The differential contribution of dopamine D(1) and D (2) receptors to mu-opioidergic immunomodulation.

Activation of mu-opioid receptors (mu-OR) by the highly selective agonist DAGO (100 microg/kg) significantly increased the immune response in CBA mice. This effect of the mu agonist was prevented by prior blockade of dopamine D(2) receptors with haloperidol (2 mg/kg). In contrast, the selective D(1) receptor antagonist SCH 23390 (1 mg/kg) had no effect on the nature of the immune reaction in response to antigen (sheep erythrocytes, 5 x 10(8) cells). However, blockade of both types of dopamine receptor led to the same effect--immunosuppression. These data lead to the suggestion that D(1) and D(2) receptors make different contributions to modulating immunogenesis on activation of mu-OR.