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Neuropharmacology Aug 2024Nicotine use produces psychoactive effects, and chronic use is associated with physiological and psychological symptoms of addiction. However, chronic nicotine use is...
Nicotine use produces psychoactive effects, and chronic use is associated with physiological and psychological symptoms of addiction. However, chronic nicotine use is known to decrease food intake and body weight gain, suggesting that nicotine also affects central metabolic and appetite regulation. We recently showed that acute nicotine self-administration in nicotine-dependent animals produces a short-term increase in food intake, contrary to its long-term decrease of feeding behavior. As feeding behavior is regulated by complex neural signaling mechanisms, this study aimed to test the hypothesis that nicotine intake in animals exposed to chronic nicotine may increase activation of pro-feeding regions and decrease activation of pro-satiety regions to produce the acute increase in feeding behavior. FOS immunohistochemistry revealed that acute nicotine intake in nicotine self-administering animals increased activation of the pro-feeding arcuate and lateral hypothalamic nuclei and decreased activation of the pro-satiety parabrachial nucleus. Regional correlational analysis also showed that acute nicotine changes the functional connectivity of the hunger/satiety network. Further dissection of the role of the arcuate nucleus using electrophysiology found that putative POMC neurons in animals given chronic nicotine exhibited decreased firing following acute nicotine application. These brain-wide central signaling changes may contribute to the acute increase in feeding behavior we see in rats after acute nicotine and provide new areas of focus for studying both nicotine addiction and metabolic regulation.
Topics: Animals; Nicotine; Male; Brain; Rats; Rats, Sprague-Dawley; Nicotinic Agonists; Feeding Behavior; Pro-Opiomelanocortin; Eating; Self Administration; Neurons; Proto-Oncogene Proteins c-fos; Anorexia
PubMed: 38648925
DOI: 10.1016/j.neuropharm.2024.109959 -
Science Translational Medicine Apr 2024Spontaneous pain, a major complaint of patients with neuropathic pain, has eluded study because there is no reliable marker in either preclinical models or clinical...
Spontaneous pain, a major complaint of patients with neuropathic pain, has eluded study because there is no reliable marker in either preclinical models or clinical studies. Here, we performed a comprehensive electroencephalogram/electromyogram analysis of sleep in several mouse models of chronic pain: neuropathic (spared nerve injury and chronic constriction injury), inflammatory (Freund's complete adjuvant and carrageenan, plantar incision) and chemical pain (capsaicin). We find that peripheral axonal injury drives fragmentation of sleep by increasing brief arousals from non-rapid eye movement sleep (NREMS) without changing total sleep amount. In contrast to neuropathic pain, inflammatory or chemical pain did not increase brief arousals. NREMS fragmentation was reduced by the analgesics gabapentin and carbamazepine, and it resolved when pain sensitivity returned to normal in a transient neuropathic pain model (sciatic nerve crush). Genetic silencing of peripheral sensory neurons or ablation of CGRP neurons in the parabrachial nucleus prevented sleep fragmentation, whereas pharmacological blockade of skin sensory fibers was ineffective, indicating that the neural activity driving the arousals originates ectopically in primary nociceptor neurons and is relayed through the lateral parabrachial nucleus. These findings identify NREMS fragmentation by brief arousals as an effective proxy to measure spontaneous neuropathic pain in mice.
Topics: Humans; Rats; Mice; Animals; Nociceptors; Eye Movements; Hyperalgesia; Rats, Sprague-Dawley; Neuralgia; Sleep; Disease Models, Animal
PubMed: 38630850
DOI: 10.1126/scitranslmed.adg3036 -
Cell Reports Apr 2024Pain that persists beyond the time required for tissue healing and pain that arises in the absence of tissue injury, collectively referred to as nociplastic pain, are...
Pain that persists beyond the time required for tissue healing and pain that arises in the absence of tissue injury, collectively referred to as nociplastic pain, are poorly understood phenomena mediated by plasticity within the central nervous system. The parabrachial nucleus (PBN) is a hub that relays aversive sensory information and appears to play a role in nociplasticity. Here, by preventing PBN Calca neurons from releasing neurotransmitters, we demonstrate that activation of Calca neurons is necessary for the manifestation and maintenance of chronic pain. Additionally, by directly stimulating Calca neurons, we demonstrate that Calca neuron activity is sufficient to drive nociplasticity. Aversive stimuli of multiple sensory modalities, such as exposure to nitroglycerin, cisplatin, or lithium chloride, can drive nociplasticity in a Calca-neuron-dependent manner. Aversive events drive nociplasticity in Calca neurons in the form of increased activity and excitability; however, neuroplasticity also appears to occur in downstream circuitry.
