Biology subjects

Sipe, G. O.

Publications and source records attributed to Sipe, G. O..

9 recordsLinked to original sources

bioRxiv2026

Citric acid water effects on mouse health, motivation, and performance in virtual reality locomotion-based tasks

Traditionally, complex behavioral tasks in mice have relied upon water restriction as an external motivator to increase task engagement. However, citric acid (CA) water, the technique whereby water is given ad libitum but made sour by the addition of CA, has emerged as an alternative to typical water restriction. Evidence suggests CA water can effectively motivate task performance while improving animal welfare in alignment with the 3Rs of animal research and reducing experimenter labor. While promising, the applicability of CA water in mice remains incompletely characterized with higher concentrations only tested in rats and "ramping" schedules, where mice progress to increasingly higher concentrations, indirectly examined. Here, we evaluate four CA concentration/schedule combinations for their effects on mouse health (weight changes, home cage behaviors, fecal counts) and motivation to drink regular water (lick counts, drinking behaviors) in female and male C57BL/6J mice. We find that a schedule ramping from 1% to 2% CA after one week is the easiest for mice to adapt to and sustained 2% CA use maintains robust lick counts for at least 5 weeks. Additionally, CA has been directly characterized for wheel-turning and touchscreen tasks, but not virtual reality (VR) tasks, an increasingly popular class of behavioral experiments. Therefore, we also assess how 2% CA affects motivation and task performance in two VR treadmill tasks (running and stopping task). We find that CA water does not improve task performance above that of mice given regular water, but does limit competing motivations and produce more uniform, reward-motivated behavior.

animal behavior and cognition↗

bioRxiv2026

Simultaneous Functional Ultrasound, Intrinsic Optical Signal and Widefield Calcium Neuroimaging

Functional ultrasound (fUS) maps cerebral blood volume (CBV) but lacks molecular and neuronal specificity. By simultaneously integrating fUS with optical imaging, we show that fUS-derived CBV correlates with both optically measured hemoglobin and neuronal calcium activity in awake mice. We further derive hemodynamic response functions linking calcium activity to CBV during spontaneous and sensory-evoked activity. Application to a mouse glioblastoma model demonstrates utility for studying neurovascular dysfunction in complex neuropathologies.

neuroscience↗

bioRxiv2024

Astrocytic modulation of population encoding in mouse visual cortex via GABA transporter 3 revealed by multiplexed CRISPR/Cas9 gene editing

Astrocytes, which are increasingly recognized as pivotal constituents of brain circuits governing a wide range of functions, express GABA transporter 3 (Gat3), an astrocyte-specific GABA transporter responsible for maintenance of extra-synaptic GABA levels. Here, we examined the functional role of Gat3 in astrocyte-mediated modulation of neuronal activity and information encoding. First, we developed a multiplexed CRISPR construct applicable for effective genetic ablation of Gat3 in the visual cortex of adult mice. Using in vivo two-photon calcium imaging of visual cortex neurons in Gat3 knockout mice, we observed changes in spontaneous and visually driven single neuronal response properties such as response magnitudes and trial-to-trial variability. Gat3 knockout exerted a pronounced influence on population-level neuronal activity, altering the response dynamics of neuronal populations and impairing their ability to accurately represent stimulus information. These findings demonstrate that Gat3 in astrocytes profoundly shapes the sensory information encoding capacity of neurons and networks within the visual cortex.

neuroscience↗

bioRxiv2024

Cortical norepinephrine-astrocyte signaling critically mediates learned behavior

Updating behavior based on feedback from the environment is a crucial means by which organisms learn and develop optimal behavioral strategies1-3. Norepinephrine (NE) release from the locus coeruleus (LC) has been shown to mediate learned behaviors4-6 such that in a task with graded stimulus uncertainty and performance, a high level of NE released after an unexpected outcome causes adaptations in subsequent behavior7. Yet, how the transient activity of LC-NE neurons, lasting tens of milliseconds, alters neuronal activity and influences behavior several seconds later is unclear. Here, we show that NE released after an unexpected outcome acts directly on cortical astrocytes via 1 adrenergic (Adra1a) receptors to elicit sustained increases in intracellular calcium. Chemogenetic blockade of astrocytic calcium dynamics prevents trial-to-trial behavioral adaptation. NE stimulation of astrocytes elicits ATP release, and imaging ATP levels in the cortex reveals an increase in extracellular ATP in response to an unexpected outcome. Blocking ATP-driven signaling to neuronal adenosine A1 receptors also prevents post-reinforcement behavioral adaptation. Finally, high density neuronal recordings in prefrontal cortex reveal that a surprising outcome alters the neuronal representation of the stimulus on the subsequent trial without sustained changes in cortical activity; blocking either astrocyte calcium dynamics or A1 receptors occludes these post-reinforcement changes in single-neuron and population neuronal encoding of task variables underlying behavioral changes. Together, these data demonstrate that astrocytes play an essential role in norepinephrine-driven learned behavior: they have prolonged calcium responses to transient norepinephrine release and convey task-relevant reinforcement information across behavioral intervals, enabling selective updating of neuronal task representations to support adaptive behavior.

