CNS ADENOSINE A(1) RECEPTORS ARE ALTERED AFTER THE ADMINISTRATION OF CONVULSANT 3-MERCAPTOPROPIONIC ACID AND CYCLOPENTYLADENOSINE - AN AUTORADIOGRAPHIC STUDY

Rat CNS adenosine A(1) receptors were studied by quantitative autoradi ography after the administration of convulsant 3-mercaptopropionic aci d (MP) and an adenosine analogue cyclopentyladenosine (CPA), using 2-c hloro-N-6-[cyclopentyl-2,3,4,5-H-3 adenosine]-([H-3]CCPA) as radioacti ve ligand. Specific binding was quantified in hippocampus, cerebellum, cerebral cortex, thalamic nuclei, superior colliculus and striatum, a nd the highest densities were found in CA1, CA2, and CA3 hippocampus s ubareas and the lowest levels in superior colliculus and striatum. MP administration (150 mg/kg, i.p.) produced significant increases in [H- 3]CCPA binding in CA1 subarea at seizure (15%) and postseizure (21%) a nd in CA2 al seizure (15%) but a tendency to decrease in dentate gyrus . There was an increase in cerebellum at seizure (18%) but no signific ant changes in the other studied regions. CPA injection (2 mg/kg, i.p. ) enhanced [H-3]CCPA binding in CA1 and CA2 areas (17-18%) but not in CA3 area of the hippocampus. When CPA was administered before MP, whic h delayed seizure onset, an increase in [H-3]CCPA binding in CA1 hippo campus subarea (19%) and cerebellum (28%) was also observed. Results s howed that the administration of convulsant MP and adenosine analogue CPA exerts differential effects on adenosine A(1) receptors in CNS are as; hippocampus is the most affected area with ail treatments, special ly CA1 subarea, supporting an essential role in convulsant activity as well as in seizure prevention.