-
Scientific Reports Mar 2023Brain growth occurs during the first 2 weeks of postnatal development in rats. This developmental period is equivalent to the third trimester of human gestation....
Brain growth occurs during the first 2 weeks of postnatal development in rats. This developmental period is equivalent to the third trimester of human gestation. Dendritic arborization, axonal growth, and gliogenesis are observed along with a strong maturation of neurotransmission during this critical development period. Furthermore, nicotine exposure during early development causes deficiencies in sensory and cognitive processing in adults. In this study, we further investigated the gene expression of neuron groups and the influence of perinatal nicotine exposure on gene expressions of neurons within the sub-regions of the ventral tegmental area (VTA) in 1 week, 2 week and 3-week-old rat pups. We exposed pregnant rats to nicotine perinatally on gestational day 7 through postnatal day 14. Pups are exposed to nicotine during pregnancy and through breastfeeding to investigate its effect in rat pups during early neuronal development. Real time PCR was used to find the relative expressions of gamma-aminobutyric acid (GABA), dopamine, and glutamate neuron markers within the three sub-regions of the VTA including the parabrachial pigmented nucleus (PBP), parainterfascicular (PIF), and paranigral nucleus (PN). Our results indicated that during early maturation, the dopamine marker tyrosine hydroxylase (TH) showed a consistently increased significance in PN sub-region compared to PIF and PBP. These results suggest that following perinatal nicotine exposure, VTA dopamine neurons, especially within the PN sub-region, are significantly excited starting from birth.
Topics: Pregnancy; Humans; Female; Rats; Animals; Nicotine; Ventral Tegmental Area; Transcriptome; Dopamine; Rats, Sprague-Dawley; Prenatal Exposure Delayed Effects; Dopaminergic Neurons
PubMed: 36966190
DOI: 10.1038/s41598-023-31997-8 -
Cell Reports Apr 2023Multiple brain regions are engaged in classical fear conditioning. Despite evidence for cerebellar involvement in fear conditioning, the mechanisms by which cerebellar...
Multiple brain regions are engaged in classical fear conditioning. Despite evidence for cerebellar involvement in fear conditioning, the mechanisms by which cerebellar outputs modulate fear learning and memory remain unclear. We identify a population of deep cerebellar nucleus (DCN) neurons with monosynaptic glutamatergic projections to the lateral parabrachial nucleus (lPBN) (DCN neurons) in mice. While optogenetic suppression of DCN neurons impairs auditory fear memory, activation of DCN neurons elicits freezing behavior only after auditory fear conditioning. Moreover, auditory fear conditioning potentiates DCN-lPBN synapses, and subsequently, auditory cue activates lPBN neurons after fear conditioning. Furthermore, DCN neuron activation can replace the auditory cue but not footshock in fear conditioning. These findings demonstrate that cerebellar nuclei modulate auditory fear conditioning via transmitting conditioned stimuli signals to the lPBN. Collectively, our findings suggest that the DCN-lPBN circuit is a part of neuronal substrates within interconnected brain regions underscoring auditory fear memory.
Topics: Mice; Animals; Cerebellar Nuclei; Parabrachial Nucleus; Neurons; Conditioning, Classical; Fear
PubMed: 36952344
DOI: 10.1016/j.celrep.2023.112291 -
Cell Reports Apr 2023Mechanical allodynia (MA) represents one prevalent symptom of chronic pain. Previously we and others have identified spinal and brain circuits that transmit or modulate...
Mechanical allodynia (MA) represents one prevalent symptom of chronic pain. Previously we and others have identified spinal and brain circuits that transmit or modulate the initial establishment of MA. However, brain-derived descending pathways that control the laterality and duration of MA are still poorly understood. Here we report that the contralateral brain-to-spinal circuits, from Oprm1 neurons in the lateral parabrachial nucleus (lPBN), via Pdyn neurons in the dorsal medial regions of hypothalamus (dmH), to the spinal dorsal horn (SDH), act to prevent nerve injury from inducing contralateral MA and reduce the duration of bilateral MA induced by capsaicin. Ablating/silencing dmH-projecting lPBN neurons or SDH-projecting dmH neurons, deleting Dyn peptide from dmH, or blocking spinal κ-opioid receptors all led to long-lasting bilateral MA. Conversely, activation of dmH neurons or their axonal terminals in SDH can suppress sustained bilateral MA induced by lPBN lesion.
