Depressive behavior induced by nonylphenol and its effect on the expression of ER- and ER- in nerve cells of rats

Objective: To investigate the effects of nonylphenol (NP) exposure on the depressive behavior in rats, and the effects of the expressions of estrogen receptor-alpha (ER-alpha) and estrogen receptor-beta (ER-beta) in nerve cells in vivo and vitro. Methods: Forty male SD rats were randomly divided into 4 groups: blank control group (0 mg/kg), low dose group (0.4 mg/kg), middle dose group (4 mg/kg) and high dose group (40 mg/kg), which were exposed to NP for 180 days. The exposure dose of NP in HT22 was 20 mu M, which was divided into4 groups: blank control group, NP group, IC1182780 group and IC1182780 + NP group. Results: In vivo, in the open field experiment, the number of entries in the central area and duration of attention in central square decreased gradually in the NP high dose group compared with the control (F = 3.561, p = .029). In forced swimming experiment, with the increase of NP dose, the immobility time increased, and the increasing degree of middle dose group and high dose group was higher than that of the low dose group (F = 3.047, p = .048). The concentrations of serum dopamine (DA) in the middle dose and high dose groups decreased greatly compared with the control (F = 3.967, p = .023). NP exposure at the doses of 4 mg/kg and 40 mg/kg induced an increase in the level of serum corticosterone compared to the control (F = 11.536, p < .001). Compared with the control group, the expression of ER-beta decreased gradually with an increase of NP dose in the NP treatment groups (F = 4.513, p = .014). In vitro, the activity of HT22 cells decreased with an increase of NP dose (F = 316.6, p < .001). When the dose of NP was 200 mu M, the growth inhibition rate of HT22 cells was (0.54 +/- 0.11)%. The expression levels of ER-alpha and ER-beta in IC1182780 + NP group was lower than those in the control and ICI182780 groups, but higher than those in the NP group (F = 1.592, p = .266; F = 10.166, p = .004). Conclusion: : Long-term exposure to NP could induce the alterations in depressive behavior, and the levels of neurotransmitters as well as the expression of ER in the hippocampus of rats. Moreover, NP could reduce the activity of HT22 cells and decrease the expression levels of ER-alpha and ER-beta in vitro.