A Genetically Encoded Fluorescent Sensor Enables Rapid and Specific Detection of Dopamine in Flies, Fish, and Mice

Intersection of GPCR trafficking and cAMP signaling at endomembranes

GPCRs comprise the largest family of signaling receptors and control essentially every physiological process. Many biochemical reactions underlying GPCR signaling are now elucidated to atomic resolution in cell-free preparations, but how elemental signaling reactions are organized in intact cells remains less clear. Significant progress has been made toward bridging this knowledge gap by leveraging new tools and methodologies enabling the experimental detection, localization, and manipulation of defined signaling reactions in living cells. Here, we chronicle advances at this rapidly moving frontier of molecular and cell biology, focusing on GPCR-initiated signaling through the classical cAMP pathway as an example. We begin with a brief review of established concepts. We then discuss the still-evolving understanding that ligand-induced GPCR signaling occurs from endomembranes as well as the plasmalemma, and that this enables cells to flexibly sculpt downstream signaling responses in both space and time. Finally, we note some key limitations of the present understanding and propose some promising directions for future investigation.

Portable paper-based microfluidic devices based on CuS@Ag2S nanocomposites for colorimetric/electrochemical dual-mode detection of dopamine

The development of integrated multiple signal outputs within a single platform is highly significant for efficient and accurate on-site biomarker detection. Herein, colorimetric/electrochemical dual-mode microfluidic paper-based analytical devices (μPADs) were designed for portable, visual and accurate dopamine (DA) detection. The dual-mode μPADs, featuring folded structure, integrate a colorimetric layer and an electrochemical layer using wax printing and laser-induced graphene (LIG) pyrolysis techniques, allowing the vertical flow of analyte solution. Copper sulfide @ silver sulfide (CuS@Ag2S) nanocomposites, with excellent laccase-like and electrocatalytic performance, were modified onto the detection zones as colorimetric/electrochemical sensing substrates for dual-mode DA recognition. In the colorimetric detection zones, the obvious violet-colored signals were generated based on the enhanced laccase-like oxidation reaction induced. Further, amplified electrical response signals toward DA were collected in electrochemical detection zone due to the epitaxial heterostructure of silver sulfide (Ag2S). Consequently, the developed CuS@Ag2S-incorporated μPADs exhibit linear responses for colorimetric and electrochemical DA detection in ranges of 2-50 μM and 0.5-70 μM, respectively, with the limit of detection (LOD) of 0.675 μM and 0.086 μM. This work integrates multiple detection modes into μPADs, providing the portable, reliable and visual alternative to traditional detection methods of DA for POCT.

Imidazole-triggered in situ fluorescence reaction system for quantitatively determination of dopamine from multiple sources

Highly selective and sensitive determination of dopamine (DA) from multiple sources remains a persistent and significant challenge. Here, we develop an imidazole-triggered in situ fluorescence reaction system for highly selective and sensitive determination of DA from various sources (human, horse, dog, rabbit, and mouse). The system operates by catalyzing the oxidation of DA with 1,5-Dihydroxynaphthalene (1,5-DHA) through a Lewis base formed by imidazole, leading to the rapid generation of yellow azamonardine fluorescent compounds (AFC). Notably, the system demonstrates minimal background noise and a high signal-to-noise ratio of up to 300-fold with a determination limit of 33.33 pM, making it 10-100 times more sensitive than conventional enzyme-linked immunosorbent assay (ELISA) methods. Moreover, selectivity tests reveal that our system can effectively distinguish between several common interfering substances, even at concentrations as low as 10 nM. The developed system shows promising results in detecting DA from diverse sources (humans, horses, dogs, rabbits, and mice), including urine samples from clinical patients, exhibiting good agreement with traditional ELISA kits. Therefore, the established in situ fluorescence reaction system holds great potential for the determination of DA-related disorders due to its impressive analytical capabilities.

