Middle Cerebral Artery Occlusion In Cats Research Articles

Comparative study of 2,3,5-triphenyltetrazolium chloride (TTC) and hematoxylin–eosin staining for quantification of early brain ischemic injury in cats

Department of Neurosurgery, Nara Medical University, Nara, Japan There are no staining methods that can reliably and unequivocally detect final infarcts in the acute stage of experimental ischemia. In most instances, 2,3,5-triphenyltetrazolium chloride (TTC) and hematoxylin and eosin (HE) stainings are accepted for this purpose, but neither is perfect. We performed a comparative study of the TTC immersion method and HE staining for quantification of early brain ischemic injury in cats, focussing on the reproducibility associated with planimetry. Focal brain ischemia was produced by middle cerebral artery (MCA) occlusion via the transorbital approach in 14 cats. After 6 h of occlusion, two slices of 3 mm thickness, passing through the optic chiasma and mammillary body, were selected for pathological examination. TTC immersion and HE staining were both used for planimetric study of the surface of the same slice. The area of the injury was traced manually with the aid of computerized digital planimetry and expressed as a percentage of the area of the contralateral hemisphere. The area of hemispheric injury and the area of gray matter injury were separately calculated in the TTC specimens, and each was compared with the area of gray matter injury in the HE-stained specimens. Measurements were repeated twice on each slice to estimate errors associated with manual tracing of the boundary of the area of injury. The mean percentage values of the area of injury in the TTC-immersed gray matter specimens were lower than those detected by HE staining, although there was a very significant correlation between the two. The differences between each two measurements of TTC-determined gray matter injury were significantly less than those between each two measurements of HE-determined gray matter injury. The differences between each two measurements of TTC-determined hemispheric injury were slightly less than those between each two measurements of TTC-determined gray matter injury, although there was no significant difference between them. For quantifying ischemic injury after 6 h of MCA occlusion in cats, the TTC immersion method is more reproducible and simpler in manner than HE staining, but the results of both are significantly correlated. [Neurol Res 2001; 23: 657-661]

AR-R15896AR reduces cerebral infarction volumes after focal ischemia in cats.

The use of competitive and noncompetitive N-methyl-D-aspartate receptor antagonists to prevent neuronal death during ischemia has been comprehensively studied. This study was performed to examine the neuroprotective effects and pharmacokinetics of the noncompetitive N-methyl-D-aspartate receptor channel blocker (S)-alpha-phenylpyridine-ethanamine dihydrochloride, AR-R15896AR (formerly designated ARL 15896AR), using a gyrencephalic cat middle cerebral artery occlusion model. In a separate experiment, three cats were used for pharmacokinetic analysis, thus establishing the optimal dose of AR-R15896AR. Focal cerebral ischemia was induced in 21 cats. After 30 minutes of a 90-min ischemic insult, the cats received an intravenous infusion (total volume, 3 ml), in a 15-minute period, of either AR-R15896AR or normal saline solution (control). Physiological data were obtained after 40 and 80 minutes of ischemia and at 2, 4, and 6 hours after ischemia. At 6 hours after ischemia, each cat was positioned for both T2- and diffusion-weighted scans (eight slices, 5-mm thick). At 8 hours after ischemia, the animals were perfusion-fixed for histopathological analysis. Pharmacokinetic studies indicated that AR-R15896AR remained in the blood at elevated levels for the 6 hours studied, with a calculated half-life of approximately 6 hours. AR-R15896AR rapidly entered the brain and exhibited a brain/plasma ratio of approximately 8:1. The infarction volumes for the AR-R15896AR-treated group were 1138.5+/-363.1, 651.3+/-428.9, and 118.6+/-50.1 mm3, as calculated using diffusion- and T2-weighted MRI and histopathological data, respectively. The infarction volumes for the control group were 3866.3+/-921, 3536+/-995.7, and 359.9+/-80.2 mm3, as calculated using diffusion- and T2-weighted MRI and histopathological data, respectively. No significant changes were observed in the physiological parameters measured (mean arterial blood pressure, pH, arterial carbon dioxide pressure, arterial oxygen pressure, sodium, potassium, chloride, and glucose levels, hematocrit, and temperature) for either the control or AR-R15896AR-treated group. Postischemic calcium levels returned to normal in the AR-R15896AR-treated cats, whereas they decreased in the control cats. When administered after ischemia, AR-R15896AR was effective in significantly reducing infarction volumes, as measured using diffusion- or T2-weighted magnetic resonance imaging data or quantitative histopathological data. This study also demonstrated that infarction volumes were greater in the diffusion- and T2-weighted magnetic resonance imaging scans than in the qualitative histopathological analyses, with the diffusion-weighted scans exibiting the largest infarction volumes.

