There is evidence that stress-induced activation of sympathoadrenal system (SAS) affects the function of immune system. The aim of our work was to investigate catecholamine (CA) levels, gene expression of CA biosynthetic enzymes and adrenoceptors (ARs) in the spleen of rats exposed to single and repeated (14×) immobilization stress (IMO). Acute IMO did not affect adrenaline or noradrenaline (NA) levels in the spleen. Repeated IMO induced a rise in both CAs suggesting increased CA biosynthesis. This stimulus was associated with the increase in tyrosine hydroxylase (TH) protein, but with undetectable TH mRNA levels. That indicates predominantly neuronal origin of this enzyme. Detection of dopamine-β-hydroxylase and phenylethanolamine-N-methyltransferase gene expression points to their local production and responsiveness to IMO. Stress differently affected individual types of splenic ARs. Exposure to acute and chronic IMO increased β2-AR mRNA, which is the major immunomodulatory AR. Gene expression of α2A- and α2C-AR, the main NA autoregulatory ARs, was reduced. As a consequence, NA level increased. Thus, exposure to stress produces the rise of CAs in the spleen. The elevation of β2-AR and a drop in α2-ARs mRNA, indicate their predominant function in immune system regulation, most probably cytokine production via β2-AR and CA turnover via α2-AR uptake as well as via CA biosynthetic enzymes activity. However, the physiological role of this observation needs further investigation.
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