Can nimodipine prevent ischaemic reperfusion injury in the rat brain?

Combined nimodipine and citicoline reduce infarct size, attenuate apoptosis and increase bcl-2 expression after focal cerebral ischemia

Cerebral ischemia triggers a multitude of pathophysiological and biochemical events that separately affect the evolution of focal ischemia and, therefore, stroke treatment should logically employ all known neuroprotective agents. We hypothesized that a treatment combining nimodipine and citicoline might have a potential neuroprotective effect. To assess this idea, Sprague-Dawley rats underwent transient bilateral common carotid artery ligation with simultaneous middle cerebral artery occlusion for 60 min. Four treatment groups were established. Animals received either: a) saline (control group); b) intracarotid nimodipine infusion during 30 min in the ischemia-reperfusion (nimodipine group); c) i.p. postischemic citicoline injections once daily for 7 days (citicoline group); or d) intracarotid nimodipine bolus during ischemia-reperfusion plus i.p. postichemic citicoline injections (combination group). They were killed after either 7 or 3 days after reperfusion. In the first case, the volume of the infarcted tissue was studied by a stereological procedure and in the second case, in situ end-labeling of nuclear DNA fragmentation (TUNEL) and Bcl-2 expression were employed to determine the level of apoptosis. The infarct volume was significantly reduced in both the nimodipine and the citicoline treatment groups after 7 days of reperfusion; combination of both drugs produced an additive effect. After 3 days of reperfusion, the number of Bcl-2-positive neurons was significantly increased while that of TUNEL-positive cells significantly decreased at the infarct border in the combined-treatment animals. Our findings demonstrate a neuroprotective effect from an acute single dose of nimodipine during ischemia-reperfusion and prolonged post-ischemic treatment with citicoline in a model of focal cerebral ischemia. These results suggest that a possible mechanism of neuroprotective action would be mediated by increased Bcl-2 expression and decreased apoptosis within the boundary zone of the infarct together with neutralization of the ischemia-reperfusion injury.

Somatosensory evoked potential and histopathological investigations in ischaemia-induced brain damage: effects of trimetazidine in rats

We studied the protective effects of trimetazidine (TMZ) on brain damage by means of somatosensory evoked potentials (SEP) in rats. The TMZ group did not show any statistically significant difference from the control group with respect to SEPs. However, the percentage of cells with ischaemic cell damage in hippocampal regions was significantly smaller in the TMZ group than the control group. Trimetazidine reduced the number of damaged cells in the cerebral tissue during the ischaemia-reperfusion damage. It was suggested that higher doses of trimetazidine may further reduce the number of cells with ischaemic damage.

Hippocampal cell loss in transient global cerebral ischemia in rats: a critical assessment

The induction of transient global cerebral ischemia by permanent vertebral occlusion and temporary carotid ligation (four-vessel occlusion) is widely accepted as a valid tool for the study of pathogenesis and treatment of ischemia. The neural damage inflicted by this intervention is often assessed by measuring pyramidal cell loss in the CA1 hippocampal field. Nevertheless studies using this model in rats often fail to control variables that are relevant to the outcome, and/or apply biased methods to quantitate histological damage. We have applied unbiased stereological methods to estimate absolute numbers of surviving neurons in CA1 in Wistar rats subjected to either 10 or 20 min global ischemia using the Sugio et al. variant of the original four-vessel occlusion model. Animal mortality was high at both times, with neuron losses averaging 39% and 31%, respectively. Post-operative mortality was reduced substantially by using decompressive craniectomies and, even more effectively, by pre-treating the rats with low doses of phenytoin. Both maneuvers led to a severely increased CA1 neuron loss, which reached 50%, after an ischemia of 10 min. This finding strongly supports that mortality biases the sample. Other noteworthy findings that emerged from this study were a linear relationship between per-ischemic blood pressure increments and animal survival, and a negative correlation between cell survival and preferentially left-sided damage.

Glutamate, glutamine, and GABA as substrates for the neuronal and glial compartments after focal cerebral ischemia in rats

BACKGROUND AND PURPOSE

Even though the utilization of substrates alternative to glucose may play an important role in the survival of brain cells under ischemic conditions, evidence on changes in substrate selection by the adult brain in vivo during ischemic episodes remains very limited. This study investigates the utilization of glutamate, glutamine, and GABA as fuel by the neuronal and glial tricarboxylic acid cycles of both cerebral hemispheres after partially reversible focal cerebral ischemia (FCI).

METHODS

Right hemisphere infarct was induced in adult Long-Evans rats by permanent occlusion of the right middle cerebral artery and transitory occlusion of both common carotid arteries. (1,2-13C2) acetate was infused for 60 minutes in the right carotid artery immediately after carotid recirculation had been re-established (1-hour group) or 23 hours later (24-hour group). Extracts from both cerebral hemispheres were prepared and analyzed separately by 13C nuclear magnetic resonance and computer-assisted metabolic modeling.

