Adrenergic suppression of peripheral blood T cell reactivity in the rat is due to activation of peripheral α2-receptors

Abstract A 20-h treatment of rats with catecholamines using s.c. implantable retard tablets markedly suppresses the in vitro reactivity of peripheral blood (PBL) T lymphocytes, provided that β-receptors are blocked with propranolol (Felsner et al., 1992). The results can be summarized as follows: (i) the suppressive effect of noradrenaline + propranolol to the concanavalin A (ConA) response of PBL was abolished by the simultaneous application of the α-blocker phentolamine. Using selective agonists, the relevant receptor was identified to belong to the α 2 -subtype. (ii) The α-adrenergic suppression of the PBL T cell response was likewise observed in adrenalectomized animals, which rules out the participation of secondarily induced glucocorticoids. Furthermore, the combination of noradrenaline with the watersoluble β-blocker nadolol was equally effective to suppress the ConA response of PBL. (iii) An analogous α-mediated suppression of T cell function of PBL, but not spleen cells, was observed 1 h after i.p. treatment with tyramine, which leads to the release of endogenous noradrenaline. From these results it is concluded that the adrenergic suppression of PBL T cell functions is primarily due to the activation of peripheral α 2 -receptors and that it is likewise observed under acute indirect sympathomimetic treatment.