Seizure activity produces differential changes in adenosine A(1) receptorswithin rat hippocampus

Specific ligand binding to rat hippocampal adenosine A(1) receptor after ad ministration of the convulsant drug 3-mercaptopropionic acid (MP) was studi ed by means of a quantitative autoradiographic method. 2-Chloro-N6-[cyclope ntyl-2,3,4,5-H-3 adenosine] ([H-3]CCPA), a potent and selective A(1) recept or ligand, was selected for binding studies. MP administration (150 mg/kg, i.p.), at seizure, caused significant increases in the following CAI layers : pyramidal (45%), radiatum (18%) and lacunosum molecular (35%); in CA2 are a, a significant decrease in stratum oriens (36%) and an increase in stratu m radiatum (14%) and lacunosum molecular (33%) layers was observed. In CA3 area a rise in pyramidal (40%) and radiatum layers (26%), as well as in hil lus (97%) was found. At postseizure, changes were restricted to CAI, CA2 an d CA3 pyramidal layers and to CAI lacunosum molecular layer, with increases ranging from 22 to 50%. These results show that [H-3]CCPA binding is modif ied diversely in intrahippocampal layers and areas, thus indicating their d issimilar role in seizure activity.