The presence of nicotinic receptors (nAChRs) in blood cells has been demonstrated. However, little is known about their functional roles. We have detected mRNA of alpha 7 nAChR in peripheral human lymphocytes and determined that its expression is highly variable among individuals and within the same individual at different times. Upregulation of alpha 7 is systematically observed after incubation of lymphocytes with nicotine or alpha-bungarotoxin. In addition, the incubation with these drugs decreases the percentage of apoptotic cells induced by the exposure to cortisol. Our results suggest that alpha 7 nAChRs are involved in the modulation of cortisol-induced apoptosis. (c) 2004 Elsevier B.V. All rights reserved.