Histopathological and analgesic effects of intrathecal dexmedetomidine, racemic ketamine, and magnesium sulfate in rats

Abstract Background This study aims to investigate the histopathological and analgesic effects of intrathecal administration of dexmedetomidine, preservative-free racemic ketamine, and magnesium sulfate in Sprague Dawley rats. This study included 40 male Sprague Dawley rats weighing between 240 and 260 g. After the intrathecal catheterization, the rats were randomly divided into four groups. Following the baseline measurements, no drugs were administered in the control group (group C). Simultaneously, 0.02 ml (1 μgr/kg) of dexmedetomidine was administered in group D, 0.02 ml (1 mg/kg) preservative-free racemic ketamine in group K and 0.02 ml (0.05 mg/kg) magnesium sulfate in group M via intrathecal route. Concomitantly, the hot-plate test was used to measure the analgesic effect of drugs. For histopathological evaluation, the rats were sacrificed to obtain the medulla spinalis. Results The hot-plate test revealed that the mean response time was 6.3 ± 1.2 s in baseline measurements without medication. However, prolongation in the mean response times of the drug-administered groups to the hot-plate test was also observed. Upon histopathological examination, myelin degeneration was detected in all study groups. No inflammation was observed in rats in group D, whereas inflammation was noted in only two rats in group K. Concerning the presence of red neurons, the only group that differed from the control group belonged to group K. Conclusions Dexmedetomidine, preservative-free racemic ketamine, and magnesium sulfate have an analgesic effect when administered intrathecally in rats. Of these drugs, preservative-free racemic ketamine stands out as the most histopathologically safe drug.