Changes Of Excitability And Ion Channels In Small Diameter Trigeminal Ganglion Neurons In Migraine Model Of Rats

Objective:To investigate the effects of the migraine model of electrical stimulation of the superior sagittal sinus dural on excitability and sodium channels,potassium channels and calcium channels in trigeminal ganglion(TG)in rats.Methods:Enzyme-linked immunosorbent assay(ELISA)was used to test the concentration of calcironin gene related peptide(CGRP)of the plasma in vena jugularis externa in rats;Immunofluorescence techniques were used to detect the expression and localization of CGRP in trigeminal ganglion(TG)and trigeminal nucleus caudate(TNC)in rats;The whole-cell patch clamp recording was used to investigate the changes of excitability and ion channels in small TG neurons after electrical sitmulation of the superior sagittal sinus dural in rats.Results:In the present sudy,we found that: 1)Compared with the operational control group(sham group),the concentration of CGRP increased 4 fold in the plasma of external jugular vein in electrical stimulation model group(ES group);2)The expression of CGRP in the ES group was significantly higher than that in the sham group in both TG and TNC,and CGRP positive neurons were mainly small diameter neurons in TG;3)IB4 staining of living cells showed that the proportion of IB4-neurons in ES group was increased.4)The firing frequency of trigeminal neurons were significantly higher in the ES group(10.14±5.11)as compared with the sham group(3.95±2.14),and the excitability of IB4-and IB4+ trigeminal neurons were signifiantly higher in the ES group;5)Electrophysiological experiments showed follows: After the electrical stimulation of the superior sagittal sinus dural,both the sodium channel and the delayed rectifier potassium channel were unaffected in trigeminal neurons,but it resulted in an obvious increased in the current density of the high voltage calcium channel in the ES group(54.07±20.30 pA/pF)as compared with the sham group(34.20±13.63pA/pF),and the current density of high voltage calcium channel of IB4-neurons and the low voltage calcium channel of IB4-neurons were significantly increased in the ES group.Contrary to that,the current density of the A-type potassium channel in ES group(65.11±17.09pA/pF)was significantly inhibited in small TG neurons as compared with the sham group(91.63±30.28 pA/pF).Conclusions:The concentration of CGRP in the plasma of the external jugular vein and the expression of CGRP in TG and TNC increase significantly after the electrical stimulation of the superior sagittal sinus dural,and the percentage of peptidergic neurons is also increased;And it can markedly increase the excitability and the current density of the high voltage calcium channel,selective increased of high voltage and low voltage calcium channel currents in IB4-neurons,and obviously inhibit the current density of the A-type potassium channel in small diameter trigeminal ganglion neurons in rats.However,there was no significant effect on the current density of sodium channels and delayed rectifier potassium channels.