Cognitive testing (delayed non-match to sample) during oral treatment of female adolescent monkeys with the estrogenic pesticide methoxychlor.

This report presents preliminary data from a study of endocrine disruption in adolescence. A delayed non-match to sample (DNMS) task was used to assess the effects of the endocrine-active agent methoxychlor (MXC; 0, 25, or 50 mg/kg/day oral administration) in adolescent female monkeys 24-36 months of age (n=7-8/group). The testing utilized an automated touchscreen operant system (Cambridge Neuropsychological Test Automated Batteries [CANTAB]) with abstract, trial-unique visual stimuli. Basic performance of the task was established prior to dosing, training with simultaneous presentation of sample and choice stimuli continued during dosing, and delays (1/2, 1 or 2 s) were introduced near the end of the dosing period. The MXC50 group performed more poorly than controls during delay testing at the end of the dosing period, as well early in training with simultaneous presentation. No interaction between treatment group and delay interval was found. No significant differences from controls were observed at the lower dose (MXC25). Thus, MXC at a daily dose of 50 mg/kg appeared to interfere in a general way with performance of this visual discrimination and memory task. Further investigation will be needed to identify the impairment leading to this performance deficit.