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INHIBITION OF BRAIN CHOLINESTERASE AND THE PHOTIC AFTER DISCHARGE OF FLASH EVOKED POTENTIALS PRODUCED BY CARBARYL IN LONG EVANS RATS.
Citation:
MWANZA, J., J. GRAFF, C. SPIVEY, AND D. W. HERR. INHIBITION OF BRAIN CHOLINESTERASE AND THE PHOTIC AFTER DISCHARGE OF FLASH EVOKED POTENTIALS PRODUCED BY CARBARYL IN LONG EVANS RATS. Presented at Society of Toxicology, San Diego, CA, March 05 - 09, 2006.
Description:
Carbaryl is a widely used N-methyl carbamate pesticide that acts by inhibiting cholinesterases (ChE), which may lead to cholinergic toxicity. Flash evoked potentials (FEPs) are a neurophysiological response often used to detect central nervous system (CNS) changes following exposure to neurotoxic compounds. Disruption of CNS function by ChE inhibitors decreases the photic after discharge (PhAD) of the FEP. To determine the dose-response for carbaryl on the PhAD, FEPs were recorded in adult male Long-Evans rats after oral gavage with carbaryl 0, 1, 3, 10, 30, 50 or 75 mg/kg in a corn oil vehicle. One week before testing, rats were implanted with electrodes over the visual cortex and allowed to recover. FEPs were recorded for 2 consecutive days to familiarize the rats with the test procedure and to develop the PhAD. On the 3rd day, pupils were dilated (40 min) and animals dosed (30 min) before testing. Immediately after testing, rats were sacrificed, and the brains removed and stored at -80oC, until determination of brain ChE levels using a radiometric assay. All doses greater than 1 mg/kg of carbaryl produced a significant inhibition of brain ChE. Three-75 mg/kg carbaryl resulted in 22-60% inhibition of brain ChE. The duration of both peak N166 and the PhAD were significantly decreased at 75 mg/kg by 18 and 48%, respectively. A correlation was obtained between brain ChE levels and the PhAD duration. A slight decrease in colonic temperature was observed at 30 and 50 mg/kg carbaryl. The peak N166 latency of treated animals did not differ from that of controls. There was no effect on the amplitude of the early components of the FEP. These results indicate that ChE inhibition produced by carbaryl disrupts the cortical processing related to the later portion of the FEP. 1Supported by a NRC Fellowship. This is an abstract of a proposed presentation and does not necessarily reflect EPA policy.