Abstracts

Rationale: Many of the types of sleep disorders associated with epilepsy are similar to those experienced by people without epilepsy which involve a dysregulation of the hypocretin system. Hypocretin neurons are located in the lateral hypothalamus (LH), stimulate arousal nuclei to elicit wakefulness and regulated by extracellular adenosine via adenosine A1 receptors (A1R). Therefore, we hypothesized that Kcna1-null mice, a model of temporal lobe epilepsy with sleep disorders, would exhibit signs of injury in the LH and adenosine dysregulation of hypocretin neurons.Methods: Rest-activity cycles were determined with 24-hour monitoring of infrared beam crossings by wild-type and Kcna1-null mice. Frozen sections containing lateral hypothalamus from WT and Kcna1-null mice were probed for mouse IGg, GFAP, hypocretin and adenosine kinase (ADK). Unbiased stereological techniques were used to assess astrogliosis, reactive astrocytes, and hypocretin neurons. Protein levels of GFAP, ADK and A1R were determined in homogenates of isolated LH with western blots. Sensitivity of LH neuronal activity to an A1R agonist, cyclopentyladenosine (CPA), or antagonist, 8-p-Sulfophenyl theophylline (8-SPT), was determined with recordings of multi-unit acquired with a multielectrode array placed in the LH. Subsequently, slices were stained for hypocretin and only electrodes with overlying hypocretin neurons were analyzed. Results: Kcna1-null mice displayed sleep disorder symptoms including inappropriate sleep-wake transitions, increased sleep fragmentation and reduced sleep efficiency. Punctate and diffuse IGg staining was prominent and the number of GFAP-positive cells increased by 100% in Kcna1-null LH compared to WT LH. Reactive astrocytes were present in Kcna1-null LH, but there was no loss of hypocretin neurons. GFAP and ADK protein levels increased, whereas A1R protein decreased. Multi-unit activity decreased and increased by 50% and 40% with application of CPA or 8-SPT, respectively, to WT LH, whereas multi-unit activity of Kcna1-null LH was relatively insensitive to both modulators. Conclusions: Kcna1-null mice exhibit sleep disorder symptoms associated with a dysregulated hypocretin system. Injury was present in Kcna1-null LH as evidenced by astrogliosis and the presence of reactive astrocytes. Furthermore, IGg staining suggests a compromised blood brain barrier in Kcna1-null LH. ADK is expressed by astrocytes and is a primary regulator of extracellular adenosine levels, therefore the increase in ADK indicates lower extracellular adenosine concentrations. Also, insensitivity to A1R modulators of Kcna1-null LH neurons occurred in conjunction with lower A1R protein levels. In conclusion, injury in Kcna1-null LH is associated with weakened adenosinergic regulation of LH neuronal activity that may contribute to sleep disorder comorbidities in the Kcna1-null mouse model of temporal lobe epilepsy.