Neurologic and histologic evaluation of almitrine + raubasine (Duxil®) in middle cerebral artery occlusion in cats

Impairment of energy metabolism is the fundamental mechanism leading to cell death in ischemia. Using the middle cerebral artery (MCA) occlusion model in cats, we studied the effect of Duxil® (almitrine and raubasine combination), which was given either before and after or only after MCA occlusion, on ischemia in terms of neurological function and histological changes. Neurological function was assessed consecutively for 7 days after MCA occlusion using a categorical rating scale in 18 cats. Neurological function was significantly improved in treated animals than in non-treated controls regarding to the motor and sensory function, walking, posture and stepping reflex. Animals were killed on the 8th day and histological changes were examined by light and electron microscopies. Significant improvement in the morphological scores based on the light-microscopy changes were found in animals treated with Duxil® compared to non-treated ones. Under the electron microscopy, the protective effects of Duxil® were characterized by retaining glycogen and mitochondria. Morphological improvement was associated with the recovery of neurological function and especially profound in penumbra areas of MCA infarction. These results suggest that Duxil® has a protective effect against ischemic damage induced by occlusion of MCA in cats.

Combined therapy with MK‐801 and nimodipine for protection of ischemic brain damage

Calcium ion can enter ischemic neurons through both receptor-operated and voltage-sensitive Ca2+ channels. To attenuate this Ca2+ entry and Ca2(+)-induced neuronal injury, we tried a combined treatment with the noncompetitive N-methyl-D-aspartate (NMDA) antagonist, MK-801, and the dihydropyridine calcium antagonist, nimodipine, in a cat middle cerebral artery occlusion (1 hour) and reperfusion (3 hours) model. We measured changes in cytosolic free calcium, nicotinamide adenine dinucleotide/reduced nicotinamide adenine dinucleotide redox state, and blood flow in the cat cortex using a newly developed fluorometric technique with indo-1, a fluorescent intracellular Ca2+ indicator. The combined treatment, starting 5 minutes into ischemia, was effective in reducing both Ca2+ entry and histologic damage and in enhancing recovery of the electroencephalogram following reperfusion. MK-801 alone was also effective, but to a lesser extent. These data suggest that the dual blockade of Ca2+ entry using MK-801 and nimodipine may be a useful tool for protection against ischemic brain damage.

The Effects of Cervical Spinal Cord Stimulation (cSCS) on Experimental Stroke

Cervical spinal cord stimulation (cSCS) has been employed as a treatment for intractable pain for the past 20 years. Recently, we reported that cSCS increased regional cerebral blood flow (rCBF) in cats and humans. The present study was designed to examine the effects of cSCS on experimental cerebral strokes, using a cat middle cerebral artery occlusion model (MCAO). A total of 31 cats were randomly assigned to three groups; Group 1: control, Group 2: sham operation, Group 3: cSCS. Mortality of the control group was 92% as long as 4 days after MCAO. Groups 2 and 3 showed a prolongation of survival rate (44% and 56%, respectively). CSCS reduced the rate of death within 24 hours after MCAO. There was no alteration of infarct size, which was estimated by the TTC method and measured by computer technique (PDP-11/23), was found in dead cats of all groups. In cats that survived in Group 3, however, drastic prevention of an infarct progression was found, compared to Group 2. The results provide a clinical application of cSCS for stroke patients, although no evident mechanism was obtained.

The effects of etomidate in the cat middle cerebral artery occlusion model of brain ischaemia. An experimental study.

The effects of etomidate on focal cerebral ischaemia following transorbital occlusion of the cat middle cerebral artery were investigated. Etomidate had no effect on CBF before or after onset of ischaemia by comparison with controls, but caused a greater fall in CBF in cats with high preocclusion or initial ischaemic CBF than in those in which CBF was lower. There were more sustained rises in Kp on SG. The established flow threshold for water accumulation was lost; more gyri with CBF above and fewer gyri with CBF below the flow threshold accumulated water. The relationship between mean occlusion CBF and in vitro GABA uptake was lost; uptakes from MG were lower and from SG and EG higher than expected. In the ischaemic penumbra there was a trend towards reduction in CBF, disruption of ion homeostasis and cerebral oedema formation, whilst in areas of lower flow there was some recovery of GABA uptake and less cerebral oedema following administration of etomidate.