Differential facilitation of N- and P/Q-type calcium channels during trains of action potential-like waveforms.

Currie KP, Fox AP
J Physiol. 2002 539 (Pt 2): 419-31

PMID: 11882675 · PMCID: PMC2290166 · DOI:10.1113/jphysiol.2001.013206

Inhibition of presynaptic voltage-gated calcium channels by direct G-protein betagamma subunit binding is a widespread mechanism that regulates neurotransmitter release. Voltage-dependent relief of this inhibition (facilitation), most likely to be due to dissociation of the G-protein from the channel, may occur during bursts of action potentials. In this paper we compare the facilitation of N- and P/Q-type Ca(2+) channels during short trains of action potential-like waveforms (APWs) using both native channels in adrenal chromaffin cells and heterologously expressed channels in tsA201 cells. While both N- and P/Q-type Ca(2+) channels exhibit facilitation that is dependent on the frequency of the APW train, there are important quantitative differences. Approximately 20 % of the voltage-dependent inhibition of N-type I(Ca) was reversed during a train while greater than 40 % of the inhibition of P/Q-type I(Ca) was relieved. Changing the duration or amplitude of the APW dramatically affected the facilitation of N-type channels but had little effect on the facilitation of P/Q-type channels. Since the ratio of N-type to P/Q-type Ca(2+) channels varies widely between synapses, differential facilitation may contribute to the fine tuning of synaptic transmission, thereby increasing the computational repertoire of neurons.

MeSH Terms (16)

Action Potentials Adrenal Glands Animals Calcium Channels, N-Type Calcium Channels, P-Type Calcium Channels, Q-Type Cattle Cells, Cultured Electric Stimulation Electrophysiology Ion Channel Gating Neuronal Plasticity Neurons Neurotransmitter Agents Patch-Clamp Techniques Recombinant Proteins

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