Barium, glibenclamide and CGS21680 prevent adenosine A1 receptor changes of ES coupling and spike threshold.
Activation of adenosine A1 receptors raised spike thresholds and induced a dissociation of excitatory postsynaptic potential (EPSP) spike coupling in hippocampal pyramidal neurones. This effect could be prevented by activation of A2A adenosine receptors. The A1 receptor agonist N6-cyclopentyladenosine caused a dissociation of the EPSP spike coupling recorded extracellularly and increased the threshold for spike generation measured intracellularly. These effects were prevented by the A2A receptor agonist CGS21680. A series of agents interfering with adenylate cyclase activity, protein kinase A or C, or nitric oxide synthase had no effect on these responses to N6-cyclopentyladenosine. Superfusion with barium or glibenclamide prevented both the dissociation of EPSP spike coupling and the increase of spike threshold. It is concluded that a barium- and glibenclamide-sensitive potassium current may be involved in the postsynaptic effects of A1 receptors on spike threshold, and it is suggested that a similar suppression of a potassium current by A2A receptors could underlie the inhibition of A1 receptor responses.
O'Kane
E Martin
EM
Institute of Biomedical and Life Sciences, West Medical Building, University of Glasgow, Glasgow, UK.
Stone
Trevor W
TW
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000241:Adenosine / Q000031:analogs & derivatives* / Q000494:pharmacology*; D058907:Adenosine A1 Receptor Agonists; D000818:Animals; D001464:Barium / Q000494:pharmacology*; D001921:Brain / Q000187:drug effects / Q000502:physiology; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects* / Q000502:physiology; D005905:Glyburide / Q000494:pharmacology*; D008297:Male; D010627:Phenethylamines / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D043682:Receptor, Adenosine A1 / Q000502:physiology*
D058907:Adenosine A1 Receptor Agonists; D010627:Phenethylamines; D043682:Receptor, Adenosine A1; C061282:2-(4-(2-carboxyethyl)phenethylamino)-5'-N-ethylcarboxamidoadenosine; D001464:Barium; D000241:Adenosine; D005905:Glyburide