Topics: Animals; Parabrachial Nucleus; Neurons; Mice; Neuronal Plasticity; Male; Mice, Inbred C57BL
PubMed: 38583149
DOI: 10.1016/j.celrep.2024.114057 -
Frontiers in Pharmacology 2024Pain is a clinically relevant health care issue with limited therapeutic options, creating the need for new and improved analgesic strategies. The amygdala is a limbic...
Pain is a clinically relevant health care issue with limited therapeutic options, creating the need for new and improved analgesic strategies. The amygdala is a limbic brain region critically involved in the regulation of emotional-affective components of pain and in pain modulation. The central nucleus of amygdala (CeA) serves major output functions and receives nociceptive information via the external lateral parabrachial nucleus (PB). While amygdala neuroplasticity has been linked causally to pain behaviors, non-neuronal pain mechanisms in this region remain to be explored. As an essential part of the neuroimmune system, astrocytes that represent about 40-50% of glia cells within the central nervous system, are required for physiological neuronal functions, but their role in the amygdala remains to be determined for pain conditions. In this study, we measured time-specific astrocyte activation in the CeA in a neuropathic pain model (spinal nerve ligation, SNL) and assessed the effects of astrocyte inhibition on amygdala neuroplasticity and pain-like behaviors in the pain condition. Glial fibrillary acidic protein (GFAP, astrocytic marker) immunoreactivity and mRNA expression were increased at the chronic (4 weeks post-SNL), but not acute (1 week post-SNL), stage of neuropathic pain. In order to determine the contribution of astrocytes to amygdala pain-mechanisms, we used fluorocitric acid (FCA), a selective inhibitor of astrocyte metabolism. Whole-cell patch-clamp recordings were performed from neurons in the laterocapsular division of the CeA (CeLC) obtained from chronic neuropathic rats. Pre-incubation of brain slices with FCA (100 µM, 1 h), increased excitability through altered hyperpolarization-activated current (I) functions, without significantly affecting synaptic responses at the PB-CeLC synapse. Intra-CeA injection of FCA (100 µM) had facilitatory effects on mechanical withdrawal thresholds (von Frey and paw pressure tests) and emotional-affective behaviors (evoked vocalizations), but not on facial grimace score and anxiety-like behaviors (open field test), in chronic neuropathic rats. Selective inhibition of astrocytes by FCA was confirmed with immunohistochemical analyses showing decreased astrocytic GFAP, but not NeuN, signal in the CeA. Overall, these results suggest a complex modulation of amygdala pain functions by astrocytes and provide evidence for beneficial functions of astrocytes in CeA in chronic neuropathic pain.
PubMed: 38576475
DOI: 10.3389/fphar.2024.1368634 -
Cell Reports Apr 2024The motivation to eat is suppressed by satiety and aversive stimuli such as nausea. The neural circuit mechanisms of appetite suppression by nausea are not well...
The motivation to eat is suppressed by satiety and aversive stimuli such as nausea. The neural circuit mechanisms of appetite suppression by nausea are not well understood. Pkcδ neurons in the lateral subdivision of the central amygdala (CeA) suppress feeding in response to satiety signals and nausea. Here, we characterized neurons enriched in the medial subdivision (CeM) of the CeA marked by expression of Dlk1. CeA neurons are activated by nausea, but not satiety, and specifically suppress feeding induced by nausea. Artificial activation of CeA neurons suppresses drinking and social interactions, suggesting a broader function in attenuating motivational behavior. CeA neurons form projections to many brain regions and exert their anorexigenic activity by inhibition of neurons of the parabrachial nucleus. CeA neurons are inhibited by appetitive CeA neurons, but also receive long-range monosynaptic inputs from multiple brain regions. Our results illustrate a CeA circuit that regulates nausea-induced feeding suppression.
Topics: Animals; Neurons; Central Amygdaloid Nucleus; Calcium-Binding Proteins; Mice; Feeding Behavior; Nausea; Male; Mice, Inbred C57BL; Intercellular Signaling Peptides and Proteins
PubMed: 38551964
DOI: 10.1016/j.celrep.2024.113990 -
Nature Apr 2024Empirical evidence suggests that heat exposure reduces food intake. However, the neurocircuit architecture and the signalling mechanisms that form an associative...
