TRIPHENYL PHOSPHITE-INDUCED IMPAIRMENT OF SPATIAL ALTERNATION LEARNING

Triphenyl phosphite (TPP) is a weak acetylcholinesterase inhibitor and a type II organophosphorus compound-induced delayed neurotoxic agent. The current study examined the cognitive effects of a single 250 mg/k g ip dose of TPP administered to either 3-mo- or 1-yr-old male Sprague -Dawley rats. Starting 4 d after TPP administration, the rats began tr aining on a T-maze spatial alternation task for food reinforcement. Ov er five sessions of acquisition training, the TPP-treated rats showed significantly lower alternation scores than controls. There was no dif ference in spatial alternation performance in the first session, when both groups were performing at near-chance levels. In sessions 2-5, th e controls improved dramatically to an average of 85.3 +/- 3.2% correc t, while the TPP-treated rats did not significantly change, with 69.7 +/- 3.1 percent correct. During sessions 2 and 3 there was a significa nt TPP treatment-related deficit. This TPP-induced choice accuracy def icit was persistent in that it was seen well after the acute exposure. With continued training the TPP-exposed-rats were able to learn the t ask as well as controls. There were no significant TPP effects on resp onse latency. These data show that acute TPP administration has persis tent effects of impairing T-maze learning that do not appear to result from effects on motor function.