With the whole‐cell patch clamp technique, the effect of the antimalarial drug, mepacrine (quinacrine) on the inward current mediated by 5‐HT3 receptors (5‐hydroxytryptamine (5‐HT)‐induced current) was investigated in isolated nodose ganglion neurones of the rat.
5‐HT and the selective 5‐HT3 receptor agonists, 2‐methyl‐5‐HT and m‐chlorophenylbiguanide elicited an inward current which reversed at around 0 mV and quickly desensitized to a steady state level.
Mepacrine dose‐dependently inhibited the peak current induced by 5‐HT with an IC50 of 2.1 μm and an apparent Hill coefficient of 0.99.
Mepacrine increased the decay rate of the 5‐HT‐induced current.
The effect of mepacrine on the 5‐HT‐induced current was reversible and not dependent on membrane potential. The reversal potential of the 5‐HT‐induced current was not affected.
Intracellular mepacrine had no significant effect on the 5‐HT‐induced current and did not block the extracellular action of mepacrine.
Concentration‐response curves in the presence and absence of mepacrine suggest a non‐competitive inhibition of 5‐HT‐induced current by mepacrine.
With the whole‐cell patch clamp technique, the effect of the antimalarial drug, mepacrine (quinacrine) on the inward current mediated by 5‐HT3 receptors (5‐hydroxytryptamine (5‐HT)‐induced current) was investigated in isolated nodose ganglion neurones of the rat.
5‐HT and the selective 5‐HT3 receptor agonists, 2‐methyl‐5‐HT and m‐chlorophenylbiguanide elicited an inward current which reversed at around 0 mV and quickly desensitized to a steady state level.
Mepacrine dose‐dependently inhibited the peak current induced by 5‐HT with an IC50 of 2.1 μm and an apparent Hill coefficient of 0.99.
Mepacrine increased the decay rate of the 5‐HT‐induced current.
The effect of mepacrine on the 5‐HT‐induced current was reversible and not dependent on membrane potential. The reversal potential of the 5‐HT‐induced current was not affected.
Intracellular mepacrine had no significant effect on the 5‐HT‐induced current and did not block the extracellular action of mepacrine.
Concentration‐response curves in the presence and absence of mepacrine suggest a non‐competitive inhibition of 5‐HT‐induced current by mepacrine.
DOI: 10.1111/j.1476-5381.1994.tb13141.x
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