0075 Chemogenetic Activation of Lateral Hypothalamic CaMKIIα Neurons in Partially and Fully Hcrt Neuron-degenerated Mice

Abstract Introduction Degeneration of the hypothalamic hypocretin/orexin (Hcrt) neurons underlies the sleep disorder Narcolepsy Type 1 (NT1), leading to excessive daytime sleepiness (EDS), cataplexy and other sleep disturbances. The lateral hypothalamus (LH) plays a critical role in sleep-wake regulation. We recently showed that LH CaMKIIα neurons are wake-active and that chemogenetic activation of these cells prolongs wakefulness for as long as 6 hours (Heiss et al., 2024, PNAS). We hypothesized that LH CaMKIIα neuron activation might compensate for the loss or dysfunction of Hcrt neurons and counteract EDS in narcolepsy, thereby serving as a potential therapy for individuals suffering from hypoarousal disorders. We present here preliminary data on the efficacy of LH CaMKIIα neuron activation to promote wakefulness in both partially and fully Hcrt neuron-degenerated mice and to reduce cataplexy in fully Hcrt degenerated mice. Methods Orexin-tTA; TetO-DTA mice (n = 8) mice were bilaterally injected with AAV2-CaMKIIα-hM3D(Gq)-mCherry into the LH and implanted with telemetry transmitters for EEG/EMG recording. Hcrt neurons were ablated by substituting doxycycline-containing chow with normal rodent chow (Dox (-) condition) for 6 weeks. When the Hcrt neurons were either partially-degenerated (2 weeks Dox (-)) or fully degenerated (6 weeks Dox (-)), LH CaMKIIα neurons were chemogenetically activated by injection of deschloroclozapine (DCZ, 0.3 mg/kg, i.p.) at ZT18. As a control, each mouse also received a saline injection on a different day. Results Activation of LH CaMKIIα neurons profoundly increased Wakefulness and reduced NREM sleep in both partially and fully (Wakefulness: p < 0.001; NREM: p < 0.001) Hcrt neuron-degenerated mice. Furthermore, DCZ treatment significantly reduced both the number of cataplexy bouts (p = 0.048) and bout duration (p = 0.035) in fully Hcrt neuron-degenerated mice. Conclusion Activation of LH CaMKIIα neurons has profound wake-promoting effects even in the absence of Hcrt neurons, indicating that the wake-promoting effects of LH CaMKIIα neurons are independent of the Hcrt system. Consequently, LH CaMKIIα neuron activation may have therapeutic effects on the primary symptoms of narcolepsy: EDS and cataplexy. Support (if any) NIH R01 NS098813 and R01 NS136808.