Abstract Opioid analgesics are powerful pain relievers; however, over time, control diminishes as analgesic tolerance develops. The molecular mechanisms initiating have remained unresolved to date. We previously shown that desensitization of the μ-opioid receptor and interaction with β-arrestins is controlled by carboxyl-terminal phosphorylation. Here we created knockin mice a series serine- threonine-to-alanine mutations render increasingly unable recruit β-arrestins. Desensitization...

Key points In addition to reductions in respiratory rate, opioids also cause aspiration and difficulty swallowing, indicating impairment of the upper airways. The Kölliker–Fuse (KF) maintains airway patency a normal pattern. this study, activation μ opioid receptors KF reduced frequency tidal volume anaesthetized rats. Nerve recordings an situ preparation showed that eliminated post‐inspiration phase cycle. brain slices, agonists hyperpolarized distinct population (61%) neurons by inwardly...

Key points The main cause of death from opioid overdose is respiratory depression due to the activation µ‐opioid receptors (MORs). We conditionally deleted MORs neurons in two key areas brainstem circuitry (the Kölliker–Fuse nucleus (KF) and pre‐Bötzinger complex (preBötC)) determine their role opioid‐induced disturbances adult, awake mice. Deletion KF attenuated rate at all doses morphine. preBötC low dose, but had no effect on following high Instead, morphine increased occurrence apnoeas....

Opioids depress breathing by inhibition of interconnected respiratory nuclei in the pons and medulla. Mu opioid receptor (MOR) agonists directly hyperpolarize a population neurons dorsolateral pons, particularly Kölliker-Fuse (KF) nucleus, that are key mediators opioid-induced depression. However, projection target synaptic connections MOR-expressing KF unknown. Here, we used retrograde labeling brain slice electrophysiology to determine project ventrolateral medulla, including preBötzinger...

Summary The locus coeruleus (LC) provides widespread noradrenergic (NAergic) modulation throughout the brain to influence a wide range of functions, including breathing. Although both anatomical and physiological evidence supports involvement LC in upstream integration downstream breathing, circuitry behind latter is unknown. Here, we show that NAergic neurons send projections Kӧlliker-Fuse nucleus (KF), critical site control Long duration activation neuron terminals pontine slices induces...

According to the lipid raft theory, plasma membrane contains small domains enriched in cholesterol and sphingolipid, which may serve as platforms organize proteins. Using methyl-β-cyclodextrin (MβCD) deplete cholesterol, many G protein-coupled receptors have been shown depend on putative rafts for proper signaling. Here we examine hypothesis that treatment of HEK293 cells stably expressing FLAG-tagged μ-opioid (HEK FLAG-μ) or δ-opioid FLAG-δ) with MβCD will reduce opioid receptor signaling...

Rett syndrome is a neurological disorder caused by loss of function mutations in the gene that encodes DNA binding protein methyl-CpG-binding 2 (Mecp2). A prominent feature disturbances respiration characterized frequent apnea and an irregular interbreath cycle. 8-Hydroxy-2-dipropylaminotetralin has been shown to positively modulate these (Abdala AP, Dutschmann M, Bissonnette JM, Paton JF, Proc Natl Acad Sci U S 107: 18208–18213, 2010), but mode action not understood. Here we show selective...

μ-Opioid receptor desensitization is considered an initial step in the development of tolerance. Curiously, commonly used opioid morphine produces robust tolerance but minimal acute desensitization. This study was designed to test hypothesis that indeed present morphine-treated animals and distinguished from cellular by time course recovery mechanism. To induce tolerance, rats were treated with continuously released for 1 week. Morphine-mediated activation G protein-coupled inwardly...

Imbalance between the dopamine and serotonin (5-HT) neurotransmitter systems has been implicated in comorbidity of Parkinson's disease (PD) psychiatric disorders. L-DOPA, leading treatment PD, facilitates production release dopamine. This study assessed action L-DOPA on monoamine synaptic transmission mouse brain slices. Application augmented D2-receptor-mediated inhibitory postsynaptic current (IPSC) neurons substantia nigra. augmentation was largely due to from 5-HT terminals. Selective...

Organization of G protein-coupled receptors and cognate signaling partners at the plasma membrane has been proposed to occur via multiple mechanisms, including microdomains, receptor oligomerization, protein scaffolding. Here, we investigate organization six types Gi/o-coupled endogenously expressed in SH-SY5Y cells. The most abundant these cells was μ-opioid (MOR), activation which occluded acute inhibition adenylyl cyclase (AC) by agonists δ-opioid (DOR), nociceptin/orphanin FQ peptide...