Topics: Mice; Animals; Hyperalgesia; Spinal Cord; Central Nervous System; Spinal Cord Dorsal Horn; Neurons; Hypothalamus
PubMed: 36952340
DOI: 10.1016/j.celrep.2023.112300 -
The parabrachial to central amygdala circuit is a key mediator of injury-induced pain sensitization.BioRxiv : the Preprint Server For... Feb 2023The spino-ponto-amygdaloid pathway is a major ascending circuit relaying nociceptive information from the spinal cord to the brain. Potentiation of excitatory synaptic...
UNLABELLED
The spino-ponto-amygdaloid pathway is a major ascending circuit relaying nociceptive information from the spinal cord to the brain. Potentiation of excitatory synaptic transmission in the parabrachial nucleus (PbN) to central amygdala (CeA) pathway has been reported in rodent models of persistent pain. At the behavioral level, the PbN→CeA pathway has been proposed to serve as a general alarm system to potential threats that modulates pain-related escape behaviors, threat memory, aversion, and affective-motivational (but not somatosensory) responses to painful stimuli. Increased sensitivity to previously innocuous somatosensory stimulation is a hallmark of chronic pain. Whether the PbN→CeA circuit contributes to heightened peripheral sensitivity following an injury, however, remains unknown. Here, we demonstrate that activation of CeA-projecting PbN neurons contributes to injury-induced behavioral hypersensitivity but not baseline nociception in male and female mice. Using optogenetic assisted circuit mapping, we confirmed a functional excitatory projection from PbN→CeA that is independent of the genetic or firing identity of CeA cells. We then showed that peripheral noxious stimulation increases the expression of the neuronal activity marker c-Fos in CeA-projecting PbN neurons and chemogenetic inactivation of these cells reduces behavioral hypersensitivity in models of neuropathic and inflammatory pain without affecting baseline nociception. Lastly, we show that chemogenetic activation of CeA-projecting PbN neurons is sufficient to induce bilateral hypersensitivity without injury. Together, our results demonstrate that the PbN→CeA pathway is a key modulator of pain-related behaviors that can amplify responses to somatosensory stimulation in pathological states without affecting nociception under normal physiological conditions.
SIGNIFICANCE STATEMENT
Early studies identified the spino-ponto-amygdaloid pathway as a major ascending circuit conveying nociceptive inputs from the spinal cord to the brain. The functional significance of this circuit to injury-induced hypersensitivity, however, remains unknown. Here, we addressed this gap in knowledge using viral-mediated anatomical tracers, electrophysiology and chemogenetic intersectional approaches in rodent models of persistent pain. We found that activation of this pathway contributes to injury-induced hypersensitivity, directly demonstrating a critical function of the PbN→CeA circuit in pain modulation.
PubMed: 36945586
DOI: 10.1101/2023.02.08.527340 -
ELife Mar 2023Defensive behaviors are critical for animal's survival. Both the paraventricular nucleus of the hypothalamus (PVN) and the parabrachial nucleus (PBN) have been shown to...
Defensive behaviors are critical for animal's survival. Both the paraventricular nucleus of the hypothalamus (PVN) and the parabrachial nucleus (PBN) have been shown to be involved in defensive behaviors. However, whether there are direct connections between them to mediate defensive behaviors remains unclear. Here, by retrograde and anterograde tracing, we uncover that cholecystokinin (CCK)-expressing neurons in the lateral PBN (LPB) directly project to the PVN. By in vivo fiber photometry recording, we find that LPB neurons actively respond to various threat stimuli. Selective photoactivation of LPB neurons promotes aversion and defensive behaviors. Conversely, photoinhibition of LPB neurons attenuates rat or looming stimuli-induced flight responses. Optogenetic activation of LPB axon terminals within the PVN or PVN glutamatergic neurons promotes defensive behaviors. Whereas chemogenetic and pharmacological inhibition of local PVN neurons prevent LPB-PVN pathway activation-driven flight responses. These data suggest that LPB neurons recruit downstream PVN neurons to actively engage in flight responses. Our study identifies a previously unrecognized role for the LPB-PVN pathway in controlling defensive behaviors.
