Early in development, there is a high amount of expression of T-type calcium channels . During maturation of the nervous system, the expression of N or L-type currents becomes more prominent.  As a result, mature neurons express more calcium channels that will only be activated when the cell is significantly depolarized . The different expression levels of low-voltage activated (LVA) and high-voltage activated (HVA) channels can also play an important role in neuronal differentiation . In developing Xenopus spinal neurons LVA calcium channels carry a spontaneous calcium transient that may be necessary for the neuron to adopt a GABAergic phenotype as well as process outgrowth .