Decrease of morphine-CPP by sinomenine via mediation of tyrosine hydroxylase, NMDA receptor subunit 2B and opioid receptor in the zebrafish brain

Yingbo Lin; Hancheng Li; Ju Peng; Chan Li; Chen Zhu; Yuting Zhou; Zhijie Chen; Jing Li; Chaohua Luo; Zhixian Mo

To study the effects of sinomenine on conditioned place preference (CPP) zebrafish induced by morphine and expression levels of intracephalic tyrosine hydroxylase (TH), NMDA receptor subunit 2B (NR2B), µ-opioid receptor (zfmor) and d-opioid receptors (zfdor1 and zfdor2), morphine (40mg/kg) was administrated to zebrafish and the effect of CPP was detected in these zebrafish treated with sinomenine. The expression of TH and NR2B was detected by immunohistochemistry; and the mRNA expression of opioid receptors zfmor, zfdor1 and zfdor2 in the zebrafish brain was assayed by RT-qPCR. In the CPP test, morphine induced significant behavioral alteration, while pretreatment with sinomenine or methadone, resulted in decreased activity time in the morphine-paired compartment significantly. Morphine also increased the integral optical density value of TH- and NR2B-positive cells in the zebrafish brain, and reduced the amount of opioid receptors. However, the compound sinomenine could attenuate these effects. These findings demonstrate that sinomenine (80mg/kg) decreased the CPP effects of zebrafish induced by morphine significantly, downregulated expression of TH and NR2B, and upregulated µ-opioid (zfmor) and d-opioid (zfdor1 and zfdor2) receptor expression in the CPP zebrafish brains.