiotensin II has no direct chronotropic effect on heart rate in either the adult or the fetus. 4. No linear relationship between arterial pressure and pulse interval was seen when angiotensin II was used to raise pressure in sheep which were treated with propranolol. Therefore the lack of cardiac slowing with pressor doses of angiotensin II was not due to concomitant activation of the sympathoadrenal system. 5. It is concluded that in both fetal and adult sheep angiotensin II reduces the increase in vagal tone which is responsible for slowing of heart rate in response to acute rises in arterial pressure.

Sympatho-adrenal medullary activity and behavior during exposure to footshock stress: A comparison of seven rat strains

The effects of footshock stress on circulating levels of norepinephrine (NE) and epinephrine (EPI) and behavioral activation were examined in male rats of seven strains: spontaneously hypertensive (SHR), stroke-prone hypertensive (SP-SHR), Wistar-Kyoto (WKY), Sprague-Dawley (SD), Osborne-Mendel (OM), Brown Norway (BN), and Charles River Wistar (CRW). A catheter was inserted into the ventral caudal artery of each rat to allow for direct measurement of blood pressure and heart rate and for repeated sampling of blood in conscious, undisturbed animals. Two days after insertion of the catheter, resting levels of plasma NE and EPI were higher in SHRs than in CRWs; no other comparisons among strains were significant. No strain differences were noted in the increments in plasma NE and EPI following transfer of rats from the home cage to a shock chamber. There were, however, significant strain differences in the responses of rats to 5 min of footshock (2.5 mA, 0.4 sec duration every 5 sec). Shock-induced increments in plasma NE and EPI were greatest in SHRs and lowest in S-D, O-M, B-N and CRW strains. In addition, there was a significant positive relationship between activity and shock-induced increments in plasma NE (r=0.89, p<0.01) and EPI (r=0.93, p<0.01). These findings indicate an association between activity of the sympatho-adrenal medullary system and behavioral activation during footshock stress. In addition, responsivity to stress was greatest in those strains (SHR and SP-SHR) which are genetically predisposed to increases in blood pressure.

Effect of Chemical Sympathectomy on Glycogen Storage in Rat Skeletal Muscle in Thermal Trauma

The glycogen storage in rat skeletal muscle is reduced after a 20% third degree burn. The reason is probably a relative deficiency of insulin caused by insulin resistance at the tissue level. Posttraumatically increased sympatho-adrenal function has been suspected to cause this insulin resistance. In an earlier study, however, it has been shown that adrenal demedullation has no effect on the glycogen storage. In the present investigation an attempt was made to assess the importance of the increased peripheric sympathetic activity. Muscle glycogen, serum insulin and blood glucose were determined at the end of a glucose infusion after infliction of a burn both in 6-hydroxy-dopamine treated rats and rats with an intact peripheric sympathetic nervous system. It was found that a chemical sympathectomy did not improve the glycogen storage. The result indicates that the increased activity of the sympatho-adrenal system after a burn is not the main cause of the reduced skeletal muscle glycogen storage.

The Effect of Physical Training on the Sympathoadrenal Response to Exercise

The urinary excretion of catecholamines was measured in six healthy male volunteers at rest and during a fixed amount of work before and after physical training. It was found that, although training resulted in a significantly lower heart rate during exercise, the output of catecholamines was unaltered, indicating that the total activation of the sympathoadrenal system by exercise was similar before and after training. A similar heart rate study before and after training was also made during beta-adrenergic receptor blockade. Under these conditions the heart rate during exercise was not significantly changed by training. It is suggested that physical training reduces the sensitivity of the beta-receptors of the heart.

Catecholamine-synthesizing enzymes in the rat adrenal gland during exposure to cold.

Catecholamine-synthesizing enzymes in the rat adrenal gland during exposure to cold.