Developmental regulation of action potential-induced Ca2+ entry in neocortical neurons

Intracellular calcium plays a critical role in the regulation of membrane excitability, synaptic integration and synaptic plasticity. Using whole-cell recording and calcium imaging, we investigated intracellular calcium dynamics in apical dendrites of layer V pyramidal cells in the immature rat neocortex. Dendritic calcium increases induced by action potentials were only small on postnatal days 4-6 (P4-6), then underwent a gradual enhancement during the second post-natal week and were 2- to 3-fold larger on P16-18 than on P4-6. At P15-18 there were no significant differences in the calcium increases among the three subclasses of layer V pyramidal neurons: adapting regular spiking (RS), non-adapting RS and intrinsically bursting (IB) neurons. Developmental regulation of dendritic calcium dynamics may be crucial for functional maturation of the neocortex.