Subsequent stress increases gene expression of catecholamine synthetic enzymes in cardiac ventricles of chronic-stressed rats.

Since previous experience of stressful situation profoundly affects response to a subsequent novel stressor, we examined changes in gene expression and protein levels of catecholamine biosynthetic enzymes in cardiac ventricles after exposure of chronic psychosocially isolated adult Wistar male rats to short-term immobilization stress. Chronic social isolation did not affect gene expression of tyrosine hydroxylase (TH) in either right or left ventricle. Subsequent immobilization of these animals produced an elevation of TH mRNA level in right and left ventricles. The levels of dopamine-β-hydroxylase (DBH) mRNA were detectable only after immobilization both in right and left ventricles of control and chronically isolated rats. Chronic isolation stress increased phenylethanolamine N-methyltransferase (PNMT) mRNA levels in the right ventricle. Immobilization led to an elevated PNMT mRNA level in right and left ventricles of both control and chronically stressed animals. Protein levels of TH, DBH, and PNMT in right and left ventricles of socially isolated rats were increased after subsequent immobilization. Taking into consideration the role of cardiac catecholamines in physiological and pathophysiological processes, it could be hypothesized that increased catecholamine synthesis in the ventricles after novel immobilization stress could point to the susceptibility of the heart to subsequent stress.