Topics: Rats; Animals; Hypothalamus; Paraventricular Hypothalamic Nucleus; Cholecystokinin; Neurons; Parabrachial Nucleus
PubMed: 36930206
DOI: 10.7554/eLife.85450 -
Neuroscience May 2023Many threats activate parabrachial neurons expressing calcitonin gene-related peptide (CGRP) which transmit alarm signals to forebrain regions. Most CGRP neurons also...
Many threats activate parabrachial neurons expressing calcitonin gene-related peptide (CGRP) which transmit alarm signals to forebrain regions. Most CGRP neurons also express tachykinin 1 (Tac1), but there are also Tac1-expressing neurons in the PBN that do not express CGRP (Tac1+;CGRP- neurons). Chemogenetic or optogenetic activation of all Tac1 neurons in mice elicited many physiological/behavioral responses resembling the activation of CGRP neurons, e.g., anorexia, jumping on a hot plate, avoidance of photostimulation; however, two key responses opposed activation of CGRP neurons. Activating Tac1 neurons did not produce conditioned taste aversion and it elicited dynamic escape behaviors rather than freezing. Activating Tac1+;CGRP- neurons, using an intersectional genetic targeting approach, resembles activating all Tac1 neurons. These results reveal that activation of Tac1+;CGRP- neurons can suppress some functions attributed to the CGRP neurons, which provides a mechanism to bias behavioral responses to threats.
Topics: Mice; Animals; Calcitonin Gene-Related Peptide; Parabrachial Nucleus; Feeding Behavior; Neurons; Tachykinins
PubMed: 36898496
DOI: 10.1016/j.neuroscience.2023.03.003 -
BioRxiv : the Preprint Server For... Mar 2023Brief stimuli can trigger longer lasting brain states. G protein-coupled receptors (GPCRs) could help sustain such states by coupling slow-timescale molecular signals to...
Brief stimuli can trigger longer lasting brain states. G protein-coupled receptors (GPCRs) could help sustain such states by coupling slow-timescale molecular signals to neuronal excitability. Brainstem parabrachial nucleus glutamatergic neurons (PBN ) regulate sustained brain states such as pain, and express G -coupled GPCRs that increase cAMP signaling. We asked whether cAMP directly influences PBN excitability and behavior. Both brief tail shocks and brief optogenetic stimulation of cAMP production in PBN neurons drove minutes-long suppression of feeding. This suppression matched the duration of prolonged elevations in cAMP, Protein Kinase A (PKA), and calcium activity and Shortening this elevation in cAMP reduced the duration of feeding suppression following tail shocks. cAMP elevations in PBN neurons rapidly lead to sustained increases in action potential firing via PKA-dependent mechanisms. Thus, molecular signaling in PBN neurons helps prolong neural activity and behavioral states evoked by brief, salient bodily stimuli.
PubMed: 36865343
DOI: 10.1101/2023.02.25.530033 -
The Journal of Neuroscience : the... Mar 2023Photoaffinity ligands are best known as tools used to identify the specific binding sites of drugs to their molecular targets. However, photoaffinity ligands have the...
