Physiology
Stephen W. Carmichael, Susan L. Stoddard in The Adrenal Medulla 1986 - 1988, 2017
Catecholamines secreted from the adrenal medulla are involved in the mediation of most physiologic processes. Plasma norepinephrine levels were decreased to half after both demedullation and sympathectomy, suggesting that paraganglia in the sheep provides some contribution to the resting levels of catecholamines. Increased sympathoadrenal activity is the primary autonomic response that occurs during exercise. The nonshivering thermogenesis that develops with prolonged cold exposure is stimulated in a nonlinear fashion by the infusion of norepinephrine. Lymphatic transport of norepinephrine was related quadratically to the infusion rate, indicating a similar relationship between infusion rate and influx of norepinephrine into the extravascular space. Intravenous injection of nicotine inhibited the gastric acid output elicited by stimulation of the vagus nerve and initially inhibited gastric mucosal blood flow; these effects were blocked by phentolamine or by adrenalectomy plus reserpine. Gastric acid secretion may be modulated by central mechanisms.
Dopamine in The Adrenal Medulla and Its Possible Role in Stress
M.D. Francesco Amenta in Peripheral Dopamine Pathophysiology, 2019
The presence of free dopamine (DA) and its relationship to norepinephrine (NE) and epinephrine levels in the adrenals of several species has not been elucidated, probably because of the difficulties involved in its specific determination. The presence of free DA in the adrenals has rarely been reported, and the lack of a specific method for its assay has not previously permitted a systematic investigation. Free DA levels in the adrenals are relatively low in all species. The adrenal release of DA is probably an integral part of the DA secretion that follows different types of sensory inputs to the central nervous system, ranging from mild physiological stimuli to severe stress. In humans, heightened free DA levels in plasma have been observed after various forms of exercise and during hypoglycemic or surgical stress. The adequacy of the sympathetic nervous system to respond to repeated stress may be reflected in the magnitude of DA release.
Adrenal Medulla
Paul V. Malven in Mammalian Neuroendocrinology, 2019
The chromaffin cells of the adrenal medulla are innervated neuroendocrine cells that secrete catecholaminergic neurohormones into the blood. The biosynthetic steps leading to norepinephrine occur in all the chromaffin cells of the adrenal medulla. In mammals, the phenylethanolamine N-methyl transferase (PNMT) enzyme is almost exclusively localized in the adrenal medulla with only small quantities in the brain and in the sympathetic nerves of the heart. The subset of chromaffin cells that contain PNMT and synthesize epinephrine are regionally localized in a species-specific manner. The primary secretory products of adrenal medullary cells are the catecholamines, norepinephrine and epinephrine. In the discussion on biological actions of catecholamines, the induced breakdown of glycogen to yield glucose was one important action that could only be accomplished by adrenomedullary secretions. Therefore, low blood glucose represents one of the most important provocative stimuli of such secretion.
Life Changes and Urinary Norepinephrine in Myocardial Infarction
Published in Journal of Human Stress, 1983
Lois Kohn, David Sleet, John Carson, Robert Gray
The relationship between norepinephrine and stress caused by life changes was assessed using urinary norepinephrine levels and responses to a 57-item stress questionnaire interview obtained from 21 post-myocardial infarction and 27 healthy control male and female subjects. High correlations between norepinephrine and duration of present stress and duration and severity of life changes, and moderate correlations between norepinephrine and anxiety and depression were found among the post-infarction group. No significant correlations were found in the control group. Post-infarction subjects with elevated norepinephrine had significantly higher scores on duration of present stress and duration and severity of life changes than did post-infarction subjects with normal norepinephrine levels. Control subjects with normal and elevated norepinephrine did not differ significantly on any of the comparison variables. Standard risk factors failed to add significantly to the prediction of norepinephrine in either group. However, 68.3 percent of the variance in norepinephrine was accounted for by a single predictor, the duration of present stress.
Plasma Catecholamines in Normal Pregnancy and in Pregnancies Complicated by Mild Chronic Hypertension
Published in Clinical and Experimental Hypertension. Part B: Hypertension in Pregnancy, 1983
R. W. O'Shaughnessy, G. D. Scott, J. D. Lams, F. P. Zuspan
Plasma epinephrine and norepinephrine were measured throughout pregnancy in an ambulatory population of normal and untreated chronically hypertensive pregnant women. There was no significant difference between trimesters for plasma epinephrine, norepinephrine, or the ratio epinephrine/norepinephrine in either the normal or chronically hypertensive group. In the first trimester of pregnancy, women with chronic hypertension demonstrated a significantly higher plasma norepinephrine and a significantly lower epinephrine/ norepinephrine ratio than normal women.
Vascular Responsiveness to Norepinephrine, Serotonin, and Potassium Chloride in Veins from Spontaneously Hypertensive and Age-matched Wistar Kyoto Rats
Published in Clinical and Experimental Hypertension, 1979
Marlene L. Cohen, Kathryn S. Wiley
Jugular veins from normotensive rats respond to norepinephrine with a beta adrenergically-mediated relaxation, and thus provide a useful tissue for the examination of changes in venous responses to norepinephrine in hypertension. Jugular veins from spontaneously hypertensive rats did not relax to norepinephrine and in some tissues, a contraction occurred. After propranolol (10-6 M), norepinephrine contracted jugular veins from both groups. However, contraction to norepinephrine was greater in veins from spontaneously hypertensive rats. Enhanced contraction was specific to norepinephrine since maximal force developed to serotonin and potassium chloride was less in veins from spontaneously hypertensive rats. Thus structural changes in venous smooth muscle cannot explain the enhanced contraction to norepinephrine. Relaxation to isoproterenol, nitroglycerin or norepinephrine (after alpha adrenoceptor blockade with prazosin) was not decreased in jugular veins from spontaneously hypertensive rats in comparison to normotensive rats. Likewise, defective relaxation of portal veins was not apparent in this hypertensive model although a defect in relaxation was confirmed in