title: [(3)H]Adenosine uptake in brainstem membranes of CD-1 mice lacking the adenosine A(2a) receptor.
abstract: Previous studies in our laboratory have demonstrated a decrease in [(3)H]nitrobenzylthioinosine binding sites in the brainstem of adenosine A(2a) receptor knockout mice, particularly in the brain nuclei involved in central control of cardiovascular function [Brain Research 877 (2000) 160]. The present study aimed to correlate this decrease, shown using autoradiography, with a functional change using a previously described method of [(3)H]adenosine uptake in a membrane preparation from the brainstem of wildtype CD - 1 and homozygous mutant mice lacking the adenosine A(2a) receptor. A statistically significant decrease was shown in the mean V(MAX) value obtained from homozygous mutant preparations (4.7 +/- 1.3 fmol/mg protein/20 s, P < 0.05, n = 4) compared to that obtained from wildtype controls (51.6 +/- 4.2 fmol/mg protein/20 s, n = 4). Competition studies using nucleoside uptake inhibitors showed a statistically significant increase in the log IC(50) values for dipyridamole (Wildtype: -4.3 +/- 0.2, Homozygous mutant: -8.3 +/- 0.4, n=5, P < 0.05) and dilazep (Wildtype: -3.9 +/- 0.8, Homozygous mutant: -8.3 +/- 0.8, n=5, P < 0.05) in the preparations using homozygous mutant tissue. The present study, in conjunction with the results of previous studies [Brain Research 877 (2000) 160], indicates that components of purinergic neurotransmission system have apparently adjusted in compensation for the lack of the A(2a) receptor.
authors.affiliation: Department of Pharmacology, Faculty of Medicine, Monash University, Clayton, Victoria, Australia.
authors.forename: Broughton J
authors.initials: BJ
authors.lastname: Snell
authors.forename: Anne
authors.initials: A
authors.lastname: Day
authors.forename: Catherine
authors.initials: C
authors.lastname: Ledent
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Lawrence
mesh_terms: D000241:Adenosine / Q000378:metabolism* / Q000493:pharmacokinetics*; D019830:Adenosine-5'-(N-ethylcarboxamide) / Q000378:metabolism; D000818:Animals; D001345:Autoradiography; D001933:Brain Stem / Q000378:metabolism*; D002352:Carrier Proteins / Q000037:antagonists & inhibitors; D004109:Dilazep / Q000378:metabolism; D004176:Dipyridamole / Q000378:metabolism; D026901:Membrane Transport Proteins; D008566:Membranes / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D033703:Nucleoside Transport Proteins; D043683:Receptors, Adenosine A2 / Q000172:deficiency*; D013997:Time Factors; D014316:Tritium / Q000378:metabolism
chemical_list: D002352:Carrier Proteins; D026901:Membrane Transport Proteins; D033703:Nucleoside Transport Proteins; D043683:Receptors, Adenosine A2; C444719:adenosine transporter; D014316:Tritium; D019830:Adenosine-5'-(N-ethylcarboxamide); D004176:Dipyridamole; D004109:Dilazep; D000241:Adenosine