Periaqueductal Gray Research Articles

Regional hypothalamic, amygdala, and midbrain periaqueductal gray matter recruitment during acute pain in awake humans: A 7-Tesla functional magnetic resonance imaging study

Over the past two decades, magnetic resonance imaging (MRI) studies have explored brain activation patterns during acute noxious stimuli. Whilst these human investigations have detailed changes in primarily cortical regions, they have generally not explored discrete changes within small brain areas that are critical in driving behavioural, autonomic, and endocrine responses to pain, such as within subregions of the hypothalamus, amygdala, and midbrain periaqueductal gray matter (PAG). Ultra-high field (7-Tesla) MRI provides enough signal-to-noise at high spatial resolutions to investigate activation patterns within these small brain regions during acute noxious stimulation in awake humans. In this study we used 7T functional MRI to concentrate on hypothalamic, amygdala, and PAG signal changes during acute noxious orofacial stimuli. Noxious heat stimuli were applied in three separate fMRI scans to three adjacent sites on the face in 16 healthy control participants (7 females). Images were processed using SPM12 and custom software, and blood oxygen level dependent signal changes within the hypothalamus, amygdala, and PAG assessed. We identified altered activity within eight unique subregions of the hypothalamus, four unique subregions of the amygdala, and a single region in the lateral PAG. Specifically, within the hypothalamus and amygdala, signal intensity largely decreased during noxious stimulation, and increased in the lateral PAG. Furthermore, we found sex-related differences in discrete regions of the hypothalamus and amygdala. This study reveals that the activity of discrete nuclei during acute noxious thermal stimulation in awake humans.

Why do mice squeak? Toward a better understanding of defensive vocalization

SummaryAlthough mice mostly communicate in the ultrasonic range, they also emit audible calls. We demonstrate that mice selectively bred for high anxiety-related behavior (HAB) have a high disposition for emitting sonic calls when caught by the tail. The vocalization was unrelated to pain but sensitive to anxiolytics. As revealed by manganese-enhanced MRI, HAB mice displayed an increased tonic activity of the periaqueductal gray (PAG). Selective inhibition of the dorsolateral PAG not only reduced anxiety-like behavior but also completely abolished sonic vocalization. Calls were emitted at a fundamental frequency of 3.8 kHz, which falls into the hearing range of numerous predators. Indeed, playback of sonic vocalization attracted rats if associated with a stimulus mouse. If played back to HAB mice, sonic calls were repellent in the absence of a conspecific but attractive in their presence. Our data demonstrate that sonic vocalization attracts both predators and conspecifics depending on the context.

Sex differences in the amygdaloid projections to the ventrolateral periaqueductal gray and their activation during inflammatory pain in the rat

Preclinical and clinical studies have reported sex differences in pain and analgesia. These differences may be linked to anatomical structures of the central nervous system pain modulatory circuitry, and/or hormonal milieu. The midbrain periaqueductal gray (PAG) is a critical brain region for descending inhibition of pain. The PAG projects to the rostral ventromedial medulla (RVM), which projects bilaterally to the spinal cord to inhibit pain. In addition to pain, this descending circuit (or pathway) can be engaged by endogenous opioids (i.e., endorphins) or exogenous opioids (i.e., morphine), and we have previously reported sex differences in the activation of this circuit during pain and analgesia. Forebrain structures, including the amygdala, project to and engage the PAG-RVM circuit during persistent inflammatory pain. However, there are limited studies in females detailing this amygdalar-PAG pathway and its involvement during persistent inflammatory pain. The objective of the present study was to delineate the neural projections from the amygdala to the PAG in male and female rats to determine if they are sexually distinct in their anatomical organization. We also examined the activation of this pathway by inflammatory pain and the co-localization of receptors for estrogen. Injection of the retrograde tracer fluorogold (FG) into the ventrolateral PAG (vlPAG) resulted in dense retrograde labeling in both the central amygdala (CeA) and medial amygdala (MeA). While the number of CeA-vlPAG neurons were comparable between the sexes, there were more MeA-vlPAG neurons in females. Inflammatory pain resulted in greater activation of the amygdala in males; however, females displayed higher Fos expression within CeA-vlPAG projection neurons. Females expressed higher ERα in the MeA and CeA and the same was true of the projection neurons. Together, these data indicate that although the MeA-vlPAG projections are denser in females, inflammatory pain does not significantly activate these projections. In contrast, inflammatory pain resulted in a greater activation of the CeA-vlPAG pathway in females. As females experience a greater number of chronic pain syndromes, the CeA-vlPAG pathway may play a facilitatory (and not inhibitory) role in pain modulation.

