Behavioral and endocrine changes induced by perinatal fenvalerate exposure in female rats.

Pyrethroid insecticides have recently been linked to endocrine disruption. Endocrine disrupting chemicals have been defined as exogenous agents that interfere with the synthesis, secretion, binding, action, or elimination of natural hormones in the body. Previous research conducted in our laboratory suggests that perinatal exposure to fenvalerate, a type-II pyrethroid, interferes with brain sexual organization in male pups, probably acting on a critical perinatal hormone-related period. In the present study we investigate the effects of maternal exposure to fenvalerate (FV) during the prenatal and postnatal periods of sexual brain organization of female offspring. Behavioral (open-field, stereotyped and sexual behaviors), physical (sexual maturation, body and uterine weights), and neuroendocrine (estrous cycle and gonadal hormone levels ) parameters were assessed. Results show that 1) sexual maturation was delayed, albeit body weight was unchanged until adulthood; 2) there was a reduction in sexual behavior; 3) the estrous cycle was abnormal, and the uterine weight at different phases of the estrous cycle was modified; 4) gonadal hormone levels in the plasma were not affected, neither was stereotypy nor open-field behaviors. These results were attributed to an anti-estrogenic effect of perinatal exposure to FV during the critical periods of female brain sexual organization.

Perinatal fenvalerate exposure: behavioral and endocrinology changes in male rats.

The effects of maternal exposure to fenvalerate during the prenatal and postnatal periods of sexual brain differentiation were studied in adult male offspring. Behavioral (open field, stereotyped, and sexual behaviors), physical (sexual maturation, body and organ weights), endocrine (testosterone levels), and neurochemical (striatal and hypothalamic monoamine and respective metabolite levels) data were assessed. The results showed that there was no change in the age of testis descent or testis weight, nor were there changes in monoamine levels or stereotyped behavior. However, there were significant reductions in ductus deferens and seminal vesicle weights and plasma testosterone concentrations. In addition, treated offspring showed decreased male sexual behavior and increased immobility in the open field. These results indicate that perinatal exposure to fenvalerate during the critical periods of male brain sexual differentiation has long-term effects on the reproductive physiology and behavior of male rats.

Effects of a pyrethroid type II pesticide on conditioned behaviors of rats.

Our present work investigated the effect of fenvalerate, a pyrethroid type II pesticide, on conditioned behaviors of rats. Pre-training administration of the pesticide did not modify passive avoidance but decreased active avoidance responses and operant conditioned responses; pre-training or pre-test administration of fenvalerate induced a facilitatory effect on passive avoidance task; pre-training and/or pre-test treatments reduced active avoidance responses of rats which received the pesticide before test; and post-training treatments were not capable of modifying both active and passive avoidance responses. Increased emotionality produced by the action of fenvalerate on the sympatho-adrenal system could be responsible for the differences observed between active and passive avoidance responses.

Effects of exposure to a pyrethroid insecticide during lactation on the behavior of infant and adult rats.

Cyhalothrin, a pyrethroid insecticide, was administered to female Wistar rats as a 0.02% solution plus 0.04% sucrose (w/v) in drinking water from whelping to pup weaning after 21 days of lactation. The pesticide did not change the maternal behavior of the dams as measured by the scoring system of Soderstein and Eneroth. The body weight of pups exposed to the pesticide and at age 90 days was not different from that of controls, and the motor activity of the pups measured in a simple photocell activity cage was not affected by pesticide treatment. Furthermore, no overt signs of neural toxicity were observed in the offspring. However, the treatment disrupted rat behavior in adulthood when assessed by using an inhibitory avoidance learning task. Thus, inhibitory avoidance tests carried out on rats at 90 days of age were capable of demonstrating neural toxicity of Cyhalothrin (0.02%) present only in the drinking water of dams during 21 days of lactation.

Effects of exposure to a pyrethroid insecticide during lactation on the behavior of infant and adult rats

Cyhalothrin, a pyrethroid insecticide, was administered to female Wistar rats as a 0.02% solution plus 0.04% sucrose (w/v) in drinking water from whelping to pup weaning after 21 days of lactation. The pesticide did not change the maternal behavior of the dams as measured by the scoring system of Sderstein and Eneroth. The body weight of pups exposed to the pesticide and at age 90 days was not different from that of controls, and the motor activity of the pups measured in a simple photocell activity cage was not affected by pesticide treatment. Furthermore, no overt sings of neural toxicity were observed in the offspring. However, the treatment disrupted rat behavior in adulthood when assessed by using an inhibitory avoidance learning task. Thus, inhibitory avoidance tests carried out on rats at 90 days of age were capable of demonstrating neural toxicity of Cyhalothrin (0.02%) present only in the drinking water of dams during 21 days of lactation