Manipulation of endogenous adenosine in the rat prepiriform cortex modulates seizure susceptibility.
A1 adenosine receptors in the rat prepiriform cortex play an important role in the inhibition of bicuculline methiodide-induced convulsions. In the present study we evaluated manipulation of endogenous adenosine in this brain area as a strategy to effect seizure suppression. All compounds evaluated were unilaterally microinjected into the rat prepiriform cortex. Administration of exogenous adenosine afforded a dose-dependent protection (ED50 = 48.1 +/- 8.4 nmol) against bicuculline methiodide-induced seizures, and these anticonvulsant effects were significantly potentiated by treatment with an adenosine kinase inhibitor, 5'-amino-5'-deoxyadenosine; by the adenosine transport blockers, dilazep or nitrobenzylthioinosine 5'-monophosphate; and by an adenosine deaminase inhibitor, 2'-deoxycoformycin. When administered alone, 5'-amino-5'-deoxyadenosine, 5'-iodotubercidin and dilazep were found to be highly efficacious as anticonvulsants with respective ED50 values of 2.6 +/- 0.8, 4.0 +/- 2.7 and 5.6 +/- 1.5 nmol. In contrast, 2'-deoxycoformycin was both less potent and less efficacious. These results suggest that accumulation of endogenous adenosine may contribute to seizure suppression, and that adenosine kinase and adenosine transport may play a pivotal role in the regulation of extracellular levels of adenosine in the central nervous system. The adenosine antagonist, 8-(p-sulfophenyl)theophylline, increased markedly the severity of bicuculline methiodide-induced seizures. Moreover, reduction of extracellular adenosine formation by a focal injection of an ecto-5'-nucleotidase inhibitor, alpha, beta-methyleneadenosine diphosphate, produced generalized seizures (ED50 = 37.3 +/- 22.7 nmol). Together the proconvulsant effect of an adenosine receptor antagonist and the convulsant action of an ecto-5'-nucleotidase inhibitor further support the role of endogenous adenosine as a tonically active antiepileptogenic substance in the rat prepiriform cortex.
Zhang
G
G
College of Pharmacy, Oregon State University, Corvallis.
Franklin
P H
PH
Murray
T F
TF
D000241:Adenosine / Q000502:physiology*; D058892:Adenosine Deaminase Inhibitors; D000244:Adenosine Diphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D000248:Adenosine Kinase / Q000037:antagonists & inhibitors; D000818:Animals; D001640:Bicuculline / Q000031:analogs & derivatives / Q000494:pharmacology; D002540:Cerebral Cortex / Q000502:physiology*; D008297:Male; D015649:Pentostatin / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011983:Receptors, Purinergic / Q000187:drug effects / Q000502:physiology; D012640:Seizures / Q000517:prevention & control*; D013806:Theophylline / Q000031:analogs & derivatives / Q000494:pharmacology; D013868:Thioinosine / Q000031:analogs & derivatives / Q000494:pharmacology
D058892:Adenosine Deaminase Inhibitors; D011983:Receptors, Purinergic; C523965:alpha,beta-methyleneadenosine 5'-diphosphate; D015649:Pentostatin; C017069:bicuculline methiodide; D013868:Thioinosine; D000244:Adenosine Diphosphate; C031433:8-(4-sulfophenyl)theophylline; D013806:Theophylline; D000248:Adenosine Kinase; C001789:4-nitrobenzylthioinosine; D000241:Adenosine; D001640:Bicuculline