Effects of daily dermal application of deet and permethrin, alone and in combination, on sensorimotor performance, blood-brain barrier, and blood-testis barrier in rats

DEET and permethrin were implicated in the development or illnesses in some veterans of the Persian Gulf War. This study was designed to investigate t he effects of daily dermal application of these chemicals, alone or in comb ination, on the permeability of the blood-brain barrier (BBB) and blood-tes tes barrier (BTB) and on sensorimotor performance in male Sprague-Dawley ra ts. Groups of five rats were treated with a dermal daily dose of 4, 40, or 400 mg/kg DEET in ethanol or 0.013, 0.13, or 1.3 mg/kg permethrin in ethano l for 60 d. A group of 10 rats receive d a daily dermal dose or ethanol and served as controls. BBB permeability was assessed by injection of an iv do se of the quaternary ammonium compound [H-3]hexamethonium iodide. While per methrin produced no effect on BBB permeability, DEET alone caused a decrea se in BBB permeability in brainstem. A combination of DEET and permethrin s ignificantly decreased the BBB permeability in the cortex. BTB permeability was decreased by treatment with DEET alone and in combination with permeth rin. The same animals underwent a battery of functional behavior tests 30, 45, and 60 d after exposure to evaluate their sensorimotor abilities. All t reatments caused a significant decline in sensorimotor performance in a dos e- and time-dependent manner. These results show that daily dermal exposure to DEET, alone or in combination with permethrin, decreased BBB permeabili ty in certain brain regions, and impaired sensorimotor performance.