Fluorescence detection of dopamine signaling to the primate striatum in relation to stimulus-reward associations

Dopamine (DA) signals to the striatum play critical roles in shaping and sustaining stimulus-reward associations. In primates, however, the dynamics of the DA signals remain unknown since conventional methods are not necessarily appropriate in terms of the spatiotemporal resolution or chemical specificity sufficient for detecting the DA signals. In our study, fiber photometry with a fluorescent DA sensor was employed to identify reward-related DA transients in the monkey striatum. This technique, which directly monitors local DA release, reveals a reward prediction error signal in the anterior putamen originating from midbrain DA neurons. Further, DA transients in the head of the caudate nucleus exhibit a value-based response to reward-predicting stimuli. These signals have been found to arise from two separate groups of DA neurons in the substantia nigra pars compacta. The present results demonstrate that fluorescence DA monitoring is applicable to detect DA signals in the primate striatum for investigating their roles.

Altered Neural Activity in the Mesoaccumbens Pathway Underlies Impaired Social Reward Processing in Shank3-Deficient Rats

Social behaviors are crucial for human connection and belonging, often impacted by conditions like Autism Spectrum Disorder (ASD). The mesoaccumbens pathway (ventral tegmental area (VTA) to the nucleus accumbense (NAc)) plays a pivotal role in social behavior and is implicated in ASD. However, the impact of ASD-related mutations on social reward processing remains insufficiently explored. This study focuses on the Shank3 mutation, associated with a rare genetic condition and linked to ASD, examining its influence on the mesoaccumbens pathway during behavior, using the Shank3-deficient rat model. Our findings indicate that Shank3-deficient rats exhibit atypical social interactions, associated with altered neuronal activity of VTA dopaminergic and GABAergic neurons and reduced dopamine release in the NAc. Moreover, they demonstrate that manipulating VTA neuronal activity can normalize this behavior, providing insights into the effects of Shank3 mutations on social reward processing  and identifying a potential neural pathway for intervention.

Investigating the effect of Arvcf reveals an essential role on regulating the mesolimbic dopamine signaling-mediated nicotine reward

The mesolimbic dopamine system is crucial for drug reinforcement and reward learning, leading to addiction. We previously demonstrated that Arvcf was associated significantly with nicotine and alcohol addiction through genome-wide association studies. However, the role and mechanisms of Arvcf in dopamine-mediated drug reward processes were largely unknown. In this study, we first showed that Arvcf mediates nicotine-induced reward behavior by using conditioned place preference (CPP) model on Arvcf-knockout (Arvcf-KO) animal model. Then, we revealed that Arvcf was mainly expressed in VTA dopaminergic neurons whose expression could be upregulated by nicotine treatment. Subsequently, our SnRNA-seq analysis revealed that Arvcf was directly involved in dopamine biosynthesis in VTA dopaminergic neurons. Furthermore, we found that Arvcf-KO led to a significant reduction in both the dopamine synthesis and release in the nucleus accumbens (NAc) on nicotine stimulation. Specifically, we demonstrated that inhibition of Arvcf in VTA dopaminergic neurons decreased dopamine release within VTA-NAc circuit and suppressed nicotine reward-related behavior, while overexpression of Arvcf led to the opposite results. Taken together, these findings highlight the role of Arvcf in regulating dopamine signaling and reward learning, and its enhancement of dopamine release in the VTA-NAc circuit as a novel mechanism for nicotine reward.

Serotonin signaling at cilia synapses

Serotonin (5-HT) is a key neuromodulator influencing cognition, mood, and sleep, yet the structural and molecular mechanisms of serotonergic signaling remain incompletely understood. Recent findings have identified a novel mode of serotonergic transmission via axo-ciliary synapses, where serotonergic axons directly contact the primary cilia of hippocampal pyramidal neurons. These synapses facilitate localized 5-HT release, activating ciliary 5-HT6R receptors and triggering intracellular signaling cascades distinct from conventional synaptic mechanisms. This pathway leads to chromatin remodeling and transcriptional regulation, providing a direct link between serotonergic signaling and neuronal gene expression. Additional volume electron microscopy studies have revealed the prevalence of axo-ciliary contacts across different brain regions, suggesting a broad role in neuromodulation. Further investigation into axo-ciliary synapses may provide critical insights into serotonergic function and its implications for neuropsychiatric disorders.

