Nifedipine, calmidazolium chloride (CMZ), and cyclosporin A (CsA) treatments inhibit neuritin‐induced increases in cerebellar granule neuron (CGN) neurite length and spine density. (a) Representative images and quantitative analysis of the effects of neuritin on neurite length in CGNs cultured in the absence or presence of nifedipine, CMZ, and CsA (Ctl, n = 41; Nrn, n = 52; Nif, n = 34; Nif + Nrn, n = 39; CMZ, n = 38; CMZ + Nrn, n = 43; CsA, n = 39; CsA + Nrn, n = 46). (b) Representative images and quantitative analysis of the effects of neuritin on total spine density in CGNs cultured in the absence or presence of nifedipine, CMZ, and CsA (Ctl, n = 28; Nrn, n = 35; Nif, n = 29; Nif + Nrn, n = 23; CMZ, n = 20; CMZ + Nrn, n = 25; CsA, n = 23; CsA + Nrn, n = 20). Results represent mean ± SEM, n indicates the number of cells. **p < 0.01 between two groups connected with a straight line (one‐way anova followed by Bonferroni post hoc test).