Effects of an organophosphate (dichlorvos) on open field behavior and locomotor activity: correlation with regional brain monoamine levels.

Dichlorvos (O,O-dimethyl-2:2-dichlorovinyl phosphate) was administered IP (3 mg/kg) daily for 10 days to a group of albino rats. Open field behavior was significantly depressed below the mean of the control group. On day 7, ambulation was reduced to 24% of the mean but recovered to 60% on day 10. Similarly, rearing response was decreased on day 7 and showed a fast recovery on day 10 but the preening response further declined on day 10. Defecation, on the contrary, was suppressed to 0% on day 7 and showed complete recovery on day 10. Motor activity showed a significant depression and fine movements were reduced more than gross movements in the second phase. Dopamine was significantly decreased on days 5 and 7 but showed a 13% recovery in the brain stem on day 10. Norepinephrine was significantly reduced in the cerebral hemisphere while serotonin was decreased both in cerebral hemisphere and brain stem. Neither of thse two amines showed significant recovery on day 10. Interesting concordance of the open field behavioral changes with the levels of dopamine, norepinephrine, and serotonin in the various regions of the rat brain was noticeable and has been discussed.