Chronic exposure to benzyl butyl phthalate (BBP) alters social interaction and fear conditioning in male adult rats: alterations in amygdalar MeCP2, ERK1/2 and ERα.

OBJECTIVES: Benzyl Butyl Phthalate (BBP) is an industrial plasticizer that has an unknown action in the central nervous system. Phthalates have recently been associated with behavioral actions that are linked to their endocrine disrupting properties. The purpose of this study was to investigate the behavioral and molecular effects of BBP treatment in male rats.

DESIGN: Male rats were chronically exposed to BBP in the drinking water (5.0 ppm and 10.0 ppm) throughout adolescence and into the adult phase of life. Their behavior was then assessed in a learning and memory task (fear conditioning), open field exploration and a test of sociability.

RESULTS: BBP treated rats showed decreased freezing in fear conditioning, no changes in open field exploration, and increased aberrant social behavior. Rats were sacrificed at post natal day 140 and blood and brains were harvested and processed. We found increased hormonally active estrogen, 17-β estradiol, in the serum of BBP treated rats. BBP treatment also induced changes in amygdalar proteins related to synaptic plasticity including decreased MeCP2 levels that correlated with tests of sociability with no changes in stress related proteins such as nuclear factor kappa B (NFkB). We also found alterations in physiological responses as measured by body weight without changes in food consumption suggesting disruption of metabolism and body homeostasis.

CONCLUSIONS: We suggest that BBP administration disrupts normal learning and social behavior, and that these effects could be related to alterations of amygdala function.