bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hypoxia Hits Below the Diaphragm: Effect of Acute Hypoxia on the Micturition Reflex
Authors: Catege Marianna , Solomon Irene C , Collins William F 
Published: November 2023

While changes in respiratory drive and associated respiratory motor function during acute hypoxia are well documented, the effect of acute hypoxia on non‐respiratory somatic or autonomic motor systems is less well studied. The goal of the present study is to characterize the effect of acute hypoxia on lower urinary tract (LUT) function with a specific focus on reflex micturition. In urethane‐anesthetized, spontaneously breathing adult female Sprague Dawley rats, bladder intravesical pressure and external urethral sphincter (EUS) EMG activity were recorded during continuous infusion of saline into the bladder to elicit reflex micturition events. The rate of saline infusion was adjusted to achieve a baseline bladder inter‐contraction interval (ICI) of approximately 4 minutes. After 30–40 minutes of baseline recording, rats were exposed to a single episode of sustained hypoxia (10–12% O2; balance N2) with a duration of 1.5, 5 or 15 minutes followed by return to room air. The episodes of hypoxia were initiated approximately midway during bladder filling and consistently produced a premature reflex micturition event. During the 5‐ and 15‐minute episodes, the reduction in ICI continued for the duration of the hypoxia and was associated with a decrease in bladder pressure threshold (reduced intravesical pressure at the onset of active bladder contraction), particularly during 15‐minute exposures. No consistent change in EUS activity during hypoxia was observed. Following return to room air, the subsequent reflex micturition event was delayed, particularly after 5‐ and 15‐minute episodes of hypoxia, and the increase in ICI was associated with increases in both bladder pressure threshold and EUS activity during bladder filling (increased EUS guarding reflex). These data suggest that acute hypoxia alters LUT function and that both autonomic and somatic components of the micturition reflex are sensitive to hypoxia.Support or Funding InformationSupport for this project was provided by The Thomas Hartman Center for Parkinson's Research at Stony Brook University and The SUNY Brain Network of Excellence.
Becoming a couple: the developing relationship between respiratory oscillators of the American Bullfrog
Authors: Trask William M , Baghdadwala Mufaddal I , Wilson Richard JA 
Published: November 2023

Many vital mammalian behaviors, including locomotion, swallowing, and breathing, are dependent upon activity of, and coupling between, neural oscillators. In the mammal, multiple respiratory oscillators—chiefly the preBötzinger complex and parafacial respiratory group—are coordinated to generate muscular outputs driving inspiratory and expiratory activity. This multiple oscillator architecture, however, is not unique to mammals. Indeed, in the bullfrog, three spatially‐distinct burst generators driving different phases of the respiratory pattern have been identified, and at least two have oscillator‐like properties. Despite extensive study of these networks in both mammals and frogs, the mechanism and development of coupling between oscillators are not fully characterized.Over metamorphosis, the bullfrog transitions from water breathing in the tadpole to air breathing in the frog. Paralleling this shift in respiratory medium are radical changes to the underlying motor pattern produced by the brainstem, shifting from buccal ventilation in the tadpole to buccal and lung ventilation in the adult frog. To investigate the question of whether the bullfrog respiratory networks producing buccal and lung bursts ‘begin coupled’ (i.e., with tight synchronicity between oscillator rhythms upon the initial appearance of the lung pattern) or if this interaction arises over development, we employed the bullfrog isolated superfused brainstem preparation.We recorded burst‐triggered respiratory outputs in facial and hypoglossal rootlets from isolated brainstems from early tadpole to juvenile frog. By evaluating variance in the offset between the two primary rhythms, we established coupling coefficients to characterize the oscillators’ interactions. We found evidence to suggest that, in the tadpole, the rhythms of the gill‐ventilating and nascent lung oscillators are uncoupled. Over the course of metamorphosis, these rhythms become increasingly tightly coupled, paralleling the structural and behavioral changes in the animal. Specifically, coupling appears to reach adult levels in unison with the eruption of the forelimbs. Our results indicate that the expression of the lung oscillator is effectively knit into the larger respiratory network over metamorphosis. These findings further our understanding of amphibian respiratory development and may have implications for the origins of modern air‐breathing.Support or Funding InformationNational Science and Engineering Council of Canada (NSERC) and Alberta Innovates Health Solutions (AIHS) provided funding for this study
Role of GABA and Glycine in the Development of Respiratory Rhythmogenesis in the Embryonic Zebra Finch
Authors: Stein Paxton S. , Pickett Kaci L. , Vincen‐Brown Michael A. , Pilarski Jason Q. 
Published: November 2023

