A new role for P2 receptors: talking with calcium-activated potassium channels
1Department of Physiology, School of Medical Sciences, University of New South Wales, Kensington, NSW, Australia. dr.p.bertrand@gmail.com
Abstract:
Purinergic fast synaptic transmission may play a very subtle role in regulating the excitability of enteric circuits. That is one of the important findings in a new paper by Ren and Galligan in the current issue of this Journal. They first provide compelling evidence that P2X(3) receptors (ionotropic purine receptors) are expressed by guinea-pig motor and interneurons and that these subtypes mediate the purinergic fast excitatory postsynaptic potential (EPSP). They also found that the P2X(3)-mediated depolarization was often followed by a hyperpolarization. This is an intriguing finding because if the purinergic fast EPSPs are also followed by a hyperpolarization, then it could play a role in truncating bursts of synaptic potentials or in shaping periodic synaptic input. The hyperpolarization is caused by calcium entry through the P2X(3) receptor which then activates a calcium-activated potassium (K(Ca)) channel. Surprisingly, the hyperpolarization was not affected by any of the standard blockers of calcium- or voltage-activated K(+) channels suggesting that a novel K(Ca) channel is present in the enteric neurons. Such a wide-spread channel could well have an important physiological role and could be an important new drug target for regulating reflex activity in the enteric nervous system.
Related Concept Videos
Calmodulin-dependent Signaling
The Ca2+-CaM complex does not have enzymatic activity by itself. Instead, the complex binds downstream target proteins, including membrane proteins or enzymes,...
Ligand-Gated Ion Channel Receptor: Gating Mechanism
G-Protein Gated Ion Channels
Sensory organs,...
The Role of Ion Channels in Neuronal Computation
Sometimes a single EPSP is strong enough to induce an action potential in the postsynaptic neuron. However, multiple presynaptic inputs must often create EPSPs around the same time for the postsynaptic neuron to be sufficiently depolarized to fire an action potential.
Mechanically-gated Ion Channels
Mechanically-gated Ion Channels

