Chick embryo exposure to carbamates alters neurochemical parameters and behavior

Recent evidence has shown that exposure to pesticides can lead to long-term neurophysiological and functional deficits. We have demonstrated previously that locomotion in chicks exposed to some organophosphates and carbamates could be altered persistently without concomitant central or peripheral esterase inhibition. Furthermore, histopathology of the ataxic chickens showed no lesions in either the central or peripheral systems. In this study, we examined whether locomotion alterations seen in chicks exposed in ovo to carbaryl and aldicarb are accompanied by perturbations in particular central neurotransmitter systems. Carbaryl and aldicarb were injected in ovo on day 15 of incubation at 6, 16 and 65 mg kg-1 egg weight and at 0.2, 0.4 and 35 mg kg-1 egg weight, respectively. Neurotransmitter levels (assayed by high performance liquid chromatography with electrochemical detection) and locomotion were measured at various times (1-43 days) after dosing. At the lower doses of both carbaryl and aldicarb, a trend towards prolonged decreases in cerebral dopamine and homovanillic acid was seen. The high dose of carbaryl significantly reduced dopamine and the high dose of both compounds significantly decreased homovanillic acid and 5-hydroxyindoleacetic acid. Persistent locomotion alterations were observed only at the higher doses of both carbaryl and aldicarb when the specific neurotransmitters measured returned to normal levels.