Dopamine receptors on isolated membranes of rat lymphocytes

Using [3H]-dopamine (DA) as the ligand of choice, we have shown that rat lymphocytes possess DA binding sites. The binding of [3H]-DA was specific, saturable, and of high affinity. The specific binding in membranes obtained from Con A-activated lymphoblasts was greater than the binding in respective unactivated lymphoid cells, and displaced by lower concentrations of unlabeled ligand. [3H]-DA was displaced specifically by DA, norepinephrine, and apormorphine. The binding sites were insensitive to neuroleptic drugs such as sulpiride, bromocryptine, and haloperidol. On the basis of these findings, we have suggested that lymphocytes possess a receptor site for catecholamines and the receptor for DA might be a D-3 receptor type.