neuroscience↗

bioRxiv2023

A paradigm for ethanol consumption in head-fixed mice during prefrontal cortical two-photon calcium imaging

The prefrontal cortex (PFC) is a hub for higher-level cognitive behaviors and is a key target for neuroadaptations in alcohol use disorders. Preclinical models of ethanol consumption are instrumental for understanding how acute and repeated drinking affects PFC structure and function. Recent advances in genetically encoded sensors of neuronal activity and neuromodulator release combined with functional microscopy (multiphoton and one-photon widefield imaging) allow multimodal in-vivo PFC recordings at subcellular and cellular scales. While these methods could enable a deeper understanding of the relationship between alcohol and PFC function/dysfunction, they require animals to be head-fixed. Here, we present a method in mice for binge-like ethanol consumption during head-fixation. Male and female mice were first acclimated to ethanol by providing home cage access to 20% ethanol (v/v) for 4 or 8 days. After home cage drinking, mice consumed ethanol from a lick spout during head-fixation. We used two-photon calcium imaging during the head-fixed drinking paradigm to record from a large population of PFC neurons (>1000) to explore how acute ethanol affects their activity. Drinking modulated activity rates in a subset of neurons on slow (minutes) and fast (seconds) time scales but the majority of neurons were unaffected. Moreover, ethanol intake did not significantly affect network level interactions in the PFC as assessed through inter-neuronal pairwise correlations. By establishing a method for binge-like drinking in head-fixed mice, we lay the groundwork for leveraging advanced microscopy technologies to study alcohol-induced neuroadaptations in PFC and other brain circuits. HighlightsO_LIC57BL/6J mice voluntarily consume ethanol to binge-like levels during head-fixation, with females consuming more ethanol than males. C_LIO_LIMice show differences in frontloading and licking behavior for head-fixed ethanol and sucrose consumption. C_LIO_LIHead-fixed paradigm enables two-photon calcium imaging in the anterior cingulate cortex subdivision of the prefrontal cortex. C_LIO_LIAcute ethanol increases and decreases single neuron activity at fast (seconds) and slow (minutes) time scales but does not alter pairwise correlations between neurons. C_LI

neuroscience↗

bioRxiv2021

Voluntary alcohol consumption disrupts coupling of prefrontal cortical activity to arousal

Alcohol use disorder (AUD) exacts a major personal, societal, and economic toll. Top-down control from the prefrontal cortex (PFC), a critical hub for decision making, executive, and other cognitive functions, is key for the regulation of alcohol consumption. Arousal exerts profound effects on cortical processing, allowing it to potentially modulate PFC functions relevant for alcohol consumption and AUD. Despite this, it is unclear whether and how arousal-mediated modulation of PFC circuits relates to voluntary alcohol drinking behaviors. Two-photon microscopy is ideally suited for dissecting the neural circuit mechanisms underlying the effect of alcohol on intact circuits in behaving animals. We addressed a major limitation of this technology by developing a novel behavioral paradigm for voluntary drinking in head-fixed mice. We recorded responses of layer 2/3 excitatory neurons in the anterior cingulate cortex (ACC) subdivision of the PFC as mice voluntarily consumed ethanol, along with video recording of the pupil to track momentary fluctuations in arousal. Ethanol consumption bidirectionally modified the activity of subsets of ACC neurons, both at slow (minutes) and fast (sub-second) time scales. Remarkably, we found that the coupling of arousal to ACC activity before drinking was associated with subsequent ethanol engagement behavior. In turn, ethanol consumption modulated neuronal-arousal coupling. Together, our results suggest neuronal-arousal coupling as a key biomarker for alcohol drinking and lays the groundwork for future studies to dissect the therapeutic potential of this process for AUD and other substance use disorders.

