Occlusive responses to adenosine A1 receptor and muscarinic M2 receptor activation on hippocampal presynaptic terminals.
There is substantial evidence for an interaction between adenosine A1 and muscarinic M1/M3 receptors in some tissues, either at the level of the receptors themselves or at the associated transduction system. We have now addressed the question of whether there is a similar interaction between A1 and presynaptic M2 receptors in the hippocampus. The effects of cyclopentyladenosine (CPA) were studied alone or in combination with the M2 receptor agonist oxotremorine-M. The ability of both to depress synaptic transmission presynaptically at the concentrations used was confirmed using paired-pulse inhibition. When combined at a range of concentrations, the effects of the two agents were less than additive, suggesting that they are acting by a common transduction system. The results indicate that the modulatory, antagonistic effects of A1 adenosine receptors are exerted not only on postjunctional M1/M3 receptors but also at M2 presynaptic receptors.
Nikbakht
M R
MR
Institute of Biomedical and Life Sciences, West Medical Building, University of Glasgow, Glasgow G12 8QQ, Scotland, UK.
Stone
T W
TW
D000241:Adenosine / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D006624:Hippocampus / Q000187:drug effects* / Q000648:ultrastructure; D066298:In Vitro Techniques; D008297:Male; D018721:Muscarinic Agonists / Q000494:pharmacology*; D010095:Oxotremorine / Q000031:analogs & derivatives / Q000494:pharmacology; D017729:Presynaptic Terminals / Q000187:drug effects*; D058906:Purinergic P1 Receptor Agonists; D051381:Rats; D017208:Rats, Wistar; D043585:Receptor, Muscarinic M2; D011976:Receptors, Muscarinic / Q000187:drug effects*
D018721:Muscarinic Agonists; D058906:Purinergic P1 Receptor Agonists; D043585:Receptor, Muscarinic M2; D011976:Receptors, Muscarinic; C048599:N(6)-cyclopentyladenosine; D010095:Oxotremorine; C042743:oxotremorine M; D000241:Adenosine