EXPERIMENTAL-MODEL STUDIES OF PESTICIDE EXPOSURE

The neurotoxic effects of Dimethoate (Dim), Dichlorvos (DDVP) and Meth yl-Parathion (MP) respectively were investigated on the central nervou s system (CNS) and peripheral nervous system (PNS) of rats after diffe rent treatment schedules at the macro and single unit cell level. At t he macro investigations 1/25 1/50 and 1/100 of the respective LD50 val ues of each pesticide were administered to different groups by gavage daily in the following programs: Pregnancy variation (P) to females fr om 5th to 15th days of pregnancy; Pregnancy and lactation variation (P +L): to females as above and during lactation for 4 weeks; Pregnancy+l actation+post weaning variation (P+L+P) as above plus to the young mal e rats (FI generation) up to 8 weeks. Neurotoxicological investigation s were conducted on the Fl rats at the age of 12 weeks. Spontaneous el ectrocorticograms (ECoG) were recorded on the anesthetized rats from t he somatosensory, visual and auditory cortex. Cortical evoked potentia ls (EP) were recorded from the same areas subsequently. Conduction vel ocity and refractory periods of the tail nerve was investigated. Treat ment by Dim, DDVP and MP during P and P+L of the mothers did not influ ence the bioelectric activity of the offsprings significantly The same treatment by the P+L+P programme, resulted in significant changes. Fr equency of the spontaneous ECoG waves grew significantly in all dose g roups of P+L+P group. Latency time become shorter after somatosensory. light or acoustic stimuli respectively on one hand and the beginning of the of answer of these by the evoked potential (EP) waves on the ot her hand. Conduction velocity of the tail nerve diminished, refractory periods grew dose dependently a nd significantly at the P+L+P program s with all the three pesticides. Cortical single unit activity was stu died after the i.p administration of 1/5 LD50 of the three organophosp hates (OP). The decrease of the firing frequencies was observed. The a mplitude of the hippocampal population spikes increased. The changes o bserved in these studies point coward a higher excitation state of the CNS and a disturbed conduction of the nervous impulses of the periphe ral nerves. These results could be taken into consideration when decid ing on human contaminations by OP-s. (C) 1998 Inter Press, Inc.