Narcolepsy is a neurological disorder characterized by a person’s inability to regulate sleep-wake cycles. Excessive daytime sleepiness and cataplexy are prominent symptoms of narcolepsy. Cataplexy is partial to full body muscle atonia usually brought on by the person with narcolepsy experiencing a positive emotion. Some features of cataplexy resemble those of REM sleep, including similar brain activity and muscle atonia. The neuronal circuit that produces cataplexy has yet to be determined. The similarities between REM sleep and cataplexy support the hypothesis that cataplexy is the result of the REM atonia pathways being activated. An emotion processing region, the central amygdala (CeA), projects to known REM regulatory regions and plays a role in cataplexy. GABAergic neurons of the CeA are sufficient and necessary to trigger cataplexy in mice and project to brainstem regions that regulate muscle tone. Cataplexy is often triggered in a social setting, such as when seeing an old friend or telling a joke. Oxytocin (OT) is involved in many social behaviors, making it a viable link between social stimuli and cataplexy. We hypothesized that oxytocin receptor (OTR) neurons of the CeA, a sub-population of GABAergic neurons, promote emotionally-triggered cataplexy. To determine the social phenotype of the narcolepsy mouse model, the orexin knock-out (OXKO) mouse, we used established behavioral assays of social interaction and social memory. To determine if social reunification influenced the amount of cataplexy, group-housed OXKO mice were isolated for a short time and reunited with their littermates. To determine if OTR neurons of the CeA were sufficient and necessary to promote socially-triggered cataplexy, we used chemogenetic technology known as Designer Receptors Exclusively Activated by Designer Drugs (DREADDs) to selectively activate or inhibit these neurons. We injected adeno-associated viral vectors coding for either the excitatory hM3 Cre-dependent DREADD or the inhibitory hM4 Cre-dependent DREADD into the CeA of orexin knock-out mice crossed with OTR-Cre mice, allowing for expression of the DREADD exclusively in the OTR neurons of the CeA. After injection with either saline or clozapine-N-oxide (CNO) we put the mice through a behavioral assay to see if emotionally-triggered cataplexy increased or decreased following the activation or inhibition of OTR neurons of the CeA. The behavioral assays showed that acute social interactions in OXKO is normal, however they do have a social memory impairment. In addition, reunification promotes cataplexy in most OXKO mice. With the chemogenetic experiments, our number of mice is too low to report if OTR neurons of the CeA are sufficient and/or necessary for cataplexy at this time. / 2020-07-03T00:00:00Z

Introduction: Cataplexy - the sudden involuntary loss of skeletal muscle tone – is a defining feature of narcolepsy. The current study aimed to determine if cataplexy is influenced by direct manipulation of REM sleep circuitry. We did this by pharmacogenetically inhibiting the REM sleep center, subcoeruleus (Sub-C). Methods: Inhibitory DREADD (hM4D-Gi) was bilaterally targeted to the Sub-C in hypocretin knockout mice (n=7). Intraperitoneal administration of clozapine-n-oxide was used to inhibit Sub-C cells expressing hM4D-Gi. Electrophysiological and behavioral criteria were used to characterize cataplexy and REM sleep. Results: Sub-C inhibition increased REM sleep and cataplexy amounts (p<0.05). Sub-C inhibition increased time spent in cataplexy amounts by increasing the number of cataplexy attacks (p<0.05). This intervention triggered increases in basal muscle tone during REM sleep, but had negligible effects on muscle tone during cataplexy (p>0.05). Conclusion: Pharmacogenetic manipulation of the Sub-C suggest that REM sleep and cataplexy are mediate by similar neural mechanism.

