| Objective:1. To study the role of the midbrain periaqueductal gray (PAG) potentially on the transmission of nociceptive information related to vascular headaches such as migraine;2. To observe the role of sympathetic nervous system on the nociceptive transmission of migraine attacks.Methods:1. The role of the PAG on the transmission of nociceptive information of migraine: 40 male Sprague-Dawley rats, weighing 220- 250g, were randomly divided into three groups: the vacuo-control(n=l 0), sham-operated(n=l 0) and stimulated group(n=20). The rats of vacuo-control group were killed after anesthetized excessively. The rats remained were drilled on their cranium by platform bur toexpose the superior sagittal sinus (SSS), and a pair electrodes were placed on the SSS gently. The dura mater near the SSS of rats in the stimulated group was stimulated with square wave current (250us, 1.5mA, 3Hz) for 2 hours after the operation. No rat was stimulated in the sham-operated group. One hour later, the rats were paralyzed and perfused to fix, which the brainstem were removed and post-fixed. Coronal sections through the midbrain PAG were cut and the expression of c-fos and NOS immuno-reactivity was detected with standard avidin-biotin peroxidase immunohistochemical techniques. 2. The role of the sympathetic nervous system on the transmission of nociceptive information of migraine: 20 male Sprague-Dawley rats, weighing 220- 250g, were randomly divided into three groups: the sham-operated (n=10) and experiment group (n=10). The right superior-cervical ganglions (SCG) of rats in the sham-operated group were exposed. The right SCGs of the rats wereremoved in the experiment group, and successful ablation was confirmed by observation of Homer's syndrome on the operated side. 10 days later, the SSS of all the animals were exposed through platform bur drilling on their cranium. The dura maters near the SSS of the rats in both groups were electrically stimulated for 2 hours after the operation. One hour later, the rats were paralyzed and perfused to fix, which the brainstem and the superior cervical spinal cord were removed and post-fixed. The expressions of c-fos and NOS immuno-reactivity were detected with standard avidin-biotin peroxidase immunohistochemical techniques.Results:1. The role of the PAG on the transmission of nociceptive information of migraine: The number of Fos and NOS positive neurons in stimulated group was increased markedly compared with that in vacuo-control group and sham-operated group respectively, and there was no significant difference between vacuo-control group andsham-operated group. The Fos and NOS immunoreactive postive neurons were observed in the ventrolateral and dorsolateral PAG, and the number of cells was increased gradually from the rostral level to the caudal level.2. The role of the sympathetic nervous system on the transmission of nociceptive information of migraine: The Fos and NOS immunoreactive postive neurons were observed in the ventrolateral and dorsolateral PAG, laminae I and II of the trigeminal nucleus caudalis and the dorsal horn of the upper cervical cord. The number of Fos and NOS positive neurons in experiment group was markedly increased compared with the sham-operated group.Conclusion:1. The PAG could be activated by stimulation of the dura mater near the SSS. The PAG could be involved in the central modulation of pain in vascular headaches such as migraine.2. The sympathectomy amplified the response of central nervous to painful stimulation, and NO could be involved inthe processing of pain on migraine. The sympathetic nervous system could be involved in the processing of nociceptive signals on migraine attacks, and may inhibit the pain. |
