bluuebunny/crossref_metadata_2025_split huggingface dataset:
Phrenic long‐term facilitation (pLTF) fluctuates over the estrous cycle and is abolished by ovariectomy in young female rats
Authors: Dougherty Brendan J. , Kopp Elizabeth S. , Watters Jyoti J. 
Published: November 2023

Circulating sex steroids modulate spinal plasticity, including phrenic long‐term facilitation (pLTF), a persistent increase in phrenic nerve activity observed after acute exposure to intermittent hypoxia (AIH; three 5 min episodes of 10.5% O2, delivered at 5 minute intervals). Previous studies indicate that young male rats require the conversion of testosterone to 17β‐estradiol (E2) to express pLTF, and pLTF is not present in estrus or diestrus (when circulating estradiol levels are low) in young female rats, suggesting that estrogen availability and signaling may underlie sexually dimorphic pLTF expression. In this study, we tested the hypothesis that pLTF would be enhanced in young female rats during proestrus when levels of circulating estrogen are high, and blunted during estrus when circulating estrogen levels are low. In addition, we hypothesized that ovarian function is specifically necessary for pLTF expression in young female rats. Phrenic nerve activity was recorded in anesthetized, paralyzed and ventilated female Sprague‐Dawley rats (3–4 mos) that were separated into the following experimental groups: ovarian intact females in estrus or proestrus, and ovariectomized (OVX) females that received daily vehicle (sesame oil) or E2 (17β‐estradiol benzoate, 100 μg/kg, i.p.) supplementation for 7 days. Initial results confirmed that females in proestrus exhibited significantly higher pLTF compared to females in estrus, and that removal of the ovaries abolished pLTF in young female rats. These data suggest that pLTF expression varies over the estrous cycle in a manner proportional to circulating E2 levels. To test the sufficiency of E2 to restore pLTF to ovariectomized females, E2 replacement studies are currently underway. Together, these data suggest that ovarian hormones exert important effects on respiratory motor plasticity, and underscore the utility of this model to dissect the role of E2 signaling in the sexually dimorphic expression of spinal neuroplasticity.Support or Funding InformationThis work was supported by R01 NS085226 and an OWHR supplement to NIH R01 HL111598.
Increased Probability of Release in Huntington's Disease Neuromuscular Junctions
Authors: Khedraki Ahmad , Reed Eric Joshua , Rich Mark M. , Voss Andrew Alvin 
Published: November 2023

Huntington's disease (HD) is a progressive and fatal degenerative disorder that results in debilitating cognitive and motor dysfunction. The majority of research related to HD has been focused on neurodegeneration in the central nervous system. Recently, we discovered defects in the membrane properties and mRNA processing of skeletal muscle from the R6/2 transgenic mouse line of HD. The decrease in the resting chloride and potassium conductance result in hyperexcitable skeletal muscle that is hypersensitive to neuronal stimulation. The objective of this study was to examine the neuromuscular events that trigger muscle excitation. We used a fully innervated ex vivo preparation of the levator auris longus muscle from late‐stage R6/2 mice and age‐matched wild type controls. Our voltage clamp records of spontaneous miniature endplate currents (mEPCs) and nerve‐evoked endplate currents (eEPCs) were independent of the changes in muscle membrane properties, unlike previous current clamp studies. Using the charge moved during the mEPCs and eEPCs, preliminary data indicates that the number of vesicles released per action potential (quantal content) was not significantly different between HD and WT muscle. This argues against denervation/renervation, which has been suggested in other studies. Furthermore, in response to trains of nerve stimulation (10 action potentials at 50 Hz), eEPCs in HD muscle reached a peak amplitude sooner and then depressed to a greater degree than in WT. This amplified depression suggests an increased probability of vesicle release in HD neuromuscular junctions. This hypothesis was supported by data obtained under low Ca2+ and high Mg2+ extracellular conditions, where quantal content in HD is higher than in WT. Because studies of central synapses face more experimental limitations, our voltage clamp examination of neuromuscular transmission is hitherto the most complete analysis of synaptic function in HD. The defects we discovered serve as a model to understand the contribution of synaptic defects to the devastating cognitive and motor symptoms in Huntington's disease.Support or Funding InformationWright State University Startup to AAV.
Tolerance to Alcohol‐Stimulated Glutamate Receptor Phosphorylation in the Central Amygdala and Prefrontal Cortex after Chronic Nicotine Exposure
Authors: McGinn Mary Adrienne , Itoga Christy A , Paulsen Rod I , Reppel Jonathan E , Farooq Muhammad A , Gilpin Nicholas W , Edwards Scott 
Published: November 2023