Introduction: Cataplexy - the sudden involuntary loss of skeletal muscle tone – is a defining feature of narcolepsy. The current study aimed to determine if cataplexy is influenced by direct manipulation of REM sleep circuitry. We did this by pharmacogenetically inhibiting the REM sleep center, subcoeruleus (Sub-C). Methods: Inhibitory DREADD (hM4D-Gi) was bilaterally targeted to the Sub-C in hypocretin knockout mice (n=7). Intraperitoneal administration of clozapine-n-oxide was used to inhibit Sub-C cells expressing hM4D-Gi. Electrophysiological and behavioral criteria were used to characterize cataplexy and REM sleep. Results: Sub-C inhibition increased REM sleep and cataplexy amounts (p<0.05). Sub-C inhibition increased time spent in cataplexy amounts by increasing the number of cataplexy attacks (p<0.05). This intervention triggered increases in basal muscle tone during REM sleep, but had negligible effects on muscle tone during cataplexy (p>0.05). Conclusion: Pharmacogenetic manipulation of the Sub-C suggest that REM sleep and cataplexy are mediate by similar neural mechanism.

Narcolepsia é uma condição neurológica crônica, o principal sintoma é a sonolência diurna excessiva, associada a cataplexia, a paralisia do sono e as alucinações hipnagógicas. Paciente com narcolepsia apresenta dificuldade em manter a atenção e vigilância nas tarefas rotineiras e monótonas, com riscos de acidentes acarretando um sério prejuízo e impacto social nas suas relações de trabalho e sócio-familiares e na percepção da qualidade de vida.Foram avaliados 40 pacientes ( 28 mulheres e 12 homens) com idade média de 42 anos. O presente trabalho teve como objetivo: a) avaliar a percepção da QV em pacientes com narcolepsia b) Avaliar a percepção do impacto social. Este estudo demonstrou que: 1) A narcolepsia acarreta comprometimento na QV dos pacientes, com prejuízo das funções físicas e emocionais, interferindo nas condições de trabalho e dinâmica familiar; 2) A narcolepsia produz um impacto social em várias esferas da vida do pacientes, comprometendo atividades instrumentais da vida diária e a situação de trabalho / Narcolepsy is a chronic neurological condition, whose main symptom is excessive daytime sleepiness, associate the cataplexy, the hypnogogic hallucinations and sleep paralysis. The patient with narcolepsy presents difficulty in keeping the attention and monitoring in the routine and monotonous tasks, with risks of accidents, causing a serious prejudice and social impact its partner-familiar, relations of work and in the perception of the quality of life. The present work had as objective: ) to evaluate the perception of the quality of life in patients with narcolepsy b) To evaluate the perception of the social impact. This study it demonstrated that: 1) The narcolepsy compromises the quality of life of the patients, with prejudice of the physical and emotional functions, intervening with the conditions of work and familiar dynamics; 2) The narcolepsy produces a social impact in some areas of the life of the patients, compromising instrumental activities of the daily life and the situation of work

Narcolepsy is a disabling sleep disorder that is characterized by persistent sleepiness, and cataplexy – an involuntary loss of waking muscle tone. Cataplexy and narcolepsy are caused by the loss of hypocretin containing neurons in the hypothalamus. However, it is hypothesized that dopamine is also involved in sleep and motor control and plays a role in cataplexy. This study investigated how manipulating dopamine affected sleep and cataplexy in narcoleptic mice devoid of hypocretin. We used d-amphetamine to increase endogenous dopamine levels and quinpirole (D2 agonist) to agonize D2 receptor sites. Amphetamine promoted wakefulness while decreasing sleep in wild-type mice, but was less effective in narcoleptic mice. Amphetamine also reduced cataplexy as well as sleep attacks (an indicator of sleepiness) in narcoleptic mice. Quinpirole had no effect on sleep or wakefulness; however, it potently increased cataplexy without affecting sleep attacks in narcoleptic mice.