Diffuse noxious inhibitory controls and conditioned pain modulation: a shared neurobiology within the descending pain inhibitory system?

Diffuse noxious inhibitory controls and conditioned pain modulation: a shared neurobiology within the descending pain inhibitory system?

Sparse genetically defined neurons refine the canonical role of periaqueductal gray columnar organization.

During threat exposure, survival depends on defensive reactions. Prior works linked large glutamatergic populations in the midbrain periaqueductal gray (PAG) to defensive freezing and flight, and established that the overarching functional organization axis of the PAG is along anatomically-defined columns. Accordingly, broad activation of the dorsolateral column induces flight, while activation of the lateral or ventrolateral (l and vl) columns induces freezing. However, the PAG contains diverse cell types that vary in neurochemistry. How these cell types contribute to defense remains unknown, indicating that targeting sparse, genetically-defined populations may reveal how the PAG generates diverse behaviors. Though prior works showed that broad excitation of the lPAG or vlPAG causes freezing, we found in mice that activation of lateral and ventrolateral PAG (l/vlPAG) cholecystokinin-expressing (CCK) cells selectively caused flight to safer regions within an environment. Furthermore, inhibition of l/vlPAG-CCK cells reduced predator avoidance without altering other defensive behaviors like freezing. Lastly, l/vlPAG-CCK activity decreased when approaching threat and increased during movement to safer locations. These results suggest CCK cells drive threat avoidance states, which are epochs during which mice increase distance from threat and perform evasive escape. Conversely, l/vlPAG pan-neuronal activation promoted freezing, and these cells were activated near threat. Thus, CCK l/vlPAG cells have opposing function and neural activation motifs compared to the broader local ensemble defined solely by columnar boundaries. In addition to the anatomical columnar architecture of the PAG, the molecular identity of PAG cells may confer an additional axis of functional organization, revealing unexplored functional heterogeneity.

Gray Matter Brain Alterations in Type 1 Diabetes - Findings Based on Detailed Phenotyping of Neuropathy Status.

This study investigated brain structure in patients of type 1 diabetes with diabetic peripheral neuropathy (DPN) and type 1 diabetes with neuropathic pain and the associations to clinical, peripheral, and cognitive measurements. Sixty individuals with type 1 diabetes and 20 healthy controls were included in the study. Nineteen individuals with type 1 diabetes and neuropathic pain, 19 with type 1 diabetes and DPN, 18 with type 1 diabetes without DPN, and 20 healthy controls were included in the brain analyses. We utilized structural brain magnetic resonance imaging to investigate total and regional gray matter volume. Significant lower gray matter volume was found in type 1 diabetes with neuropathic pain and in type 1 diabetes without DPN compared to healthy controls (p=0.024 and p=0.019, respectively). Lower insula volume was observed in all three diabetes groups (all p≤0.050). Thalamus and hippocampus volume was lower in type 1 diabetes with neuropathic pain, cerebellum volume was lower in type 1 diabetes with DPN, and somatosensory cortex volume was lower in type 1 diabetes without DPN (all p≤0.018). Attenuated memory was associated with lower gray matter volume in type 1 diabetes with DPN. No associations were found between gray matter volume and clinical/peripheral measurements. We demonstrated lower gray matter volume in individuals with type 1 diabetes regardless of the presence of DPN and neuropathic pain. Hence, central gray matter alteration was not associated with peripheral alterations.