Photoaffinity ligands are best known as tools used to identify the specific binding sites of drugs to their molecular targets. However, photoaffinity ligands have the potential to further define critical neuroanatomic targets of drug action. In the brains of WT male mice, we demonstrate the feasibility of using photoaffinity ligands to prolong anesthesia via targeted yet spatially restricted photoadduction of azi--propofol (aziPm), a photoreactive analog of the general anesthetic propofol. Systemic administration of aziPm with bilateral near-ultraviolet photoadduction in the rostral pons, at the border of the parabrachial nucleus and locus coeruleus, produced a 20-fold increase in the duration of sedative and hypnotic effects compared with control mice without UV illumination. Photoadduction that missed the parabrachial-coerulean complex also failed to extend the sedative or hypnotic actions of aziPm and was indistinguishable from nonadducted controls. Paralleling the prolonged behavioral and EEG consequences of on target photoadduction, we conducted electrophysiologic recordings in rostral pontine brain slices. Using neurons within the locus coeruleus to further highlight the cellular consequences of irreversible aziPm binding, we demonstrate transient slowing of spontaneous action potentials with a brief bath application of aziPm that becomes irreversible on photoadduction. Together, these findings suggest that photochemistry-based strategies are a viable new approach for probing CNS physiology and pathophysiology. Photoaffinity ligands are drugs capable of light-induced irreversible binding, which have unexploited potential to identify the neuroanatomic sites of drug action. We systemically administer a centrally acting anesthetic photoaffinity ligand in mice, conduct localized photoillumination within the brain to covalently adduct the drug at its sites of action, and successfully enrich irreversible drug binding within a restricted 250 µm radius. When photoadduction encompassed the pontine parabrachial-coerulean complex, anesthetic sedation and hypnosis was prolonged 20-fold, thus illustrating the power of photochemistry to help unravel neuronal mechanisms of drug action.
Topics: Animals; Male; Mice; Adrenergic Neurons; Anesthesia, Intravenous; Brain; Electrocorticography; Electroencephalography; Hypnosis; Hypnotics and Sedatives; Ligands; Locus Coeruleus; Mice, Inbred C57BL; Parabrachial Nucleus; Photoaffinity Labels; Propofol; Time Factors; Ultraviolet Rays; Anesthetics, Intravenous
PubMed: 36849414
DOI: 10.1523/JNEUROSCI.1884-22.2023 -
Brain, Behavior, and Immunity May 2023Anorexia is a common symptom during infectious and inflammatory disease. Here we examined the role of melanocortin-4 receptors (MC4Rs) in inflammation-induced anorexia....
Anorexia is a common symptom during infectious and inflammatory disease. Here we examined the role of melanocortin-4 receptors (MC4Rs) in inflammation-induced anorexia. Mice with transcriptional blockage of the MC4Rs displayed the same reduction of food intake following peripheral injection of lipopolysaccharide as wild type mice but were protected against the anorexic effect of the immune challenge in a test in which fasted animals were to use olfactory cues to find a hidden cookie. By using selective virus-mediated receptor re-expression we demonstrate that the suppression of the food-seeking behavior is subserved by MC4Rs in the brain stem parabrachial nucleus, a central hub for interoceptive information involved in the regulation of food intake. Furthermore, the selective expression of MC4R in the parabrachial nucleus also attenuated the body weight increase that characterizes MC4R KO mice. These data extend on the functions of the MC4Rs and show that MC4Rs in the parabrachial nucleus are critically involved in the anorexic response to peripheral inflammation but also contribute to body weight homeostasis during normal conditions.
Topics: Mice; Animals; Parabrachial Nucleus; Anorexia; Neurons; Body Weight; Inflammation; Melanocortins; Eating
PubMed: 36813210
DOI: 10.1016/j.bbi.2023.02.014 -
Nature Communications Feb 2023Breathing is regulated automatically by neural circuits in the medulla to maintain homeostasis, but breathing is also modified by behavior and emotion. Mice have rapid...
Breathing is regulated automatically by neural circuits in the medulla to maintain homeostasis, but breathing is also modified by behavior and emotion. Mice have rapid breathing patterns that are unique to the awake state and distinct from those driven by automatic reflexes. Activation of medullary neurons that control automatic breathing does not reproduce these rapid breathing patterns. By manipulating transcriptionally defined neurons in the parabrachial nucleus, we identify a subset of neurons that express the Tac1, but not Calca, gene that exerts potent and precise conditional control of breathing in the awake, but not anesthetized, state via projections to the ventral intermediate reticular zone of the medulla. Activating these neurons drives breathing to frequencies that match the physiological maximum through mechanisms that differ from those that underlie the automatic control of breathing. We postulate that this circuit is important for the integration of breathing with state-dependent behaviors and emotions.
Topics: Mice; Animals; Neurons; Respiration; Medulla Oblongata
PubMed: 36810601
DOI: 10.1038/s41467-023-36603-z