Effects of depression, cigarette smoking, and age on monoamine oxidase B in amygdaloid nuclei

Abstract

Altered concentrations of dopamine transporter and D2/D3 receptors have been observed in the amygdaloid complex of subjects with major depression. These findings are suggestive of neurochemical abnormalities in the limbic dopamine system in depression. Monoamine oxidase-B (MAO-B) is a key enzyme in the catabolism of biogenic amines, including dopamine, and alterations in this enzyme may underlie dopaminergic abnormalities associated with depression. The specific binding of [ 3 H]lazabemide to MAO-B was measured in the right amygdaloid complex of 15 major depressive subjects and 16 psychiatrically normal controls. Subjects of the two study groups were matched as close as possible for age, sex, and postmortem interval. Examination of the regional distribution of MAO-B revealed lower [ 3 H]lazabemide binding to MAO-B in the lateral and basal nuclei of the amygdala and higher binding in the medial nucleus. A modest elevation in binding to MAO-B observed in all amygdaloid nuclei in major depressive subjects as compared to control subjects failed to reach statistical significance. A significant decrease in binding to MAO-B was observed when cigarette smokers were compared to nonsmoking subjects. The amount of MAO-B binding positively correlated with the age of subjects in all nuclei investigated. A decreased amount of MAO-B in smokers further validates the pharmacological effect of tobacco smoke on this enzyme.

The lack of association between monoamine oxidase (MAO) intron 13 polymorphism and platelet MAO-B activity among men

“…(Oreland, 2004), that have been shown to increase platelet MAO-B activity. Although older age has been associated with increased values of MAO-B in platelets (Nicotra et al, 2004), and in brain (Fowler et al, 2003;Karolewitz et al, 2005), but also the lack of significant effect of age on platelet MAO-B activity has been observed (Coccini et al, 2005), we did not find any significant correlation between platelet MAO-B activity and age of the subjects either in smokers or in nonsmokers. In addition, age as a covariate did not affect significantly platelet MAO-B activity in the large groups of control male subjects in our study, presumably because our 225 healthy male blood donors were 42 years old (the dispersion of the age data was less than 2%), and slight nonsignificant age-related increase of platelet MAO-B activity was detected only in the older male subjects than the group used in our study (Coccini et al, 2005).…”

“…Smoking is a factor contributing to a lower MAO-B activity (Fowler et al, 2003;Pivac et al, 2005), and decreased binding of 3H-lazabemide to MAO-B in the right amygdaloidal complex has been found in postmortem brains of the smoking subjects (Karolewitz et al, 2005). It is assumed that factors in the cigarette smoke might be associated with development of addiction (Fowler et al, 2003).…”

Dopamine receptor gene expression in human amygdaloid nuclei: Elevated D4 receptor mRNA in major depression

“…Human brain tissue was collected at autopsy at the Cuyahoga County Coroner's Office in Cleveland, Ohio, in accordance with an approved Institutional Review Board Protocol, as described previously (Karolewicz et al, 2005). For the study of receptor mRNA distribution, discarded brain tissues from 7 subjects (5 males, 2 females) were collected at autopsy and detailed medication and psychiatric histories were unavailable.…”

Dual-Target–Directed Drugs that Block Monoamine Oxidase B and Adenosine A Receptors for Parkinson's Disease

“…12,13 Furthermore, inhibitors of the MAOs may also exert a neuroprotective effect by decreasing the production of potentially hazardous by-products of dopamine metabolism in the brain. 14 Considering that MAO-B activity exhibits an age-related increase in the human brain, [15][16][17] whereas MAO-A activity remains constant, 18 inhibition of this enzyme is especially relevant in PD.…”