Empirical evidence suggests that heat exposure reduces food intake. However, the neurocircuit architecture and the signalling mechanisms that form an associative interface between sensory and metabolic modalities remain unknown, despite primary thermoceptive neurons in the pontine parabrachial nucleus becoming well characterized. Tanycytes are a specialized cell type along the wall of the third ventricle that bidirectionally transport hormones and signalling molecules between the brain's parenchyma and ventricular system. Here we show that tanycytes are activated upon acute thermal challenge and are necessary to reduce food intake afterwards. Virus-mediated gene manipulation and circuit mapping showed that thermosensing glutamatergic neurons of the parabrachial nucleus innervate tanycytes either directly or through second-order hypothalamic neurons. Heat-dependent Fos expression in tanycytes suggested their ability to produce signalling molecules, including vascular endothelial growth factor A (VEGFA). Instead of discharging VEGFA into the cerebrospinal fluid for a systemic effect, VEGFA was released along the parenchymal processes of tanycytes in the arcuate nucleus. VEGFA then increased the spike threshold of Flt1-expressing dopamine and agouti-related peptide (Agrp)-containing neurons, thus priming net anorexigenic output. Indeed, both acute heat and the chemogenetic activation of glutamatergic parabrachial neurons at thermoneutrality reduced food intake for hours, in a manner that is sensitive to both Vegfa loss-of-function and blockage of vesicle-associated membrane protein 2 (VAMP2)-dependent exocytosis from tanycytes. Overall, we define a multimodal neurocircuit in which tanycytes link parabrachial sensory relay to the long-term enforcement of a metabolic code.
Topics: Animals; Female; Male; Mice; Agouti-Related Protein; Arcuate Nucleus of Hypothalamus; Brain Stem; Dopamine; Eating; Ependymoglial Cells; Feeding Behavior; Glutamic Acid; Hot Temperature; Hypothalamus; Neural Pathways; Neurons; Parabrachial Nucleus; Thermosensing; Time Factors; Vascular Endothelial Growth Factor A
PubMed: 38538787
DOI: 10.1038/s41586-024-07232-3 -
CNS Neuroscience & Therapeutics Mar 2024The new daily persistent headache (NDPH) is a rare primary headache disorder. However, the underlying mechanisms of NDPH remain incompletely understood. This study aims...
OBJECTIVES
The new daily persistent headache (NDPH) is a rare primary headache disorder. However, the underlying mechanisms of NDPH remain incompletely understood. This study aims to apply seed-based analysis to explore the functional connectivity (FC) of brainstem nuclei in patients with NDPH using resting-state functional magnetic resonance imaging (MRI).
METHODS
The FC analysis from the region of interest (ROI) to whole brain voxels was used to investigate 29 patients with NDPH and 37 well-matched healthy controls (HCs) with 3.0 Tesla MRI. The 76 nuclei in the brainstem atlas were defined as ROIs. Furthermore, we explored the correlations between FC and patients' clinical characteristics and neuropsychological evaluations.
RESULTS
Patients with NDPH exhibited reduced FC in multiple brainstem nuclei compared to HCs (including right inferior medullary reticular formation, right mesencephalic reticular formation, bilateral locus coeruleus, bilateral laterodorsal tegmental nucleus-central gray of the rhombencephalon, median raphe, left medial parabrachial nucleus, periaqueductal gray, and bilateral ventral tegmental area-parabrachial pigmented nucleus complex) and increased FC in periaqueductal gray. No significant correlations were found between the FC of these brain regions and clinical characteristics or neuropsychological evaluations after Bonferroni correction (p > 0.00016).
CONCLUSIONS
Our results demonstrated that patients with NDPH have abnormal FC of brainstem nuclei involved in the perception and regulation of pain and emotions.
Topics: Humans; Brain Stem; Brain; Magnetic Resonance Imaging; Medulla Oblongata; Brain Mapping; Headache
PubMed: 38516817
DOI: 10.1111/cns.14686 -
Journal of Pharmacological Sciences Apr 2024The monosynaptic connection from the lateral parabrachial nucleus (LPB) to the central amygdala (CeA) serves as a fundamental pathway for transmitting nociceptive...
Presynaptic inhibition of excitatory synaptic transmission from the calcitonin gene-related peptide-containing parabrachial neurons to the central amygdala in mice - unexpected influence of systemic inflammation thereon.