Nicotine and alcohol are two of the most commonly abused substances. Nicotine use increases alcohol drinking, suggesting that the combination of these drugs may produce synergistic effects in activating reward circuitry. Alternatively, use of either of these drugs may facilitate the development of cross‐tolerance to the other to promote intake escalation. Mechanisms underlying these interactions are largely unknown, and there is little information on neuronal signaling events that occur in animals exposed to both drugs. In the present experiment, adult male Wistar rats were exposed to room air (non‐dependent group) or intermittent nicotine vapor (nicotine‐dependent group) for 12 hours per day (resulting in 12 hours of withdrawal per day) for three weeks. This treatment regimen has been shown to produce symptoms of nicotine dependence as evidenced by hyperalgesia and elevated nicotine self‐administration during withdrawal. On the final day of nicotine exposure, at 10 hours of withdrawal, animals were challenged with either saline or alcohol (1 g/kg, IP) and euthanized 15 minutes later. Brains were snap frozen and dissected for processing via Western analysis. We examined changes in the phosphorylation status of glutamate receptor subunits in stress‐ and reward‐related brain regions since excitatory neuroadaptations are heavily implicated in both alcohol and nicotine addiction. We discovered differential alterations in glutamate receptor subunit phosphorylation following nicotine withdrawal and alcohol challenge. For example, alcohol significantly increased PKA phosphorylation of GluR1 (a subunit of the AMPA receptor) across multiple brain regions, including the hippocampus, dorsomedial prefrontal cortex (dmPFC), and central amygdala (CeA). However, this neuroadaptation was largely absent in the dmPFC and CeA in animals exposed to chronic intermittent nicotine vapor (significant interaction between alcohol challenge and nicotine exposure). These data suggest a molecular tolerance to alcohol‐stimulated phosphorylation of GluR1 (a subunit of the AMPA receptor) in these regions in the context of nicotine dependence. As a consequence, more alcohol may be required to influence glutamatergic plasticity in the nicotine‐dependent state, and this may in part mediate increased drinking in heavy smokers.Support or Funding InformationOur research is supported by the following grants from the National Institute on Alcohol Abuse and Alcoholism: R01AA023305 (NWG) R00AA020839 (SE) T32AA007577 (MAM)
Kv4.2/4.3 Channels in the Hypothalamic PVN Contribute to Sympathetic Activation in Angiotensin II‐Salt Hypertension
Authors: Toney Glenn M , Andrade MaryAnn 
Published: November 2023

