Document Type : Original Article
Introduction: In this study, the role of adenosine A1 receptors of hippocampal CA1 region neurons onentorhinal cortex kindled seizures was investigated.
Material and Methods: A tripolar(stimulating and recording) electrode was implanted in entorhinalcortex and two guide cannulae were implanted in the CA1 region of the left and right hippocampi of allanimals. A week after surgery, animals were stimulated daily to be kindled. In full kindled animals, N6-cyclohexyladenosine (CHA; 1, 10 and 50ãM a selective A1 receptor agonist ) and 1,3- dimethyl -8-cyclohexylxanthine (CPT; 5 and 10ãM a selective A1 receptor antagonist) were microinfused (1ãl/2min) intothe CA1 region of hippocampus and animals were stimulated at 5, 15 and 120 min after drug injection. Allanimals received artificial cerebrospinal fluid, 24 h before each drug injection and the results were used ascontrol.
Results: Obtained data showed that 5 and 15 min after injection, CHA at concentrations of 10 and 50 ãM,reduced entorhinal cortex afterdischarge and stage 5 seizure durations and increased stage 4 latency. It alsodecreased seizure duration only at concentration of 50ãM. CHA (1 ãM) did not alter seizure parameters. CPTat concentration of 5ãM could not produce any changes in seizure parameters, but at concentration of 10 ãMincreased after discharge and stage 5 durations and decreased stage 4 latency. Intrahippocampal (CA1 region)pretreatment with CPT (5 ãM) before CHA (10 and 50 ãM) reduced the effects of CHA on seizureparameters.
Conclusion: It may be suggested that hippocampal CA1 region plays an important role in seizurepropagation from entorhinal cortex to other brain region/s and activation of adenosine A1 receptors in thisregion have anticonvulsant effects on entorhinal cortex kindled seizures.