A model of bilateral hemispheric ischemia--modified four-vessel occlusion in rats.

Letters to the Editor will be published, if suitable, as space permits. They should not exceed 1,000 words (typed double-spaced) in length and may be subject to editing or abridgment. To the Editor: The four-vessel occlusion method developed by Drs. Pulsi-nelli and Brierley is widely used as an experimental model for bilateral hemispheric ischemia in the field of pathophysiology. 1-2 However, this model has a major problem in the difficulty of confirming complete electrocauterization of the vertebral arteries at the level of the first cervical vertebra. 3-4 We found that in Sprague-Dawley rats both the vertebral arteries at the level of the second cervical vertebra are visible and can be completely electrocauterized. We have established the occurrence of bilateral hemispheric ischemia after occlusion of both carotid arteries following electrocauterization of the vertebral arteries at the level of the second cervical vertebra. We compare our results obtained by this method with those in the original four-vessel occlusion model. For these studies, we used male Sprague-Dawley rats weighing 320-380 g. Both of the vertebral arteries in anesthetized rats were permanently electrocauterized by insertion of an electrocautery needle into the right and left foramina of the second cervical vertebra. Twenty-four hours after electrocau-terization, both of the carotid arteries were occluded for 15 and 45 minutes, after which recirculation was allowed to occur. In the original method of Pulsinelli and Brierley, 2 occlusion of the vertebral arteries without visualization at the level of the first cervical vertebra was often incomplete so that ischemic rats were selected based on the righting reflex and electroencepha-lograms. However, in our modification of the original model, we found that in rats without successful occlusion of both vertebral arteries, there was severe bleeding following the insertion of a 27-gauge needle into the right and left alar foramina of the cervical vertebra. Such bleeding was not observed in rats with permanent occlusion of both vertebral arteries. When the rats were treated using the four-vessel occlusion method of Pulsinelli and Brierley, 2 six of 15 rats lost their righting reflex during 45 minutes of carotid artery occlu-sion (seven of 14 rats during 15 minutes of ischemia) and there was a relatively low mortality rate by Day 3. No rat with occlusion of one vertebral artery at the level of the second cervical vertebra lost its righting reflex during carotid artery occlusion. These rats also survived the experiments without any neurologic deficits (Table …