Recent studies in mice implicate increased NMDA receptor expression and function in the PVN in development of the slow pressor model of angiotensin II (AngII) hypertension. Here, we studied adult male rats with AngII‐salt hypertension. Rat were placed on a high salt (2% NaCl) diet for 6 weeks with systemic AngII treatment (150 ng/kg/min, s.c.) for the final 2 weeks. Consistent with studies in mice, we found that responsiveness to PVN NMDA was increased in hypertensive rats as was PVN NMDA receptor tonus. Previous studies of rats with reno‐vascular hypertension reported increased excitability of pre‐sympathetic PVN neurons accompanied by diminution of the transient potassium A‐current. In the PVN, Kv4.2/4.3 channels are major mediators of A‐current, but the present studies revealed that acute and selective blockade of these channels with phrixotoxin (5 pmol in 50 nl) had no effect on resting MAP, RSNA or SSNA in anesthetized normotensive or AngII‐salt hypertensive rats – suggesting that A‐current is not a significant determinant of in vivo spike probability among PVN pre‐sympathetic neurons of either group. However, phrixotoxin did enhance pressor and sympatho‐excitatory response to PVN injections of NMDA (200 nmol in 50 nl) in normotensive rats (P<0.05 – 0.01), while failing to do so in hypertensive rats. These findings suggest several alternative explanation for A‐current function in the PVN. Most parsimoniously, Vm of pre‐sympathetic neurons could be sufficiently hyperpolarized and discharge sufficiently sparse under normal conditions that A‐current is maintained at a relatively low level of steady state inactivation, allowing it to actively attenuate spiking induced by activation of glutamatergic input (NMDA). By contrast, Vm depolarization and more frequent spiking of neurons in rats with AngII‐salt hypertension could prevent hyperpolarization‐induced de‐inactivation of A‐current and thereby increase steady‐state inactivation such that A‐current mediated by Kv4.2/4.3 channels cannot effectively oppose spiking. The latter is consistent with lack of enhancement of responses to PVN NMDA by phrixotoxin in hypertensive rats. The above model of diminished PVN A‐current contribution to AngII‐salt hypertension requires further study to assess whether diminished Kv4.2/4.3 channel expression and ongoing covalent modulation of channel gating might also contribute to PVN activation and heightened PVN support of sympathetic activity in AngII‐salt hypertension.Support or Funding InformationHL102310 & HL088052 (GMT)
Neuronal specific Caveolin‐1 overexpression enhances dendritic growth and arborization in differentiated human neuronal stem cells derived from induced pluripotent stem cells
Authors: Zhang Zheng , Almenar‐Queralt Angels , Roth David M. , Patel Hemal H. , Head Brian P. 
Published: November 2023

IntroductionNeuroplasticity is evoked by extracellular signals that bind receptors in the plasma membrane to induce signal transduction that results in polarized actions in the neuronal plasma membrane. Membrane/lipid rafts (MLR) and cholesterol binding protein caveolin‐1 (Cav‐1) provide a signaling membrane platform that tethers and regulates cytoskeletal components necessary for proper dendritic growth, maintenance and neuroplasticity. Our lab has demonstrated in rodents primary neurons that overexpression of neuronal cav‐1 enhances pro‐growth/pro‐survival signaling, and improves dendritic growth and arborization. We utilized neurons derived from human induced pluripotent stem cells (iPSCs) to ask whether Cav‐1 controls similar signaling and functions in human neurons as it does in rodent neurons. We overexpressed Cav‐1 driven by the neuronal specific synapsin promoter (SynCav1) and evaluated changes in dendritic morphology after the differentiation process.MethodsiPSC derived neuronal stem cells (NSCs) were cultured in DMEM/F12+Gluamax media with N‐2 supplement, B‐27 supplement, Pen/Strep, and basic Fibroblast Growth Factor (bFGF). Neuronal differentiation was started by bFGF withdrawal from media. NSCs were transfected with either SynCav1 or SynGFP as control when differentiation was started. Cells were fixed 3 weeks after differentiation and stained for Cav‐1, the dendritic marker microtubule‐associated protein 2 (MAP2), and the axonal marker neurofilament (SMI‐31). Dendritic length, branching (arborization), area, and volume were measured by Autoneuron (MBF Bioscience), a tracing algorithm that measures 3D image volume stacks. Cells were also collected and homogenized to measure Cav‐1 levels via western blots.ResultsWestern blots showed that Cav‐1 was increased in the cells transfected with SynCav‐1 compared to SynGFP 3 weeks after differentiation. Compared with SynGFP, SynCav1 transfection significantly enhanced dendritic length (p=0.002), branching points/arborization (p=0.0004), dendrite area (p=0.003), and dendrite volume (p=0.009)ConclusionNeuron‐targeted expression of Cav‐1 significantly enhanced dendritic growth of human iPSC‐derived neurons suggesting the presence of efficient Cav‐1 dependent signaling in these cells.
Gender Differences in the Association of Neutrophil Gelatinase‐Associated Lipocalin with Cognitive Impairment and Depression in Heart Failure
Authors: Schoemaker Regien G , Gouweleeuw Leonie , Hovens Iris B , Liu Hui , Naude Pieter JW , Eisel Uli ML 
Published: November 2023

