ALTERED BEHAVIORAL-RESPONSES IN 2,4-DICHLOROPHENOXYACETIC ACID-TREATED AND AMPHETAMINE CHALLENGED RATS

Although the mechanism of 2,4-D neurotoxicity remains unknown the sero tonergic system appears to mediate some of the effects of 2,4-D in rat s as reported in our previous studies. In the present study we examine the concept that a challenge to a system may overcome compensatory me chanisms and thereby reveal otherwise hidden neurotoxicant-induced dam age. We report the behavioral results of 50 or 100 mg/kg 2,4-Dichlorop henoxyacetic acid (2,4-D) acute exposure plus amphetamine challenge of rats. The ''Seroton in Syndrome'' (SS) involving prominently head mov ement, piloerection, moist fur, backing, hunching, Straub tail, fore p aw tapping of the nose and pivoting, was exhibed by these rats, being females more affected than males. Immobility, social apathy and asymme try were also observed. All behaviors were not seen in the 2,4-D treat ed rats. Stereotyped behaviors were observed earlier and were more pro longed in 2,4-D treated and amphetamine challenged rats than in rats t reated only with 5 or 10 mg/kg amphetamine. Spiperone blocked all the SS behaviors. In addition, in these rats, rearing and rotation behavio rs were showed and were also sex dependent. We also demonstrate that h aloperidol, in a non cataleptic dose, induced catalepsy in 2,4-D treat ed rats. 2,4-D appears to act through serotonergic and dopaminergic me chanisms. The intensity of the response is sex dependent. Our study de monstrates that 2,4-D plus amphetamine induces a Serotonergic Syndrome plus additional Dopaminergic modulation. (C) 1995 Intox Press, Inc.