·     Requirements for Monkey Ischemia Model

Nonhuman primate models offer distinct advantages when it comes to comparability with humans, particularly when developing clinically useful strategies to improve patient outcome after stroke. Functional deficits in nonhuman primates can be easily assessed before animal euthanasia and represent clinically relevant outcome measures that are limited with rodent subjects. In addition, both ratios of white matter to gray matter and the degree of microvascular collaterals are more comparable, especially between rhesus monkey and humans.

A newly developed monkey model is tested, several conditions that the model must fulfill have been proposed for focal ischemia.

-          A single artery- Middle Cerebral Artery- can be reproducibly occluded

-          The vascular occlusion results in predictable changes in blood flow, i.e., focal or regional ischemia.

-          No surgical manipulation of the brain or exposure of it to the air.

-          No barbiturates are used at the time of the arterial occlusion.

-          The method of arterial occlusion should be compatible with subsequent reperfusion of the ischemic territory.

-          Neuroimaging studies such as autoradiography, MRI, MRS, and PET can be carried out economically and easily.

CPRC has professional neurosurgeon to perform the surgery and experienced neurological doctors to observe the neurological deficits for monkey ischemic model.

·     Intraluminal monkey model has been developed in CPRC

-          Physiological Monitoring

-          Anesthesia: Using a face mask, animals are anesthetized with 3.5% isofluorane and anesthesia is maintained with 1.0% isofluorane in O₂ .

-          Transient Middle Cerebral Artery Occlusion: A monofilament nylon suture, blunted at the tip and coated with poly-L-lysine, is introduced into the internal carotid artery through the external carotid artery stump and up to the origin of the middle cerebral artery (MCA). After a period of proximal MCA occlusion, blood flow was restored by removal of the nylon suture to allow the blood reperfusion.

-          Regional Cerebral Blood Flow (rCBF): Transcranial measurements of rCBF is made using a laser-Doppler flowmetry. Steady-state baseline values are recorded before MCA occlusion, and rCBF is recorded immediately after occlusion, just before and just after withdrawal of the suture, initiating reperfusion as well as 3 hrs after reperfusion. Data are expressed as percentage of the baseline values.

-          Neurological Deficit Evaluation: Daily neurological assessments are performed by 2 investigators blinded to all imaging data using a 100-point neurological scale developed by Spetzler and associates (Spetzler et al. 1980,  Neurosurgery. 7:257–261).

• Hemiparesis in the extremities is graded from 1 to 75 (10=severe, 25=mild, 55=favors normal side, and 70=normal) and
• Hemiparesis in face (1=facial paresis and 5=normal facial strength).
• Behavior and level of alertness are scored from 0 to 20 (0=dead, 1=comatose, 5=aware but inactive, 15=aware but less active, and 20=normal),
• Visual field deficits are assigned 1 if present or 5 points if absent.

-          Radiographic Imaging: Brain MRI for monitoring cerebral infarction

-          Measurement of Infarct Size and Infarct Volume: 

• At the end of reperfusion the brains from selected animals are removed and the brain is cut coronally at 3 mm thikness distal from the frontal pole by using the rat Brain Matrix.
• The brain slices are then stained with 2% (w/vol) 2,3,5-triphenyltetrazolium chloride (TTC, Sigma) in Dulbecco's phosphate buffer (pH 7.4) at 37^oC for 20 minutes.

The infarcted areas of the brain slice are quantitated by an image-analysis system.