Possible anxiogenic effects of fenvalerate, a type II pyrethroid pesticide, in rats

Pyrethroids are insecticides extensively used to control pests around houses as well as in agriculture. It has been suggested that type II pyrethroids may act on GABA receptors as benzodiazepine antagonists. Because benzodiazepines are used in anxiety, the present study was undertaken to investigate the possible anxiogenic effects of fenvalerate, a type II pyrethroid, in rats. Behavior in the open-field, social interaction, plus-maze behavior, and one-way passive avoidance were studied in rats orally treated with 1, 10, or 30 mg/kg fenvalerate. This pyrethroid reduced locomotion and rearing frequencies and increased immobility duration. Ten and 30 mg/kg of fenvalerate reduced social interaction, whereas the 1 mg/kg dose had no effect on this behavior. Fenvalerate administration did not change the plus-maze behavior of rats. Pretraining administration (1, 10, and 30 mg/kg) did not modify the behavior of rats during the training session of a passive avoidance task, while in the test session 10 mg/kg fenvalerate caused an increase in the crossing latency, and the 30 mg/kg dose reduced this parameter and increased the percent of animals crossing to the shock compartment. The behavioral alterations observed in this study suggest that fenvalerate has an anxiolytic effect on rats. (C) 1999 Elsevier Science Inc.