Biology subjects

Lodder, B.

Publications and source records attributed to Lodder, B..

6 recordsLinked to original sources

bioRxiv2026

An organotypic neocortical slice culture for studying neuroglial interactions

Organotypic slice cultures (OSCs) are widely used to study cellular properties in a functional and developmental tissue context. With the recent advent of transgenic mouse lines and viral tools we postulated that OSCs may enable the study of multicellular glial and neuroglial interactions in development, as well homeostatic and pathological conditions. Here, we made mouse cortical OSCs and used markers for oligodendroglial, microglial states and neuronal types between 1 to 28 days in vitro (DIV). The OSC was characterized by in-vivo like cortical layering, including layer 5 pyramidal neurons and produced highly robust synchronized period bursts resembling Up- and Down states. Glial cells showed a strong cortical layer- and time-dependent development pattern: in the first week (DIV 1-7), slicing-related debris clearance and developmentally restricted sparse oligodendroglial myelination created an environment with highly phagocytic, non-homeostatic microglia (assessed with CD68 and purinergic receptor P2Y12, respectively). Between DIV 14 and 21, however, slices showed stereotypical cortical myelin patterns and the emergence of a homeostatic microglia phenotype while exhibiting continued phagocytosis. Furthermore, live two-photon imaging and morphometric analyses revealed highly ramified microglia and myelinated axons with compact myelination, exceeding lamellae count compared to age-matched in vivo axons. Lastly, from DIV 28 and onwards, myelin integrity became impaired and associated with phagocytic microglia. Together, the results indicate that between DIV14 and 21 cortical OSCs are well suited for live imaging of homeostatic and activity-dependent neuron-glia interactions, bridging the gap between in vivo investigations and primary cell cultures.

neuroscience↗

bioRxiv2025

Rapid fluorescence lifetime sensor development of LifeCamp enables transient and baseline absolute calcium measurements

Genetically encoded calcium sensors (GECIs) have been instrumental for studying neuronal activity and intracellular signaling. GECIs are typically fluorescence-intensity sensors that change brightness upon calcium binding. Iterative improvements in GECIs have yielded indicators that report action potential-evoked calcium entry with high sensitivity and temporal resolution, enabling measurement of network activity across thousands of neurons. However, fluorescence intensity-based measurements generally cannot report baseline or absolute calcium levels and may confound neuromodulatory regulation of calcium handling with changes in action potential firing. Fluorescence lifetime sensors are insensitive to many artifacts that plague intensity-based measures and report absolute substrate levels, including those at rest. However, relatively few lifetime sensors for neuronal signals exist, and developing new sensors is typically difficult and low-yield. Here, we introduce a new rapid lifetime sensor development (RALISED) platform, which we use to build a new GCaMP8m-based high-speed lifetime calcium sensor, termed LifeCamp. We show that LifeCamp enables comparison of baseline calcium signals in cell culture, brain slices, and mice. In addition, we show that LifeCamp enables the detection of fast action potential-evoked calcium transients in single neurons from brain slices and in behaving mice. Using LifeCamp, we discovered calcium baseline changes associated with neuronal activity in brain slices and behaving mice, as well as slow average calcium changes in neuronal populations of freely moving mice. Altogether, this study highlights the utility of the RALISED method to rapidly develop new lifetime sensors and the application of the LifeCamp calcium lifetime sensor to study fast and slow calcium signaling. Significance statementWe developed a new high-speed, sensitive calcium lifetime sensor (LifeCamp) using a novel rapid lifetime sensor development (RALISED) platform. LifeCamp has high sensitivity and a large substrate-dependent lifetime change (<1ns), allowing for the capture of baseline calcium levels, transient calcium changes, and neuronal firing in vitro and behaving animals. LifeCamp lifetime measurement is insensitive to artifacts that plague conventional intensity imaging and enables absolute comparison of baseline and transient calcium changes across cells, brain regions, and experimental conditions. Hence, LifeCamp is a powerful tool that enables a more accurate and in-depth understanding of neuronal activity and calcium signaling.

neuroscience↗

bioRxiv2025

Absolute measurement of fast and slow neuronal signals with fluorescence lifetime photometry at high temporal resolution

