Biology subjects

Downs, A. M.

Publications and source records attributed to Downs, A. M..

10 recordsLinked to original sources

bioRxiv2026

INTERFERON-REGULATORY FACTOR 7: A NEUROIMMUNE ROLE FOR VAPOR-INDUCED ESCALATIONS IN ETHANOL SELF-ADMINISTRATION

Neuroimmune signaling is increased in postmortem brain tissue from individuals with alcohol use disorder (AUD), and growing evidence suggests that it contributes to persistent alcohol-related neuroadaptations. Interferon regulatory factor 7 (IRF7), a transcription factor downstream of endosomal Toll-like receptor signaling, is induced in alcohol-relevant brain regions and may contribute to escalated drinking. Here, we tested whether chronic intermittent ethanol (CIE) vapor exposure engages IRF7 signaling during subsequent alcohol self-administration and whether this is associated with altered molecular E/I balance in the aIC and altered functional E/I balance in aICnucleus accumbens projection neurons. Female Wistar rats (n=30) were trained to self-administer alcohol (15% v/v; FR2 vs inactive lever) during 30-minute sessions. After establishing baseline drinking, rats underwent 1-3 cycles of CIE, which increased alcohol self-administration at the 72 h post vapor test. This increase positively correlated with IRF7 levels in the anterior insular cortex (aIC) and nucleus accumbens, while molecular, and immunofluorescence showed that CIE shifted aIC excitatory/inhibitory (E/I) balance toward reduced excitation. Electrophysiological recordings further showed reduced functional E/I balance in aIC neurons projecting to the nucleus accumbens. Knockdown of IRF7 in the aIC attenuated CIE induced escalation of alcohol self-administration, supporting a role for insular IRF7 signaling in alcohol related neuroadaptations that promote escalated drinking.

neuroscience↗

bioRxiv2025

Loss of excitatory inputs and decreased tonic and evoked activity of locus coeruleus neurons in aged P301S mice

Tau pathology in the locus coeruleus (LC) is associated with several neurodegenerative conditions including Alzheimers disease and frontotemporal dementia. Phosphorylated tau accumulates in the LC and results in inflammation, synaptic loss, and eventually cell death as the disease progresses. Loss of LC neurons and noradrenergic innervation is thought to contribute to the symptoms of cognitive decline later in disease. While loss and degeneration of LC neurons has been well studied, less is known about changes in LC physiology at advanced stages of tau pathology that precedes neurodegeneration. In this study, we investigated the ex vivo electrophysiological properties of LC neurons in male and female mice from the P301S mouse model of tauopathy at 9 months of age, a time-point when significant tau accumulation, cell death, and cognitive impairments are observed. We found a reduction in excitatory inputs and changes in excitatory post-synaptic current kinetics in male and female P301S. There was also a decrease in spontaneous discharge of LC neurons and an increase in AP threshold in P301S mice of both sexes. Finally, we observed a decrease in excitability and increase in rheobase current in P301S mice. Despite the decrease in LC activity in slice, we did not identify differences in total tissue norepinephrine (NE) or NE metabolites in prefrontal cortex or hippocampus. Together these findings demonstrate reductions in the activity and excitability of LC neurons at late stages of tau accumulation. However, compensatory mechanisms may maintain normal NE levels in LC projection regions in vivo.

neuroscience↗

bioRxiv2024

Diversity of ancestral brainstem noradrenergic neurons across species and multiple biological factors

The brainstem cell group, locus coeruleus (LC), is present across vertebrates and influences cardiorespiratory, metabolic, immune, and cognitive functions by activating in two putatively distinct firing patterns. Yet, the degree to which the LC firing rates and patterns are homogenous across species has never been assessed due to inherently limited sample sizes. To remedy this, we pooled cross-species data from 20 laboratories to show that firing rates differ across species and are modulated by sex, age, and type of in vitro or in vivo preparation. Contrary to the prevailing dual-mode firing pattern schema, we observed patterns spread across a low-dimensional manifold, with subregions enriched for specific biological factors and neurodegenerative disease models. Our findings show considerable diversity in an ancestral vertebrate neuromodulatory system.

