Objective: To explore the expression of the N-methyl-D-aspartate (NMDA) receptor in the rat model of orchialgia and its possible mechanisms.
Methods: According to Yoshioka's method, the male rats in the control group were injected with 0.2 ml saline, and those in the experimental group with 0.2 ml 2% acetic acid solution. Then we tested the behavioral responses of the rats and determined the expressions of the subunits NR1 and NR2B of the NMDA receptor in the dorsal root ganglion and spinal dorsal horn by Western blot, RT-qPCR and immunofluorescence staining.
Results: The withdrawal latency was decreased in the model rats, reaching the lowest value at 4 hours after modeling, significantly lower than in the controls (［4.15 ± 0.84］ vs ［12.32 ± 1.05］, P < 0.05). Compared with the controls, the model rats showed remarkably increased mRNA and protein expressions of NR2B in the dorsal root ganglion (P < 0.05) but not in the spinal dorsal horn at 4 hours. However, no statistically significant difference was found in the expression of NR1 either in the dorsal root ganglion or in the spinal dorsal horn between the two groups (P > 0.05).
Conclusions: The NMDA receptor plays an important role in pathogenesis of orchialgia in rats. In the early stage of pain, upregulating the expression of the subunit NR2B of the NMDA receptor can mediate peripheral hyperalgesia and consequently orchialgia.
Keywords: N-methyl-D-aspartate receptor; dorsal root ganglion; rat; spinal dorsal horn; orchialgia.