Adenosine-dopamine receptor interactions in the isolated rat nodose ganglion but not in membranes of dorsal vagal complex.
The present study has employed in vitro electrophysiology and radioligand binding assays to determine whether dopamine and adenosine receptors interact with each other on rat vagal afferent neurons. Preincubation of the isolated rat nodose ganglion with the adenosine A2a agonists CGS 21 680 or DPMA (Both 1 microM) resulted in a functional antagonism of the ability of dopamine to depolarise the preparation. Specifically, the concentration-response curve to dopamine was significantly shifted to the right in the presence of CGS 21 680 and DPMA. On the other hand, adenosine itself, A1 and A3 receptor agonists and ATP were all incapable of modulating the electrophysiological response to dopamine. In contrast to the nodose ganglion, CGS 21 680 did not significantly affect the ability of the dopamine D2 ligands quinpirole or raclopride to displace [125I]NCQ298 binding to dopamine D2 receptors in membranes prepared from rat dorsal brain stem. These data indicate the presence of an interaction between high affinity adenosine A2 receptors and dopamine D2 receptors on the soma of rat vagal afferent neurons, whereas the situation in the brain stem remains less clear.
Lawrence
A J
AJ
Department of Pharmacology, Monash University, Clayton, Victoria, Australia.
Krstew
E
E
Jarrott
B
B
D000241:Adenosine / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D001933:Brain Stem / Q000187:drug effects / Q000502:physiology*; D004298:Dopamine / Q000494:pharmacology; D004594:Electrophysiology; D008297:Male; D008566:Membranes / Q000502:physiology; D009620:Nodose Ganglion / Q000187:drug effects / Q000502:physiology*; D010627:Phenethylamines / Q000494:pharmacology; D058906:Purinergic P1 Receptor Agonists; D011869:Radioligand Assay; D051381:Rats; D017207:Rats, Sprague-Dawley; D043705:Receptor, Adenosine A2A; D017448:Receptors, Dopamine D2 / Q000187:drug effects / Q000502:physiology*; D018047:Receptors, Purinergic P1 / Q000502:physiology*
D010627:Phenethylamines; D058906:Purinergic P1 Receptor Agonists; D043705:Receptor, Adenosine A2A; D017448:Receptors, Dopamine D2; D018047:Receptors, Purinergic P1; C061282:2-(4-(2-carboxyethyl)phenethylamino)-5'-N-ethylcarboxamidoadenosine; C056426:CGS 24012; D000241:Adenosine; D004298:Dopamine