Afferent innervation influences HVA Ca2+ current expression in cultured neocortical neurones.

Voltage-activated Ca2+ channels represent a major pathway of Ca2+ entry into neurones. The regulation of the expression of functional Ca2+ channels thus plays a central role in neuronal differentiation. To study the influence of afferent innervation on Ca2+ current expression, we compared HVA Ca2+ currents in two categories of cultured neocortical neurones that showed pronounced differences in synaptic innervation density. Neurones strongly innervated by a presynaptic explant had a two-fold greater HVA Ca2+ current density than neurones not innervated by explant fibres. Chronic blockade of synaptic activity did not affect HVA Ca2+ current density in innervated neurones. Our results thus suggest an activity-independent regulation of HVA Ca2+ current expression by afferent innervation.