Neutral red staining for the assessment of acute outcome in rat focal cerebral ischemia models

Fischer-344 rats are unsuitable for the MCAO filament model due to their cerebrovascular anatomy

Middle cerebral artery occlusion (MCAO) in Fischer-344 rats results in a small variance of infarct size. However, complications are frequent especially in aged Fisher-344 rats undergoing endovascular suture occlusion of the middle cerebral artery. Analyzing our experiences with 165 Wistar, 13 Sprague-Dawley and 10 F-344 rats, we compared the incidence of impossible thread advancement and subarachnoid hemorrhage, respectively. Magnetic resonance angiography (MRA) was applied to study the course of the internal carotid artery (ICA) in Fischer and Wistar rats. Finally, we performed a structured review of the literature from 1991 to 2005 evaluating reports on Fischer rats subjected to intraluminal filament MCAO. Complications like fruitless filament advancement or subarachnoid hemorrhage were found to be significantly more frequent in Fischer rats than in other strains. MRA revealed significantly more pronounced kinking of the ICA in F-344 than in Wistar rats. In seven publications available on filament MCAO in F-344 rats, complication rates of 50-100% were reported, corroborating our data. Surgical difficulties accompanied by high complication rates due to their cerebrovascular anatomy make Fischer rats unsuitable for filament MCAO. If the use of Fischer rats for studies on focal cerebral ischemia is indicated, other ischemia models than intraluminal suture occlusion should be chosen.

Moderately different NADPH-diaphorase positivity in the selected peripheral nerves after ischemia/ reperfusion injury of the spinal cord in rabbit

1. To vicariously investigate the nitric oxide synthase (NOS) production after spinal cord injury, NADPH-d histochemistry was performed on the selected peripheral nerves of adult rabbits 7 days after ischemia. The effect of transient spinal cord ischemia (15 min) on possible degenerative changes in the motor and mixed peripheral nerves of Chinchilla rabbits was evaluated. 2. The NADPH-diaphorase histochemistry was used to determine NADPH-diaphorase activity after ischemia/reperfusion injury in radial nerve and mediane nerve isolated from the fore-limb and femoral nerve, saphenous nerve and sciatic nerve separated from the hind-limb of rabbits. The qualitative analysis of the optical density of NADPH-diaphorase in selected peripheral nerves demonstrated different frequency of staining intensity (attained by UTHSCSA Image Tool 2 analysis for each determined nerve). 3. On the seventh postsurgery day, the ischemic spinal cord injury resulted in an extensive increase of NADPH-d positivity in isolated nerves. The transient ischemia caused neurological disorders related to the neurological injury--a partial paraplegia. The sciatic, femoral, and saphenous nerves of paraplegic animals presented the noticeable increase of NADPH-d activity. The mean of NADPH-diaphorase intensity staining per unit area ranged from 134.87 (+/-32.81) pixels to 141.65 (+/-35.06) pixels (using a 256-unit gray scale where 0 denotes black, 256 denotes white) depending on the determined nerve as the consequence of spinal cord ischemia. The obtained data were compared to the mean values of staining intensity in the same nerves in the limbs of control animals (163.69 (+/-25.66) pixels/unit area in the femoral nerve, 173.00 (+/-32.93) pixels/unit area in saphenous nerve, 186.01 (+/-29.65) pixels/unit area in sciatic nerve). Based on the statistical analysis of the data (two-way unpaired Mann-Whitney test), a significant increase (p< or =0.05) of NADPH-d activity in femoral and saphenous nerve, and also in sciatic nerve (p< or =0.001) has been found. On the other hand, there was no significant difference between the histochemically stained nerves of fore-limbs after ischemia/reperfusion injury and the same histochemically stained nerves of fore-limbs in control animals. 4. The neurodegenerative changes of the hind-limbs, characterized by damage of their motor function exhibiting a partial paraplegia after 15 min spinal cord ischemia and subsequent 7 days of reperfusions resulted in the different sensitivity of peripheral nerves to transient ischemia. Finally, we suppose that activation of NOS indirectly demonstrable through the NADPH-d study may contribute to the explanation of neurodegenerative processes and the production of nitric oxide could be involved in the pathophysiology of spinal cord injury by transient ischemia.

Middle cerebral artery occlusion in the rat: consistent protocol for a model of stroke

Variability in the effects of the intraluminal suture method of middle cerebral artery occlusion (MCAO) in the rat has been a common and disadvantageous finding. Therefore, we systematically investigated the effects of suture type and rat strain on outcome. First, the clinical and neuropathological effects of permanent MCAO with either an uncoated or a silicone-coated nylon suture were studied over 7 days in Sprague-Dawley rats (n = 36 for each type of suture). Outcome was less severe with the uncoated compared with the silicone-coated suture (e.g. total cerebral infarct volume at 24 h before any fatalities was 119.9 +/- 79.8 mm3, cf. 183.0 +/- 36.5 mm3, n = 12 for each, P < 0.05; and overall mortality rate was 12.5% cf. 33%, respectively), but much more variable (coefficient of variation was 66.6% cf. 19.9%, respectively). Second, being more consistent in its effects, the silicone-coated suture was further studied in Wistar and Fischer-344 rats (n = 12 for each). Seventy-five per cent of the Wistar's died prematurely from gross hemispheric oedema. Motor deficit and extent of infarction in the Fischer-344 rats were both significantly greater compared with Sprague-Dawley rats (e.g. total cerebral infarct volume at 24 h in the former was 253.6 +/- 25.4 mm3, n = 11, P < 0.05), and more consistent (coefficient of variation was only 10.0%). It was concluded that the silicone-coated suture and the Fischer-344 rats strain produced the most consistent results and their novel combination provides a reliable acute stroke model.