Adenosine A(1) and A(3) receptors mediate inhibition of synaptic transmission in rat cortical neurons.
Intracellular recordings were made in rat brain slice preparations containing pyramidal cells of the associative frontal cortex in order to characterize the action of selective adenosine A(1) and A(3) receptor ligands on synaptic neurotransmission. The selective A(1) receptor agonist N(6)-cyclopentyladenosine (CPA) inhibited concentration-dependently the excitatory postsynaptic potentials (PSPs) which were evoked by focal electrical stimulation. The CPA-mediated inhibition was blocked by 1, 3-dipropyl-8-cyclopentylxanthine (DPCPX), a highly A(1) receptor-selective antagonist. The A(3) receptor agonist N(6)-(3-iodobenzyl)-adenosine-5'-N-methylcarboxamide (IB-MECA) inhibited concentration-dependently the evoked PSPs while the A(1) receptors were blocked continuously by DPCPX. Under these conditions, the A(3) receptor antagonist 9-chloro-2-(2-furanyl)-5-[(phenylacetyl)amino]-1,2,4-triazolo[1, 5-c]quinazoline (MRS 1220) did not influence the PSPs but inhibited completely the effect of IB-MECA. The inhibitory effect of IB-MECA was unaffected by DPCPX. CPA additionally inhibited the PSPs when applied after IB-MECA. Pharmacological dissociation of the N-methyl-D-aspartate (NMDA) and non-NMDA receptor components of the PSPs showed that CPA as well as IB-MECA reduced both. We conclude that adenosine A(1) and A(3) receptors are present on cortical pyramidal cells and involved in the inhibition of excitatory neurotransmission. Our results indicate no interplay between the two receptor subtypes. The separate inhibition may become particularly evident in situations where there are high levels of endogenously released adenosine, as seen in hypoxia.
Brand
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A
Department of Pharmacy, University of Leipzig, Brüderstrasse 34, D-04103, Leipzig, Germany.
Vissiennon
Z
Z
Eschke
D
D
Nieber
K
K
D000241:Adenosine / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D002540:Cerebral Cortex / Q000166:cytology / Q000187:drug effects*; D004347:Drug Interactions; D004558:Electric Stimulation; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D009474:Neurons / Q000187:drug effects*; D058906:Purinergic P1 Receptor Agonists; D058915:Purinergic P1 Receptor Antagonists; D011799:Quinazolines / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D043684:Receptor, Adenosine A3; D018047:Receptors, Purinergic P1 / Q000187:drug effects*; D009435:Synaptic Transmission / Q000187:drug effects*; D014230:Triazoles / Q000494:pharmacology; D014970:Xanthines / Q000494:pharmacology
C110041:9-chloro-2-(2-furyl)-5-phenylacetylamino(1,2,4)triazolo(1,5-c)quinazoline; D058906:Purinergic P1 Receptor Agonists; D058915:Purinergic P1 Receptor Antagonists; D011799:Quinazolines; D043684:Receptor, Adenosine A3; D018047:Receptors, Purinergic P1; D014230:Triazoles; D014970:Xanthines; C046756:5'-N-methylcarboxamideadenosine; C048599:N(6)-cyclopentyladenosine; C051360:1,3-dipropyl-8-cyclopentylxanthine; D000241:Adenosine