Seizure Activity Produces Differential Changes in Adenosine A1 Receptors within Rat Hippocampus

Specific ligand binding to rat hippocampal adenosine A₁ receptor after administration of the convulsant drug 3-mercaptopropionic acid (MP) was studied by means of a quantitative autoradiographic method. 2-Chloro-N6-cyclopentyl-2,3,4,5-³H adenosine] (³H]CCPA), a potent and selective A₁ receptor ligand, was selected for binding studies. MP administration (150 mg/kg, i.p.), at seizure, caused significant increases in the following CA1 layers: pyramidal (45%), radiatum (18%) and lacunosum molecular (35%); in CA2 area, a significant decrease in stratum oriens (36%) and an increase in stratum 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 hillus (97%) was found. At postseizure, changes were restricted to CA1, CA2 and CA3 pyramidal layers and to CA1 lacunosum molecular layer, with increases ranging from 22 to 50%. These results show that ³H]CCPA binding is modified diversely in intrahippocampal layers and areas, thus indicating their dissimilar role in seizure activity.