Responses of Trigeminal Ganglion Neurons to Electrical and Mechanical Stimulation of the Middle Meningeal Artery, Superior Sagittal Sinus and Transverse Sinus in Rats

ABSTRACT

The intracranial blood vessels of the dura and the pia receive sensory afferent innervations from trigeminal nerve which has been believed to play a critical role in the mediation of vascular headache such as migraine. The purpose of this study was to discover the mechanism by which the interaction between trigeminal ganglion neurons and the function of cerebral blood vessels. Using electrophysiological recording, we studied the responses of trigeminal ganglion neurons to electrical stimulation of middle meningeal artery(MMA), superior sagittal sinus(SS) and transverse sinus(TS) in rats. Sumatriptan is a highly selective agonist for 5-HT1D receptor subtype which mediates vasoconstriction of cerebral blood vessels. We observed responses to electrical stimulation in trigeminal ganglion neurons and meningeal blood flow(MBF) after intravenous injection of sumatriptan. The results were as follows 1) The presumed mean conduction velocities of the cells activated MMA, SS and TS by electrical stimulation were approximately 1.5, 2.9 and 2.9m/s, respectively. These were presumed to be nociceptive small myelinated or unmylinated sensory fibers. 2) The action potential discharges of trigeminal ganglion neurons on MMA, SS and TS in the experimental control groups were 671+/-39.49, 856+/-63.95 and 494+/-21.54microV, respectrely. The action potential discharges of sumatriptan groups on MMA, SS and TS(393+/-20.10, 562+/-32.26 and 262+/-18.94microV, respectively) were significantly decreased compared to that of the experimental control groups. 3) The mean MBF of normal control group was 63.29+/-7.54ml/100g/min. The mean MBF of the experimental control groups on MMA, SS and TS were 97.13+/-9.91, 104.28+/-12.54 and 91.82+/-6.41ml/100g/min, respectively(p<0.05). MBF of sumatriptan group before stimulation was significantly decreased(compared to normal 37.17+/-4.76ml/100g /min vs 63.29+/-7.54ml/100g/min). The mean MBF of sumatriptan groups on MMA, SS and TS were 57.11+/-4.48, 66.56+/-6.23 and 56.07+/-5.00ml/100g/min, respectively. Compared to that of the experimental control groups, the MBF of the sumatriptan groups were significantly decreased. In conclusion, the activation of trigeminal sensory afferents by the electrical stimulation of the dural vessel may create vasodilatation and increase cerebral blood flow which may lead to vascular headaches via trigeminal ganglion to brain stem This pathway can be important for understanding the neural mechanism for the development of pharmacological and surgical approach to alleviate vascular headache.