Principles and Design of Molecular Tools for Sensing and Perturbing Cell Surface Receptor Activity

Cell-surface receptors are vital for controlling numerous cellular processes with their dysregulation being linked to disease states. Therefore, it is necessary to develop tools to study receptors and the signaling pathways they control. This Review broadly describes molecular approaches that enable 1) the visualization of receptors to determine their localization and distribution; 2) sensing receptor activation with permanent readouts as well as readouts in real time; and 3) perturbing receptor activity and mimicking receptor-controlled processes to learn more about these processes. Together, these tools have provided valuable insight into fundamental receptor biology and helped to characterize therapeutics that target receptors.

A genetically encoded fluorescent whole-cell biosensor for real-time detecting estrogenic activities in water samples

Real-time monitoring of estrogenic activity in the aquatic environment is a challenging task. Current biosensors face difficulties due to their limited response speed and environmental tolerance, especially for detecting wastewater, the major source of estrogenic compounds in aquatic environments. To address these difficulties, this study developed a single fluorescent protein (FP) -based whole-cell bacterial biosensor named ER-Light, which was achieved by inserting the sensing domain of the estrogen receptor (ER) into the FP Citrine and expressing it in the periplasm of Escherichia coli. As designed, ER-Light enables the detection of net estrogenic activity in mixtures, represented by estradiol equivalent concentration (EEQ). ER-Light detects EEQ in 40 s with a detection limit of 4.55 × 10-7 μM and a maximum working range of 1.1 × 10-4 μM, demonstrating sufficient response speed, sensitivity, and working range. In addition, the ER-Light can survive and tolerate wastewater effluent. Satisfactory recoveries (91.0 % to 102.1 %) eliminated concerns about the matrix effect of wastewater. EEQs (Not detected-2.9 ×10-5 µM) measured by ER-Light from the effluent of 9 wastewater treatment plants validate its practicality in detecting wastewater. This is the first attempt to integrate ER into FP-based biosensors for environment monitoring. Our findings provide valuable design rules for real-time detection of bioactivity effects in the environment, contributing to the safeguarding of ecological and human health.

Sequential transitions of male sexual behaviors driven by dual acetylcholine-dopamine dynamics

The neural mechanisms underlying the sequential transitions of male sexual behaviors, including mounting, intromission, and ejaculation, remain largely unexplored. Here, we report that acetylcholine (ACh)-dopamine (DA) dynamics in the ventral shell of the nucleus accumbens (vsNAc) regulate these sexual transitions in male mice. During intromission, the vsNAc displays a unique pattern of dual ACh-DA rhythms, generated by reciprocal regulation between ACh and DA signaling via nicotinic ACh receptors (nAChRs) and DA D2 receptors (D2Rs). Knockdown of choline acetyltransferase (ChAT) or D2R in the vsNAc diminishes the occurrence of intromission and ejaculation. Optogenetic manipulations demonstrated that DA signaling maintains sexual behaviors by suppressing D2RvsNAc neurons. Moreover, ACh signaling promotes the initiation of mounting and intromission and facilitates the intromission-ejaculation transition by inducing a slowdown in DA rhythm. Together, these findings reveal that coordinated ACh-DA dynamics in the vsNAc play a critical role in orchestrating the sequential transitions of male sexual behaviors.

Amphetamine in Adolescence Induces a Sex-Specific Mesolimbic Dopamine Phenotype in the Adult Prefrontal Cortex

Drugs of abuse in adolescence impact brain maturation and increase psychiatric risk, with differences in sensitivity between males and females. Amphetamine in adolescent male, but not female mice, causes dopamine axons intended to innervate the nucleus accumbens and to grow ectopically to the prefrontal cortex (PFC). This is mediated by drug-induced downregulation of the Netrin-1 receptor DCC. How off-target dopamine axons function in the adult PFC remains to be determined. Here we report that males and females show place preference for amphetamine in adolescence. However, only in males, amphetamine increases PFC dopamine transporter expression in adulthood: leading to aberrant baseline dopamine transients, faster dopamine release, and exaggerated responses to acute methylphenidate. Upregulation of DCC in adolescence, using CRISPRa, prevents all these changes. Mesolimbic dopamine axons rerouted to the PFC in adolescence retain anatomical and functional phenotypes of their intended target, rendering males enduringly vulnerable to the harmful effects of drugs of abuse.

