Activity-dependent changes in voltage-dependent calcium currents and transmitter release

Voltage-dependent Ca²⁺ channels are important in the regulation of neuronal structure and function, and as a result, they have received considerable attention. Recent studies have begun to characterize the diversity of their properties and the relationship of this diversity to their various cellular functions. In particular, Ca²⁺ channels play a prominent role in depolarization-secretion coupling, where the release of neurotransmitter is very sensitive to changes in voltage-dependent Ca²⁺ currents. An important feature of Ca²⁺ channels is their regulation by electrical activity. Depolarization can selectively modulate the properties of Ca²⁺ channel types, thus shaping the response of the neuron to future electrical activity. In this article, we examine the diversity of Ca²⁺ channels found in vertebrate and invertebrate neurons, and their short- and long-term regulation by membrane potential and Ca²⁺ influx. Additionally, we consider the extent to which this activity-dependent regulation of Ca²⁺ currents contributes to the development and plasticity of transmitter releasing properties. In the studies of long-term regulation, we focus on crustacean motoneurons where activity levels, Ca²⁺ channel properties, and transmitter releasing properties can be followed in identified neurons.