Primordial breathing‐related neural networks in the avian brainstem become active during the early embryonic period (day 4) but are not functional until embryonic day 12 (E12) when internal pipping occurs. At this time, birds, unlike mammals, employ active inspiration and expiration during each ventilatory cycle, but the extent to which GABA and glycine contribute to the cycle is still unknown. We aim to test the role of chloride‐mediated neurotransmission (NT) throughout this respiratory‐related development in ovo using the altricial Zebra Finch (T. guttata), which allows for unimpeded access to neural circuits during the entire embryonic period. We measured spontaneous rhythmic activity from cranial nerve IX (glossopharyngeal) between E4 and hatching (E14) in the presence and absence of the GABA/glycine antagonists bicuculline and strychnine using the in vitro brainstem spinal cord preparation. Results indicate that GABA/glycine NT is excitatory from E4 through E11. However, near E11, blocking GABA/glycine NT had little effect on the frequency of cranial nerve IX discharge but significantly increased burst area, which suggests an increase in phasic excitation of the glossopharyngeal motor nucleus.Support or Funding InformationIDeA Network of Biomedical Research Excellence (INBRE), NIH grant P20 PR016454NIH Academic Research Enhancement Award (AREA) Program, 1R15NS087521‐01A1
ATP Excitation of the PreBötzinger Complex and Inspiratory Neurons in vitro is Mediated in Part via a PLC/IP3‐mediated increase In [Ca2+]i
Authors: Zhang Yong , Gourine Alexander , Kasparov Sergey , Alvares Tucaaue , Funk Gregory 
Published: November 2023

The ventilatory response to hypoxia comprises an initial increase in ventilation followed by a secondary depression that can be life‐threatening in premature infants. ATP released within the ventral respiratory column, including the preBötzinger Complex (preBötC, critical site for inspiratory rhythm generation), during hypoxia attenuates this depression. Astrocytes sense hypoxia via a mitochondrial mechanism that involves mitochondrial depolarization, free radical production, lipid peroxidation, phospholipase C (PLC) and inositol trisphosphate (IP3) activation followed by an increase in intracellular Ca2+ and vesicular ATP release. Our working hypothesis is that ATP released from preBötC astrocytes during hypoxia acts in an autocrine/paracrine manner to enhance gliotransmission and also excites local inspiratory neurons directly via a P2Y1 receptor (R)‐dependent mechanism to increase inspiratory frequency (freq). Our first objective was to determine if the ATP excitation of inspiratory neurons includes an astrocytic glutamate component (i.e., do astrocytes release glutamate in response to P2Y1 receptor activation?). Using 700 μm rhythmically‐active medullary slices, we obtained whole‐cell recordings from preBötC inspiratory neurons and compared neuronal ATP (5 mM) currents evoked before and after bath application of glutamate R antagonists AP5 (100 μM) and CNQX (10 μM) (in 0.5 μM TTX). AP5 and CNQX had no effect on ATP currents (n=8). Our second objective was to identify the signaling pathways through which ATP excites the preBötC network and neurons. Simultaneous application of the PLC blocker U73122 (20 μM) to the bath (20 μM) and into the preBötC (10 μM) via pressure injection shortened the duration of MRS2365 (100 μM)‐evoked frequency increase but had no effect on the peak frequency (n=9). 2‐APB (100 μM), an IP3R inhibitor, reduced the ATP‐evoked freq increase from 232.14 ± 39% to 147 ± 12% (n=5). In contrast, intracellular dialysis of U73122 (2 μM, n=6) and 2‐APB (50 μM, n=4) attenuated ATP‐evoked inward currents in inspiratory neurons by 50 ± 7% and 42 ± 17%, respectively. Bath application of U73122 had no effect on the ATP‐induced inward current (n=4), suggesting that bath‐applied U73122 does not access the neurons. Intracellular dialysis of sarco/endoplasmic reticulum Ca2+‐ATPase (SERCA) blocker thapsigargin (4 μM, n=3) also attenuated the ATP‐induced inward currents in inspiratory neurons by 29.3 ± 1.03%. These data suggest that although the excitation of preBötC inspiratory neurons by ATP does not include a glial‐derived glutamatergic component, network excitation is brought about, at least in part, via activation in inspiratory neurons of a PLC, IP3 receptor‐mediated release of Ca2+ from intracellular stores.Support or Funding InformationSupported by CIHR, AIHS, CFI, WCHRI and ALA.
Acetylcholine combined with acetylcholinesterase blockade within the commissural nucleus of the solitary tract increases respiratory activity
Authors: Furuya Werner Issao , Bassi Mirian , Colombari Eduardo , Menani Jose Vanderlei , Zoccal Daniel Breseghello , de Almeida Colombari Débora Simões 
Published: November 2023

