Effects of repeated administration of soman on schedule-controlled behavior and brain in the rat

The effects of repeated SC administration of soman on schedule-controlled performance and brain pathology were studied in the rat. Soman suppressed response rates in both components of a multiple fixed interval 50-sec fixed-ratio 25 (mult. FI 50-sec FR 25) schedule of reinforcement, although all animals revealed marked tolerance to repeated drug administration. Response rates generally recovered to baseline levels within 1-3 sessions. Three of the six animals studied, however, demonstrated marked deterioration of steady state schedule performance, particularly during the FI 50-sec component of the multiple schedule. Compared to untreated controls, all soman-treated animals exhibited pathological changes in brain. The most salient finding was glial cell proliferation in layer 4 and deep parts of layer 3 of the cerebral cortex. Glial cell proliferation was most marked in animals that exhibited deterioration of steady state schedule performance.