Dopamine Drives Feedforward Inhibition to Orexin Feeding System, Mediating Weight Loss Induced by Morphine Addiction

Feeding behavior changes induced by opioid addiction significantly contribute to the worsening opioid crisis. Activation of the reward system has shown to provoke binge eating disorder in individuals with opioid use disorder, whereas prolonged opioid exposure leads to weight loss. Understanding the mechanisms underlying these phenomena is essential for addressing this pressing societal issue. This study demonstrates that weight loss resulting from feeding behavior changes during morphine addiction requires the activation of the ventral tegmental area dopamine (DA) system, which suppresses the orexin feeding center. Specifically, DA exerts an inhibitory effect on orexin neurons in the lateral hypothalamus area (LHA) through a feedforward inhibition mediated by GABA neurons in the LHA, involving D1 receptors (D1R) and T-type Ca2+ channels. Moreover, the morphine addiction-induced reduction in body weight and food intake can be reversed by the D1R antagonist SCH23390 and chemogenetic silencing of GABA neurons in the LHA. These findings delineate a neuromodulatory mechanism underlying morphine addiction-associated feeding behavior changes and weight loss.

Batch-fabricated full glassy carbon fibers for real-time tonic and phasic dopamine detection

Dopamine (DA) is a critical neurotransmitter that is key in regulating motor functions, motivation, and reward-related behavior. Measuring both tonic (baseline, steady-state) and phasic (rapid, burst-like) DA release is essential for elucidating the mechanisms underlying neurological disorders, such as schizophrenia and Parkinson's disease, which are associated with dysregulated tonic and phasic DA signaling. Carbon fiber microelectrodes (CFEs) are considered the gold standard for measuring rapid neurotransmitter changes due to their small size (5-10 µm), biocompatibility, flexibility, and excellent electrochemical properties. However, achieving consistent results and large-scale production of CFE arrays through manual fabrication poses significant challenges. We previously developed flexible glassy carbon (GC) microelectrode arrays (MEAs) and GC fiber-like MEAs (GCF MEAs) for neurotransmitter detection and electrophysiology recording. We also demonstrated the feasibility of fabricating GC MEA with both GC electrodes and interconnects made from a single homogeneous material, eliminating the need for metal interconnections and addressing related concerns about electrical and mechanical stability under prolonged electrochemical cycling. Building on our prior experience, we now present a double-etching microfabrication technique for the batch production of 10 μm × 10 µm full GC fibers (fGCFs) and fGCF arrays, composed entirely of homogeneous GC material. This process uses a 2 µm-thick low-stress silicon nitride as the bottom insulator layer for the fGCFs. The effectiveness of the fabrication process was validated through scanning electron microscophy (SEM) and energy dispersive X-ray spectroscopy (EDS) elemental analyses, which confirmed the uniformity of the Si₃N₄ insulation layer and ensured the overall integrity of the fGCFs. Using finite element analysis, we optimized the fGCF form factor to achieve self-penetration up to 3 mm into the mouse striatum without additional support. The electrochemical characterization of fGCFs demonstrated high electrical conductivity and a wide electrochemical window. The ability of fGCFs to detect phasic and tonic DA release was confirmed using fast scan cyclic voltammetry (FSCV) and square wave voltammetry (SWV), respectively, both in vitro and in vivo. With their high sensitivity for phasic and tonic DA detection, combined with a scalable fabrication process and self-supporting insertion capability, fGCFs are promising sensors that offer enhanced practicality for comprehensive DA monitoring.

Cold induces brain region-selective cell activity-dependent lipid metabolism

It has been well documented that cold is an enhancer of lipid metabolism in peripheral tissues, yet its effect on central nervous system lipid dynamics is underexplored. It is well recognized that cold acclimations enhance adipocyte functions, including white adipose tissue lipid lipolysis and beiging, and brown adipose tissue thermogenesis in mammals. However, it remains unclear whether and how lipid metabolism in the brain is also under the control of ambient temperature. Here, we show that cold exposure predominantly increases the expressions of the lipid lipolysis genes and proteins within the paraventricular nucleus of the hypothalamus (PVH) in male mice. Mechanistically, by using innovatively combined brain-region selective pharmacology and in vivo time-lapse photometry monitoring of lipid metabolism, we find that cold activates cells within the PVH and pharmacological inactivation of cells blunts cold-induced effects on lipid peroxidation, accumulation of lipid droplets, and lipid lipolysis in the PVH. Together, these findings suggest that PVH lipid metabolism is cold sensitive and integral to cold-induced broader regulatory responses.

