Effect of stellate ganglion block on substance P of spinal cord in rabbits following formalin stimulation / 中华麻醉学杂志

ABSTRACT

Objective To investigate the effect of stellate ganglion block (SGB) on substance P of spinal cord in rabbits following formalin stimulation and the possible mechanism. Methods Rabbits of both sexes weighting 2.5-3.0 kg were anesthetized with 20% urethane 1 g?kg-1 . Spontanous breathing was maintained. Right stellate ganglion was exposed aseptically. An epidural catheter was fixed with one end placed closed to stellate ganglion and the other end outside the neck through a hole on the skin for administration of drugs. One week later, nineteen healthy rabbits were randomly divided into three groups sham operation group (group A, n = 5), SGB group (group B, n=7) and control group (group C, n = 7) . In group B and group C, 3 % formalin 0.2 ml was injected subcutaneously into plantar region of the right paw. Pain response was observed. 1h after formalin injected, 0.25% bupivacaine 0.5 ml was injected through the catheter in group B while normal saline 0.5 ml was injected in group C. The effect of SGB was confirmed by ptosis and miosis. 1h after using of bupivacaine or normal saline, rabbits were deeply anesthetized and chest was opened, 1 000 ml of normal saline was infused via left ventricle then followed by 2000-2500 ml of 4% paraformaldehyde in 0.1mol/L phosphate buffer pH7.4 infusion for fixation of tissue, 60 min later spinal cord of cervical 6-8(C6-8) and thoracic 6-8(T6-8 ) were removed. In group A the spinal cord were extracted similar to the other groups. The content of SP in spinal cord use immumohistochemistry technique of strept avidin biotin enzyme complex (SABC) to display. Results Immunoreaction of SP were distributed mainly in lamina Ⅰ and Ⅱ of dorsal horn of spinal cord. Compared with group A, the optical density(OD) of SP in cervical slices were decreased significantly in group B and group C(P 0.05 ). Conclusions The content of SP in spinal cord decreased significantly after subcutaneous injection of formalin in rabbits. SGB can reverse the phenomena partly and increase the content of SP of cervical spinal cord in rabbits following formalin stimulation. This may be the possible mechanism of analgesia provided by SGB.