Abstracts

Rationale: Adenosine has an inhibitory effect on excitatory synapses via the adenosine 1 receptor (A1R) within the hippocampus (HC) and the lateral hypothalamus (LH). Its neuromodulatory role reduces the output of pyramidal neurons in CA3 and CA1 of the HC, while suppressing activity of wake-promoting neurons in the LH. Thus, changes in its concentrations will have effects on network activity relating to epileptic activity and sleep. We tested whether adenosine levels differed between a control and a murine model of epilepsy, the Kcna1 knockout (KO) mouse. We hypothesize a decreased adenosine tone in the HC with increased levels in the LH. Methods: Adenosine levels were measured from mice that underwent focal microwave irradiation. Whole brain concentrations were then measured with RP-HPLC. To determine local concentrations in the LH and HC, a combination of electrophysiology and pharmacological methods was used to assess adenosine tone in the HC and LH. Expression levels of the A1R were assessed by Western blot. All values are reported as mean and SEM, p < 0.05 was deemed as statistically significant. Results: Differences in adenosine concentrations from whole brains of wildtype (WT) and KO mice were not statistically significant. However, KOs showed a decreasing trend, so we measured levels in the HC and the LH. KO HC levels of adenosine were 39.1% lower than their WT counterpart. In the LH, there was no statistically significant difference in the levels of adenosine or in the firing frequency of the principle cells in between the two. However, the firing rate of KO interneurons was reduced by 59.7% compared to WT. A1R expression in the LH was statistically significant lower in KO compared to WT. Conclusions: Changes in the levels of adenosine has effects at the network level and therefore can produce or exacerabate pathological conditions such as seizures and disruptions in sleep. In our model, decreases in adenosine levels in the HC of Kcna1 KOs are consistent with other models of epilepsy and along with increased network activity in the KO. Somnogen levels increase with sleep deprivation, we predicted that the Kcna1 KO should have higher adenosine levels due to their disrupted sleep architecture. However, we observed an increasing trend with regards to adenosine levels, but saw reduced A1R expression. We do report a decrease in the overall activity of the interneuron population in the Kcna1 KO mice, which may have a disinhibitory effect on other wake-promoting neurons in the LH (e.g, histaminergic neurons). The decreased adenosine tone in the HC is consistent with the epileptic phenotype of the Kcna1 mouse and other models, while a decrease in the activity of inhibitory neurons in the LH is consistent with the sleep disorder seen in these animals. Funding: This work was supported by a grant from the NIH: KAS R01NS072179