Opioids can suppress breathing via actions throughout the brainstem, including dorsolateral pons. The respiratory phenotype of pontine neurons inhibited by opioids is unknown. Here, we describe effect highly potent opioid fentanyl on firing activity these neurons. Inspiratory were largely silenced fentanyl, whereas expiratory not. We provide a framework whereby this differential sensitivity to contribute pattern deficits and apnea.

Impaired chemoreflex responses are a central feature of opioid-induced respiratory depression, however, the mechanism through which mu opioid receptor agonists lead to diminished chemoreflexes is not fully understood. One brainstem structure involved in impairment nucleus solitary tract (NTS), contains population neurons that express receptors. Here, we tested whether caudal NTS activated during challenge receptors and overlap with by opioids. Using genetic labeling receptor-expressing cFos...

Acute desensitization of mu opioid receptors is thought to be an initial step in the development tolerance opioids. Given resistance respiratory system develop tolerance, neurons Kölliker-Fuse (KF), a key area circuit, was examined. The activation G protein–coupled inwardly rectifying potassium current measured using whole-cell voltage-clamp recordings from KF and locus coeruleus (LC) contained acute rat brain slices. A saturating concentration agonist [Met⁵]-enkephalin (ME)...

ABSTRACT Fatal opioid overdoses in the United States have nearly tripled during past decade, with greater than 92% involving a synthetic like fentanyl. Fentanyl potently activates μ-opioid receptor to induce both analgesia and respiratory depression. The danger of illicit fentanyl has recently been exacerbated by adulteration xylazine, an α2-adrenergic agonist typically used as veterinary anesthetic. In 2023, over 1,000% increase xylazine-positive was reported some regions U.S. Xylazine...

Respiratory depression is a potentially fatal side effect of opioid analgesics and major limitation to their use. G protein-biased agonists have been proposed as “safer” with less respiratory depression. These are biased activate proteins rather than β-arrestin signaling. has shown correlate both protein bias intrinsic efficacy, recent work refuted the role signaling in opioid-induced In addition, there substantial evidence that do, fact, mediate by actions respiratory-controlling brainstem...

Orexins are neuropeptides originating from the hypothalamus that serve broad physiological roles, including regulation of autonomic function, sleep-wake states, arousal and breathing. Lack orexins may lead to narcolepsy sleep disordered Orexinergic hypothalamic neurons send fibers Kӧlliker-Fuse (KF) directly project rostroventral respiratory group, phrenic hypoglossal motor neurons. These connections indicate a potential role orexin-modulated KF in functionally linking control...

The gustatory cortex (GC) region of the insular processes taste information in manners important for taste-guided behaviors, including food intake itself. In addition to oral stimuli, GC activity is also influenced by physiological states hunger. specific cell types and molecular mechanisms that provide with such abilities are unclear. Glucagon-like peptide 1 (GLP-1) produced neurons brain, where it can act on GLP-1 receptor-expressing (GLP-1R+) found several brain regions. these regions,...

While respiratory complications following opioid use are mainly mediated via activation of mu receptors, long-latency off-target signalling innate immune toll-like receptor 4 (TLR4) may impair other essential elements breathing control such as motor plasticity. In adult rats, pre-treatment with a single dose morphine blocked long-term facilitation (LTF) phrenic output TLR4-dependent mechanism. the nucleus, triggered microglial p38 MAPK - key enzyme that orchestrates inflammatory and is known...

Opioids are powerful analgesics, but carry a risk of overdose that has become pressing issue to public health in the United States. Overdose deaths caused by opioid-induced shutdown neuronal circuits operate unconscious breathing cycles, leading respiratory depression. Respiratory depression, alongside antinociception, is mediated activation μ-opioid receptors, which coupled inhibitory heterotrimeric G proteins. Recent studies have shown gallein, Gβγ subunit inhibitor, amplifies...

Opioids profoundly depress breathing which can be fatal in the case of overdose. Despite growing knowledge pontine and medullary respiratory control circuits that are inhibited by opioids, circuit cellular mechanisms opioid induced depression not fully understood. Serotonin neurons located caudal raphe modulate possess mu receptors. Therefore, we hypothesized serotonin-producing contribute to depression. To test this, employed experimental approaches: 1) arterially perfused situ working...