neuroscience↗

bioRxiv2020

Astrocytic glutamate uptake coordinates experience-dependent, eye-specific refinement in developing visual cortex

The uptake of glutamate by astrocytes actively shapes synaptic transmission, however its role in the development and plasticity of neuronal circuits remains poorly understood. The astrocytic glutamate transporter, GLT1 is the predominant source of glutamate clearance in the adult mouse cortex. Here, we examined the structural and functional development of the visual cortex in GLT1 heterozygous (HET) mice using two-photon microscopy, immunohistochemistry and slice electrophysiology. We find that though eye-specific thalamic axonal segregation is intact, binocular refinement in the primary visual cortex is disrupted. Eye-specific responses to visual stimuli in GLT1 HET mice show altered binocular matching, with abnormally high responses to ipsilateral compared to contralateral eye stimulation and a greater mismatch between preferred orientation selectivity of ipsilateral and contralateral eye responses. Furthermore, the balance of excitation and inhibition in cortical circuits is dysregulated with an increase in somatostatin positive interneurons, decrease in parvalbumin positive interneurons, and increase in dendritic spine density in the basal dendrites of layer 2/3 excitatory neurons. Monocular deprivation induces atypical ocular dominance plasticity in GLT1 HET mice, with an unusual depression of ipsilateral open eye responses; however, this change in ipsilateral responses correlates well with an upregulation of GLT1 protein following monocular deprivation. These results demonstrate that a key function of astrocytic GLT1 function during development is the experience-dependent refinement of ipsilateral eye inputs relative to contralateral eye inputs in visual cortex. SIGNIFICANCEWe show that astrocytic glutamate uptake via the transporter GLT1 is necessary for activity-dependent regulation of cortical inputs. Dysregulation of GLT1 expression and function leads to a disruption of binocular refinement and matching in visual cortex. Inputs from the ipsilateral eye are stronger, and monocular deprivation, which upregulates GLT1 expression in a homeostatic fashion, causes a paradoxical reduction of ipsilateral, non-deprived eye, responses. These results provide new evidence for the importance of glutamate transport in cortical development, function, and plasticity.

neuroscience↗

bioRxiv2019

Noradrenergic signaling in wakeful states inhibits microglial surveillance and synaptic plasticity in the mouse visual cortex.

Microglia are the innate immune cells of the brain with roles in neuroimmunology and synaptic plasticity. Microglial processes continuously survey the brain parenchyma interacting with synaptic elements and maintaining tissue homeostasis. However, the mechanisms that control surveillance and its role in synaptic plasticity are poorly understood. Microglial dynamics in vivo have been primarily studied in anesthetized animals, where slow-wave neural activity resembles sleep-like states. We report that microglial surveillance and injury response in awake animals are reduced compared to when animals are anesthetized, suggesting that arousal state profoundly modulates microglial roles in the physiological brain. Stimulating {beta}2-adrenergic receptors recapitulated these observations and also disrupted experience-dependent plasticity only when intact {beta}2-adrenergic receptors were present in microglia specifically. These results indicate that microglial roles in surveillance and synaptic plasticity in the healthy brain are modulated by noradrenergic fluctuations between arousal states and raises new considerations for sleep/wake disruption in neurodevelopment and neuropathology.

neuroscience↗

bioRxiv2018

Bidirectional control of orienting behavior by distinct prefrontal circuits

Sensorimotor behaviors require processing of behaviorally relevant sensory cues and the ability to select appropriate responses from a vast behavioral repertoire. Top-down modulation by the prefrontal cortex (PFC) is thought to be key for both processes but the precise role of specific circuits remains unclear. We examined the sensorimotor function of anatomically distinct outputs from a subdivision of the mouse PFC, the anterior cingulate cortex (ACC). Using a visually guided two-choice behavioral paradigm with multiple cue-response mappings, we dissociated the sensory and motor response components of sensorimotor control. Projection-specific two-photon calcium imaging and optogenetic manipulations show that ACC outputs to the superior colliculus, a key midbrain structure for response selection, principally coordinate specific motor responses. Importantly, ACC outputs exert top-down control by reducing the innate response bias of the superior colliculus. In contrast, ACC outputs to the visual cortex facilitate sensory processing of visual cues. Our results ascribe motor and sensory roles to ACC projections to the superior colliculus and the visual cortex and demonstrate for the first time a circuit motif for PFC function wherein anatomically non-overlapping output pathways coordinate complementary but distinct aspects of visual sensorimotor behavior.

neuroscience↗