neuroscience↗

bioRxiv2024

Lgr5+ ductal cells of von Ebner's glands are stem cells for turnover of posterior tongue taste buds

Taste bud cells have a limited lifespan and must be continuously replaced along with the papilla epithelium in which they reside. Previous work has shown that expression of leucine- rich G protein-coupled receptor 5 (Lgr5), a Wnt pathway agonist, serves as a marker of adult stem/progenitor cells for taste buds located in posterior tongue (circumvallate and foliate), but not anterior tongue (fungiform), taste papillae. However, the specific location/niche of the Lgr5-expressing cells supporting renewal and their phenotypic properties have not been fully explored. To address this, the genesis and fate of Lgr5+ cells were examined in developing and adult mice using genetic reporter strains. Evidence from Lgr5-lacZ and Lgr5- GFP mice shows that, while Lgr5 is broadly expressed in the epithelium of nascent circumvallate papillae and their trenches during embryonic development, it becomes concentrated within the ducts of adjacent von Ebners salivary glands during the first postnatal week, co-incident with the appearance of differentiated taste buds. In posterior tongue taste papillae of adult animals, sites of highest Lgr5 expression are found in excretory ducts, restricted to the outer (basal) layer of the bi-layered excretory zone. These Lgr5+ cells are immunoreactive for keratin 14, like cells in the basal layer of extragemmal taste epithelium, and for Sox9, a marker of exocrine gland duct cells. Lineage tracing experiments with an Lgr5-EGFP-IRES-CreERT2;R26-mTmG reporter show that Lgr5+ ductal cells become labeled one day following Cre induction, prior to the appearance of descendent cells in taste buds and extragemmal epithelium. These data support a role for Lgr5+ ductal cells as stem cells and suggest that a cooperative interaction exists between posterior taste epithelium and its associated salivary glands in taste cell turnover.

developmental biology↗

bioRxiv2023

Oral Fentanyl Consumption Alters Sleep Rhythms, Promotes Avoidance Behaviors, and Impairs Fear Extinction Learning in Male and Female Mice

The number of opioid overdose deaths has increased over the past several years, mainly driven by an increase in the availability of highly potent synthetic opioids, like fentanyl, in the un-regulated drug supply. Over the last few years, changes in the drug supply, and in particular the availability of counterfeit pills containing fentanyl, have made oral use of opioids a more common route of administration. Here, we used a drinking in the dark (DiD) paradigm to model oral fentanyl self-administration using increasing fentanyl concentrations in male and female mice over 5 weeks. Fentanyl consumption peaked in both female and male mice at the 30 {micro}g/mL dose, with female mice consuming significantly more fentanyl than male mice. Mice consumed sufficient fentanyl such that withdrawal was precipitated with naloxone, with males having more withdrawal symptoms, despite lower pharmacological exposure. We also performed behavioral assays to measure avoidance behavior and reward-seeking during fentanyl abstinence. Female mice displayed reduced avoidance behaviors in the open field assay, whereas male mice showed increased avoidance in the light/dark box assay. Female mice also exhibited increased reward-seeking in the sucrose preference test. Fentanyl-consuming mice of both sexes showed impaired cued fear extinction learning following fear conditioning and increased excitatory synaptic drive and increased excitability of BLA principal neurons. Our experiments demonstrate that long-term oral fentanyl consumption results in wide-ranging physiological and behavioral disruptions. This model could be useful to further study fentanyl withdrawal syndrome and behaviors and neuroplasticity associated with protracted fentanyl withdrawal.

neuroscience↗

bioRxiv2022

Tauopathy and alcohol consumption interact to alter locus coeruleus excitatory transmission and excitability in male and female mice