Depressive symptoms are correlated with periaqueductal gray matter functional connectivity in migraine

IntroductionDepression is the most common comorbidity of migraine. The brain of migraineurs with depression shows differences compared to migraine only or depression only patients. The comorbidity may affect specific regions such as the periaqueductal gray matter (PAG) which is important in negative emotion regulation and pain modulatory system.ObjectivesWe hypothesized that the alterations in PAG functional connectivity (FC) may play a role in migraineurs vulnerability for depression.MethodsA resting-state fMRI was conducted with 34 episodic migraine without aura patients and 41 control subjects. All participants were medication free and they did not have any psychiatric or chronic disorders. Depressive symptoms were measured with Zung Self-Rating Depression Scale. To investigate the relationship between depressive symptoms and PAG functional connectivity, Zung scores were used as covariates in each groups’ PAG-FC analysis using the Statistical Parametric Mapping (SPM12) toolbox in MATLAB environment.Results There were no significant difference between migraine and control group in Zung scores (p=0.394). Negative correlation was found between Zung scores and PAG-FC with thalamus, fusiform gyrus, middle occipital gyrus and calcarine (pFWE<0.05) in migraine group. However, there was no significant correlation between Zung scores and PAG-FC in healthy control group.ConclusionsOur results suggest that PAG-FC with emotion and pain processing areas is affected by depressive symptoms in migraine patients, but not in healthy controls. Migraine patients without comorbid depression might have vulnerable neuronal pathways for depressive symptoms. A follow-up of these patients could be interesting to determine whether these connectivity alterations predict the possible comorbid depression.DisclosureHungarian Brain Research Program (2017-1.2.1-NKP-2017-00002, KTIA_13_NAPA-II/14, KTIA_NAP_13-1-2013- 0001, KTIA_NAP_13-2- 2015-0001); 2020-4.1.1.-TKP2020; ERA PerMed (2019-2.1.7-ERA-NET-2020-00005); ÚNKP-21-4-I-SE-15 (DB).

Proposing a neural framework for the evolution of elaborate courtship displays

In many vertebrates, courtship occurs through the performance of elaborate behavioral displays that are as spectacular as they are complex. The question of how sexual selection acts upon these animals’ neuromuscular systems to transform a repertoire of pre-existing movements into such remarkable (if not unusual) display routines has received relatively little research attention. This is a surprising gap in knowledge, given that unraveling this extraordinary process is central to understanding the evolution of behavioral diversity and its neural control. In many vertebrates, courtship displays often push the limits of neuromuscular performance, and often in a ritualized manner. These displays can range from songs that require rapid switching between two independently controlled ‘voice boxes’ to precisely choreographed acrobatics. Here, we propose a framework for thinking about how the brain might not only control these displays, but also shape their evolution. Our framework focuses specifically on a major midbrain area, which we view as a likely important node in the orchestration of the complex neural control of behavior used in the courtship process. This area is the periaqueductal grey (PAG), as studies suggest that it is both necessary and sufficient for the production of many instinctive survival behaviors, including courtship vocalizations. Thus, we speculate about why the PAG, as well as its key inputs, might serve as targets of sexual selection for display behavior. In doing so, we attempt to combine core ideas about the neural control of behavior with principles of display evolution. Our intent is to spur research in this area and bring together neurobiologists and behavioral ecologists to more fully understand the role that the brain might play in behavioral innovation and diversification.

Korsakoff Syndrome: A Chronic Nutritional Deficiency Neuropsychiatric condition

In this review we have focused on Korsakoff syndrome, which is an aftermath of Wernicke encephalopathy (WE). Wernicke-Encephalopathy is neuropathologically marked by thiamine or vitamin B1 deficiency, typically induced by excessive alcohol use over an extended period of time in alcoholic patients, while in Nonalcoholic patients, it may be due to impaired utilization or accelerated usage of thiamine. Wernicke-Korsakoff syndrome (WKS) affects the brain region such as the mammillary bodies, periaqueductal and periventricular grey matter, colliculi bodies, and thalamus. The classic triads of WE are ophthalmoplegia, Nystagmus, and ataxia. The brain is examined using MRI and shows damage to the nuclei or memory transit- papez circuit that connects mamillary bodies to the anterior thalamus using the mammillothalamic tract responsible for the recollective memory in the diencephalon. Patients can be treated by parenteral thiamine administration and by abstinence of alcohol within their lifestyle. Keywords: Korsakoff Syndrome, alcoholic, non-alcoholic, Alzheimer's, memory-loss Wernicke encephalopathy, Wernicke-Korsakoff syndrome

Contribution of G Protein-Coupled Receptor 55 to Periaqueductal Gray-Mediated Antinociception in the Inflammatory Pain.

