The role of adenosine A1 receptors in the interaction between amygdala and entorhinal cortex of kindled rats

In this study the effect of adenosine A1 receptors of the entorhinal cortex (EC) and amygdala on kindled seizures was investigated. Animals were kindled by daily electrical stimulation of amygdala (group 1) or EC (group 2). In the fully kindled animals, N6-cyclohexyladenosine (CHA), a selective A1 receptor agonist, and 1,3-dimethyl-8-cyclopenthylxanthine (CPT), a selective A1 receptor antagonist, were microinjected bilaterally into the EC (group 1) or amygdala (group 2). The seizure parameters were measured at 5, 15, 60 and 120 min post injection. Obtained data showed that in group 1, intra-EC microinjection of CHA at concentration of 10 μM reduced amygdala- and, EC-afterdischarge duration and stage 5 seizure duration at 5, 15, 60 and 120 min post drug injection. It also increased the latency to stage 4 seizure but no alteration was observed in seizure stage. At concentrations of 0.1 and 1 μM, CHA reduced only EC-afterdischarge duration at 5 and 15 min post drug infusion. Bilateral microinjection CPT at concentrations of 5 and 10 μM into the EC did not alter seizure parameters. Intra-EC microinjection of CPT (5 μM), 5 min before CHA (10 μM), blocked the anticonvulsant effects of CHA. On the other hand, in group 2 animals, intra-amygdala CHA (10, 50 and 100 μM) or CPT (5 and 10 μM) had no significant effect on seizure parameters of EC-kindled rats. These results suggest that adenosine A1 receptors activation of the EC may have an inhibitory effect on amygdala-kindled seizures. But, despite of reciprocal interconnections between these two regions, activation of the A1 receptors of the amygdala has no effect on EC-kindled seizures.