The aim of the study was to evaluate the neurotoxic effect of a dermally-applied
mixture of chlorpyrifos and cypermethrin in rats based on cognitive function,
activity of the blood cholinesterase and brain acetylcholinesterase, as well as
histologic brain examination. Nurelle D 550 EC (500 g of chlorpyrifos and 50 g
of cypermethrin) was used in the study. The application liquid was in the form
of a water solution. The investigation covered eight groups of animals: six
experimental groups and two control groups, of 15 rats each. Experimental groups
received 5.6 mg/cm² chlorpyrifos and 0.5 mg/cm²
cypermethrin, or 27.8 mg/cm² chlorpyrifos and 2.7 mg/cm²
cypermethrin dermally, for one day, one week and four weeks, except for
Saturdays and Sundays. The preparations examined were applied to the tail skin
of rats. The animals were anaesthetized at the end of exposure period. Plasma
cholinesterase and brain acetylcholinesterase activities were determined. The
brain for histological examination was perfused with a solution of methanol,
formalin and glacial acetic acid, and the sections stained by the Nissel method.
The behaviour of the animals was evaluated in the open field test four times:
before exposure, and after one, two and four weeks of the experiment. The
results of the study showed that chlorpyrifos and cypermethrin applied in a
mixture caused an inhibition of cholinesterase and acetylcholinesterase activity
and elicited the pycnosis of brain neurocytes