Dopamine D<sub>1</sub>- and D<sub>2</sub>-Receptors in Immunostimulation under Activation of Mu-Opioid Receptors in Mice with Different Psychoemotional States

Abstract

The purpose of the present study was to analyze the effect of activation of mu-opioid receptors (mu-OR) on the immune response under blockade of postsynaptic D 1-and D 2-receptors in mice of the C57BL/6J strain displaying either aggressive or depressive-like behaviors in the social conflict model. It is shown that activation of activation of mu-OR with a highly selective agonist DAGO (100 µg/kg) increased significantly IgM-immune response not only in C57BL/6J mice with an unchanged psychoemotional state but also in mice displaying aggressive or depressive-like behaviors in the social stress model (10 days of agonistic confrontations). Selective blockade of DA receptors of the D 1-type with SCH-23390 (1.0 mg/kg with DAGO administration) caused a more pronounced elevation of IgM-immune response than DAGO alone while DAGO effect was completely blocked by prior administration of D 2-receptor antagonist haloperidol (1.0 mg/kg). At the same time, both SCH-23390 and haloperidol prevented the immune response increase induced by DAGO injection in mice engaged in aggressive or depressive-like behaviors. Thus, in animals not subjected to social stress DAGO-induced immunostimulation is provided only by D 2-receptors, whereas in animals with altered psychoemotional state mu-opioid immunostimulation is mediated by both types of DA receptors-D 1 and D 2. These data provide evidence for different impacts of the main subtypes of DA receptors in the mediation of immunomodulating effects of mu-opioid system under normal and stressful conditions.