Alcohol use disorder is a major public health concern in the United States. Recent work has suggested a link between chronic alcohol consumption and the development of tauopathy disorders, such as Alzheimers Disease and Frontal-Temporal Dementia. However, relatively little work has investigated changes in neural circuitry involved in both tauopathy disorders and alcohol use disorder. The locus coeruleus (LC) is the major noradrenergic nuclei in the brain and is one of the earliest sites to be affected by tau lesions. The LC is also implicated in the rewarding effects of ethanol and alcohol withdrawal. In this study we assessed effects of long-term ethanol consumption and tauopathy on the physiology of LC neurons. Male and female P301S mice, a humanized transgenic mouse model of tauopathy, underwent 16 weeks of intermittent access to 20% ethanol from 3 to 7 months of age. We observed higher total alcohol consumption in female mice regardless of genotype. Male P301S mice consumed more ethanol and had a greater preference for ethanol than WT males. At the end of the drinking study, LC function was assessed using ex vivo whole cell electrophysiology. We found significant changes in excitatory inputs to the LC due to both ethanol and genotype., We found significantly increased excitability of the LC due to ethanol with greater effects in female P301S mice than WT. Our study identifies significant changes in the LC due to interactions between tauopathy and long-term ethanol use. These findings could have important implications regarding LC activity and changes in behavior due to both ethanol and tauopathy related dementia.

neuroscience↗

bioRxiv2022

Effects of Long-Term Alcohol Consumption on Behavior in the P301S (Line PS19) Tauopathy Mouse Model

Alcohol consumption and misuse remain prevalent public health issues with recent reports of increased heavy consumption in older populations in the United States. Several studies have identified alcohol consumption as a risk factor for developing multiple forms of dementia. The behavioral and psychological symptoms of dementia (BPSD), such as changes in affective behavior (e.g. anxiety), precede and coincide with cognitive decline. While many studies have characterized the intersection of alcohol use and affective behaviors, little is known regarding alcohol consumption and BPSD. This study characterizes the impact of long-term alcohol consumption on various behaviors in the P301S (line PS19) tauopathy mouse model. Male and female P301S and littermate control mice underwent two-bottle choice intermittent access to alcohol for sixteen weeks starting at 12 weeks of age. There were no significant differences in total ethanol consumption between wildtype and P301S mice of the same sex; however, drinking behavior differed among genotypes, and female mice of each genotype drank significantly more ethanol than males of each genotype. Following drinking studies, mice were run through a battery of behavioral tests during a period of forced abstinence, including approach/avoidance assays, social behavior tests, and memory and cognition tests. Across these tests we observed differences between groups due to genotype, alcohol history, and interactions between alcohol exposure and genotype. These differences were not always consistent between the sexes. In total, this study reveals significant alcohol-tauopathy interactions in subsequent behavior, which may have implications for understanding how alcohol may impact BPSD in conditions associated with tauopathy like Alzheimers disease and frontotemporal dementia.

neuroscience↗

bioRxiv2021

Differential expression of striatal proteins in a mouse model of DOPA-responsive dystonia reveals shared mechanisms among dystonic disorders

Dystonia is characterized by involuntary muscle contractions that cause debilitating twisting movements and postures. Although basal ganglia dysfunction is implicated in many forms of dystonia, the underlying mechanisms are unclear. Therefore, to reveal abnormal striatal cellular processes and pathways implicated in dystonia, we used an unbiased proteomic approach in a knockin mouse model of DOPA-responsive dystonia, a model in which the striatum is known to play a central role in the expression of dystonia. Fifty-seven of the 1805 proteins identified were differentially regulated in DOPA-responsive dystonia mice compared to control mice. Most differentially regulated proteins were associated with gene ontology terms that implicated either mitochondrial or synaptic dysfunction whereby proteins associated with mitochondrial function were generally over-represented whereas proteins associated with synaptic function were largely under-represented. Remarkably, nearly 20% of the differentially regulated proteins identified in our screen are associated with pathogenic variants that cause inherited dystonic disorders in humans suggesting shared mechanisms across many different forms of dystonia.

