The Right Rodent for the Job: Infarct Variability Between Strains and Its Impact on Logistics of Experimental Animal Studies

This chapter will discuss the variability in infarct size after ischaemic stroke in rat models of stroke, drawing example from our experience with the thread occlusion model. We will describe how the neuroprotective effect of a novel treatment diminished over the course of our testing, with post hoc analysis revealing wide variability in infarct volume in the experiments where the treatment was not shown to be protective. Application of various inclusion criteria failed to reduce variability, only reducing the number of animals. We then compared infarct variability in the Sprague-Dawley strain to other strains of rat used in our laboratory. The spontaneously hypertensive rat proved to be the most consistent strain of rat, having the least variable infarct volume, and stroke being successfully induced in all animals. The ability to include more animals in experimental groups is advantageous in terms of the absolute number of animals used, the time an experiment will take to complete and the cost of preclinical research.