An Experimental Study On Trigeminal Neuralgia Following Chronic Constriction Injury

Classical trigeminal neuralgia(CTN)is one of the common diseases of the nervous system, which can impair the life quality of suffers. Now its pathogenicity and pathologic mechanism are not decided. Although it is administered in various ways, the effect is unsatisfactory. To further elucidate the mechanism and find the better treatments of TN, we performed CCI-ION to imitate the clinical classical trigeminal neuralgia caused microvascular compression. The objectives were as follows:To observe the pain-related behaviours and histological changes before and after chronic constriction injury of the rat trigeminal nerve, explore the machanise of trigeminal neuralgia and provide the basic research for therapy.Using the model, the analgesic effect and mechanism of Analgecine in treatment of trigeminal neuralgia was observed.Methods:1.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, the ION was only exposed using the same procedure but not be ligated. The pain-related behaviours and histological changes were observed at the different times before and after chronic constriction injury of the rat trigeminal nerve.2.S-D rats were performed an unilateral CCI-ION. After two weeks, rats with the allodynia were randomly divided into three groups: Analgecine, carbamazepine and saline groups. Analgecine (100u/kg), carbamazepine (50mg/kg) and saline(10ml/kg)was respectively administered i.p. The behavioral reaction and the mechanical response threshold(Pain threshold)were observed at different time after administration.3.Rats with loosely ligated unilateral trigeminal nerve were randomly allocated into two groups in the supersensitive state of pain. Analgecine (100u/kg)and salin(e10ml/kg)was given respectively by intraperitoneal injection. After two weeks, histological changes in the territory of ligated ION were observed, and the expression of c-fos were detected in the dorsal horn of CM and UCSC by using immunohistochemistry.Results:1.An allodynia to mechanical stimulation on the territory of ligated ION was found from the 2nd to the 8th week after operation. There was significant difference (P<0.01) in pain threshold, compared with the pre-operation. The thresholds started to increase gradually from the 4th week and reached the original level on 12th week after operation. On the 2nd, 4th and 8th week after operation, the fibers of the ION were obviously injured. On the 12th week after operation, the injured nerve almost recovered to normal.2. The Analgecine's analgesic effect was created gradually after administration. the pain threshold increased notably and the allodynia disappeared. The pain threshold was significantly greater than that in saline group and pre-administered (P<0.01). The maximal analgesic effect of carbamazepine was reached in 60 min after administration, there is no difference compared to the Analgecine group(P>0.05)but the analgesic effect disappeared after three hours.3.On the 2th week post- operation, the fiber on the territory of ligated ION were obviously degeneration; On the 2th week post-administration, the fiber of saline group were edema and demyelination.In Analgecine group, the demyelination of nerves were significantly recovered. Two weeks after administration, the labeled c-fos neurons of two groups were concentrated in laminateâ… ,â…¡of CM and UCSC. The expressions of c-fos in Analgecine group was significantly reduced(P<0.01) compared with the saline group.Conclution:1.The abnormal Pain-related behaviours of CCI-ION rats appeared to be closely linked to the histological changes in the ION. This model imitates the clinical trigeminal neuralgia caused microvascular compression,and its histological changes was similar to this of clinical trigeminal neuralgia. Our experiment observed primary pathologic change of trigeminal neuralgia is demyelination of peripheral branch .2.Analgecine can increase pain threshold ,reduce the abnormal Pain-related behaviours in treatment of rats with loosely ligated unilateral trigeminal nerve. The analgesic effect of Analgecine for trigeminal neuralgia has potential value. It deserves to be managed.3.The analgesic effect of Analgecine related to recovering of injured nerve, inhibiting of noxious impulse into medulla, decreasing dorsal horn neuronal activation in response to noxious stimuli.