TY - JOUR
T1 - Comparison of N- and P/Q-type voltage-gated calcium channel current inhibition
AU - Currie, Kevin P.M.
AU - Fox, Aaron P.
PY - 1997
Y1 - 1997
N2 - Activation of N- and P/Q-type voltage-gated calcium channels triggers neurotransmitter release at central and peripheral synapses. These channels are targets for regulatory mechanisms, including inhibition by G-protein- linked receptors. Inhibition of P/Q-type channels has been less well studied than the extensively characterized inhibition of N-type channels, but it is thought that they are inhibited by similar mechanisms although possibly to a lesser extent than N-type channels. The aim of this study was to compare the inhibition of the two channel types. Calcium currents were recorded from adrenal chromaffin cells and isolated by the selective blockers ω-conotoxin GVIA (1 μM) and ω-agatoxin IVA (400 nM). The inhibition was elicited by ATP (100 μM) or intracellular application of GTP-γ-S. It was classified as voltage-sensitive (relieved by a conditioning prepulse) or voltage- insensitive (present after a conditioning prepulse). The voltage-insensitive inhibition accounted for a 20% reduction of both currents, whereas the voltage-sensitive inhibition reduced the N-type current by 48% but the P/Q- type current by 18%. However, the voltage dependence of the inhibition, the time course of relief from inhibition during a conditioning prepulse, and the time course of reinhibition after such a prepulse showed few differences between the N- and P/Q-type channels. Assuming a simple bimolecular reaction, our data suggest that changes in the kinetics of the G-protein/channel interaction alone cannot explain the differences in the inhibition of the N- and P/Q-type calcium channels. The subtle differences in inhibition may facilitate the selective regulation of neurotransmitter release.
AB - Activation of N- and P/Q-type voltage-gated calcium channels triggers neurotransmitter release at central and peripheral synapses. These channels are targets for regulatory mechanisms, including inhibition by G-protein- linked receptors. Inhibition of P/Q-type channels has been less well studied than the extensively characterized inhibition of N-type channels, but it is thought that they are inhibited by similar mechanisms although possibly to a lesser extent than N-type channels. The aim of this study was to compare the inhibition of the two channel types. Calcium currents were recorded from adrenal chromaffin cells and isolated by the selective blockers ω-conotoxin GVIA (1 μM) and ω-agatoxin IVA (400 nM). The inhibition was elicited by ATP (100 μM) or intracellular application of GTP-γ-S. It was classified as voltage-sensitive (relieved by a conditioning prepulse) or voltage- insensitive (present after a conditioning prepulse). The voltage-insensitive inhibition accounted for a 20% reduction of both currents, whereas the voltage-sensitive inhibition reduced the N-type current by 48% but the P/Q- type current by 18%. However, the voltage dependence of the inhibition, the time course of relief from inhibition during a conditioning prepulse, and the time course of reinhibition after such a prepulse showed few differences between the N- and P/Q-type channels. Assuming a simple bimolecular reaction, our data suggest that changes in the kinetics of the G-protein/channel interaction alone cannot explain the differences in the inhibition of the N- and P/Q-type calcium channels. The subtle differences in inhibition may facilitate the selective regulation of neurotransmitter release.
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U2 - 10.1523/jneurosci.17-12-04570.1997
DO - 10.1523/jneurosci.17-12-04570.1997
M3 - Article
C2 - 9169518
AN - SCOPUS:0030919908
SN - 0270-6474
VL - 17
SP - 4570
EP - 4579
JO - Journal of Neuroscience
JF - Journal of Neuroscience
IS - 12
ER -