Comparison of infarct volume and behavioral deficit in Wistar Kyoto and spontaneously hypertensive rat after transient occlusion of the middle cerebral artery

Abstract

Rodent models of focal cerebral ischemia are important tools in experimental stroke research. Such models have proven instrumental for the understanding of injury mechanisms in cerebral stroke and helped to identify potential new therapeutic options. A plethora of neuroprotective substances have been shown to be effective in preclinical stroke research but failed to prove effectiveness in subsequent clinical trials. Interestingly, preclinical studies have shown that neuroprotective agents are selectively effective in different rat strains. The underlying mechanisms for this discrepancy are so far unknown, but differences in initial stroke volume with concomitant neuroinflammatory processes in the expanding stroke area might be relevant. In the current project, we compared the stroke volume and behavioral outcome between Wistar Kyoto (WKY) and spontaneously hypertensive rats (SHR), subjected to transient middle cerebral artery occlusion (tMCAO) for 1 h, followed by 23 h reperfusion. We further analyzed the expression of well-known pro-inflammatory mediators in the cortical peri-infarct area region using a TTC-based isolation approach. Initial reduction of local cerebral blood flow was comparable between both strains. Mean infarct volume and the extent of tMCAO-provoked functional deficits did not differ between WKY and SHR rats. Furthermore, the induction of pro-inflammatory mediators, among CCL3 and CCL5, in the isolated ischemic peri-infarct area region was equal in both rat strains. We were able to demonstrate that stroke outcome is comparable 23 h after transient MCAO in WKY and SHR rats. Future studies have to show whether this observation confirms in the long-term, and which factors contribute to differences observed with respect to therapeutic responsiveness.

Keywords: Behavior; SHR; Stroke; WKY; Wistar; tMCAO.

Figure 1

rCBF and cortical infarct volume. (A) Representative Laser-Doppler measurement of relative cerebral blood (rCBF) flow over the ipsilateral middle cerebral artery territory before and during tMCAO (1 h). Reduction of rCBF is given as percentage of baseline values. (B) TTC-stained 2 mm coronal brain slices show the white infarct area 24 h after tMCAO. Red color indicates intact tissue. (C) Arrowhead indicates the cingulated cortex, arrow the hippocampus. Quantitative data of the measurement of lesion volumes are given in (D). Note that lesion volumes are comparable in WKY and SHR rat strains. Data represent means ± SEM. For further abbreviations see text.

Figure 2

Behavioral testing. (A/B) Results of behavioral testing of WKY and SHR rats 24 h after initiation of tMCAO. A total of six sub-tests were performed resulting in a maximum of 18 scores in sham-operated animals (no tMCAO). Note that behavioral outcome is comparable in both rat strains. Data represent means ± SEM. For further abbreviations see text. ***p< 0.001 sham compared to tMCAO.

Figure 3

Gene expression in the peri-infarct area. Gene expression studies in tissue obtained from the cerebral cortex peri-infarct area after tMCAO. (A) interleukin 6 expression, (B) CD68 expression, (C) chemokine (C-C motif) ligand 3 expression, (D) chemokine (C-C motif) ligand 5 expression. Data represent means ± SEM. For further abbreviations see text.