Analysis of Sigma-1 Receptor Binding Ability Under Emotional Stress and Upon Administration of the Anxiolytic Afobazole

Specific binding of the sigma-1 receptor (Sigma1R) ligand [ 3 H]-(+)-pentazocine was determined in the P2 and P3 fractions of brain homogenates from inbred BALB/c and C57BL/6 mice after emotional stress in the open-field (OF) test and outbred CD-1 mice after administration of the anxiolytic afobazole. Exposure in the OF test increased specific binding of [ 3 H]-(+)-pentazocine to the P3 fraction of BALB/c mice brain homogenates as characterized by catatonia in the OF test and did not affect ligand binding in C57BL/6 mice with active behavior in the OF test. Afobazole at a dose of 5 mg/kg increased specific binding of [ 3 H]-(+)-pentazocine to the P2 fraction of outbred CD-1 mice brain homogenates. The results indicated that Sigma1R was involved in the formation mechanism of emotional stress responses and in afobazole pharmacodynamics.