The monosynaptic connection from the lateral parabrachial nucleus (LPB) to the central amygdala (CeA) serves as a fundamental pathway for transmitting nociceptive signals to the brain. The LPB receives nociceptive information from the dorsal horn and spinal trigeminal nucleus and sends it to the "nociceptive" CeA, which modulates pain-associated emotions and nociceptive sensitivity. To elucidate the role of densely expressed mu-opioid receptors (MORs) within this pathway, we investigated the effects of exogenously applied opioids on LPB-CeA synaptic transmission, employing optogenetics in mice expressing channelrhodopsin-2 in LPB neurons with calcitonin gene-related peptide (CGRP). A MOR agonist ([D-Ala,N-Me-Phe,Glycinol]-enkephalin, DAMGO) significantly reduced the amplitude of light-evoked excitatory postsynaptic currents (leEPSCs), in a manner negatively correlated with an increase in the paired-pulse ratio. An antagonist of MORs significantly attenuated these effects. Notably, this antagonist significantly increased leEPSC amplitude when applied alone, an effect further amplified in mice subjected to lipopolysaccharide injection 2 h before brain isolation, yet not observed at the 24-h mark. We conclude that opioids could shut off the ascending nociceptive signal at the LPB-CeA synapse through presynaptic mechanisms. Moreover, this gating process might be modulated by endogenous opioids, and the innate immune system influences this modulation.
Topics: Mice; Animals; Calcitonin Gene-Related Peptide; Central Amygdaloid Nucleus; Synaptic Transmission; Neurons; Synapses; Receptors, Opioid, mu; Analgesics, Opioid
PubMed: 38485344
DOI: 10.1016/j.jphs.2024.02.004 -
Journal of Chemical Neuroanatomy Apr 2024Fluid satiation is an important signal and aspect of body fluid homeostasis. Oxytocin-receptor-expressing neurons (Oxtr) in the dorsolateral subdivision of the lateral...
Fluid satiation is an important signal and aspect of body fluid homeostasis. Oxytocin-receptor-expressing neurons (Oxtr) in the dorsolateral subdivision of the lateral parabrachial nucleus (dl LPBN) are key neurons which regulate fluid satiation. In the present study, we investigated brain regions activated by stimulation of Oxtr neurons in order to better characterise the fluid satiation neurocircuitry in mice. Chemogenetic activation of Oxtr neurons increased Fos expression (a proxy marker for neuronal activation) in known fluid-regulating brain nuclei, as well as other regions that have unclear links to fluid regulation and which are likely involved in regulating other functions such as arousal and stress relief. In addition, we analysed and compared Fos expression patterns between chemogenetically-activated fluid satiation and physiological-induced fluid satiation. Both models of fluid satiation activated similar brain regions, suggesting that the chemogenetic model of stimulating Oxtr neurons is a relevant model of physiological fluid satiation. A deeper understanding of this neural circuit may lead to novel molecular targets and creation of therapeutic agents to treat fluid-related disorders.
Topics: Animals; Parabrachial Nucleus; Mice; Receptors, Oxytocin; Neurons; Satiation; Male; Mice, Inbred C57BL; Brain
PubMed: 38452468
DOI: 10.1016/j.jchemneu.2024.102403 -
Nature Communications Mar 2024The "dorsal pons", or "dorsal pontine tegmentum" (dPnTg), is part of the brainstem. It is a complex, densely packed region whose nuclei are involved in regulating many...
The "dorsal pons", or "dorsal pontine tegmentum" (dPnTg), is part of the brainstem. It is a complex, densely packed region whose nuclei are involved in regulating many vital functions. Notable among them are the parabrachial nucleus, the Kölliker Fuse, the Barrington nucleus, the locus coeruleus, and the dorsal, laterodorsal, and ventral tegmental nuclei. In this study, we applied single-nucleus RNA-seq (snRNA-seq) to resolve neuronal subtypes based on their unique transcriptional profiles and then used multiplexed error robust fluorescence in situ hybridization (MERFISH) to map them spatially. We sampled ~1 million cells across the dPnTg and defined the spatial distribution of over 120 neuronal subtypes. Our analysis identified an unpredicted high transcriptional diversity in this region and pinpointed the unique marker genes of many neuronal subtypes. We also demonstrated that many neuronal subtypes are transcriptionally similar between humans and mice, enhancing this study's translational value. Finally, we developed a freely accessible, GPU and CPU-powered dashboard ( http://harvard.heavy.ai:6273/ ) that combines interactive visual analytics and hardware-accelerated SQL into a data science framework to allow the scientific community to query and gain insights into the data.
Topics: Humans; Animals; Mice; In Situ Hybridization, Fluorescence; Pontine Tegmentum; Brain Stem; Locus Coeruleus; Parabrachial Nucleus; Ascomycota
PubMed: 38438345
DOI: 10.1038/s41467-024-45907-7