Cerebellum (2012) 11:246–258 251 Fig. 2 Abnormal motor behavior in Cacna1a Purkinje cell-specific knockout mice. a–c Rotarod testing revealed severe impairments in motor performance of PCα1KO mice compared to WT littermates. The latency to fall is expressed as the maximal rotating speed in rotations per min (rpm) for P18 (a), P30 (b), and P200–250 (c) PCα1KO mice and WT littermates. d, e Additional assessment of motor behavior to classify by type of movement disorder. d P30 PCα1KO mice did not (F (4, 16) = 0.48, p = 0.75). Using a similar rotarod protocol for P200–250 mice (n = 5 per genotype), we found the same extend of motor deficit (Fig. 2c). PCα1KO mice of P200–250 were not able to stay on the accelerating rotarod for more than 57±14.3 s on the fifth day and fell off at a significantly lower rotating speed than did wild type mice (F (1, 8)=908.84, p<0.001) who managed to stay on the rotarod for 248±28.4 s on the fifth day. Although the genotype X change in performance over time interaction effect was not significant, it did show a clear trend (F (4, 32)=2.47, p=0.064). This trend is confirmed since PCα1KO mice did not show an improvement over time (F (4, 16) = 0.87, p=0.51), whereas WT mice did (F (4, 16)=4.07, p<0.02). These data should, however, be inter- preted with caution in the sense that lack of improvement on the rotarod test in PCα1KO mice does not necessarily reflect a learning deficit, e.g. the ataxic phenotype may have prevented an improvement in performance in this test. Because it is difficult to determine the specific deficit that causes impaired rotarod performance, motor function was also assessed using a dyskinesia rating scale (see PCα1KO mice (n=5) but not WT littermates (n=5) showed ataxic movements, tremors, tonic, and clonic movements. Note the predom- inant ataxic component. e P200-250 PCα1KO mice (n=5) but not WT littermates (n=5) showed ataxic movements, tremors, tonic, and clonic movements. Note the similarity in behavioral classification between P30 and P200–250 PCα1KO mice “Materials and Methods” for details). There was signifi- cantly more ataxia compared to tremor, tonic movements, or clonic movements in both P30 PCα1KO (n = 4) mice (ataxia vs. tremor: U = 16.00, p < 0.01; ataxia vs. tonic: U = 16.00, p < 0.01; ataxia vs. clonic: U = 16.00, p < 0.01) and P200–250 PCα1KO mice (n = 5; ataxia vs. tremor: U = 25.00, p < 0.01; ataxia vs. tonic: U = 25.00, p < 0.01; ataxia vs. clonic: U = 25.00, p < 0.01) (Fig. 2d, e). Ataxia, but not other movements, was significantly increased in young (P30) PCα1KO mice compared with age-matched WT mice (n = 4; U = 16.00, p < 0.01), whereas all abnormal movement types were significantly increased in old (P200–250) PCα1KO mice compared with age-matched WT littermates (n = 5; ataxia: U = 25.00, p < 0.01; tremor: U = 25.00, p < 0.01; tonic: U = 25.00, p < 0.01; clonic: U = 25.00, p < 0.01). In PCα1KO mice, there was a slight but significant increase in tremor with age (U = 20.00, p < 0.01) and a trend for an increase in ataxia and clonus with age (Us = 18 and 17, respectively), but their relative contribution to the abnormal motor behavior in mutant mice remained similar irrespec- tive of their age.