The effect of endocrine disruptors on the monogamous pine vole (Microtus pinetorum).

Abstract

Since the discovery in the 1960s that synthetic chemicals in the environment could alter normal hormonal functioning in wildlife, the study of endocrine disruptors has grown rapidly. Most xenobiotic endocrine disrupting chemicals (EDCs) arise from sources such as pesticides, and either mimic estrogens or act as antiandrogens. Previous research has focused largely on physiological and anatomical endpoints. The objective of this research was to examine the effects of EDCs on the behaviors and corresponding neural receptor distribution associated with monogamy in the pine vole.

Female pine voles were orally administered an EDC or corn oil control throughout gestation and lactation of pups. As adults, these pre- and neonatally exposed pups were examined for behavioral and physiological alterations. AGD and seminal vesicle weights were masculinized in flutamide exposed males, suggesting flutamide may have acted as androgen rather than antiandrogen. Vinclozolin acted as antiandrogen. Diethylstilbestrol (DES) and methoxychlor are both estrogenic EDCs.

Preference for the mate versus a stranger was assessed via a three-chambered apparatus. Flutamide treated males did not show a preference for their mate, but instead spent most of their time alone in the neutral chamber. Their parental behaviors were unaffected. Vinclozolin treated males' preference for their mate was unaltered, but their paternal responsiveness decreased.

DES exposed females were more aggressive toward the stranger than any other treatment group. Methoxychlor females showed a strong trend toward spending more time alone in the neutral chamber, like the flutamide males. There were no differences in maternal behavior.

Receptor autoradiography was performed to examine any effect on arginine vasopressin receptor binding in males and oxytocin receptor binding in females. The cingulate cortex had decreased binding in flutamide males and methoxychlor females.

These findings demonstrate that exposure to endocrine disrupting compounds during early development can alter adult brain receptor distribution and mating system behaviors.