Evaluating Performance Effects of Low-Level Inhalation Exposure to Nerve Agents in Rats

Abstract

To investigate cognitive and general performance effects of low-level exposure to an organophosphorus chemical warfare agents (CWA), we evaluated behavior in rats inhalation-exposed (whole body, 60 min duration) to GB (1.7 mg/m3 -4.0 mg/m3 X 1; 4.0 mg/m3 x 3) and GF (1.6-5.2 mg/m 3 X 1). Before exposure, rats were trained on a variable-interval 56 sec schedule of reinforcement (VI56), which served as a general index of behavioral performance. Beginning 48 hours after inhalation exposure, testing on the VI56 continued and acquisition of a four-of-eight, radial-arm maze task began. Performance on the maze task provided a measure of acquisition of a new task having a substantial cognitive component (i.e., spatial memory). Evaluations using both procedures were conducted during 55 sessions occurring during approximately 11 weeks following exposure. Performance deficits were observed, as a decrease in response rate, on the VI56 procedure following the highest concentrations tested of GB and GF. The deficits, however, were small and resolved relatively quickly. Small differences in the initial phases of acquisition on the maze task were observed in that some CWA-exposed rats tended to take longer to solve the maze and to make more errors. All rats, however, learned and maintained proficiency on the task. No deficits were observed to have a delayed onset. These results demonstrate that, in rats, low-level, largely asymptomatic, inhalation exposure to CWA can produce small performance deficits, but the deficits are not persistent.