IntroductionHeart failure increases the risk to develop depression, which worsens prognosis. Depression is more common in women than in men. Neutrophil Gelatinase‐Associated Lipocalin (NGAL), a regulator of inflammation and indicator of prognosis in heart failure patients, is also associated with depression. The aim of this study was to investigate the association of NGAL with behavior in both male and female rats with heart failure.MethodsMale and female Wistar rats were subjected to coronary artery ligation (MI) or sham surgery. Three weeks later, depressive symptoms were obtained from the open field test (OF) and cognitive functioning from the novel object and novel location test. Plasma levels of NGAL were measured with Elisa, and NGAL expression in the brain was obtained using immunohistochemistry.ResultsIn males, but not in females, plasma NGAL appeared correlated to infarct size. We found both a gender (F=6.53, p=0.005) and an MI (F=6.63, p=0.013) effect in plasma NGAL levels, with higher levels in male compared to female rats and MI compared to sham rats. An MI effect (F=4.19, p=0.049) and interaction effect (F=7.87, p=0.09) were found in the number of NGAL positive cells in the paraventricular nucleus of the hypothalamus (PVN), post‐hoc analysis showed that NGAL was elevated only in male rats upon MI. Spatial object recognition was impaired in male MI compared to sham rats (discrimination index 54.3% vs 78.3%, p<0.01). No significant effect of MI was seen in the OF. In male rats, plasma NGAL showed a negative correlation with distance in the OF (r=−0.384, p=0.044) and discrimination index of the moved object in the novel location test (r=−0.570, p=0.033). Additionally, PVN NGAL negatively correlated to distance spent in the OF in male rats (r=0.464, p=0.039). In female rats no behavioral changes were seen after MI and NGAL did not correlate with behavioral outcomes.DiscussionData indicate gender specific effects of MI on the expression of NGAL and on behavior. This suggests that post‐MI inflammatory processes and their potential effects on depressive‐like behavior and cognition, may be differently regulated in male and female rats.
Altered Microglia Morphology in The Hypothalamus after Myocardial Infarction in Mice
Authors: Schoemaker Regien G , Gouweleeuw Leonie , Wajant Harald , Maier Olaf , Eisel Uli ML 
Published: November 2023

BackgroundMyocardial infarction (MI) evokes an inflammatory response that may present itself in the brain as neuroinflammation in the paraventricular nucleus of the hypothalamus (PVN), which may contribute to the elevated sympathetic nerve activity found in heart failure. Since increased expression of TNF‐alpha has been implicated in neuroinflammation, we investigated whether interference with TNF‐alpha signaling could affect neuroinflammation after MI by affecting the brain immune cells; microglia.MethodsMale 12‐week old C57bl/6 mice underwent coronary artery ligation or sham surgery. MI mice were treated with either saline, the TNF‐inhibitor etanercept, a TNF‐R1 antagonist or a TNF‐R2 agonist, starting 60 minutes after MI. Sham mice received saline injections. Mice were sacrificed 18 days later and the dorsal hippocampus and PVN were stained with an anti‐Iba1 antibody to visualize microglia. Changes in microglia were obtained from cell density, total coverage, and activity. The latter is based on morphology and calculated as the ratio of cell body/total cell size.ResultsWhereas in the hippocampus no differences in the number, cell size or cell body/cell size ratio were observed between groups, in the PVN a significant decrease in the number of microglia in the MI+TNF‐R2 agonist group was found compared to sham (16.1 ± 1.6 vs 27.4 ± 7.5, p<0.05). The cell body/cell size ratio was significantly decreased in all MI groups compared to sham (4.3 ± 1.5 – 5.5 ± 0.8 vs 8.0 ± 0.7%, p<0.05), which could be attributed to an increase in dendrite size, since cell body size did not differ between groups.ConclusionIn conclusion, interference with TNF‐alpha signaling after MI in mice resulted in area‐specific changes in microglia, with TNF‐R2 agonist treatment resulting in a lower number of microglia in the PVN. Morphological analysis suggests hyperramification of microglia in the PVN after MI. This might indicate a polarization towards type M2 microglia, associated with protective functions; though to be confirmed with specific markers.
Association of Impaired Hypoxia‐Inducible Factor‐1 Transcriptional Activity with Severer Brain Injury in Aged Rats in Comparison with Young Rats after Acute Ischemic Stroke
Authors: Guo Yingjia , Li Xianglong , Han Pengfei , Xiao Ying , Zhu Ping , Gou Zhaoyu , Kang Y. James 
Published: November 2023