The brain mechanism of inflammatory pain is an understudied area of research, particularly concerning the descending pain modulatory system. The G protein-coupled receptor 55 (GPR55) is a lysophosphatidylinositol-sensitive receptor that has also been involved in cannabinoid signaling. It is widely expressed throughout the central nervous system, including the periaqueductal gray (PAG), a brainstem area and key element of the descending pain modulatory system. In this study, we used behavioral, stereotaxic injections, pharmacological tools, and two inflammatory pain models (formalin and carrageenan) to determine if GPR55 in the PAG plays a role in the pain associated with inflammation in rats. It was found that the blockade of GPR55 action in PAG can drive the descending pain modulatory system to mitigate inflammatory pain. These data show that GPR55 plays a role in the descending pain modulatory system in inflammatory pain.

Cystic Neuronal Necrosis of Posterior Thalami in Neonatal Hypoxic Ischemic Encephalopathy: A Case Report of an Unusual Radiological Finding

Background: Neonatal hypoxic ischemic encephalopathy (HIE) occurs as a result of any event that causes hypoxia and hypoperfusion to the developing neonatal brain. In addition to being a major cause of neonatal mortality, it is also associated with significant long-term neurological deficits. Multicystic encephalomalacia is a sequelae to global hypoxic ischemic injury which is characterized by cortical atrophy, basal ganglia/thalamic atrophy, and cystic necrosis of cerebral white matter. In this report, we present an unusual finding of cystic necrosis of thalami in HIE. Case Presentation: We present the case of a term neonate with a history of prolonged labor and meconium aspiration who developed HIE stage III. The neonate initially required ventilator support and was gradually weaned off but was reintubated in view of neonatal sepsis. Magnetic resonance imaging done on day 23 revealed diffuse cortical and white matter atrophy, signal intensity alteration in basal ganglia and thalami, and multiple well-defined areas of cerebrospinal fluid signal intensity in the white matter, consistent with multicystic encephalomalacia. An additional unusual finding was cystic necrosis, symmetrically involving bilateral posterior thalami. Conclusion: According to our observation, severe prolonged hypoxic ischemic insult does not only result in central gray matter atrophy but can also cause cystic neuronal necrosis of the same.

The neural distribution of the avian homologue of oxytocin, mesotocin, in two songbird species, the zebra finch and the canary: A potential role in song perception and production.

The avian homologue of oxytocin (OT), formerly called mesotocin, influences social behaviors in songbirds and potentially song production. We sought to characterize the distribution of OT peptide in the brain of two songbird species: canaries (Serinus canaria) and zebra finches (Taeniopygia guttata). To visualize OT, we performed immunocytochemistry using an antibody previously shown to identify OT in avian species. In both canaries and zebra finches, dense OT‐ir perikarya were located in the paraventricular nucleus (PVN), preoptic area (POA), supraoptic nucleus (SON), and medial bed nucleus of the stria terminalis (BNSTm). We also observed morphologically distinct OT‐ir cells scattered throughout the mesopallium. OT‐ir fibers were observed in the PVN, ventral medial hypothalamus (VMH), periaqueductal gray (PAG), intercollicular nucleus (ICo), and ventral tegmental area (VTA). We also observed punctate OT‐ir fibers in the song control nucleus HVC. In both male and female canaries, OT‐ir fibers were present in the lateral septum (LS), but innervation was greater in males. We did not observe this sex difference in zebra finches. Much of the OT staining observed is consistent with general distributions within the vertebrate hypothalamus, indicating a possible conserved function. However, some extra‐hypothalamic distributions, such as perikarya in the mesopallium, may be specific to songbirds and play a role in song perception and production. The presence of OT‐ir fibers in HVC and song control nuclei projecting dopaminergic regions provides anatomical evidence in support of the idea that OT can influence singing behavior—either directly via HVC or indirectly via the PAG, VTA, or POA.

Medullary kappa-opioid receptor neurons inhibit pain and itch through a descending circuit.

