Mouse neostriatal slices were preincubated with U73122 (12.5 μm for 20 min), BAPTA/AM (BAPTA, 20 μm for 20 min), or cyclosporin A (Cy A, 5 μm for 60 min) and then without or with DHPG (100 μm for 2 min) or ionomycin (Iono., 2 μm for 2 min). Slices were homogenized, and Cdk5 was immunoprecipitated with anti-Cdk5 (C-8) antibody. Cdk5 activity was assayed using histone H-1 as substrate, and samples were analyzed by SDS-PAGE and autoradiography. The top and middle panels show autoradiograms indicating histone H-1 phosphorylation. The bottom panel shows cumulative data (means ± S.E.) from three experiments. Data for each sample were normalized to the total level of cdk5 (determined by immunoblotting, not shown). Data were then normalized to the value obtained in the absence of any addition (−DHPG, set as 1). *, p < 0.05, Student’s t test, compared with untreated slices.