Chronic Sleep Deprivation Blocks Voluntary Morphine Consumption but Not Conditioned Place Preference in Mice

Biological sex influences sleep phenotype in mice experiencing spontaneous opioid withdrawal

Aversive symptoms, including insomnia experienced during opioid withdrawal, are a major drive to relapse; however, withdrawal-associated sleep symptomatology has been little explored in preclinical models. We describe here a model of opioid withdrawal in mice that resembles the sleep phenotype characteristic of withdrawal in humans. Male and female C57BL/6 mice were instrumented with telemeters to record electroencephalogram, electromyogram, activity and subcutaneous temperature. All mice received two treatments separated by a 16-day washout period: (1) saline (volume: 10 ml kg-1); or (2) ascending doses of morphine (5, 10, 20, 40 and 80 mg kg-1; volume: 10 ml kg-1) for 5 days at Zeitgeber time 1 and Zeitgeber time 13. Recordings for the first 71 hr after treatment discontinuation (withdrawal days 1-3) and for 24 hr on withdrawal days 5 and 7 were scored for sleep/wake state, and sleep architecture and electroencephalogram spectral data were analysed. Morphine was acutely wake- and activity-promoting, and non-rapid eye movement and rapid eye movement sleep were increased during the dark phase on withdrawal day 2 in both sexes. While non-rapid eye movement delta power (0.5-4.0 Hz), a measure of sleep intensity, was reduced during the light phase on withdrawal day 1 and the dark phase on withdrawal day 2 in both sexes, female mice also exhibited changes in the duration and the number of bouts of sleep/wake states. These observations of fragmented sleep on withdrawal days 1-3 suggest poorer sleep consolidation and a more pronounced withdrawal-associated sleep phenotype in female than in male mice. These data may indicate a greater sensitivity to morphine, a more distinct aversive sleep phenotype and/or a faster escalation to dependence in female mice.

The effects of sleep restriction during abstinence on oxycodone seeking: Sex-dependent moderating effects of behavioral and hypothalamic-pituitary-adrenal axis-related phenotypes

During opioid use and abstinence, sleep disturbances are common and are thought to exacerbate drug craving. In this study, we tested the hypothesis that sleep restriction during abstinence from oxycodone self-administration would increase drug seeking during extinction and footshock reinstatement tests. We also performed behavioral phenotyping to determine if individual variation in responses to stressors and/or pain are associated with oxycodone seeking during abstinence, as stress, pain and sleep disturbance are often co-occurring phenomena. Sleep restriction during abstinence did not have selective effects on oxycodone seeking for either sex in extinction and footshock reinstatement tests. Some phenotypes were associated with drug seeking; these associations differed by sex and type of drug seeking assessment. In female rats, pain-related phenotypes were related to high levels of drug seeking during the initial extinction session. In male rats, lower anxiety-like behavior in the open field was associated with greater drug seeking, although this effect was lost when correcting for oxycodone intake. Adrenal sensitivity prior to oxycodone exposure was positively associated with footshock reinstatement in females. This work identifies sex-dependent relationships between HPA axis function and opioid seeking, indicating that HPA axis function could be a therapeutic target for the treatment of opioid use disorder, with tailored approaches based on sex. Sleep disturbance during abstinence did not appear to be a major contributing factor to opioid seeking.

Endogenous opiates and behavior: 2022

This paper is the forty-fifth consecutive installment of the annual anthological review of research concerning the endogenous opioid system, summarizing articles published during 2022 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides and receptors as well as effects of opioid/opiate agonists and antagonists. The review is subdivided into the following specific topics: molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors (1), the roles of these opioid peptides and receptors in pain and analgesia in animals (2) and humans (3), opioid-sensitive and opioid-insensitive effects of nonopioid analgesics (4), opioid peptide and receptor involvement in tolerance and dependence (5), stress and social status (6), learning and memory (7), eating and drinking (8), drug abuse and alcohol (9), sexual activity and hormones, pregnancy, development and endocrinology (10), mental illness and mood (11), seizures and neurologic disorders (12), electrical-related activity and neurophysiology (13), general activity and locomotion (14), gastrointestinal, renal and hepatic functions (15), cardiovascular responses (16), respiration and thermoregulation (17), and immunological responses (18).