In this thesis I investigated the neural circuits that trigger cataplexy in mice. Specifically, I first addressed the theory that cataplexy is a REM sleep disorder. I then investigated a role for the noradrenergic and dopaminergic systems in murine cataplexy. Finally, I addressed the role of the amygdala in triggering cataplexy. From this work several specific conclusions can be drawn: 1. Cataplexy does not share a common executive mechanism with REM sleep, although the two may share a common mechanism that generates muscle atonia. Muscle tone during REM sleep and cataplexy is similar, however increasing REM sleep pressure does not increase cataplexy and positive affective stimuli that can increase cataplexy tend to decrease REM sleep. 2. Systemic manipulation of dopamine receptors can modulate cataplexy without affecting behavioral state. Specifically, manipulation of D2-like dopamine receptors at specific doses can modulate cataplexy while having no affect on sleep-wake state or sleep attacks, and manipulation of D1-like receptors potently affects sleep-wake state and sleep attacks without affecting cataplexy. 3. Systemic modulation of noradrenergic activity in orexin KO mice is sufficient to modulate cataplexy. Specifically, activation of excitatory α1 receptors reduces the occurrence of cataplexy while blockade of these receptors exacerbates it. 4. Withdrawal of an endogenous α1-mediated noradrenergic drive from motor neurons during wakefulness contributed to the loss of muscle tone during cataplexy. Re-establishing this excitatory drive exogenously alleviated cataplexy-dependant muscle atonia. 5. The amygdala is a critical part of the neural mechanism that triggers cataplexy in orexin KO mice. Ablation of the amygdala resulted in significant decreases in both baseline cataplexy and emotionally-induced cataplexy. The amygdala may trigger cataplexy through direct projections to brainstem areas that regulate muscle atonia.

Narcolepsy is a disabling sleep disorder that is characterized by persistent sleepiness, and cataplexy – an involuntary loss of waking muscle tone. Cataplexy and narcolepsy are caused by the loss of hypocretin containing neurons in the hypothalamus. However, it is hypothesized that dopamine is also involved in sleep and motor control and plays a role in cataplexy. This study investigated how manipulating dopamine affected sleep and cataplexy in narcoleptic mice devoid of hypocretin. We used d-amphetamine to increase endogenous dopamine levels and quinpirole (D2 agonist) to agonize D2 receptor sites. Amphetamine promoted wakefulness while decreasing sleep in wild-type mice, but was less effective in narcoleptic mice. Amphetamine also reduced cataplexy as well as sleep attacks (an indicator of sleepiness) in narcoleptic mice. Quinpirole had no effect on sleep or wakefulness; however, it potently increased cataplexy without affecting sleep attacks in narcoleptic mice.

In this thesis I investigated the neural circuits that trigger cataplexy in mice. Specifically, I first addressed the theory that cataplexy is a REM sleep disorder. I then investigated a role for the noradrenergic and dopaminergic systems in murine cataplexy. Finally, I addressed the role of the amygdala in triggering cataplexy. From this work several specific conclusions can be drawn: 1. Cataplexy does not share a common executive mechanism with REM sleep, although the two may share a common mechanism that generates muscle atonia. Muscle tone during REM sleep and cataplexy is similar, however increasing REM sleep pressure does not increase cataplexy and positive affective stimuli that can increase cataplexy tend to decrease REM sleep. 2. Systemic manipulation of dopamine receptors can modulate cataplexy without affecting behavioral state. Specifically, manipulation of D2-like dopamine receptors at specific doses can modulate cataplexy while having no affect on sleep-wake state or sleep attacks, and manipulation of D1-like receptors potently affects sleep-wake state and sleep attacks without affecting cataplexy. 3. Systemic modulation of noradrenergic activity in orexin KO mice is sufficient to modulate cataplexy. Specifically, activation of excitatory α1 receptors reduces the occurrence of cataplexy while blockade of these receptors exacerbates it. 4. Withdrawal of an endogenous α1-mediated noradrenergic drive from motor neurons during wakefulness contributed to the loss of muscle tone during cataplexy. Re-establishing this excitatory drive exogenously alleviated cataplexy-dependant muscle atonia. 5. The amygdala is a critical part of the neural mechanism that triggers cataplexy in orexin KO mice. Ablation of the amygdala resulted in significant decreases in both baseline cataplexy and emotionally-induced cataplexy. The amygdala may trigger cataplexy through direct projections to brainstem areas that regulate muscle atonia.