RESULTS

FCI decreased the oxidative metabolism of glucose in the brain in a time-dependent manner. Reduced glucose oxidation was compensated for by increased oxidations of (13C) glutamate and (13C) GABA in the astrocytes of the ipsilateral hemispheres of both groups. Increased oxidative metabolism of (13C) glutamine in the neurons was favored by increased activity of the neuronal pyruvate recycling system in the 24-hour group.

CONCLUSIONS

Data were obtained consistent with time-dependent changes in the utilization of glutamate and GABA or glutamine as metabolic substrates for the glial or neuronal compartments of rat brain after FCI.

Nimodipine improves brain energy metabolism and blood rheology during ischemia and reperfusion in the gerbil brain

Whether nimodipine improves cerebral blood flow (CBF) and metabolism in cerebral ischemia remains a controversial issue. We investigated the effect of nimodipine on CBF, brain energy metabolism, using a laser-Doppler flowmeter and in vivo 31phosphorus nuclear magnetic resonance (31P NMR) spectroscopy, and blood rheology during forebrain ischemia and reperfusion in gerbils. Eighty-three adult gerbils received nimodipine (1 micrograms/kg/min), or an equal volume of the vehicle, or saline, over 60 min prior to a transient forebrain ischemia for 60 min. We measured sequential changes in phosphocreatine (PCr) / inorganic phosphate (Pi) ratio, beta-ATP/Pi ratio, and intracellular pH (pHi) during ischemia and reperfusion by 31P NMR spectroscopy, and the measurement of whole blood viscosity (WBV) at 60 min after reperfusion. CBF was measured continuously throughout the study by a laser-Doppler flowmeter. During forebrain ischemia, PCr/Pi and beta-ATP/Pi ratios were higher significantly in the nimodipine-treated group (p < 0.05 and 0.01) than in the vehicle- or saline-treated groups. During reperfusion, PCr/Pi and beta-ATP/Pi ratios recovered significantly only in the nimodipine-treated group (p < 0.05 and 0.01). The WBV at high shear rate (562.5 s-1) lowered significantly in the nimodipine-treated group (p < 0.05) compared with the vehicle- or saline-treated group. CBF was higher significantly only during administration of nimodipine in the nimodipine-treated group (p < 0.01) than other groups. Nimodipine improved brain energy metabolism and blood rheology during forebrain ischemia and reperfusion in the gerbil brain.

Reduction of infarct size by intra-arterial nimodipine administered at reperfusion in a rat model of partially reversible brain focal ischemia

BACKGROUND AND PURPOSE

When blood flow to a brain region that has undergone an ischemic attack is reestablished, additional injury is to be expected from the reperfusion. The purpose of the study was to determine the effect of the intra-arterial injection of nimodipine at reperfusion on infarct volume in rats subjected to partially reversible focal neocortical ischemia.

METHODS

Two groups of Long-Evans rats with transient bilateral common carotid artery occlusion and permanent middle cerebral artery occlusion were subjected to retrograde cannulation of the external carotid artery close to the carotid bifurcation to allow the administration of isotonic saline (group 1) or nimodipine solution (group 2) just before and during reperfusion. The estimate for the actual amount of infarcted cortex was calculated by the volume ratio between the spared cortex in the infarcted hemisphere and the total cortex of the contralateral hemisphere by means of a serological method based on the Cavalieri principle.

RESULTS

The percentage of cortex that was infarcted in control rats was 63.8 +/- 3.1%, whereas nimodipine-treated rats exhibited a significantly smaller (P < .005) percentage of infarct volume (31.3 +/- 12.7%).

CONCLUSIONS

Our data show that the intra-arterial injection of nimodipine just before and during reperfusion reduced neocortical infarct volume in rats subjected to partially reversible focal cerebral ischemia.

Morphometric study of focal cerebral ischemia in rats: a stereological evaluation

An efficient, unbiased stereological method for estimating and evaluating volumetric parameters of cortical infarction is presented. Long-Evans rats were subjected to a standard procedure for achieving focal cerebral ischemia, consisting of permanent ligation of the right middle cerebral artery and temporary occlusion of both common carotid arteries. Animals were killed 24 h later by perfusion fixation and the brains were embedded in celloidin, serially sectioned at 60 microns and stained with Cresyl violet. All cases showed identifiable areas of infarction of variable extent within the territory of the right middle cerebral artery. Involvement of allocortical or subcortical structures was variable and in three cases there were small foci of infarct in the contralateral hemisphere. The absolute volumes of the infarcted tissue and of the spared cortex of both hemispheres were obtained by means of an unbiased estimator of volume based on Cavalieri's principle. The best estimate of the actual amount of infarcted cortex was found to be given by the volume ratio between the spared cortex of the right (infarcted) hemisphere and the total cortex of the left (control) hemisphere. This approach avoided the error introduced by the accompanying edema and decreased the observed interanimal variance. Sample size predictions for therapeutic-pharmacological trials show that relatively few animals would be needed using the model of ischemia and quantitative morphometry presented here to detect a 30-40% change in infarct volume.