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Nonylphenol ethoxylate (NPE) is a non-ionic surfactant, that is degraded to short-chain NPE and 4-nonylphenol (NP) by bacteria in the environment. NP, one of the most common environmental endocrine disruptors, exhibits weak estrogen-like activity. In this study, we investigated whether oral administration of NP (at 0.5 and 5 mg/kg doses) affects spatial learning and memory, general activity, emotionality, and fear-motivated learning and memory in male and female Sprague-Dawley (SD) rats. SD rats of both sexes were evaluated using a battery of behavioral tests, including an appetite-motivated maze test (MAZE test) that was used to assess spatial learning and memory. In the MAZE test, the time required to reach the reward in male rats treated with 0.5 mg/kg NP group and female rats administered 5 mg/kg NP was significantly longer than that for control animals of the corresponding sex. In other behavioral tests, no significant differences were observed between the control group and either of the NP-treated groups of male rats. In female rats, inner and ambulation values for animals administered 0.5 mg/kg NP were significantly higher than those measured in control animals in open-field test, while the latency in the group treated with 5 mg/kg NP was significantly shorter compared to the control group in step-through passive avoidance test. This study indicates that oral administration of a low-dose of NP slightly impairs spatial learning and memory performance in male and female rats, and alters emotionality and fear-motivated learning and memory in female rats only, The Journal of Toxicological Sciences, 40(1), pp.43-53; 2015

Bisphenol A (BPA) is an estrogenic endocrine disruptor used for producing polycarbonate plastics and epoxy resins. This study investigated the effects of perinatal BPA exposure on learning and memory, general activity, and emotionality in male Sprague Dawley rats using a battery of behavioral tests, including an appetite-motivated maze test (MAZE test) used to assess spatial learning and memory. Mother rats were orally administered BPA (50 or 500 μg・kg-1/day) or vehicle (1 ml・kg-1/day) from gestational day 10 to postnatal day 14. In the MAZE test, compared to the offspring of vehicle-treated rat mothers, male offspring of mothers exposed to 50 μg・kg-1/day of BPA, but not those of mothers exposed to 500 μg・kg-1/day of BPA, needed significantly more time to reach the reward. Although male offspring of mothers exposed to 50 μg・kg-1/day of BPA showed an increase in a behavioral measure of wariness after repeated testing in the open-field test, no significant effects were observed in locomotor activities. No significant differences were observed in any other behavioral test including the elevated plus-maze test. The present study suggests that perinatal exposure to low-dose BPA specifically and non-monotonically impairs spatial learning and memory in male offspring rats., Journal of Pharmacological Sciences, 123(2), pp.132-139; 2013

4-Nonylphenol (NP) has weak estrogen-like activity, and can therefore act as an endocrine disruptor. This study examined the effects of perinatal exposure to low-dose NP on learning and memory, general activity, and emotionality in male rat offspring. Dams were orally administered 1 or 10 mg/kg/day of NP or vehicle from gestational day 10 to postnatal day 14. The male offspring were evaluated using a battery of behavioral tests, including an appetite-motivated maze test (MAZE test) used to assess spatial learning and memory. In the MAZE test, times to reach goal (food) for both groups treated with NP were significantly shorter than those for the control group. In other behavioral tests (the open-field, elevated plus-maze, and step-through passive avoidance tests), NP did not affect any of each behavioral parameter. Thus, this study indicates perinatal exposure to low-dose NP specifically improves spatial learning and memory in male rat offspring.