Narcolepsia é uma condição neurológica crônica, o principal sintoma é a sonolência diurna excessiva, associada a cataplexia, a paralisia do sono e as alucinações hipnagógicas. Paciente com narcolepsia apresenta dificuldade em manter a atenção e vigilância nas tarefas rotineiras e monótonas, com riscos de acidentes acarretando um sério prejuízo e impacto social nas suas relações de trabalho e sócio-familiares e na percepção da qualidade de vida.Foram avaliados 40 pacientes ( 28 mulheres e 12 homens) com idade média de 42 anos. O presente trabalho teve como objetivo: a) avaliar a percepção da QV em pacientes com narcolepsia b) Avaliar a percepção do impacto social. Este estudo demonstrou que: 1) A narcolepsia acarreta comprometimento na QV dos pacientes, com prejuízo das funções físicas e emocionais, interferindo nas condições de trabalho e dinâmica familiar; 2) A narcolepsia produz um impacto social em várias esferas da vida do pacientes, comprometendo atividades instrumentais da vida diária e a situação de trabalho / Narcolepsy is a chronic neurological condition, whose main symptom is excessive daytime sleepiness, associate the cataplexy, the hypnogogic hallucinations and sleep paralysis. The patient with narcolepsy presents difficulty in keeping the attention and monitoring in the routine and monotonous tasks, with risks of accidents, causing a serious prejudice and social impact its partner-familiar, relations of work and in the perception of the quality of life. The present work had as objective: ) to evaluate the perception of the quality of life in patients with narcolepsy b) To evaluate the perception of the social impact. This study it demonstrated that: 1) The narcolepsy compromises the quality of life of the patients, with prejudice of the physical and emotional functions, intervening with the conditions of work and familiar dynamics; 2) The narcolepsy produces a social impact in some areas of the life of the patients, compromising instrumental activities of the daily life and the situation of work

Narcolepsy is a disorder of unstable wake and sleep states caused by the lack of orexin neurons which degenerate most likely as a consequence of an autoimmune process. The state instability of narcolepsy includes rapid eye movement (REM) sleep intruding into wake in the form of dream-like hallucinations and cataplexy, muscle paralysis (atonia) much like occurs in REM sleep. In mice lacking orexin peptides, cataplexy is also observed with similar presentation as in humans of muscle paralysis during wakefulness which is often triggered by positive emotions. Prior research showed that the activation of the central amygdala is sufficient to promote cataplexy in a mouse model of narcolepsy. The central amygdala (CeA) contains a variety of neuronal types, and we hypothesize that γ-aminobutyric acid (GABA)-ergic neurons expressing the oxytocin receptor (OTR) mediate cataplexy as these neurons project to a known REM sleep atonia-regulating region, the ventrolateral periaqueductal gray (vlPAG)/lateral pontine tegmentum (LPT), and, as oxytocin (OT) sensitive neurons in the amygdala, likely participate in emotional processing and social behavior. In this study, we used fiber photometry to investigate the behavior of these neurons in response to social and rewarding stimuli, during emotion-triggered cataplexy, and across arousal states in an effort to define their potential role in emotion-triggered cataplexy. Initial recordings were conducted at too low an excitation light power to stimulate the green fluorescent calcium indicator, GCaMP6s, but were useful in optimizing MATLAB analysis and behavioral tests later done at higher LED power. The second series of recordings with higher excitation light power and better signal to noise ratio, showed increased activity in response to social interaction and reward, prior to REM transitions, and decreased activity during cataplexy confirming patterns seen in initial recordings. In recordings with higher excitation light, these responses appear to occur before interaction with stimulus mice or reward stimulus. In the future, additional recordings with a higher signal to noise ratio will be needed to confirm these results. In conclusion, responses of CeA-OTR neurons to social and rewarding stimuli, cataplexy, and at REM transitions are in support of a possible role of these neurons in emotion-triggered cataplexy which can be tested using additional methods, such as optogenetics.