An Experimental Study On Mechanism Of Trigeminal Neuralgia

Trigeminal neuralgia(TN) is a chronic pain syndrome. Although it is administered in various ways, the effect is unsatisfactory. The basic reason is that the etiology and patho-physiological mechanisms is incompletely understood. Our present experiment was performed to further elucidate the mechanism and find the better treatments of TN. The objectives were as follows:1. To establish a reliable animal model for trigeminal neuralgia, which can simulate clinical condition for the basic research on the mechanism and therapy.2. To study the changes in the dorsal horn of caudal medulla and upper cervical spinal cord of rats with TN using fos-related proteins as a marker for neuronal activation in the CNS.3. To research the analgesic effect and tolerance of subarchnoid space transplantation with chromaffin cells for trigeminal neuralgia .4. To investigate the changes in CNS after subarchnoid space transplantation with chromaffin cells.Methods:1. 20 male S-D rats were randomly divided into the operative group and the sham-operative group. In the operative group, an unilateral chronic constriction injury (CCI) was produced by placing loose chromic gut ligatures around the infraorbital nerve (ION). In the sham-operative group, theION was only exposed using the same procedure but not ligated. The behavioral reactions and the mechanical response threshold were observed at the different times after operation.2. 20 male S-D rats were randomly divided into the operative group and the sham-operative group. In the operative group, an unilateral CCI-ION was performed. In the sham-operative group, the ION was only exposed using the same procedure but not ligated. Following the appearance of allodynia, the expressions of c-fos were detected in the dorsal horn of caudal medulla (CM) and upper cervical spinal cord (UCSC) by using immunohistochemistry.3. Male S-D rats were performed an unilateral CCI-ION. After two weeks, 30 rats with the allodynia were randomly divided into three groups. Bovine chromaffin cell(BCC) group: lOul BCC were transplanted into subarachnoid space(SAS). Carbamazepine group: carbamazepine (50mg/kg) were administered i.p.. In control group, no treatment was administered. The pain thresholds (PT) in the territory of ligated ION=were observed according to the different times after transplantation.4. Male S-D rats were performed an unilateral CCI-ION, After two weeks, 20 rats with the allodynia were randomly divided into BCC group(10 l BCC were transplanted into SAS) and control group (10 l saline were transplanted into SAS). Two weekslater, the expressions of c-fos were detected in the dorsal horn of CM and UCSC by using immunohistochemistry. Results:1. In the operative group: an allodynia to mechanical stimulation of the territory of the ligated nerve was found on 15th day after operation. And compared with the pre-operative group , the sham-operative group and contralateral side of operative group, there was significant difference ( P<0. 01 ) in pain threshold. Low-intensity mechanical sensory input ( 0. 21 卤 0. 062g ) could arouse hyper-responsiveness, such as withdrawal, asymmetric face grooming, and attack. The thresholds increased gradually from the 30th day and were the same with the pre-operation on 80th day after operation.2. Both CCI-ION and sham-operative groups, the labeled c-Fos neurons were concentrated in the CM and UCSC dorsal horn superficial laminae (laminae I-II). The total number of c-Fos neurons of the ipsilateral medullary dorsal horn in CCI-ION group was significantly greater than that of the contralateral side in the same group and both sides in the sham-operative group (P<0. 01) .3. BBC group: At the second week after the cell transplantation, the analgesic effect reached the maximum, and the allodynia disappeared. Such analgesic effect remained until the 7th week after transplantation (P>0. 05), and the pain thresholdwas greater than that in control group and pre-transplantation (P<0. 01). Until the 8th week after transplanta...