Acetylcholine (ACh) microinjections in the commissural nucleus of the solitary tract (cNTS) increase phrenic nerve (PN) burst frequency. However, the effects of the activation of cholinergic mechanisms in the cNTS on the activity of other motor respiratory outputs are still unknown. In the present study, we recorded the hypoglossal nerve (HN), cervical vagus nerve (cVN) and PN activities using decorticated arterially‐perfused in situ preparations of juvenile male Holtzman rats (70–90 g, n=8), and evaluated the effects elicited by microinjections of ACh in the cNTS, combined with prior physostigmine administration (PHY, acetylcholinesterase inhibitor) in the same area. Microinjections of ACh (10 mM, 60 nL) were performed 5 min after PHY (1 mM, 40–60 nL, 0.3 and 0.6 mm caudal to calamus scriptorius) in the cNTS and the changes in the respiratory motor activities were analyzed during 1 min following microinjections. The combination of PHY and ACh within the cNTS induced an initial (6 s after ACh) slight increase in the PN burst frequency (4.8 ± 1.9 vs. vehicle 2.9 ± 1.0%, p > 0.05) and amplitude (9.0 ± 1.8 vs. vehicle 2.7 ± 0.5%, p < 0.05). The amplitude of post‐inspiratory (post‐I) activity in the cVN (18.7 ± 3.8 vs. vehicle 3.5 ± 0.9%, p < 0.05) and the pre‐inspiratory period (pre‐I) of the HN (425 ± 46 vs. vehicle 100 ± 43 ms, p < 0.05) also increased. Sixty seconds after ACh microinjections, PN frequency decreased (−27.1 ± 0.4 vs. vehicle 2.4 ± 0.6 %, p < 0.05). On the other hand, PN amplitude (11.2 ± 0.5 vs. vehicle 3.4 ± 0.3%, p < 0.05), cVN post‐I amplitude (16.5 ± 0.9 vs. vehicle 1.9 ± 0.5%, p < 0.05) and the HN pre‐I period (436 ± 26 vs. vehicle 149 ± 57 ms, p < 0.05) were maintained. The data show that stimulation of cholinergic receptors in the cNTS promotes significant changes in different respiratory motor nerves that resemble the respiratory responses elicited by peripheral chemoreflex activation (early tachypnea followed by bradypnea, increase in the PN and cVN amplitude and increase in the pre‐I period of HN), which might suggest an involvement of cholinergic mechanisms in the cNTS on chemoreflex pathway.Support or Funding InformationFAPESP, CAPES and CNPq.
Cardiorespiratory Coupling is Dependent on a Conditionally Expressed Inspiratory Antecedent in the In Situ Rodent Preparation
Authors: Baekey David M 
Published: November 2023