In perilous and stressful situations, the ability to suppress pain can be critical for survival. The rostral ventromedial medulla contains neurons that robustly inhibit nocioception at the level of the spinal cord through a top-down modulatory pathway. Although much is known about the role of the rostral ventromedial medulla in the inhibition of pain, the precise ability to directly manipulate pain-inhibitory neurons in the rostral ventromedial medulla has never been achieved. We now expose a cellular circuit that inhibits nocioception and itch in mice. Through a combination of molecular, tracing and behavioural approaches, we found that rostral ventromedial medulla neurons containing the kappa-opioid receptor inhibit itch and nocioception. With chemogenetic inhibition, we uncovered that these neurons are required for stress-induced analgesia. Using intersectional chemogenetic and pharmacological approaches, we determined that rostral ventromedial medulla kappa-opioid receptor neurons inhibit nocioception and itch through a descending circuit. Lastly, we identified a dynorphinergic pathway arising from the periaqueductal grey that modulates nociception within the rostral ventromedial medulla. These discoveries highlight a distinct population of rostral ventromedial medulla neurons capable of broadly and robustly inhibiting itch and nocioception.

Whole-brain mapping of efferent projections of the anterior cingulate cortex in adult male mice.

The anterior cingulate cortex (ACC) is a key cortical region that plays an important role in pain perception and emotional functions. Previous studies of the ACC projections have been collected primarily from monkeys, rabbits and rats. Due to technological advances, such as gene manipulation, recent progress has been made in our understanding of the molecular and cellular mechanisms of the ACC-related chronic pain and emotion is mainly obtained from adult mice. Few anatomic studies have examined the whole-brain projections of the ACC in adult mice. In the present study, we examined the continuous axonal outputs of the ACC in the whole brain of adult male mice. We used the virus anterograde tracing technique and an ultrahigh-speed imaging method of Volumetric Imaging with Synchronized on-the-fly-scan and Readout (VISoR). We created a three-dimensional (3D) reconstruction of mouse brains. We found that the ACC projected ipsilaterally primarily to the caudate putamen (CPu), ventral thalamic nucleus, zona incerta (ZI), periaqueductal gray (PAG), superior colliculus (SC), interpolar spinal trigeminal nucleus (Sp5I), and dorsal medullary reticular nucleus (MdD). The ACC also projected to contralateral brain regions, including the ACC, reuniens thalamic nucleus (Re), PAG, Sp5I, and MdD. Our results provide a whole-brain mapping of efferent projections from the ACC in adult male mice, and these findings are critical for future studies of the molecular and synaptic mechanisms of the ACC and its related network in mouse models of brain diseases.

Tonic pain alters functional connectivity of the descending pain modulatory network involving amygdala, periaqueductal gray, parabrachial nucleus and anterior cingulate cortex

IntroductionResting state functional connectivity (FC) is widely used to assess functional brain alterations in patients with chronic pain. However, reports of FC accompanying tonic pain in pain-free persons are rare. A network we term the Descending Pain Modulatory Network (DPMN) is implicated in healthy and pathologic pain modulation. Here, we evaluate the effect of tonic pain on FC of specific nodes of this network: anterior cingulate cortex (ACC), amygdala (AMYG), periaqueductal gray (PAG), and parabrachial nuclei (PBN). MethodsIn 50 pain-free participants (30F), we induced tonic pain using a capsaicin-heat pain model. functional MRI measured resting BOLD signal during pain-free rest with a 32 °C thermode and then tonic pain where participants experienced a previously warm temperature combined with capsaicin. We evaluated FC from ACC, AMYG, PAG, and PBN with correlation of self-report pain intensity during both states. We hypothesized tonic pain would diminish FC dyads within the DPMN. ResultsOf all hypothesized FC dyads, only PAG and subgenual ACC was weakly altered during pain (F = 3.34; p = 0.074; pain-free>pain d = 0.25). After pain induction sACC-PAG FC became positively correlated with pain intensity (R = 0.38; t = 2.81; p = 0.007). Right PBN-PAG FC during pain-free rest positively correlated with subsequently experienced pain (R = 0.44; t = 3.43; p = 0.001). During pain, this connection's FC was diminished (paired t=-3.17; p = 0.0026). In whole-brain analyses, during pain-free rest, FC between left AMYG and right superior parietal lobule and caudate nucleus were positively correlated with subsequent pain. During pain, FC between left AMYG and right inferior temporal gyrus negatively correlated with pain. Subsequent pain positively correlated with right AMYG FC with right claustrum; right primary visual cortex and right temporo-occipitoparietal junction ConclusionWe demonstrate sACC-PAG tonic pain FC positively correlates with experienced pain and resting right PBN-PAG FC correlates with subsequent pain and is diminished during tonic pain. Finally, we reveal PAG- and right AMYG-anchored networks which correlate with subsequently experienced pain intensity. Our findings suggest specific connectivity patterns within the DPMN at rest are associated with subsequently experienced pain and modulated by tonic pain. These nodes and their functional modulation may reveal new therapeutic targets for neuromodulation or biomarkers to guide interventions.

