Rat models of 4-vessel occlusion-induced global cerebral ischemia have better stability, effectiveness and feasibility in the experiment. This model was initially proposed by Pulsinelli and has been considered a replicable method which can cause serious cerebral ischemia after repeated experiments
[7-9]. Intrathecal catheterization was put forward by Yaksh
et al [10], and this method has been widely used in animal studies
[1, 11-12]. But studies regarding use of 4-vessel occlusion global cerebral ischemia combined with intrathecal catheterization in animal experiments have been rarely reported. Under the neuroprotection of HWTX-Ⅰ, the present study established animal models of global cerebral ischemia with intrathecal catheterization. The present study attempted to establish ischemia model and perform intrathecal catheterization and concluded that this method resulted in a high mortality. For this reason, the present study modified the Pulsinelli method that only vertebral artery cauterization and intrathecal catheterization were performed in the first day and the common carotid artery was clamped on the second day, which alleviates the damage of catheterization and ischemia to rats. The precise location of PE10 tube is the key to success in modeling. Muscular convulsion on the back and four limbs were observed when the tube was inserted
via the subarachnoid cavity, indicating that PE10 tube maybe oppress the spinal cord
via the spinal pia mater. Therefore, the tube was slowly and slightly rotated into the subarachnoid space to avoid the damage of spinal cord. Fan
et al[13] reported that a complete occlusion of vertebral artery is also a key to modeling. Indirect cauterization of vertebral artery is effective with steel wire inserted into the alar foramen. Re-bleeding can be avoided if the steel wire was left in the alar foramen. The electric soldering iron with a tip head was directly inserted into the alar foramen after heating and left in place for 1-2 seconds.
How to enhance the survival rate of rat models of global cerebral ischemia/reperfusion with intrathecal catheterization is a basis for ensuring the studies on neuroprotective effect of HWTX-Ⅰ. Liang et al[14] reported that rat survival rate increased from 50% to 80% after proper modification of 4-vessel occlusion-induced global cerebral ischemia-reperfusion models. According to the experience from other researchers, the survival rate of rats receiving intrathecal catheterization under the foramen magnum is about 70%. Firstly, rats that underwent clamping the common carotid artery more than 20 minutes showed a high mortality. The mortality rate can be decreased if the time needed for ocduding common carotid artery is controlled within 10 minutes. Secondly, a correct location of alar foramen is the key to occluding the vertebral artery during the surgery. There is a small incision in the front of alar foramen and is easily mistaken as the alar foramen if muscle is not completely isolated. If cauterization of this incision would easily burn spinal cord, even brain stem, finally resulting in death. Thirdly, during the isolation of common carotid artery, vessels in particular the vagus nerve in the artery sheath should be thoroughly separated, otherwise, clamping of vessels would damage the vagus nerve, causing the death of suffocation. In addition, rats should be acclimated for 5-7 days. The above-mentioned improvements make the survival rate of model rats over 70%.
Taken together, intrathecal catheterization for delivery of neuroprotective drugs is frequently used in the clinic. A novel model was established which combined 4-vessel occlusion global cerebral ischemia/reperfusion with intrathecal catheterization in small animals. It provided a novel drug delivery means for studying global cerebral ischemia-related injuries and is a novel animal model which can be administered neuroprotective drugs
via the subarachnoid space. Many animal experiments have suggested that this model allows complete blockage of blood supply, provides precise location of catheterization, and shows safe and reliable curative effects. Therefore, the successful construction of this model lays a solid foundation for studying the neuroprotective effects of HWTX-Ⅰ.
