Immune response during activation of pre- and postsynaptic serotonin 5-HT(1A) receptors in C57Bl/6J mice at various stages of a depression-like state

The development of a depression-like state in C57Bl/6J mice with repeated defeat experience (10 and 20 days) was accompanied by inhibition of the immune response (evaluated from the number of IgM antibody-producing cells). Activation of postsynaptic 5-HT(1A) receptors with a selective agonist 8-OH-DPAT (1.0 mg/kg) in these animals had no effect on the immune reaction. In mice without the experience of confrontations, stimulation of postsynaptic receptors caused a decrease in the number of IgM antibody-producing cells at the peak of the immune response induced by sheep erythrocytes (5×10(8) cells). However, the count of these cells remained unchanged in mice with a depression-like state (irrespective of the stage of disorder). Activation of presynaptic 5-HT(1A) receptors with 8-OH-DPAT (0.1 mg/kg) in control animals and mice with 10-day defeat experience was followed by immune stimulation. These changes were not observed in mice with a depression-like state caused by 20-day social stress.