Cypermethrin-induced apoptosis in the telencephalon of Physalaemus biligonigerus tadpoles (Anura : Leptodactylidae)

Worldwide attention has been focussed recently on amphibians because of con cerns that populations are declining globally (Wake 1991; Hedges 1993). Pes ticide pollution is probably one of the most important factors causing amph ibian decline in agricultured regions (Berrill et al., 1994). Cypermethrin (CY) (RS)-alpha-cyano-3-phenoxybenzyl (1RS)-cis-, trans-3-(2,2 , - dichlorovinyl)-2,2-dimethylcyclopropane carboxylate) is a highly active synthetic pyrethroid type II. Synthetic pyrethroids have increased in popu larity for control of insect pest in agricultural and aquatic systems (Smit h and Stratton 1986). They are characterized by strong, broad-spectrum inse cticidal activity, based on their neurotoxicity (Salibian 1992). Salibian a nd Marazzo (1995) noted that the biocidal action of most pyrethroids is lik ely produced by alterations in the ion conductance of nerve cell membranes. Berlin et al. (1984) showed that pyrethroids cause increase transmembrane sodium influx and inhibition of ion-dependent ATPases in nervous tissues of insects, squids and toads. Moreover, pyrethroids have been recently postul ated to induce apoptosis in the testicular tissues of the rat, by mechanism s mediated via nitric oxide and other reactive oxygen species (El-Gohary et al. 1999). The purpose of this work was to examine under laboratory conditions the sub -lethal and acute doses of CY in Physalaemus biligonigeuus tadpoles, throug h their survival and the effects of CY on brain morphology.