F Cellular/Molecular L Channels in Dendritic Spines

Calcium entry into the dendritic spines of excitatory neurons is important for many forms of synaptic plasticity. In this issue, Hoogland and Saggau continue efforts to inventory the calcium channels that function in dendritic spines. They evoked backpropagating action potentials at the soma of CA1 neurons in rat hippocampal slices and recorded calcium transients in basal dendrites and spines using calcium imaging. Voltage-dependent calcium transients in spines were driven primarily by R-type, and perhaps T-type, channels, whereas L-type channels provided a seemingly small contribution under normal conditions. When 2 adrenergic receptors ( 2-ARs) were activated, however, the L-type channel contribution increased dramatically. This local modulation acted through protein kinase A, as described previously in other cells. The authors propose that under basal conditions, L-type channels act in so-called mode 1 with short openings, but with 2-AR activation, they move into mode 2 with long open times and a high open probability. ΠDevelopment/Plasticity/Repair