INFLUENCE OF NEONATAL TREATMENT WITH THE PYRETHROID INSECTICIDE CYPERMETHRIN ON THE DEVELOPMENT OF DOPAMINE-RECEPTORS IN THE RAT-KIDNEY

The influence of neonatal treatment with the pyrethroid insecticide cy permethrin ((R,S)alpha-cyano-3-phenoxybenzyl rans-3-(2,2-dichloro-viny l)-2-dimethylcyclopropane carboxylate) on postnatal development of ren al dopamine receptors was investigated by radioligand binding assay te chniques. Treatment with cypermethrin was made on rats from the 10th t o the 16th day after birth. Dopamine D-1- and D-2-like receptors were assayed in frozen sections of kidney of 21-, 30-, 60- and 90-day-old r ats using as ligands of dopamine D-1- and D-2-like receptors oro-2,3,4 ,5,-tetrahydro-5-phenyl-1,4,-benzazepinal hemimaleate) (SCH 23390) and [H-3]spiperone, respectively. Treatment with cypermethrin was without effect on the affinity (K-d value) or the density (B-max value) of do pamine D-1- and D-2-like receptors of rats of 21 days of age. In older groups, treatment with the compound reduced the affinity and increase d the density of dopamine D-1-like receptors, whereas it was without e ffect on the affinity of dopamine D-2-like receptors and decreased the ir density. These findings indicate that neonatal treatment with the p yrethroid insecticide cypermethrin induces long-lasting impairment of renal dopamine D-1- and D-2-like receptors, and that kidney is a targe t of the toxic action of the compound. Renal dopamine receptor changes caused by cypermethrin are consistent with possible alterations of re nal tubular function and of sympathetic neuroeffector modulation. The above data suggest also that, different from the adult, neonatal expos ure to pyrethroid insecticides may induce toxic effects. (C) 1998 Else vier Science Ireland Ltd. All rights reserved.