A high-performance GRAB sensor reveals differences in the dynamics and molecular regulation between neuropeptide and neurotransmitter release

The co-existence and co-transmission of neuropeptides and small molecule neurotransmitters within individual neuron represent a fundamental characteristic observed across various species. However, the differences regarding their in vivo spatiotemporal dynamics and underlying molecular regulation remain poorly understood. Here, we develop a GPCR-activation-based (GRAB) sensor for detecting short neuropeptide F (sNPF) with high sensitivity and spatiotemporal resolution. Furthermore, we investigate the in vivo dynamics and molecular regulation differences between sNPF and acetylcholine (ACh) from the same neurons. Interestingly, our findings reveal distinct spatiotemporal dynamics in the release of sNPF and ACh. Notably, our results indicate that distinct synaptotagmins (Syt) are involved in these two processes, as Syt7 and Sytα for sNPF release, while Syt1 for ACh release. Thus, this high-performance GRAB sensor provides a robust tool for studying neuropeptide release and shedding insights into the unique release dynamics and molecular regulation that distinguish neuropeptides from small molecule neurotransmitters.

G-Quadruplex DNAzyme-Based Biocatalysis Combined with an Intelligent Electromagnetic-Actuated Microfluidic Chip for Tetracycline Detection

In this study, we present an intelligent electromagnetic-actuated microfluidic chip integrated with a G-quadruplex DNAzyme-based biocatalysis platform for rapid and sensitive tetracycline (TC) detection. In this sensing system, TC significantly quenches fluorescent magnetic carbon dots (M-CDs) via the internal filtration effect and dynamic quenching (the excitation and emission wavelength at 350 and 440 nm, respectively). Then, the G-quadruplex on the M-CDs-Aptamer is exposed and bound with hemin to form hemin-G-quadruplex DNAzyme, catalyzing the conversion of 3,3',5,5'-tetramethylbenzidine to produce blue color. This enables the fluorescence/colorimetric detection of TC. Importantly, an automatic electromagnet-integrated microfluidic chip was designed to control the shuttling of magnetic materials in each function slot according to a programmed sequence. Under the optimal conditions, the detection limits of TC for fluorescence and colorimetric methods were 11 and 43 μmol/L, respectively. The detection results for tilapia (Oreochromis nilotica) were comparable to those of traditional high-performance liquid chromatography. This platform offers excellent performance for TC determination and potential for portable, intelligent detection of trace pollutants in food and the environment.

Sexually dimorphic dopaminergic circuits determine sex preference

Sociosexual preference is critical for reproduction and survival. However, neural mechanisms encoding social decisions on sex preference remain unclear. In this study, we show that both male and female mice exhibit female preference but shift to male preference when facing survival threats; their preference is mediated by the dimorphic changes in the excitability of ventral tegmental area dopaminergic (VTADA) neurons. In males, VTADA projections to the nucleus accumbens (NAc) mediate female preference, and those to the medial preoptic area mediate male preference. In females, firing-pattern (phasic-like versus tonic-like) alteration of the VTADA-NAc projection determines sociosexual preferences. These findings define VTADA neurons as a key node for social decision-making and reveal the sexually dimorphic DA circuit mechanisms underlying sociosexual preference.

Enhanced motivated behavior mediated by pharmacological targeting of the FGF14/Nav1.6 complex in nucleus accumbens neurons

