Manipulation of endogenous adenosine in the rat prepiriform cortex modulates seizure susceptibility

• Published in: The Journal of pharmacology and experimental therapeutics Vol. 264; no. 3; p. 1415
• Main Authors: Zhang, G, Franklin, P H, Murray, T F
• Format: Journal Article
• Language: English
• Published: United States 01-03-1993
• Subjects: Adenosine - physiology; Adenosine Deaminase Inhibitors; Adenosine Diphosphate - analogs & derivatives; Adenosine Diphosphate - pharmacology; Adenosine Kinase - antagonists & inhibitors; Animals; Bicuculline - analogs & derivatives; Bicuculline - pharmacology; Cerebral Cortex - physiology; Male; Pentostatin - pharmacology; Rats; Rats, Sprague-Dawley; Receptors, Purinergic - drug effects; Receptors, Purinergic - physiology; Seizures - prevention & control; Theophylline - analogs & derivatives; Theophylline - pharmacology; Thioinosine - analogs & derivatives; Thioinosine - pharmacology
• ISSN: 0022-3565

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.