Increased Periaqueductal Gray Activation and Pain Unpleasantness in People with Alzheimer's Disease

Pain continues to be underrecognized and undertreated in people with Alzheimer's disease (AD). The periaqueductal gray (PAG) is essential to pain processing and modulation yet is damaged by AD. Evidence exists of altered neural processing of pain in AD, but there has not been a focused investigation of the PAG during pain in people with AD. This study aimed to investigate the role of the PAG in sensory and affective pain processing for people living with AD. Participants from a larger study completed psychophysics and then a perceptually matched heat pain task (warmth, mild, and moderate pain) during a functional MRI scan. In this cross-sectional study, we examined BOLD responses in the PAG and other pain-related regions in participants with AD (n=18) and cognitively intact older adults (age- and sex-matched, n=18) with SPM12. Associations of Percent Signal Change and psychophysics were also examined. There were significant main effects of AD status on the temperature need to reach each perception of warmth or pain. Furthermore, participants with AD rated mild and moderate pain as more unpleasant than controls. PAG BOLD activation was greater in AD relative to controls during warmth and mild pain percepts. No significant differences were found for moderate pain or in other regions of interest. Greater PAG activation during mild pain was associated with higher affective/unpleasantness ratings of mild pain in people with AD but not in controls. Results suggest a role for the PAG in altered pain responses in people with AD. The PAG is the primary source of endogenous opioid pain inhibition in the neuroaxis, thus, altered PAG function in AD suggests possible changes in descending pain inhibitory circuits. Therefore, people with AD may have a greater risk of suffering from pain compared to cognitively intact older adults. Grant support from NIH National Institute on Aging grants of co-author Monroe include K23AG046379 and R21AG045735.

