INTRATHECAL INJECTION OF DEXMEDETOMIDINE ALLEVIATES HYPERALGESIA IN CESAREAN SECTION RATS BY REDUCING SPLEEN C-FOS PROTEIN EXPRESSION

Quan Ling¹, Yong Chen¹, Xiao-Zu Liao¹, Xue-Xia Zou¹, Bin-Fei Li^{2, *} 

¹The First Department of Anesthesiology, Zhongshan People’s Hospital, Zhongshan, 528403, China - ²Zhongshan People’s Hospital, Zhongshan, 528403, China

Objective: To study the mechanism of the intrathecal injection of dexmedetomidine to reduce hyperalgesia in cesarean section rats.

Method: Several clean-grade, healthy male and female SD rats were selected randomly. During the estrus period, the female rats and a total of 60 female rats were reared together in a 2:1 ratio. The female rats were reared in cages and, on the 14th day, were determined to be pregnant. The rats were randomly divided into the sham operation group (rats that had not undergone a cesarean section operation; 12 cases), the model group (rats that had undergone a cesarean section operation and had a micro spiral catheter placed between the 1.5 and 1.6 spinal space and were injected with 20 μL of saline; 12 cases), the dexmedetomidine low-dose group (12 cases), the dexmedetomidine mid-dose group (12 cases), the dexmedetomidine high-dose group (rats that had undergone a cesarean section and had a micro spiral catheter placed between the 1.5 and 1.6 spinal space and were injected with 15μg/kg, 30μg/kg, and 45μg/kg of dexmedetomidine, respectively; 12 cases). The expression of spleen c-fos protein in each group was determined through immunohistochemistry. The changes in the threshold latency of mechanical foot reflex pain and that of heat reflex foot pain were measured by using an electronic mechanical pain threshold detector and automatic thermal pain stimulator before and after modeling in each group of rats at 12h, 24h, and 48h.

Results: Spleen c-fos protein was mainly expressed in the nucleus, presenting with a large number of brown particles under the microscope. Compared with the sham operation group, the spleen c-fos protein expression level was significantly increased in the model group (p<0.05); compared with the model group, which had an increased dexmedetomidine dose, the spleen c-fos protein expression level was significantly reduced (p<0.05). There was no significant difference between the threshold latency of mechanical foot reflex pain and that of heat reflex foot pain before modeling in each group (p > 0.05). Compared with the sham operation group, the model group had significantly shorter latent threshold periods of mechanical reflex pain and thermally contracted reflex pain (p<0.05); compared with the model group, which had an increased dexmedetomidine dose, the latent period gradually increased (p<0.05).

Conclusion: The intrathecal injection of dexmedetomidine can alleviate mechanical pain and hyperalgesia in cesarean section rats by reducing spleen c-fos protein expression.