ISSN:
1471-4159
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Medicine
Notes:
The effects of adenosine on high-voltage-activated calcium channel currents in tiger salamander retinal ganglion cells were investigated in a mini-slice preparation. Adenosine produced a concentration-dependent decrease in the amplitude of calcium channel current with a maximum inhibition of 26%. The effects of adenosine on calcium channel current were both time- and voltage-dependent. In cells dialyzed with GTP-γ-s, adenosine caused a sustained and irreversible inhibition of calcium channel current, suggesting involvement of a GTP-binding protein. The inhibitory effect of adenosine on calcium channel current was blocked by the A1 antagonist 8-cyclopentyltheophylline (DPCPX, 1–10 µm), but not by the A2 antagonist 3-7-dimethyl-1-propargylxanthine (DMPX, 10 µm), and was mimicked by the A1 agonist N 6-cyclohexyladenosine (CHA, 1 µm) but not by the A2 agonist 5′-(N-cyclopropyl) carbox-amidoadenosine (CPCA, 1 µm). Adenosine's inhibition of calcium channel current was not affected by the L-type calcium channel blocker nifedipine (5 µm). However, adenosine's inhibition of calcium channel current was reduced to approximately 10% after application of ω-conotoxin GVIA (1 µm), suggesting that adenosine inhibits N-type calcium channels. These results show that adenosine acts on an A1 adenosine receptor subtype via a G protein-coupled pathway to inhibit the component of calcium channel current carried in N-type calcium channels.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1046/j.1471-4159.2002.00832.x
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