CONICET | Buscador de Institutos y Recursos Humanos

Neurotoxicol. Teratol. 2015 Sep 15; 52(Pt A):1-10. doi: 10.1016/j.ntt.2015.09.005doi: 10.1016/j.ntt.2015.09.005Most pyrethroid (PYR) insecticides may be classified either as type-I compounds, which produce whole body tremors and hyperthermia, or type-II compounds, which produce salivation, choreoathetosis, and hypothermia. This dual classification is based on clinical observations in adult rats and mice after intracerebro-ventricular or intravascular administration of highly effective acute (bolus) doses. PYR neurotoxicity in infant animals is not characterized as much as in adult animals. Endpoints informing on vital determinants of mammal?s maturation, such as the thermoregulatory response, may help recognizing age-related differences in susceptibility to PYRs. In this work, body temperature (Tb) was monitored at 30-min intervals after acute oral exposure to bifenthrin (BIF), cypermethrin (CYPM), and a BIF-CYPM mixture in weanling rats by using subcutaneous temperature monitoring system. In both single-compound assays, a time- and dose-related decline of Tb was the most evident impact on thermoregulation observed starting at ~2-3 h after dosing. Moreover, 15-18 mg/kg BIF induced a mild increase in Tb before the hypothermic action was apparent. The lowest effective dose for thermoregulatory response was 15 mg/kg for BIF and 10 mg/kg for CYPM, and moderate neurobehavioral alterations were evident at 12 and 10 mg/kg, respectively. When low effective doses of BIF and CYPM were co-administered mild behavioral effects and a transient increase in Tb (p = 0.02) were observed at 1-2 h, and no Tb decline was apparent afterwards compared to control animals. Our results suggest that the thermoregulatory response may be useful as a complementary endpoint to reveal qualitative age-specific pesticide effects in rats.