Acute sleep deprivation induces synaptic remodeling at the soleus muscle neuromuscular junction in rats

Sleep is important for cognitive and physical performance. Sleep deprivation not only affects neural functions but also results in muscular fatigue. A good night's sleep reverses these functional derangements caused by sleep deprivation. The role of sleep in brain function has been extensively studied. However, its role in neuromuscular junction (NMJ) or skeletal muscle morphology is sparsely addressed although skeletal muscle atonia and suspended thermoregulation during rapid eye movement sleep possibly provide a conducive environment for the muscle to rest and repair; somewhat similar to slow-wave sleep for synaptic downscaling. In the present study, we have investigated the effect of 24 h sleep deprivation on the NMJ morphology and neurochemistry using electron microscopy and immunohistochemistry in the rat soleus muscle. Acute sleep deprivation altered synaptic ultra-structure viz. mitochondria, synaptic vesicle, synaptic proteins, basal lamina, and junctional folds needed for neuromuscular transmission. Further acute sleep deprivation showed the depletion of the neurotransmitter acetylcholine and the overactivity of its degrading enzyme acetylcholine esterase at the NMJ. The impact of sleep deprivation on synaptic homeostasis in the brain has been extensively reported recently. The present evidence from our studies shows new information on the role of sleep on the NMJ homeostasis and its functioning.

Differential Effects of Cocaine and Morphine on the Diurnal Regulation of the Mouse Nucleus Accumbens Proteome

Substance use disorders are associated with disruptions in sleep and circadian rhythms that persist during abstinence and may contribute to relapse risk. Repeated use of substances such as psychostimulants and opioids may lead to significant alterations in molecular rhythms in the nucleus accumbens (NAc), a brain region central to reward and motivation. Previous studies have identified rhythm alterations in the transcriptome of the NAc and other brain regions following the administration of psychostimulants or opioids. However, little is known about the impact of substance use on the diurnal rhythms of the proteome in the NAc. We used liquid chromatography coupled to tandem mass spectrometry-based quantitative proteomics, along with a data-independent acquisition analysis pipeline, to investigate the effects of cocaine or morphine administration on diurnal rhythms of proteome in the mouse NAc. Overall, our data reveal cocaine and morphine differentially alter diurnal rhythms of the proteome in the NAc, with largely independent differentially expressed proteins dependent on time-of-day. Pathways enriched from cocaine altered protein rhythms were primarily associated with glucocorticoid signaling and metabolism, whereas morphine was associated with neuroinflammation. Collectively, these findings are the first to characterize the diurnal regulation of the NAc proteome and demonstrate a novel relationship between the phase-dependent regulation of protein expression and the differential effects of cocaine and morphine on the NAc proteome. The proteomics data in this study are available via ProteomeXchange with identifier PXD042043.

Mu-opioid receptor-expressing neurons in the paraventricular thalamus modulate chronic morphine-induced wake alterations

Disrupted sleep is a symptom of many psychiatric disorders, including substance use disorders. Most drugs of abuse, including opioids, disrupt sleep. However, the extent and consequence of opioid-induced sleep disturbance, especially during chronic drug exposure, is understudied. We have previously shown that sleep disturbance alters voluntary morphine intake. Here, we examine the effects of acute and chronic morphine exposure on sleep. Using an oral self-administration paradigm, we show that morphine disrupts sleep, most significantly during the dark cycle in chronic morphine, with a concomitant sustained increase in neural activity in the Paraventricular Nucleus of the Thalamus (PVT). Morphine binds primarily to Mu Opioid Receptors (MORs), which are highly expressed in the PVT. Translating Ribosome Affinity Purification (TRAP)-Sequencing of PVT neurons that express MORs showed significant enrichment of the circadian entrainment pathway. To determine whether MOR + cells in the PVT mediate morphine-induced sleep/wake properties, we inhibited these neurons during the dark cycle while mice were self-administering morphine. This inhibition decreased morphine-induced wakefulness but not general wakefulness, indicating that MORs in the PVT contribute to opioid-specific wake alterations. Overall, our results suggest an important role for PVT neurons that express MORs in mediating morphine-induced sleep disturbance.

Differential Effects of Cocaine and Morphine on the Diurnal Regulation of the Mouse Nucleus Accumbens Proteome

Substance use disorders (SUDs) are associated with disruptions in sleep and circadian rhythms that persist during abstinence and may contribute to relapse risk. Repeated use of substances such as psychostimulants and opioids may lead to significant alterations in molecular rhythms in the nucleus accumbens (NAc), a brain region central to reward and motivation. Previous studies have identified rhythm alterations in the transcriptome of the NAc and other brain regions following the administration of psychostimulants or opioids. However, little is known about the impact of substance use on the diurnal rhythms of the proteome in the NAc. We used liquid chromatography coupled to tandem mass spectrometry-based (LC-MS/MS) quantitative proteomics, along with a data-independent acquisition (DIA) analysis pipeline, to investigate the effects of cocaine or morphine administration on diurnal rhythms of proteome in the mouse NAc. Overall, our data reveals cocaine and morphine differentially alters diurnal rhythms of the proteome in the NAc, with largely independent differentially expressed proteins dependent on time-of-day. Pathways enriched from cocaine altered protein rhythms were primarily associated with glucocorticoid signaling and metabolism, whereas morphine was associated with neuroinflammation. Collectively, these findings are the first to characterize the diurnal regulation of the NAc proteome and demonstrate a novel relationship between phase-dependent regulation of protein expression and the differential effects of cocaine and morphine on the NAc proteome.

