Dynamic changes in cortical NADH fluorescence in rat focal ischemia: Evaluation of the effects of hypothermia on propagation of peri-infarct depolarization by temporal and spatial analysis

Abstract

Suppression of peri-infarct depolarizations (PIDs) is one of the major mechanisms of hypothermic protection against transient focal cerebral ischemia. Previous studies have shown the lack of hypothermic protection against permanent focal ischemia. We hypothesized the lack of hypothermic protection was due to the poor efficacy in suppression of PIDs. To examine the hypothesis, we elucidated the effects of hypothermia on the manner of propagation of PIDs with temporal and spatial resolutions using NADH (reduced nicotinamide adenine dinucleotide) fluorescence images by illuminating the parietal-temporal cortex with ultraviolet light. Spontaneously hypertensive rats (n=14) were subjected to permanent focal ischemia by occlusion of the middle cerebral and left common carotid arteries. 2-h hypothermia (30 degrees C) was initiated before ischemia. Although hypothermia delayed the appearance of PIDs, it did not suppress their appearance. Furthermore, 54% of the PIDs enlarged the high-intensity area of NADH fluorescence in the hypothermia group, similar to the normothermia group (53%). The high-intensity area of NADH fluorescence widened by each PID was larger in the hypothermia group than in the normothermia group. These findings suggest that PIDs even in hypothermia are one of the major factors causing growth of infarction, emphasizing the importance of therapy that targets suppression of PIDs even during hypothermia.

Effect of lidocaine on dynamic changes in cortical reduced nicotinamide adenine dinucleotide fluorescence during transient focal cerebral ischemia in rats

“…The present and previous studies (Higuchi et al, 2002;Sasaki et al, 2009) have shown that the majority of the high-intensity NADH fluorescence area forms in approximately 5 min, and that PID-like waves then propagate around the high-intensity area and occasionally enlarge it. Therefore, in this study, we defined the ischemic core as the area of high-intensity NADH fluorescence that forms in 5 min and then gradually enlarges with PID-like waves, and the penumbra (potentially salvageable area) as the distal area external to the high-intensity NADH fluorescence area into which the PID-like waves propagate.…”

“…The technique used for cortical NADH fluorescence imaging has previously been described in detail (Hashimoto et al, 2000;Higuchi et al, 2002;Sasaki et al, 2009). …”

“…NADH fluorescence has been used in the past to identify the redox state of mitochondria (Eng et al, 1989;Takeda et al, 2004) due to the unique behavior of NADH which, when excited with ultraviolet light (366 nm), the reduced form (NADH) fluoresces (460 nm emission), while the oxidized form (NAD + ) does not. Because membrane depolarization is accompanied by an increase in energy demand that leads to accumulation of NADH in mitochondria, dynamic changes on the cortical surface can be visualized by NADH fluorescence (Strong et al, 1996;Higuchi et al, 2002;Sasaki et al, 2009). …”

The biological effect of contralateral forepaw stimulation in rat focal cerebral ischemia: a multispectral optical imaging study

“…Our experience with filament occlusion in rat shows that the number of flow transients clearly correlate with the histological outcome but not in a definite stepwise fashion (Luckl et al, 2009). Similarly, NADH fluorescence studies in focal ischemia showed that recurrent depolarization increases the severity of neuronal injury but only a proportion of spreading depolarizations enlarge the core (Higuchi et al, 2002; Sasaki et al, 2009). In the present study we found that the number of flow transients were significantly higher in the stimulated group.…”

Hypothermia as an Alternative for the Management of Cerebral Ischemia

“…Hypothermia (30ºC) maintained 2 h and applied before ischemia, showed that hypothermia delays the appearance, however does not modify the dynamics of propagation of peri-infarct depolarizations. The authors suggest that peri-infarct depolarizations could have a greater effect on the infarct area in hypothermic rats (Sasaki et al, 2009) and that the inefficacy to suppress peri-infarct depolarizations is the cause of the absence of hypothermia protection in several models of cerebral ischemia.…”