Figure 2.

Persistent multiple CF Innervation of PCs confined to the rostral cerebellum in mature PLCβ4 mutant mice. (A and B) EPSCs elicited by stimulation of CFs in the granule cell layer in wild-type (A) and PLCβ4 mutant (B) PCs. Records were taken from mice at P50 (A, upper), P80 (A, lower), P46 (B, upper), and p46 (B, lower), respectively. One or two traces are superimposed at each threshold intensity. Stimuli were applied at 0.2 Hz. Holding potential was −10 mV except for the lower trace in B that was taken at 0 mV. The number of CFs innervating the recorded PC was estimated by the number of discrete CF-EPSC steps. (C and D) Spatial distribution of mono-innervated (open circles) and multiply-innervated (filled circles) PCs of the wild-type (C) and PLCβ4 mutant (D) cerebella. Recording sites of PCs obtained from six wild-type (n = 108 PCs) and six PLCβ4 mutant (n = 86 PCs) cerebella were plotted on the standard midsagittal plane of the vermis. The broken line indicates the demarcation of the border of the rostral and caudal cerebellum that corresponds to the border of the two cerebellar regions in terms of PLCβ4 and PLCβ3 mRNA expression patterns (see Fig. 3). Note that multiply-innervated PCs were much more numerous in the rostral than in the caudal cerebellum in PLCβ4 mutant mice. (E and F) Summary histograms showing the number of discrete steps of CF-EPSCs of the wild-type (open columns) and PLCβ4 mutant (hatched-columns) PCs sampled in the rostral (E) and caudal (F) cerebellum. Data were obtained from mice at P22-P109. Note that the percentage of multiply-innervated PCs is significantly higher for the PLCβ4 mutant than the wild type mice (P < 0.0001, χ² test for independent samples) in the rostral cerebellum. The wild-type and mutant PCs almost all were analyzed before knowledge of the mouse genotype was revealed.