Protein/protein interactions (PPI) play crucial roles in neuronal functions. Yet, their potential as drug targets for brain disorders remains underexplored. The fibroblast growth factor 14 (FGF14)/voltage-gated Na+ channel 1.6 (Nav1.6) complex regulates excitability of medium spiny neurons (MSN) of the nucleus accumbens (NAc), a central hub of reward circuitry that controls motivated behaviors. Here, we identified compound 1028 (IUPAC: ethyl 3-(2-(3-(hydroxymethyl)-1H-indol-1-yl)acetamido)benzoate), a brain-permeable small molecule that targets FGF14R117, a critical residue located within a druggable pocket at the FGF14/Nav1.6 PPI interface. We found that 1028 modulates FGF14/Nav1.6 complex assembly and depolarizes the voltage-dependence of Nav1.6 channel inactivation with nanomolar potency by modulating the intramolecular interaction between the III-IV linker and C-terminal domain of the Nav1.6 channel. Consistent with the compound's effects on Nav1.6 channel inactivation, 1028 enhances MSN excitability ex vivo and accumbal neuron firing rate in vivo in murine models. Systemic administration of 1028 maintains behavioral motivation preferentially during motivationally deficient conditions in murine models. These behavioral effects were abrogated by in vivo gene silencing of Fgf14 in the NAc and were accompanied by a selective reduction in accumbal dopamine levels during reward consumption in murine models. These findings underscore the potential to selectively regulate complex behaviors associated with neuropsychiatric disorders through targeting of PPIs in neurons.

Dopaminergic signaling to ventral striatum neurons initiates sniffing behavior

Sniffing is a motivated behavior displayed by nearly all terrestrial vertebrates. While sniffing is associated with acquiring and processing odors, sniffing is also intertwined with affective and motivated states. The systems which influence the display of sniffing are unclear. Here, we report that dopamine release into the ventral striatum in mice is coupled with bouts of sniffing and that stimulation of dopaminergic terminals in these regions drives increases in respiratory rate to initiate sniffing whereas inhibition of these terminals reduces respiratory rate. Both the firing of individual neurons and the activity of post-synaptic D1 and D2 dopamine receptor-expressing neurons are coupled with sniffing and local antagonism of D1 and D2 receptors squelches sniffing. Together, these results support a model whereby sniffing can be initiated by dopamine's actions upon ventral striatum neurons. The nature of sniffing being integral to both olfaction and motivated behaviors implicates this circuit in a wide array of functions.

Aggression experience and observation promote shared behavioral and neural changes

The ability to observe the social behavior of others and use observed information to bias future action is a fundamental building block of social cognition1,2. A foundational question is whether social observation and experience engage common circuit mechanisms that enable behavioral change. While classic studies on social learning have shown that aggressive behaviors can be learned through observation3, it remains unclear whether aggression observation promotes persistent neural changes that generalize to new contexts. Here, to directly compare the effects of aggression experience and observation at brain-wide scale, we develop a strategy to perform large-scale cell-type specific recordings across subcortical networks for social behavior control and learning. We record longitudinally while animals "train" through direct experience or observation, then probe shared differences in behavior and neural activity in a novel "hard" aggression context. Using supervised and unsupervised methods for behavioral quantification, we detect unique signatures of a shared behavioral strategy not present in animals with no training. During observation, we find widespread activation that mimics experience in networks for behavior generation, with critical differences in signals associated with reward and threat learning. After observation, we observe that changes persist into the novel aggression context, with increased similarity in the neural dynamics between experience and observation groups. Network-level modeling reveals persistent shared changes to a core aggression network, with widespread decoupling of inhibition from a key hypothalamic output region. This demonstrates that "experience-like" activity during observation can recruit a shared plasticity mechanism that biases behavior toward adaptive defensive strategies in new contexts.

In vivo multiplex imaging of dynamic neurochemical networks with designed far-red dopamine sensors

Neurochemical signals like dopamine (DA) play a crucial role in a variety of brain functions through intricate interactions with other neuromodulators and intracellular signaling pathways. However, studying these complex networks has been hindered by the challenge of detecting multiple neurochemicals in vivo simultaneously. To overcome this limitation, we developed a single-protein chemigenetic DA sensor, HaloDA1.0, which combines a cpHaloTag-chemical dye approach with the G protein-coupled receptor activation-based (GRAB) strategy, providing high sensitivity for DA, sub-second response kinetics, and an extensive spectral range from far-red to near-infrared. When used together with existing green and red fluorescent neuromodulator sensors, Ca2+ indicators, cAMP sensors, and optogenetic tools, HaloDA1.0 provides high versatility for multiplex imaging in cultured neurons, brain slices, and behaving animals, facilitating in-depth studies of dynamic neurochemical networks.

