Influence of Permethrin and Cypermethrin on Behavior in the Mouse

Permethrin and Cypermethrin are synthetic pyrethroids, belonging to a group of insecticides with low mammalian toxicity and high insecticidal activity. The present study evaluated sub-acute toxicity of dermally administrated permethrin and cypermethrin in mice. Behavioral examination included assessments of lethality, weight gain, grooming, analgesymetry, anxiety, grasping, motor activity, and despair in response to inescapable swim stress. The study was conducted on 70 adult male mice, which were exposed dermally via the whole tail zone for 10 s once daily for 28 consecutive days at concentrations of 0%, 0.1%, 1% and 10% of each compound. No significant changes were observed in body weight gain, grooming behavior or pain sensation among the treated and control groups. However, the following effects were observed in the experimental groups: a tendency towards increased motor activity compared to controls (47% in P0.1% group, P = 0.025), a tendency to lose grasping faster than controls (48% and 40% decreased in P10% and C1% groups, respectively, (P < 0.05), shorter stay in the long arms and longer stay in the short arms on the elevated plus maze task compared to controls (up to 84% difference, P < 0.05), and failure in terms of floating on the inescapable swim stress task (500% and 900% increase in interruption times in the P10% and C10% groups, respectively, P < 0.05). In conclusion, upon long-term dermal exposure, synthetic pyrethroids may lead to increased motor activity, decreased grasping tendency and/or ability, increased apathy, and increased despair in the mouse animal model.