The in situ rodent model was previously used to describe respiratory modulation of cardiovascular activities expressed in heart rate (RSA), sympathetic nerves (SNA), and vascular pressure. While this previous study implicated both medullary and pontine involvement, the neural substrate for this coordination remains undefined. Our hypothesized model assumes some direct connectivity within the medulla, wherein the respiratory central pattern generating (rCPG) nuclei influence more caudal premotor respiratory populations (VRG) and adjacent autonomic nuclei (RVLM/CVLM), but recent observations challenge the straightforwardness of this proposed network. A retrospective analysis of 37 preparations in which the phrenic nerve was recorded prior to the first reanimated breath revealed features suggesting involvement of a unique inspiratory neural population. To observe this coupling, juvenile rats are anaesthetized, subdiaphragmatically bisected, decerebrated, and submerged in ice cold artificial cerebrospinal fluid (aCSF) during surgical exposure of neural recording sites. Aortic cannulation and perfusion with aCSF warms the preparations and provides dissolved O2 and CO2 (95/5) while electrodes are placed to monitor respiratory and autonomic nerves. A gradual increase in perfusion flow results in respiratory efforts as noted by both visible contraction of the chest musculature prior to application of paralytic and bursting activity of respiratory efferents thereafter. Phrenic nerve activity (PNA) has a relatively consistent expression at 12–15 breaths per minute with no initial coordination of heart rate, modulation of SNA, or oscillations of perfusion pressure. As phrenic bursting continues, one of two patterns occurs: 1) a sudden transition to ramp patterned PNA with reduced Ti and increased Te (N=30), or 2) high amplitude, short duration phrenic bursts are interspersed amongst the stable baseline rhythm, eventually entraining and merging with the baseline pattern to form the ramping phrenic with reduced Ti and increased Te (N=7). The significance of both pattern changes is that they occur simultaneously with expression of RSA and respiratory modulation of vascular pressure. In the interspersed expression, cardiorespiratory coupling was limited to the short duration, high amplitude bursts. In summary, this suggests that cardiorespiratory coupling requires activation of a conditionally expressed neural population that is active during late inspiration. Given that cardio‐respiratory coupling is reduced with aging and decreased RSA is proposed as a predictor of mortality, identification and modulation of this “missing link” might provide a powerful therapeutic target in prevention of cardiovascular disease.Support or Funding InformationThis research was supported by a UF CVM Faculty Award.
Improvement in Cerebral Autoregulation During Recovery Phase Following Concussion is associated with Reduced Postural Sway: A Pilot Study
Authors: Maffuid Kaitlyn , Ryan Larry , Murphy Megan N , Davis Peter F , Purkayastha Sushmita 
Published: November 2023

ObjectivePostural instability has been reported in patients with concussion and this symptom may be related to compromised cerebral blood flow regulation as a result of the injury. The purpose of the study was to examine whether changes in cerebral autoregulation from acute injury phase to the recovery phase following a concussion were associated with changes in postural sway in collegiate athletes participating in high‐contact sports.MethodsFive NCAA Division I male athletes (21±2 years) with a confirmed sports‐related concussion were enrolled in the study. Data was collected on days 3 and 21 post‐concussion. Arterial blood pressure (ABP) was obtained with finger photoplethysmography. Middle cerebral artery blood velocity (MCAV) was collected using transcranial Doppler ultrasound for 12 minutes while subjects were seated upright. Dynamic cerebral autoregulation was estimated from transfer function analysis of beat‐to‐beat fluctuations in ABP and MCAV. Postural control was measured from the deviation in the center of pressure in both the mediolateral and anterioposterior directions during quiet standing on a force plate for 60 seconds. Four trials were randomized, two with eyes closed and two with eyes open. Multiple linear regression analyses were used to examine the association between changes in low frequency (LF, 0.07–0.2 Hz) transfer function phase and mediolateral range and variability of postural sway on days 3 and 21 post‐concussion.ResultsImprovement in LF transfer function phase from day 3 to day 21 post‐concussion was associated with reductions in mediolateral range (β estimate= −19, p=0.02) and variability (β estimate= −4.3, p=0.04) of postural sway with eyes closed.ConclusionCerebral blood flow regulation is associated with alterations in postural control and may be useful as a potential vascular biomarker for tracking recovery following concussion.Support or Funding InformationSupported by: University Research Council Grant at SMU, Dallas, Texas
Depletion of Brain Perivascular Macrophages Mitigates Depressive‐like Behavioral Consequences of Chronic Mild Stress
Authors: Grigoleit Jan‐Sebastian , Alvarez Elena , Farrokhi Catherine Borna , Sawchenko Paul E. 
Published: November 2023

