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NEUROBEHAVIORAL EFFECTS OF CHRONIC DIETARY AND REPEATED HIGH-LEVEL SPIKE EXPOSURE TO CHLORPYRIFOS IN RATS.
Citation:
MOSER, V. C., P. PHILLIPS, K. MCDANIEL, R. S. MARSHALL, D. L. HUNTER, AND S. J. PADILLA. NEUROBEHAVIORAL EFFECTS OF CHRONIC DIETARY AND REPEATED HIGH-LEVEL SPIKE EXPOSURE TO CHLORPYRIFOS IN RATS. . TOXICOLOGICAL SCIENCES. Society of Toxicology, RESTON, VA, 86(2):375-386, (2005).
Description:
This study aimed to model long-term subtoxic human exposure to an organophosphorus pesticide, chlorpyrifos, and to examine the influence of that exposure on the response to intermittent high-dose acute challenges. Adult rats were maintained on a chlorpyrifos-containing diet to produce an intake of 0, 1, or 5 mg/kg/day. During the year-long exposure, half of the rats in each dose group received bi-monthly challenges (spikes) of chlorpyrifos, and the other half received vehicle. Rats were periodically tested using a neurological battery of evaluations and motor activity to evaluate the magnitude of the acute response (spike days) as well as recovery and ongoing chronic effects (non-spike days). Effects of the spikes differed as a function of dietary level for several endpoints (e.g., tremor, lacrimation), and in general, the high-dose feed groups showed greater effects of the spike doses. Animals receiving the spikes also showed some neurobehavioral differences among treatment groups (e.g., hypothermia, sensory and neuromotor differences) in the intervening months. During the eleventh month, rats were tested in a Morris water maze. Cognitive deficits were demonstrated by slightly longer latency during spatial training, and decreased preference for the correct quadrant on probe trials. A consistent finding in the water maze was one of altered swim patterning, or search strategy. The high-dose feed groups showed more tendency to swim in the outer annulus or to swim very close to the walls of the tank; this thigmotaxic behavior could be considered to be indicative of anxiety. Overall, dietary exposure to chlorpyrifos produced long-lasting neurobehavioral changes and also altered the response to intermittent high-dose challenges