Modulation of Ca2+ channels by activation of adenosine A1 receptors in rat striatal glutamatergic nerve terminals.
We determined that activation of adenosine A1 receptors in striatal synaptosomes with 100 nM N6-cyclopentyladenosine (CPA) inhibited both the release of endogenous glutamate and the increase of intracellular free Ca2+ concentration ([Ca2+]i), due to 4-aminopyridine (4-AP) stimulation, by 28 and 19%, respectively. Furthermore, CPA enhanced the inhibition of endogenous glutamate release due to omega-conotoxin GVIA (omega-Cgtx GVIA), omega-Cgtx MVIIC or omega-Cgtx GVIA plus omega-Cgtx MVIIC. Similar effects were observed in the [Ca2+]i signal. The inhibitory effects of CPA and omega-Cgtx GVIA were additive, but the effects of CPA and omega-Cgtx MVIIC were only partially additive. These results suggest that P/Q-type Ca2+ channels and other type(s) of Ca2+ channel(s), coupled to glutamate release, are inhibited subsequently to activation of adenosine A1 receptors.
Ambrósio
A F
AF
Department of Zoology and Faculty of Medicine, University of Coimbra, Portugal.
Malva
J O
JO
Carvalho
A P
AP
Carvalho
C M
CM
D000200:Action Potentials / Q000502:physiology; D000241:Adenosine / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D001711:Biotransformation / Q000502:physiology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000378:metabolism*; D004347:Drug Interactions; D005470:Fluorometry; D018698:Glutamic Acid / Q000378:metabolism / Q000502:physiology*; D008297:Male; D008564:Membrane Potentials / Q000502:physiology; D017072:Neostriatum / Q000166:cytology / Q000378:metabolism*; D017729:Presynaptic Terminals / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D018047:Receptors, Purinergic P1 / Q000378:metabolism*
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D018047:Receptors, Purinergic P1; D018698:Glutamic Acid; C048599:N(6)-cyclopentyladenosine; D000241:Adenosine