Despite intensive research, the etiology of depression remains poorly understood. Stress is implicated in the pathogenesis of most depressive disorders, as reflected by the preponderance of animal models that employ chronic stress to induce depressive‐like behavior. There is increasing evidence for involvement of immune/inflammatory mechanisms in the genesis of depression, in part by mediating the effects of stress, with microglia and also macrophage‐type immune cells in the brain being implicated. Recent work from our laboratory has identified brain perivascular macrophages (PVM), not only as crucial mediators of inflammatory signaling from the periphery to the CNS, but as also involved in mediating the consequences of acute emotional stress on central neuroendocrine and inflammatory responses. The objective of the current pilot experiment was to evaluate the potential involvement of brain PVM in the induction of depressive‐like behaviors caused by chronic stress exposure. Adult male rats either remained untreated (n=6) or received an intracerebroventricular injection of mannosylated liposomes containing the pro‐apoptotic drug, clodronate (n=6), to exploit the constitutive phagocytic activity of PVM, leading to depletion of this cell type, but not microglia, throughout the brain within 3–5 d. Both groups were then subjected to 5 weeks of chronic mild stress (CMS), a well‐established protocol for the induction of depression through repeated and unpredictable exposure to a variety of mild insults. Anhedonic behavior, a key component of depression, was assessed by monitoring sucrose intake (provided as a 2% solution twice weekly before and during the CMS phase). Additional behavioral tests (open field/OF, elevated plus maze/EPM, Porsolt forced swim test/PFST) were used to assess further key components of depressive‐like behavior. All animals preferred sucrose strongly over normal drinking water. However, there was a significant drop in sucrose intake after 1 week of CMS in the control group, which was sustained for the duration of the experiment. No such effect was observed in the PVM‐depleted group. In addition, stressed control animals displayed a significant decrease in exploratory behavior in the EPM, remaining almost exclusively in the closed arms of the maze, an effect that was not observed in PVM‐depleted rats. In the PFST, which is often used to assess the potency of anti‐depressant drugs, PVM‐depleted rats tried significantly longer to escape from a water‐filled jar than animals from the control group. No differences in general locomotor activity (OF) were observed among groups at any time point. These findings support the hypothesis that brain PVMs are involved in depressive behaviors seen in a chronic mild stress model.Support or Funding InformationNIH grant NS21182, Clayton Medical Research Foundation, German Research Foundation (DFG) grant GR4370/1‐1, CONACyT Mexico
Differential Responses of Male and Female Microglia to LPS and Estrogen May Contribute to Sexually Dimorphic Effects of Inflammation on Phrenic Long‐term Facilitation
Authors: Gardner Alyssa N. , Dougherty Brendan J. , Watters Jyoti J 
Published: November 2023

Chronic intermittent hypoxia (CIH) is a hallmark of obstructive sleep apnea (OSA) that causes neuroinflammation, and acutely (1 night) impairs one form of respiratory motor plasticity, phrenic long‐term facilitation (pLTF). The prevalence of OSA is sexually dimorphic (higher in males) although this difference greatly decreases after menopause, suggesting that estrogen may play a role in protecting the respiratory system in females. Preliminary data suggest that impairment of pLTF by neuroinflammation induced by challenge with gram‐negative bacterial lipopolysaccharide (LPS; 0.1 mg/kg) may also be sexually dimorphic; LPS treatment abolished pLTF in gonadally intact males but not in females treated with estrogen. Although estrogen is well‐known to be anti‐inflammatory, little is known about its ability to control neuroinflammation as it impacts respiratory neuroplasticity. We tested the hypothesis that LPS‐induced neuroinflammation is higher in males, and that estrogen exerts sex‐specific effects on neuroinflammatory gene expression. To begin to test this hypothesis, primary microglia from P4‐P6 male and female rat pups were cultured separately and treated with LPS (100 ng/ml) in the presence and absence of 17β‐estradiol (E2; 1nM). Total RNA was isolated and gene arrays (SA Biosciences) were performed; individual gene changes were confirmed by qRT‐PCR. Whereas LPS increased the expression of multiple pro‐inflammatory cytokines and chemokines in microglia from both sexes, the effects were stronger in male microglia. E2 treatment alone strongly reduced basal pro‐inflammatory gene expression in female microglia, but had little effect in male microglia. E2 had generally similar effects on LPS‐induced gene expression in microglia from both sexes. These data suggest that male microglia have stronger pro‐inflammatory responses to LPS, and that reductions in basal levels of inflammatory genes by estrogen are greater in female microglia. Together, these mechanisms may contribute to higher levels of neuroinflammation in the male CNS following LPS, and to the corresponding sex differences in inflammation‐mediated impairment of pLTF. Results from this work will provide significant insight into mechanisms that can be exploited to minimize destabilization of respiratory plasticity by inflammation in both sexes.Support or Funding InformationSupported by R01 NS085226 and an OWHR supplement to R01 HL111598