Repeated forced swim stress has additive effects in anxiety behavior and in cathecolamine levels of adult rats exposed to deltamethrin

• Behavioral and neurochemical effects of deltamethrin (DTM) plus stress were studied.
• Social interaction, serum corticosterone and neurotransmitter levels were measured.
• DTM increased anxiety and the corticosterone levels. Stress also enhanced these effects.
• Behavior and neurochemical data did not show an interaction between stress and DTM.
• These results may be important for implementing pyrethroid insecticide safety standards.

Deltamethrin (DTM) is a type II pyrethroid insecticide that elicits autonomic and neuroendocrine responses that indicate high levels of stress, presumably caused by the neurotoxic effect of the insecticide. This study investigated the effect of DTM exposure (10 mg/kg, p.o.) and an additional stress induced in the forced swim test (FST) in behavioral tasks related to anxiety, serum corticosterone levels, and striatal neurotransmitter levels. Open field behavior and social interaction were evaluated after DTM administration (10 mg kg− 1, p.o). DTM per se reduced rearing frequency in the open field, but no alterations in locomotion frequency or immobility duration were detected. Stress increased immobility duration compared with non-stressed animals. DTM reduced social interaction and increased corticosterone levels, and these effects were enhanced in stressed animals. Mainly stress affected dopaminergic and serotoninergic activity. In anxiety behavior and in both neurotransmitters and metabolites levels it was observed an additive effect of stress in DTM treated rat data. These results indicate that DTM enhanced the anxiogenic responses and stress had an additive effect over the DTM stress. The neurochemical data did not indicate an interaction between stress and DTM exposure. The present results may be important for implementing pyrethroid insecticide safety standards.

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