| Objective1.To stimulate the spinal nucleus of trigeminal nerve,the primary center of orofacial pain pathways,the rats were microinjected into subarachnoid space with penicillin G-K that was a nociception to induce trigeminal neuralgia and then the ideal experimental animal model of trigeminal neuralgia was established.It was to assess the role of the central thesis in the pathogenesis oftrigeminal neuralgia.2.After the rat model of trigeminal neuralgia being established successfully,the changes of Substance P and beta-Endorphin in hypothalamus and the Pituitary Gland were measured to discuss the mechanism of the creation of pain that Substance P and beta-Endorphin conducted as neurotransmitters and to further explore neuropeptides'important role in the pathogenesis of trigeminal neuralgia.Methods28 male adult Sprague-Dawley rats were randomly assigned to the experimental group(Group A),Sodium Chloride group(Group B)and the control group(Group C).1.In Group A,the rats were injected with 3 ul penicillin G-K into the subarchnoid space inferiolateral 2mm from the obex,then the rat model was established.We determined the concentrations of SP andβ-EP by radioimmunological assay(RIA)together after executing the rats and excising their brain tissue that was treated as radioimmunological methods request later.2.In Group B,the progress was the same as Group A except that they were injected with 3 ul Sodium Chloride and executed 30 minutes later.3.In Group C,they were executed directly,others just following Group A.Results 1.The rat model of primary trigeminal neuralgia establishedThe rats of group A shrieked,swung their head,scratched their face and their left eyelids turned off quickly et.al soon after microinjected penicillin G-K.The trigeminal neuralgia syndrome occurrences rate was(156.36±15.30)times in 30 minutes.The rat model of primary trigeminal neuralgia in Group A was successfully established,but it was not in Group B.2.The content of Substance P in rats' hypothalamus and the Pituitary Gland with trigeminal neuralgiaThe contents of Substance P in Group A,Group B and Group C were(1658.52±158.19)pg/mg,(1368.25±130.47)pg/mg,(1359.87±120.36)pg/mg respectively.There was significant difference of the content of Substance P among the three groups(P＜0.01).The content of Substance P in Group A was higher than that in Group B and Group C(P＜0.01).It was a little higher in Group B than that in Group C,which had no significance between them(P＞0.05).The data indicates that the content of Substance P is increased in the processing of trigeminal neuralgia.3.The content of beta-Endorphin in rats' hypothalamus and the Pituitary Gland with trigeminal neuralgiaThe contents of beta-Endorphin in Group A,Group B and Group C were (168.23±15.23)pg/mg,(205.36±20.96)pg/mg,(210.89±22.37)pg/mg respectively.There was significant difference of the content of beta-Endorphin among the three groups(P＜0.01).The content of beta-Endorphin in Group A was lower than that in Group B and Group C(P＜0.01).It was a little lower in Group B than that in Group C,which had no significance between them(P＞0.05).The data indicates that the content of beta-Endorphin is decreased in the processing of trigeminal neuralgia.Conclusions1 The animal model of trigeminal neuralgia is established successfully by penicillin G-K which was microinjected into the subarachnoid space and stimulated the spinal trigeminal nucleus as a nociception.2.The content of Substance P which mediates the conduction of the nociceptive signals is increased because of its more synthesis and release during the conduction of the pain,and it lead to the attack of pain.3.The content of beta-Endorphin in the brain is decreased because of its less synthesis and release during the conduction of the pain,which contributes to the increase of Substance P with the attack followed.4.The pathogenesis of trigeminal neuralgia is complicated,and we think that many factors may react each other.The central factor is essential and important to the typical symptoms and neuropeptides also contribute to the attack.The experiment is to guide the clinical treatment for trigeminal neuralgia.
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