A role for the circadian transcription factor NPAS2 in the progressive loss of non-rapid eye movement sleep and increased arousal during fentanyl withdrawal in male mice

RATIONALE

Synthetic opioids like fentanyl are contributing to the rise in rates of opioid use disorder and drug overdose deaths. Sleep dysfunction and circadian rhythm disruption may worsen during opioid withdrawal and persist during abstinence. Severe and persistent sleep and circadian alterations are putative factors in opioid craving and relapse. However, very little is known about the impact of fentanyl on sleep architecture and sleep-wake cycles, particularly opioid withdrawal. Further, circadian rhythms regulate sleep-wake cycles, and the circadian transcription factor, neuronal PAS domain 2 (NPAS2) is involved in the modulation of sleep architecture and drug reward. Here, we investigate the role of NPAS2 in fentanyl-induced sleep alterations.

OBJECTIVES

To determine the effect of fentanyl administration and withdrawal on sleep architecture, and the role of NPAS2 as a factor in fentanyl-induced sleep changes.

METHODS

Electroencephalography (EEG) and electromyography (EMG) was used to measure non-rapid eye movement sleep (NREMS) and rapid eye movement sleep (REMS) at baseline and following acute and chronic fentanyl administration in wild-type and NPAS2-deficient male mice.

RESULTS

Acute and chronic administration of fentanyl led to increased wake and arousal in both wild-type and NPAS2-deficient mice, an effect that was more pronounced in NPAS2-deficient mice. Chronic fentanyl administration led to decreased NREMS, which persisted during withdrawal, progressively decreasing from day 1 to 4 of withdrawal. The impact of fentanyl on NREMS and arousal was more pronounced in NPAS2-deficient mice.

CONCLUSIONS

Chronic fentanyl disrupts NREMS, leading to a progressive loss of NREMS during subsequent days of withdrawal. Loss of NPAS2 exacerbates the impact of fentanyl on sleep and wake, revealing a potential role for the circadian transcription factor in opioid-induced sleep changes.

Sleep loss and addiction

Reducing sleep hours is a risk factor for developing cardiovascular, metabolic, and psychiatric disorders. Furthermore, previous studies have shown that reduction in sleep time is a factor that favors relapse in addicted patients. Additionally, animal models have demonstrated that both sleep restriction and sleep deprivation increase the preference for alcohol, methylphenidate, and the self-administration of cocaine. Therefore, the present review discusses current knowledge about the influence of sleep hours reduction on addictivebehaviors; likewise, we discuss the neuronal basis underlying the sleep reduction-addiction relationship, like the role of the orexin and dopaminergic system and neuronal plasticity (i.e., delta FosB expression). Potentially, chronic sleep restriction could increase brain vulnerability and promote addictive behavior.

Sleep Disturbance Alters Cocaine-Induced Locomotor Activity: Involvement of Striatal Neuroimmune and Dopamine Signaling

Sleep disorders have high comorbidity with drug addiction and function as major risk factors for developing drug addiction. Recent studies have indicated that both sleep disturbance (SD) and abused drugs could activate microglia, and that increased neuroinflammation plays a critical role in the pathogenesis of both diseases. Whether microglia are involved in the contribution of chronic SDs to drug addiction has never been explored. In this study, we employed a mouse model of sleep fragmentation (SF) with cocaine treatment and examined their locomotor activities, as well as neuroinflammation levels and dopamine signaling in the striatum, to assess their interaction. We also included mice with, or without, SF that underwent cocaine withdrawal and challenge. Our results showed that SF significantly blunted cocaine-induced locomotor stimulation while having marginal effects on locomotor activity of mice with saline injections. Meanwhile, SF modulated the effects of cocaine on neuroimmune signaling in the striatum and in ex vivo isolated microglia. We did not observe differences in dopamine signaling in the striatum among treatment groups. In mice exposed to cocaine and later withdrawal, SF reduced locomotor sensitivity and also modulated neuroimmune and dopamine signaling in the striatum. Taken together, our results suggested that SF was capable of blunting cocaine-induced psychoactive effects through modulating neuroimmune and dopamine signaling. We hypothesize that SF could affect neuroimmune and dopamine signaling in the brain reward circuitry, which might mediate the linkage between sleep disorders and drug addiction.