NeuroScale, the battery of behavioral tests with novel scoring system for phenotyping of transgenic rat model of tauopathy

We have previously shown that transgenic rats expressing misfolded tau protein developed neurofibrillary tangles and axonal degeneration in the brain and spinal cord, which led to impairment of sensorimotor and neuromuscular functions. To quantify neurobehavioral phenotype of the transgenic rats we have designed a testing protocol and a novel scoring system – NeuroScale – that reliably reflects progression of functional impairment of transgenic rats. NeuroScale consists of three variants of beam walking test with different sensitivity and a rapid neuromuscular and neurological examination, where animal performance is evaluated and scored according to a pre-defined rating scale. The range of the rating scale was developed to increase homogeneity of the collected behavioral data without lowering sensitivity of the testing methods. Finally, all awarded points were summed up to obtain a complete quantitative behavioral readout, the NeuroScale score, from animals under investigation. Increase in the NeuroScale score faithfully mirrored disease progression and allowed statistically significant discrimination (p < 0.001) between behavioral responses of transgenic and control animals during the whole disease process. The method was suitable for a high-throughput test whereby an experienced operator can examine up to 60 rats per day.We show that this multi-test battery with novel sensitive scoring system – NeuroScale – represents a rapid, simple to perform, high throughput method for quantitative evaluation of behavioral phenotype of transgenic rats that could serve as a valuable primary read-out for in vivo validation of therapeutic agents.