Behavioral alterations induced in rats by a pre- and postnatal exposure to 2,4-dichlorophenoxyacetic acid.

The purpose of this study was to determine whether the behavioral development pattern was altered by a pre- and postnatal exposure to 2,4-Dichlorophenoxyacetic acid (2,4-D). Pregnant rats were daily orally exposed to 70 mg/kg/day of 2,4-D from gestation day (GD) 16 to postnatal day (PND) 23. After weaning, the pups were assigned to one of the two subgroups: T1 (fed with untreated diet until PND 90) and T2 (maintained with 2,4-D diet until PND 90). Effects on offsprings were evaluated with a neurotoxicological test battery. Neuromotor reflexes, spontaneous motor activity, serotonin syndrome, circling, and catalepsy were analyzed during various postnatal ages. 2,4-D neonatal exposure induced delay of the ontogeny of righting reflex and negative geotaxis accompanied by motor abnormalities, stereotypic behaviors (excessive grooming and vertical head movements), and hyperactivity in the open field. Adult rats of both sexes (T2 group) showed a diminution of ambulation and rearing, while excessive grooming responses were only observed in T2 males. Besides, these animals manifested serotonin syndrome behaviors, catalepsy, and right-turning preference. Some behaviors were reversible, but others were permanent, and some were only expressed after pharmacological challenges.