Effects of epidural capsaicin on pain threshold, neurological function and spinal neurons in rabbits / 中华麻醉学杂志

ABSTRACT

Objective To evaluate the effects of different doses of epidural capsaicin on pain threshold, neurological function and spinal neurons.Methods Thirty-six male New Zealand white rabbits weighing 2.5-3.0 kg were randomly divided into 4 groups (n = 9 each): control group and 3 capsaicin groups (Cap 1, 2, 3). The animals were anesthetized with 10% chloral hydrate 50-75 mg?kg-1 i.v. . An intrathecal catheter was inserted at L6,7 interspace and correct placement was confirmed by outflow of CSF. 1 ml of 0.1 % ( Cap1) , 0.25 % ( Cap2 ) or 0.5% (Cap3 ) capsaicin was injected intrathecally 24 h after IT catheter was placed. Threshold to noxious thermal stimuli was measured and gait of the hind limbs were assessed using Johnson score (5 = normal, 0 = completely paralyzed), before and 1, 3, 7, 10, 15, 20, 25, 30 days after IT injection. On the 2nd day after IT injection 3 animals were killed in each group and the lumbar segment of spinal cord (L6,7) was immediately removed for light and electron microscopic examination. Results The threshold to noxious thermal stimuli was significantly higher in the 3 capsaicin groups than in control group ( P