Article date: July 1997
By: R J Docherty, J C Yeats, A S Piper, in Volume 121, Issue 7, pages 1461-1467
We have found that capsazepine, a competitive antagonist at the vanilloid (capsaicin) receptor, blocks voltage‐activated calcium currents in sensory neurones.
The block of calcium current was slow to develop with a half time of about one minute at 100 μM and lasted for the duration of the experiment. The rate of block of calcium current was strongly concentration‐dependent.
The EC50 for the blocking effect at 0 mV was 7.7±1.4 μM after 6 min exposure to capsazepine. The EC50 at equilibrium was estimated to be 1.4±0.2 μM.
The block of calcium current showed some voltage‐dependence but there was no indication of any selectivity of action for a calcium channel subtype. The characteristics of the blocking action of capsazepine on the residual current of cells which were pretreated with either □Omega;‐conotoxin or nimodipine were similar to control.
The data suggest that capsazepine, in addition to its competitive antagonism of vanilloid receptors, has a non‐specific blocking action on voltage‐activated calcium channels which should be taken into account when interpreting the effects of this substance on intact preparations in vitro or in vivo.
We have found that capsazepine, a competitive antagonist at the vanilloid (capsaicin) receptor, blocks voltage‐activated calcium currents in sensory neurones.
The block of calcium current was slow to develop with a half time of about one minute at 100 μM and lasted for the duration of the experiment. The rate of block of calcium current was strongly concentration‐dependent.
The EC50 for the blocking effect at 0 mV was 7.7±1.4 μM after 6 min exposure to capsazepine. The EC50 at equilibrium was estimated to be 1.4±0.2 μM.
The block of calcium current showed some voltage‐dependence but there was no indication of any selectivity of action for a calcium channel subtype. The characteristics of the blocking action of capsazepine on the residual current of cells which were pretreated with either □Omega;‐conotoxin or nimodipine were similar to control.
The data suggest that capsazepine, in addition to its competitive antagonism of vanilloid receptors, has a non‐specific blocking action on voltage‐activated calcium channels which should be taken into account when interpreting the effects of this substance on intact preparations in vitro or in vivo.
DOI: 10.1038/sj.bjp.0701272
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