Ageing catecholamine levels

Studies on the catecholamine levels of the adrenal gland in adult subjects have not revealed any certain variation with age. In an early investigation by Ingier and Schmorl (1911) which included analyses of adrenal glands from 409 individuals between 20 and 89 years, the calculated mean values for various decades showed a range only between 33 and 44... 

A comprehensive investigation of the epinephrine and norepinephrine contents of adult adrenal glands was made by Lcmbeck and Obrccht (1953). On the basis of values listed for individual samples, the mean concentrations have been calculated for various age groups as st cn from Table XXVI, no significant variations with age in the total catecholamine concentration or in the proportions of epinephrine and norepinephrine were encountered between the ages of 30 and 70 years. A summary of other recent studies on adult adrenal samples is presented in Table XXVII although notable differences are noted betAveen the values observed by the various authors, no certain variation with a in the tissue catecholamine levels was reported in these publications. 

In an in vitro rabbit carotid body preparation, Bairam et al. found that hypoxia-induced DA release was minimal in 1-15-day-old rabbits and only became significant after 25 days of age (49). Similarly, using carbon fiber electrodes in rat carotid bodies, peak free tissue catecholamine levels in response to anoxia were low in newborns and increased >10 fold over the frrst month of life (10). Thus, studies to date indicate low baseline DA levels and increasing DA release during the frrst weeks of life in rabbits and rats, which does not support the hypothesis that declining carotid body catecholamine levels account for the maturational increase in nerve activity or O2 sensitivity. However, catecholamine release by nerve terminals (56) may be altered in an in vitro cut-CSN preparation and, therefore, the question has not been fully resolved. 

Adler LE, Hoffer LD, Wiser A, et al Normalization of auditory physiology by cigarette smoking in schizophrenic patients. Am J Psychiatry 150 1856-1861, 1993 Adolfsson R, Gottfries GG, Oreland L, et al Reduced levels of catecholamines in the brain and increased activity of monoamine oxidase in platelets in Alzheimer s disease therapeutic implications, in Alzheimer s Disease Senile Dementia and Related Disorders [Ageing, Vol 7). Edited by Katzman R, Terry RD, Bick KL. New York, Raven, 1978, pp 441-451... 

Biochemically, norepinephrine possesses a higher affinity for the o c-AR subtype, suggesting that this receptor is able to respond to low-level circulating catecholamines and minute alterations of them. Alternatively, higher concentrations of norepinephrine will occupy the lower affinity o a-ARs and involve them in regulating neurotransmitter release. The unique properties of these subtypes play a critical role in vivo o c-AR / mice display significantly elevated plasma norepinephrine levels in contrast to wild-type, o a-AR , a2, -ARw. and a2C-AR mice. Assessment of hearts from a2 AC-AR / mice at 4 mo of age revealed marked hypertrophy with decreased left ventricular contractility (21,90). Thus,... 

Reference intervals for plasma and urinary catecholamines and catecholamine metabolites also differ according to sex and age. Females have lower plasma concentrations of epinephrine and metanephrine than males. Similarly, 24-hour urinary outputs of catecholamines and metanephrines are lower in women than men for epinephrine this difference remains significant when values are normalized for creatinine excretion Plasma levels of norepinephrine and normetanephrine increase with advancing age in adults, whereas plasma levels of epinephrine and metanephrine are little affected. Age-related increases in 24-hour urinary outputs of norepinephrine and normetanephrine have also been reported,but not consistently by all studies. In general, the influences of age... 

The potential for maturational changes in the sensitivity of a putative O2 sensor does not, of course, exclude the possibility of other maturational changes occurring at sites more distal to the sensor. Indeed, a significant body of evidence has been gathered to demonstrate a postnatal elevation in catecholamine, specifically dopamine, mRNA levels in carotid body and pelrosal ganglion tissue (86,87). Additionally, the amount of catecholamine released with hypoxia (88,89) but not with elevated extracellular K concentration (89) increases with postnatal age. 

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