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Neuron. 1991 Jan;6(1):13-20.

Activation of mu opioid receptors inhibits transient high- and low-threshold Ca2+ currents, but spares a sustained current.

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Department of Cell Biology and Physiology, Washington University, St. Louis, Missouri 63110.


Opioids and opiates decrease the duration of action potentials and the amount of neurotransmitter released from sensory neurons. The mu-type opioid receptor, the binding site for morphine, is thought to act exclusively on K+ channels. Here, we show that activation of the mu receptor inhibits Ca2+ channels in rat sensory neurons; the effect is blocked by a mu antagonist and is not mimicked by kappa or delta receptor agonists. Both low-threshold (T-type) and high-threshold Ca2+ currents are partially suppressed. omega-Conotoxin-sensitive and omega-conotoxin-insensitive, high-threshold Ca2+ currents are inhibited. The kinetic effect on high-threshold current is like that caused by diminished rest potential: the transient component is selectively lost, whereas the sustained component is spared.

[Indexed for MEDLINE]

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