neuroscience↗

bioRxiv2020

Cell-intrinsic effects of TorsinA(ΔE) disrupt dopamine release in a mouse model of DYT1-TOR1A dystonia

DYT1-TOR1A dystonia is an inherited dystonia caused by a three base-pair deletion in the TOR1A gene (TOR1A{Delta}E). Although the mechanisms underlying the dystonic movements are largely unknown, abnormalities in striatal dopamine and acetylcholine neurotransmission are consistently implicated whereby dopamine release is reduced while cholinergic tone is increased. Because striatal cholinergic neurotransmission mediates dopamine release, it is not known if the dopamine release deficit is mediated indirectly by abnormal acetylcholine neurotransmission or if Tor1a({Delta}E) acts directly within dopaminergic neurons to attenuate release. To dissect the microcircuit that governs the deficit in dopamine release, we conditionally expressed Tor1a({Delta}E) in either dopamine neurons or cholinergic interneurons in mice and assessed striatal dopamine release using ex vivo fast scan cyclic voltammetry or dopamine efflux using in vivo microdialysis. Conditional expression of Tor1a({Delta}E) in cholinergic neurons did not affect striatal dopamine release. In contrast, conditional expression of Tor1a({Delta}E) in dopamine neurons reduced dopamine release to 50% of normal, which is comparable to the deficit in Tor1a+/{Delta}E knockin mice that express the mutation ubiquitously. Despite the deficit in dopamine release, we found that the Tor1a({Delta}E) mutation does not cause obvious nerve terminal dysfunction as other presynaptic mechanisms, including electrical excitability, vesicle recycling/refilling, Ca2+ signaling, D2 dopamine autoreceptor function and GABAB receptor function, are intact. Although the mechanistic link between Tor1a({Delta}E) and dopamine release is unclear, these results clearly demonstrate that the defect in dopamine release is caused by the action of the Tor1a({Delta}E) mutation within dopamine neurons.

neuroscience↗

bioRxiv2020

BLOCKADE OF M4 MUSCARINIC RECEPTORS ON STRIATAL CHOLINERGIC INTERNEURONS NORMALIZES STRIATAL DOPAMINE RELEASE IN A MOUSE MODEL OF DYT1-TOR1A DYSTONIA

Trihexyphenidyl (THP), a non-selective muscarinic receptor (mAChR) antagonist, is commonly used for the treatment of dystonia associated with TOR1A, otherwise known as DYT1 dystonia. A better understanding of the mechanism of action of THP is a critical step in the development of better therapeutics with fewer side effects. We previously found that THP normalizes the deficit in striatal dopamine (DA) release in a mouse model of TOR1A dystonia (Tor1a+/{Delta}E knockin (KI) mice), revealing a plausible mechanism of action for this compound, considering that abnormal DA neurotransmission is consistently associated with many forms of dystonia. However, the mAChR subtype(s) that mediate the rescue of striatal dopamine release remain unclear. In this study we used a combination of pharmacological challenges and cell-type specific mAChR conditional knockout mice of either sex to determine which mAChR subtypes mediate the DA release-enhancing effects of THP. We determined that THP acts in part at M4 mAChR on striatal cholinergic interneurons to rescue DA release in both Tor1a+/+ and Tor1a+/{Delta}E KI mice. Further, we found that the subtype selective M4 antagonist VU6021625 recapitulates the effects of THP. These data implicate a principal role for M4 mAChR located on striatal cholinergic interneurons in the mechanism of action of THP and suggest that subtype selective M4 mAChR antagonists may be effective therapeutics with fewer side effects than THP for the treatment of TOR1A dystonia.

pharmacology and toxicology↗