A comparative study of L-type voltage sensitive Ca2+ channels in rat brain regions and cultured neuronal cells

Radioligand binding studies using the L-type voltage sensitive Ca2+ channel (VSCC) antagonist (+)-[H-3]PN200-110 revealed the following rank order channel density in rat brain and cultured neuronal cell homogenates: striatum greater than or equal to cerebrocortex >> cerebellum = brainstem > SH-SY5Y cell line > NG108-15 cell line > 1321N1 cell line > PC12 cell line. There were no significant differences in the equilibrium dissociation constant, K-d for (+)-[H-3]PN200-110 or pK(50) for nifedipine. K+ depolarization in SH-SYSY cells and NG108-15 cells evoked a biphasic and monophasic increase in [Ca2+](i). The L-type Ca channel antagonist nifedipine (1 mu M) produced a 66 and 87% inhibition of the K+-evoked rise in the peak and plateau phase [Ca2+](i) in SH-SYSY cells and abolished the monophasic response in NG108-15 cells. The L-channel activator S(-)Bay K 8644 (1 mu M) enhanced the K+-evoked increase in [Ca2+](i) in both cell lines. These data demonstrate a comparatively low density of L-VSCC in undifferentiated SH-SYSY cells, NG108-15 cells, 1321N1 cells and PC12 cells that are functionally active in at least SH-SYSY cells and NG108-15 cells. (C) 1997 Elsevier Science Ireland Ltd.