Effects Of Early Postnatal Exposure To M-tolyl Methylcarbamate On Neurobehavior Of Mice Before Adult

Backgroundm-tolyl methylcarbamate(MTMC)is one of carbamates pesticides often used in our country, to which human are exposed in various environment. MTMC is neurotoxicity and can inhibit acetylcholinesteras(eAChE)activity. Previous studies have showed that MTMC has acute toxicity, however, its chronic and developmental neurotoxicity exposured to low dosage is still unknown and unconcerned.ObjectiveTo observe the effects of early postnatal exposure to low-dose m-tolyl methylcarbamate(MTMC)on neurobehavior and spatial learning and memory ability in adolescence and early adult mice, and to determine when to affect those ability.MethodsICR mice pups randomly divided into 5 groups were received intraperitoneal injections (i.p.) of different doses of MTMC (5,0.5,0.05 mg·kg-1 ), DMSO solution and normal saline respectively every other day during postnatal days (PND) 3-13. The general physiological condition and neural development of mice during experiment were evaluated, and a battery of tasks i.e. hole-board test, spontaneous locomotor apparatus, beam walking, open field, Morris water maze (MWM), was used to assess them spontaneous motor activity, sensorimotor activity, anxiety and spatial learning and memory ability in different time. Whole blood and cortex acetylcholinesterase(AChE)activity was assayed on PND98 and 24h after last injections.All analyses were carried out using the statistical software SPSS13.0 for windows.ResultsThere was a significant delay in eye opening in MTMC-exposure groups compared with NS control. Scores were negatively correlated to the doses of MTMC by Spearman rank correlation analysis in beam walking on PND60(rs=-0.418,P<0.05). There were no significant differences among all groups in hole-board test and open field. Numbers of platform-site crossovers in probe phases of MWM procedure immediately after learning phases and next day about on PND60 were negatively correlated to the doses of MTMC by Spearman rank correlation analysi(srs=-0.361 and -0.277,P<0.05). Time in the target quadrant in probe phases of MWM procedure about on PND90 were negatively correlated to the doses of MTMC by Spearman rank correlation analysis(rs=-0.390,P<0.05). Noteworthy, principal components analysis showed that spatial learning and memory performance may be not related to performance in any of the three sensorimotor tasks.ConclusionsPostnatal early exposure to MTMC may initiate to affect spatial memory ability at least in adolescence mice, that would be the critical cues for the damage of spatial memory ability in adult mice.