Antisense oligonucleotides against α(1E) reduce R-type calcium currents in cerebellar granule cells

Many neurons of the central nervous system display multiple high voltage-activated Ca(2+) currents, pharmacologically classified as L-, N-, P-, Q-, and R-type. Of these current types, the R-type is the least understood. The leading candidate for the molecular correlate of R-type currents in cerebellar granule cells is the α(1E) subunit, which yields Ca(2+) currents very similar to the R-type when expressed in heterologous systems. As a complementary approach, we tested whether antisense oligonucleotides against α(1E) could decrease the expression of R-type current in rat cerebellar granule neurons in culture. Cells were supplemented with either antisense or sense oligonucleotides and whole-cell patch clamp recordings were obtained after 6–8 days in vitro. Incubation with α(1E) antisense oligonucleotide caused a 52.5% decrease in the peak R-type current density, from −10 ± 0.6 picoamperes/picofarad (pA/pF) (n = 6) in the untreated controls to −4.8 ± 0.8 pA/pF (n = 11) (P < 0.01). In contrast, no significant changes in the current expression were seen in sense oligonucleotide-treated cells (−11.3 ± 3.2 pA/pF). The specificity of the α(1E) antisense oligonucleotides was supported by the lack of change in estimates of the P/Q current amplitude. Furthermore, antisense and sense oligonucleotides against α(1A) did not affect R-type current expression (−11.5 ± 1.7 and −11.7 ± 1.7 pA/pF, respectively), whereas the α(1A) antisense oligonucleotide significantly reduced whole cell currents under conditions in which P/Q current is dominant. Our results support the hypothesis that members of the E class of α(1) subunits support the high voltage-activated R-type current in cerebellar granule cells.