The concentrations of extracellular and intracellular signaling molecules, such as dopamine and cAMP, change over both fast and slow timescales and impact downstream pathways in a cell-type specific manner. Fluorescence sensors currently used to monitor such signals in vivo are typically optimized to detect fast, relative changes in concentration of the target molecule. They are less well suited to detect slowly-changing signals and rarely provide absolute measurements of either fast and slow signaling components. Here, we developed a system for fluorescence lifetime photometry at high temporal resolution (FLIPR) that utilizes frequency-domain analog processing to measure the absolute fluorescence lifetime of genetically-encoded sensors at high speed but with long-term stability and picosecond precision in freely moving mice. We applied FLIPR to investigate dopamine signaling in two functionally distinct regions in the striatum, the nucleus accumbens core (NAC) and the tail of striatum (TOS). We observed higher tonic dopamine levels at baseline in the TOS compared to the NAC and detected differential and dynamic responses in phasic and tonic dopamine to appetitive and aversive stimuli. Thus, FLIPR enables simple monitoring of fast and slow time-scale neuronal signaling in absolute units, revealing previously unappreciated spatial and temporal variation even in well-studied signaling systems.

neuroscience↗

bioRxiv2024

Hunger modulates exploration through suppression of dopamine signaling in the tail of striatum

Caloric depletion leads to behavioral changes that help an animal find food and restore its homeostatic balance. Hunger increases exploration and risk-taking behavior, allowing an animal to forage for food despite risks; however, the neural circuitry underlying this change is unknown. Here, we characterize how hunger restructures an animals spontaneous behavior as well as its directed exploration of a novel object. We show that hunger-induced changes in exploration are accompanied by and result from modulation of dopamine signaling in the tail of the striatum (TOS). Dopamine signaling in the TOS is modulated by internal hunger state through the activity of agouti-related peptide (AgRP) neurons, putative "hunger neurons" in the arcuate nucleus of the hypothalamus. These AgRP neurons are poly-synaptically connected to TOS-projecting dopaminergic neurons through the lateral hypothalamus, the central amygdala, and the periaqueductal grey. We thus delineate a hypothalamic-midbrain circuit that coordinates changes in exploration behavior in the hungry state.

neuroscience↗

bioRxiv2024

Elevated synaptic PKA activity and abnormal striatal dopamine signaling in Akap11 mutant mice, a genetic model of schizophrenia and bipolar disorder

AbstractLoss-of-function mutations in AKAP11 (a protein kinase A (PKA)-binding protein) greatly increase the risk of bipolar disorder and schizophrenia. To determine the neurobiological functions of AKAP11, we conduct multi-omic and neurobiological analyses of Akap11 mutant mouse brains. We find that AKAP11 is a key regulator of PKA proteostasis in the brain whose loss leads to dramatically increased levels of PKA subunits and phosphorylated PKA substrates, especially in synapses. Akap11 mutant mice show extensive transcriptomic changes throughout the brain, including prominent decreases in synapse-related genes sets. Gene expression is highly impacted in spiny projection neurons of the striatum, a brain region implicated in motivation, cognition and psychotic disorders. Real-time measurements of PKA activity reveal elevated basal PKA activity in the striatum of Akap11-/- mice, with exaggerated additional response to dopamine receptor antagonists. Behaviorally, Akap11 mutant mice show abnormally prolonged locomotor response to amphetamine, deficits in associative learning and contextual discrimination, as well as depression-like behaviors. Our study connects molecular changes to circuit dysfunction and behavioral disturbance in a genetically valid animal model of psychotic disorder.

neuroscience↗

bioRxiv2019

Cell-type specific asynchronous modulation of PKA by dopamine during reward based learning

Canonical reinforcement learning models postulate that dopamine neurons encode reward prediction error (RPE) and provide a teaching signal to striatal spiny projection neurons (SPNs) in the form of dopamine (DA) release. DA is thought to guide learning via dynamic modulation of protein kinase A (PKA) in SPNs. However, this fundamental assumption remains untested in behaving animals. Here we utilized multi-channel fiber photometry and fluorescence lifetime photometry (FLiP) to monitor the activity of DA neurons, extracellular DA levels, and net PKA activity in SPNs in the nucleus accumbens during learning. We found dynamic encoding of RPE in the activity of DA neurons, which is both necessary and sufficient to explain striatal DA levels and SPN PKA activity. The modulation of PKA in SPNs that express type-1 (D1R-SPNs) and type-2 (D2R-SPNs) DA receptors was dichotomous such that in each cell class it is selectively sensitive to increases and decreases in DA, respectively, and occur at and support different phases of learning. Thus, PKA-dependent pathways in D1R- and D2R-SPNs are asynchronously engaged by RPE-encoding DA signals to promote different aspects of reinforcement learning: the former responsible for the initial association between action and outcome and the latter responsible for refining the learned association.

neuroscience↗