Endogenous adenosine facilitates neurotransmission via A2A adenosine receptors in the rat superior colliculus in vivo.
The concentration of endogenous adenosine in the cerebrospinal fluid increased 2-3-fold of the original level in the area of rat superior colliculus after the intraperitoneal administration of an adenosine deaminase inhibitor, EHNA (erythro-9-(2-hydroxy-3-nonyl)adenosine, 10 mg/kg). Potentials evoked in the superior colliculus by optic tract stimulation were also facilitated by 120-160% of their initial amplitudes. A selective A1 adenosine receptor antagonist, DPCPX (8-cyclopentyl-1,3-dipropylxanthine), failed to reduce such EHNA-induced facilitation. However, a selective A2A adenosine receptor antagonist, KF17837 (8(3,4-dimethoxystyryl)-1,3-dipropyl-7-methylxanthine) completely eliminated the facilitatory effects of EHNA. Northern blot analysis demonstrated abundant expression of A1 adenosine receptor mRNA in the superior colliculus. RT-PCR analysis was able to detect the concomitant expression of A2A adenosine receptor mRNA, but at levels lower than one-tenth of the striatal expression. In the superior colliculus, A2A adenosine receptors function predominantly on the facilitatory effects of adenosine, irrespective of the ubiquitous expression of A1 adenosine receptors.
Ishikawa
S
S
Department of Physiology, Kobe University School of Medicine, Chuo-ku, Japan.
Saijoh
K
K
Okada
Y
Y
D000225:Adenine / Q000031:analogs & derivatives / Q000494:pharmacology; D000241:Adenosine / Q000235:genetics / Q000502:physiology*; D000818:Animals; D004594:Electrophysiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D058914:Purinergic Antagonists; D011687:Purines / Q000134:cerebrospinal fluid; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D018047:Receptors, Purinergic P1 / Q000502:physiology*; D013477:Superior Colliculi / Q000502:physiology*; D009435:Synaptic Transmission / Q000187:drug effects; D014970:Xanthines / Q000494:pharmacology
D004791:Enzyme Inhibitors; C104314:KF 17387; D058914:Purinergic Antagonists; D011687:Purines; D012333:RNA, Messenger; D018047:Receptors, Purinergic P1; D014970:Xanthines; C010192:9-(2-hydroxy-3-nonyl)adenine; C051360:1,3-dipropyl-8-cyclopentylxanthine; D000225:Adenine; D000241:Adenosine