Volume 55 (2005) Issue: 2005 No#2-3

Modulatory effects of neurotoxic insecticides on the peripheral and central GABA-ergic action

Author(s): Stanković Jasmina, Varagić V, Milovanović S

Keywords:malathion, lindan, permethrine, enteric nervous system, barbiturate sleeping time.

On the terminal part of the guinea-pig ileum GABA produces contraction, whereas on the preterminal it produces an initial shortlasting contraction, followed by a prolonged relaxation. The increasing range of concentrations of GABA produces a concentration-dependent decrease in contractions and an increase in contractions of the preterminal ileum. Both contractions and relaxations can be blocked by atropine, indicating the cholinergic nature of the responses. These effects are due to the action on GABAA receptors. Depending on the duration of the incubation period (3 and 60 sec) GABA produced either potentiation or depression of the contractile effects of acetylcholine on the ileum. All the three neurotoxic insecticides (lindan, malathion, permethrine) affect the contractile effects of acetylcholine on the ileum. Lindan and permetrine antagonized the contractile effects of acetylcholine, whereas malathion produced a potentiation. Malathion significantly depressed the contractile effects of the electrical field stimulation of the ileum. This effect is probably realized through the local release of GABA. Both lindan and permethrine were found to decrease the duration of the barbiturate sleeping time, whereas malathion significantly prolonged its duration. The action of lindan and permethrine is presumably realized by blocking or interfering with the function of GABAA receptors. Malathion is an anticholinesterase, thus producing an accumulation of acetylcholine at the critical sites, consequently producing a prolongation of the barbiturate sleeping time. In conclusion, neurotoxic insecticides (lindan, permethrine, malathion) affect both central and peripheral GABA-ergic systems. They can produce either depression or stimulation of these systems. They also highly significantly modulate the activity of the cholinergic system in the isolated guinea-pig ileum.