| ObjectiveMigraine is one of the most common primary headaches that mainly influences middle-aged women. The prevalences of migraine in Chinese adult men and women were 5.9% and 12.8%, respectively. Nowadays the susceptibility of women for migraine has been thought relate to the periodic fluctuation of estrogen(mainly estradiol). However, the underlying mechanism is unclear. This study aimed to investigate the effect of estrogen on the glutamate-glutamine shuttle by ovariectomy. Immunofluorescence staining and Western blot were used to detect the expression of glutamine synthetase (GS) and glutamate transporter (EAATs) in the satellite glial cells(SGCs) within the trigeminal ganglion (TG). Subcutaneous injection of nitroglycerin was used for establishment of migraine model rat. The expression of nitroglycerin induced c-fos in TG was detected after administration of GS inhibitor L-MSO and normal saline.Materials and methods1. Adult female Wistar rats (N=45) were randomly divided into three groups:Sham group (Sham, N=15), Ovariectomy group (OVX, N=15) and Ovariectomy+estrogen replacement group (OVX+E, N=15).2. Enzyme immunoassay analysis was used to detect serum estradiol concentrations of each group to make sure the model was validly established.3. Western blot and immunofluorescence staining method were used to detect the expression and co-location of glutamine synthetase(GS), glial fibrillary acidic protein(GFAP) and glutamate transporter in trigeminal ganglion in each group.4. The subcutaneous administration of Glyceryl trinitrate(GTN) was applied for establishment of migraine model rat. After the application of GS inhibitor L-MSO or normal saline(NS), the animal behavior scores were observed and the expression of c-fos in TG was detected by using Western blot in each group.Results1. Compared with control group, ovariectomy could significantly reduce serum estradiol levels and exogenous estrogen replacement could increase serum estradiol levels(P<0.05).2. Immunofluorescence staining and Western blot results showed that the expression of glutamine synthetase(GS) in TG was significantly decreased in group OVX (P<0.05)and recovered after administration of estrogen replacement, compared with the control group.3. Compared with subcutaneous injection of NS, the GTN group got higher behavior scores and the frequency of scratching head, licking hair and climbing cage increased(P< 0.05). GTN could also induce increased early immediate gene c-fos expression in trigeminal ganglion afferent neurons of rat(P<0.05).4. Ovariectomy or administration of GS inhibitor could increase the behavior score and GTN induced c-fos expression in trigeminal ganglion neurons(P<0.05).Conclusion1.Estrogen up-regulates the expression of glutamine synthetase in the satellite glial cells of trigeminal ganglia, which implies that estrogen may promote the glutamate-glutamine shuttle between neurons and satellite glial cells within trigeminal ganglion.2. Estrogen regulates the activation of trigeminal afferent nerves in the migraine model rats, which prompts estrogen may be involved in the pathophysiology of migraine.3. Estrogen may play a role in the pathophysiology of migraine by regulating the glutamate-glutamine cycling in trigeminal ganglion. |
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