Aged mammals in comparison with young suffer severer damage post ischemic stroke, and hypoxia‐inducible factor‐1 (HIF‐1) activation is neuroprotective in ischemic stroke. The present study was undertaken to investigate whether there is a difference in HIF‐1 between aged and young rats and its association with the degree in brain damage post ischemic stroke. Aged (18–20 months) and young (3–4 months) male Sprague‐Dawley rats were subjected to transient middle cerebral artery occlusion (MCAO) for 60‐min, followed by reperfusion for 3, 7, 14, or 21 days. There was no significant difference in the infarct volume in the brain between aged and young rats 3 days after MCAO, but the infarct volume in the aged was significantly larger than in the young animals 21 days after MCAO. The overall survival rate in the aged was significantly lower than in the young rats. In addition, delayed body weight gain, retarded neurobehavioral recovery, and depressed angiogenesis were observed in the aged rats compared to the young at 3, 7, and 21 days after MCAO. There was no significant difference in the protein levels of HIF‐1 accumulated in the ischemic area between the aged and the young rats at 3 days after MCAO, however, the HIF‐1 transcriptional activity was significantly suppressed, along with increased apoptotic cell death, in the aged rats. Furthermore, the levels of mRNAs involved in modulating HIF‐1α stabilization and HIF‐1 target genes were dramatically different between aged and young rats. These findings thus revealed the association of impaired HIF‐1 transcriptional activity with the delayed neurobehavioral recovery after focal ischemic stroke in aged rats.Support or Funding InformationThe National Basic Research Program of China (973 Program Grant no. 2013CB530702).
Persistent Memory Deficits and Histone Modification after a Systemic Inflammatory Event
Authors: Collette Katie , Donzis Elissa , Tronson Natalie C 
Published: November 2023

Inflammatory events, including myocardial infarction (MI), illness, or major surgery, commonly lead to cognitive deficits that persist for months or years, far beyond the duration of inflammation. The cognitive deficits correlate with poorer outcomes as well as increased morbidity and mortality. These clinical observations are paralleled in animal models of MI and inflammation. However, the mechanisms mediating such persistent effects remain unknown. Epigenetic modifications induced by cytokine signaling are one potential mechanism. In particular, dysregulation of histone acetylation can be triggered by inflammation and also induce memory deficits. We hypothesized that, although the initial cytokine signaling would be resolved within 8 weeks after MI, changes in histone modifications would persist and mediate lasting cognitive impairments.MethodsWe used a surgical model of MI in male and female mice, with sham‐operated (sham) and non‐operated (non‐op) control groups. Eight weeks after the MI group's surgery, memory was assessed using context fear conditioning (3 min exposure to context followed by a single 0.8mA, 2sec foot shock). In separate animals, hippocampus and blood serum were collected 8 weeks after MI. We used multiplex cytokine analysis to determine levels in the hippocampus. In addition, we conducted western blotting to determine persistent alterations in histone acetylation, phospho‐acetylation and methylation. Finally, we analyzed hearts from MI and sham animals to determine infarct size.Results and DiscussionEight weeks after MI surgery, both male and female mice exhibited impairments in fear conditioning compared with non‐op control animals. In addition, female ‐ but not male ‐ sham mice exhibited deficits in context fear conditioning. This suggests that female mice are more susceptible to persistent memory deficits even after a lower level inflammatory event. There were no differences in peripheral or hippocampal cytokine levels 8 wks post‐MI; therefore, the cognitive deficits were not due to ongoing inflammatory signaling. Future work will determine a causal role for dysregulated histone acetylation in the persistent memory deficits following an inflammatory event. Identifying the mechanisms underlying this process will provide novel targets for prevention and treatment of persistent cognitive deficits after MI, illness or major surgery.Support or Funding InformationThis research was supported by a National Institutes of Health grant (R00 MH093459, NCT)