MP07-18 IDENTIFICATION OF THE MAJOR NADPH OXIDASE SUBTYPE IN THE MICTURITION CENTRE – PATHOLOGICAL IMPLICATIONS

You have accessJournal of UrologyCME1 May 2022MP07-18 IDENTIFICATION OF THE MAJOR NADPH OXIDASE SUBTYPE IN THE MICTURITION CENTRE – PATHOLOGICAL IMPLICATIONS Qin Wu, Ayse Gurpinar, Patrizia Camelliti, Maxwell Roberts, Michael Ruggieri, and Changhao Wu Qin WuQin Wu More articles by this author , Ayse GurpinarAyse Gurpinar More articles by this author , Patrizia CamellitiPatrizia Camelliti More articles by this author , Maxwell RobertsMaxwell Roberts More articles by this author , Michael RuggieriMichael Ruggieri More articles by this author , and Changhao WuChanghao Wu More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000002529.18AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: Oxidative inflammatory damage to the brain may lead to dysfunction of peripheral organs including bladder disorders. However, the source of reactive oxygen species (ROS) in specific brain regions that regulate the function of peripheral systems is poorly understood. Of all ROS-generating enzymes, the NADPH oxidase (Nox) family produces ROS as its sole function and offers an advantage over other enzymes as a drug targetable molecule to selectively control excessive ROS. Our pilot study demonstrated such system in the bladder. This study tested the hypothesis that the major Nox subtype, Nox 2 is expressed in the micturition regulatory regions - Pontine micturition centre (PMC) and periaqueductal gray (PAG), and such system is able to produce substantial superoxide. METHODS: Male adult C57BL/6J mice (2-5 months) were used. PAG, PMC were dissected according to a mouse stereotaxic atlas. Cardiac and bladder tissues were isolated under microscopic guidance. Western blot determined Nox 2 expression using Nox 2 primary antibody and Infra-red dye-conjugated secondary antibodies. Lucigenin enhanced chemiluminescence quantified real-time superoxide production in live tissues, verified by the superoxide scavenger Tiron. Paired and non-paired t-test tested the difference in two group means and ANOVA with pairwise comparisons tested multiple means. RESULTS: Western blot experiments demonstrated the presence of Nox 2 in PAG and PMC tissues, with a density comparable to that of positive control (n=6). There was a significant level of NADPH dependent superoxide production in both brain tissues (RLU/mg, PMC: 127±17; PAG102±13, N=11, higher than that from cardiac tissue (32±3, P<0.01); similar to that from bladder smooth muscle (91±19, p>0.05) and lower than that in bladder mucosa (262±55, p<0.01). The time course analysis shows that the rise of superoxide production in these two brain tissues was more sustained than in bladder mucosa and smooth muscle (Half peak duration PD50, minutes: PMC, 101±2; PAG, 99±2; bladder mucosa, 48±3, p<0.01; smooth muscle, 67±9, p<0.01). The superoxide generation from these brain tissues was significantly suppressed by the Nox inhibitor diphenyleneiodonium (DPI). CONCLUSIONS: These data provide the first evidence for the presence of Nox 2 in brain micturition centres and its high capacity to produce superoxide. The study has also identified the sustained nature of the superoxide rise from this ROS-generating pathway. The predominance of this system and its characteristics revealed by this study provide mechanistic basis for the pathology of aging and inflammation associated neurogenic bladder disorders. Source of Funding: BBSRC (BB/P004695/1)NIA (NIA1R01AG049321-01A1)QW: Jiangsu Overseas Visiting Scholar Program for University Prominent Young and Middle-aged Teachers and Presidents © 2022 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 207Issue Supplement 5May 2022Page: e122 Advertisement Copyright & Permissions© 2022 by American Urological Association Education and Research, Inc.MetricsAuthor Information Qin Wu More articles by this author Ayse Gurpinar More articles by this author Patrizia Camelliti More articles by this author Maxwell Roberts More articles by this author Michael Ruggieri More articles by this author Changhao Wu More articles by this author Expand All Advertisement PDF DownloadLoading ...

Conditioned pain modulation is associated with heightened connectivity between the periaqueductal grey and cortical regions.

Conditioned pain modulation (CPM) is a psychophysical assessment used to estimate the efficiency of an individual's endogenous modulatory mechanisms. Conditioned pain modulation has been used as a predictive assessment for the development of chronic pain and responses to pain interventions. Although much is known about the spinal cord mechanisms associated with descending pain modulation, less is known about the contribution of supraspinal and especially cortical regions. We aimed to explore how whole-brain connectivity of a core modulatory region, the periaqueductal grey (PAG), is associated with conditioned pain modulation, and endogenous pain modulation more broadly. We measured CPM and resting-state connectivity of 35 healthy volunteers, absent of chronic pain diagnoses. As a region of interest, we targeted the PAG, which is directly involved in endogenous modulation of input to the spinal cord and is a key node within the descending pain modulation network. We found that CPM was associated with heightened connectivity between the PAG and key regions associated with pain processing and inhibition, such as the primary and secondary somatosensory cortices, as well as the motor, premotor, and dorsolateral prefrontal cortices. These findings are consistent with connectivity findings in other resting-state and event-related fMRI studies. These findings indicate that individuals who are efficient modulators have greater functional connectivity between the PAG and regions involved in processing pain. The heightened connectivity of these regions may contribute to the beneficial outcomes in clinical pain management, as quantified by CPM. These results may function as brain-based biomarkers for vulnerability or resilience to pain.

