ABSTRACT
Aim To investigate the effects of morphine preconditioning (MPC) on transient receptor potential vanilloid 1 (TRPV1) channel current in rat dorsal root ganglia (DRG) neurons and the phosphorylation (p) of TRPV1 and extracellular regulated protein kinases (ERK) in PC12 cells that sensitized by nerve growth factor (NGF). Methods DRG neurons isolated from T2-T8 segments of 10 days old SD rat or pheochromo-cytoma (PC12) cells were seeded into 24-well plates or 6-well plates, respectively, and randomly divided into 5 groups:control group (group C), NGF sensiti-zation group (group NGF), and morphine precondi-tioning groups (group MPC 0.3, group MPC 1.0 and group MPC 3.0). DRG neurons were identified by im-munofluorescent method with neuronal specific enolase (NSE). Cells were treated by morphine, NGF and capsaicin to simulate the effects of MPC on DRG neu-rons in T2-T8 segments during myocardial ischemia reperfusion injury (IRI). Afterwards, the inward cur-rent of DRG neurons induced by capsaicin in all groups were detected by whole cell recording; the expression and phosphorylation of TRPV 1 and ERK in PC12 cells were detected by Western blot. Results DRG neu-rons survived and grew nicely,and the staining of neu-ronal specific markers,NSE,was positive. In compar-ison with group C, the inward current of group NGF was enhanced (P <0.05), while MPC inhibited the enhancement (P <0.05). The relative expression of TRPV1,p-TRPV1 and p-ERK in group NGF was up-regulated when compared with group C (P <0.05).Moreover, the up-regulation was also suppressed by MPC (P <0.05). Conclusions MPC inhibits TR-PV1 channel current sensitized by NGF in neurocytes, and the mechanism might be associated with the down-regulation of TRPV1 p-TRPV1 and p-ERK expression.