Involvement of calcium channels in depolarization-evoked release of adenosine from spinal cord synaptosomes.
The potential involvement of L- and N-type voltage-sensitive calcium (Ca2+) channels and a voltage-independent receptor-operated Ca2+ channel in the release of adenosine from dorsal spinal cord synaptosomes induced by depolarization with K+ and capsaicin was examined. Bay K 8644 (10 nM) augmented release of adenosine in the presence of a partial depolarization with K+ (addition of 6 mM) but not capsaicin (1 and 10 microM). This augmentation was dose dependent from 1 to 10 nM and was followed by inhibition of release from 30 to 100 nM. Nifedipine and nitrendipine inhibited the augmenting effect of Bay K 8644 in a dose-dependent manner, but neither antagonist had any effect on release of adenosine produced by K+ (24 mM) or capsaicin (1 and 10 microM). omega-Conotoxin inhibited K(+)-evoked release of adenosine in a dose-dependent manner but had no effect on capsaicin-evoked release. Ruthenium red blocked capsaicin-induced release of adenosine but had no effect on K(+)-evoked release. Although L-type voltage-sensitive Ca2+ channels can modulate release of adenosine when synaptosomes are partially depolarized with K+, N-type voltage-sensitive Ca2+ channels are primarily involved in K(+)-evoked release of adenosine. Capsaicin-evoked release of adenosine does not involve either L- or N-type Ca2+ channels, but is dependent on a mechanism that is sensitive to ruthenium red.
Cahill
C M
CM
Department of Pharmacology, Dalhousie University, Halifax, Nova Scotia, Canada.
White
T D
TD
Sawynok
J
J
D000241:Adenosine / Q000378:metabolism*; D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000502:physiology*; D002211:Capsaicin / Q000494:pharmacology; D004095:Dihydropyridines / Q000494:pharmacology*; D004594:Electrophysiology; D010456:Peptides, Cyclic / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D012430:Ruthenium Red / Q000494:pharmacology; D013116:Spinal Cord / Q000378:metabolism / Q000502:physiology*; D013574:Synaptosomes / Q000378:metabolism / Q000502:physiology*; D020960:omega-Conotoxins
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D004095:Dihydropyridines; D010456:Peptides, Cyclic; D020960:omega-Conotoxins; C053423:Conus magus toxin; D012430:Ruthenium Red; D000241:Adenosine; D011188:Potassium; D002211:Capsaicin