TRPV1-Expressing Sensory Neuron Stimulation-based Model of Inflammatory Injury Enhances the Excitability of Spinal Neurons Targeting the Periaqueductal Gray

Modeling inflammatory injury via high-intensity stimulation of peripheral afferents at low frequencies (LFS) potentiates excitatory input onto spinal neurons projecting (PNs) to the midbrain periaqueductal gray (PAG), a region critical to pain processing. Therefore, we sought to identify the underlying afferent population driving this potentiation and how this enhanced synaptic drive might affect spino-PAG PN output to supraspinal pain circuits. We used 3–6-week-old male and female mice expressing Cre recombinase driven by expression of the TRPV1 gene, which is expressed in the lineage of virtually all C fibers, and Cre-dependent channelrhodopsin to stimulate C fibers. Spinal PNs were retrogradely labeled from the PAG using diI. We performed whole-cell patch-clamp recordings in spino-PAG PNs using a semi-intact spinal cord preparation. Stimulation of TRPV1-expressing (TRPV1+) peripheral afferents induced burst firing in virtually all spino-PAG PNs sampled. Inflammation increases the firing rates of C fibers to 1-2 Hz; therefore, we used LFS (1 ms, 470 nm LED pulses at 2 Hz for 2 mins) to model inflammatory injury. LFS induced a persistent (≥20 min) increase in the number of action potentials (APs) within a C fiber-induced burst (n=10, p=0.029), rise in the frequency of synaptically evoked after discharge (n=10, p=0.0004), and decrease in intraburst afterhyperpolarization (n=10, p=0.037). Furthermore, LFS induced a transient membrane depolarization (Mean=6.796 mV, n=12, p<0.0001). Additional experiments suggested the enhanced synaptic excitability relied on postsynaptic G protein-coupled signaling, NMDA receptors, and TRPV1+ afferent input. Finally, LFS may increase the intrinsic excitability of spino-PAG PNs—by decreasing AP threshold (n=14, p=0.015) and increasing membrane resistance (n=14, p=0.0003). LFS had no effect on the membrane potential nor the firing frequency of spino-PAG PNs. In summary, this work suggests that LFS of TRPV1+ fibers persistently enhances spino-PAG projection neuron output, likely leading to a lasting increase in the activation of PAG neural circuits. Grant support from F32NS123008 NINDS; Brewer, C. B. T32DA035165 NIDA; Mackey, S. C. R01DA011289 NIDA; Kauer, J. A.

Histochemical Characterization of the Dorsal Raphe-Periaqueductal Grey Dopamine Transporter Neurons Projecting to the Extended Amygdala.

The dorsal raphe (DR) nucleus contains many tyrosine hydroxylase (TH)-positive neurons which are regarded as dopaminergic (DA) neurons. These DA neurons in the DR and periaqueductal gray (PAG) region (DADR-PAG neurons) are a subgroup of the A10 cluster, which is known to be heterogeneous. This DA population projects to the central nucleus of the amygdala (CeA) and the bed nucleus of the stria terminalis (BNST) and has been reported to modulate various affective behaviors. To characterize, the histochemical features of DADR-PAG neurons projecting to the CeA and BNST in mice, the current study combined retrograde labeling with Fluoro-Gold (FG) and histological techniques, focusing on TH, dopamine transporter (DAT), vasoactive intestinal peptide (VIP), and vesicular glutamate transporter 2 (VGlut2). To identify putative DA neurons, DAT-Cre::Ai14 mice were used. It was observed that DATDR-PAG neurons consisted of the following two subpopulations: TH+/VIP– and TH–/VIP+ neurons. The DAT+/TH–/VIP+ subpopulation would be non-DA noncanonical DAT neurons. Anterograde labeling of DATDR-PAG neurons with AAV in DAT-Cre mice revealed that the fibers exclusively innervated the lateral part of the CeA and the oval nucleus of the BNST. Retrograde labeling with FG injections into the CeA or BNST revealed that the two subpopulations similarly innervated these regions. Furthermore, using VGlut2-Cre::Ai14 mice, it was turned out that the TH–/VIP+ subpopulations innervating both CeA and BNST were VGlut2-positive neurons. These two subpopulations of DATDR-PAG neurons, TH+/VIP– and TH–/VIP+, might differentially interfere with the extended amygdala, thereby modulating affective behaviors.