Effects of VX on Acoustic Startle Response and Acquisition of Operant Behavior in Rats

摘要

This study evaluated the dose-response effects of subacute exposure to sublethal doses of VX on acoustic startle response (ASR) and operant behavior of rats. ASR baseline was established and rats were exposed to 2 consecutive daily doses of fractions (0.2, 0.4, and 0.6) of the established LD50 of VX (16 micrograms/kg). ASR testing continued for 4 days post-exposure. Subsequently animals were dietary restricted and trained to lever press for food under an autoshaping procedure; then a series of escalating fixed ratio (FR) schedules was introduced. Four sessions were conducted under a differential reinforcement of low response rate 10. (DRL 10 s) schedule. Performance under an ascending and descending series of geometric progressive ratio schedules was evaluated. VX decreased the magnitude of ASR on injection days to 100-dB pulses for all exposed groups and to 120-dB pulses only for the 0.4 and 0.6 LD50 groups. VX increased the latency to peak startle magnitude in animals receiving 0.4 and 0.6 LD50 on injection days. There were no significant dose-related effects on prepulse inhibition and no significant dose-related differences on the acquisition of lever pressing via autoshaping, lever pressing under escalating FR schedules, responding under DRL 10 s schedules of reinforcement, nor responding under geometric progressive ratio schedules. These data indicate few persistent effects of subacute VX exposure on the acquisition of operant behavior.