Activation of P2Y1 Nucleotide Receptors Induces Inhibition of the M-Type K+ Current in Rat Hippocampal Pyramidal Neurons

We have shown previously that stimulation of heterologously expressed P2Y1 nucleotide receptors inhibits M-type K+ currents in sympathetic neurons. We now report that activation of endogenous P2Y1 receptors induces inhibition of the M-current in rat CA1/CA3 hippocampal pyramidal cells in primary neu...

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Bibliographic Details
Published in:The Journal of neuroscience 2006-09, Vol.26 (36), p.9340-9348
Main Authors: Filippov, Alexander K, Choi, Roy C. Y, Simon, Joseph, Barnard, Eric A, Brown, David A
Format: Article
Language:English
Subjects:
Action Potentials - physiology
Animals
Cells, Cultured
Hippocampus - physiology
Membrane Potentials - physiology
Neural Inhibition - physiology
Potassium - metabolism
Potassium Channels - physiology
Pyramidal Cells - physiology
Rats
Receptors, Purinergic P2 - metabolism
Receptors, Purinergic P2Y1
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Summary:We have shown previously that stimulation of heterologously expressed P2Y1 nucleotide receptors inhibits M-type K+ currents in sympathetic neurons. We now report that activation of endogenous P2Y1 receptors induces inhibition of the M-current in rat CA1/CA3 hippocampal pyramidal cells in primary neuron cultures. The P2Y1 agonist adenosine 5'-[beta-thio]diphosphate trilithium salt (ADPbetaS) inhibited M-current by up to 52% with an IC50 of 84 nM. The hydrolyzable agonist ADP (10 microM) produced 32% inhibition, whereas the metabotropic glutamate receptor 1/5 agonist DHPG [(S)-3,5-dihydroxyphenylglycine] (10 microM) inhibited M-current by 44%. The M-channel blocker XE991 [10,10-bis(4-pyridinylmethyl)-9(10H)-anthracenone dihydrochloride] produced 73% inhibition at 3 microM; neither ADPbetaS nor ADP produced additional inhibition in the presence of XE991. The effect of ADPbetaS was prevented by a specific P2Y1 antagonist, MRS 2179 (2'-deoxy-N'-methyladenosine-3',5'-bisphosphate tetra-ammonium salt) (30 microM). Inhibition of the M-current by ADPbetaS was accompanied by increased neuronal firing in response to injected current pulses. The neurons responding to ADPbetaS were judged to be pyramidal cells on the basis of (1) morphology, (2) firing characteristics, and (3) their distinctive staining for the pyramidal cell marker neurogranin. Strong immunostaining for P2Y1 receptors was shown in most cells in these cultures: 74% of the cells were positive for both P2Y1 and neurogranin, whereas 16% were only P2Y1 positive. These results show the presence of functional M-current-inhibitory P2Y1 receptors on hippocampal pyramidal neurons, as predicted from their effects when expressed in sympathetic neurons. However, the mechanism of inhibition in the two cell types seems to differ because, unlike nucleotide-mediated M-current inhibition in sympathetic neurons, that in hippocampal neurons did not appear to result from raised intracellular calcium.
ISSN:0270-6474
1529-2401
DOI:10.1523/JNEUROSCI.2635-06.2006