Genetic Tools in Rodents to Study Cannabinoid Functions

During the past 30 years, the endocannabinoid system (ECS) has emerged as a major signalling system in the mammalian brain regulating neurotransmission in numerous brain regions and in various cell populations. Endocannabinoids are able to regulate specific physiological functions and thus modify their behavioural manifestations and allostatic alterations of the ECS linked to different pathological conditions. As discussed in detail in other chapters of this book, endocannabinoids are involved in learning and memory, stress, and anxiety, feeding, energy balance, development, and ageing. Likewise, many CNS disorders (e.g. schizophrenia, epilepsy, substance use disorders, and multiple sclerosis) are associated with dysregulation of the ECS. Discerning the physiological functions of the synthetic and degrading enzymes of endocannabinoids and their receptors is a challenging task because of their distinct and complex expression patterns. Techniques of genetic engineering have been able to shed light on a number of complex ECS-related tasks during the past years. In this chapter, first, we take a critical look at the toolbox available to researchers who would like to investigate cannabinoid effects using genetic engineering techniques, then we comprehensively discuss genetically modified rodent models in various neuronal and non-neuronal cell populations, both within and outside the nervous system.

Affinity Peptide-Based Circularly Permuted Fluorescent Protein Biosensors for Non-Small Cell Lung Cancer Diagnosis

Non-small cell lung cancer (NSCLC) is the predominant form of lung cancer and poses a significant public health challenge. Early detection is crucial for improving patient outcomes, with serum biomarkers such as carcinoembryonic antigen (CEA), squamous cell carcinoma antigen (SCCAg), and cytokeratin fragment 19 (CYFRA 21-1) playing a critical role in early screening and pathological classification of NSCLC. However, due to being mainly based on corresponding antibody binding reactions, existing detection technologies for these serum biomarkers have shortcomings such as complex operations, high false positive rates, and high costs. This study aimed to develop new methods for detecting CEA, SCCAg, and CYFRA 21-1 to assist in the diagnosis of NSCLC. Affinity peptides of CEA, SCCAg, and CYFRA 21-1, respectively, were screened by phage display technology, and the peptides' binding affinities were determined by enzyme-linked immunosorbent assay and biolayer interferometry. Peptides with high affinity were then integrated as binding domains into biosensors by fusing them with circularly permuted fluorescent proteins (cpFPs) through genetic coding. The resulting biosensors, C4 biosensor for CEA, S1 biosensor for SCCAg, and Y3 biosensor for CYFRA 21-1, demonstrated robust sensitivity and specificity even at concentrations as low as 1 ng/mL for their respective tumor markers. When applied to clinical samples and recalibrated for the upper limit of normal concentrations, the biosensors exhibited enhanced sensitivity and specificity for NSCLC diagnosis. This study introduced innovative biosensors for the detection of CEA, SCCAg, and CYFRA 21-1, providing a highly sensitive, specific, rapid, and cost-effective diagnostic alternative that could significantly improve NSCLC screening rates.

Enhancing striatal acetylcholine facilitates dopamine release and striatal output in parkinsonian mice

BACKGROUND

L-DOPA has been considered the first-line therapy for treating Parkinson's disease (PD) via restoring striatal dopamine (DA) to normalize the activity of local spiny projection neurons (SPNs) in the direct (dSPNs) pathway and the indirect (iSPNs) pathway. While the changes in striatal acetylcholine (ACh) induced by increasing DA have been extensively discussed, their validity remains controversial. Inhibition of striatal cholinergic signaling attenuates PD motor deficits. Interestingly, enhancing striatal ACh triggers local DA release, suggesting the pro-kinetic effects of ACh in movement control. Here, we investigated the in-vivo dynamics of ACh in the dorsolateral striatum (DLS) of the 6-OHDA-lesioned mouse model after L-DOPA administration, as well as its underlying mechanism, and to explore its modulatory role and mechanism in parkinsonian symptoms.

RESULTS

Using in vivo fiber photometry recordings with genetically encoded fluorescent DA or ACh indicator, we found L-DOPA selectively decreased DLS ACh levels in parkinsonian conditions. DA inhibited ACh release via dopamine D2 receptors and dSPNs-mediated activation of type-A γ-aminobutyric acid receptors on cholinergic interneurons. Restoring DLS ACh levels during L-DOPA treatment induced additional DA release by activating nicotinic acetylcholine receptors, thereby promoting the activity of dSPNs and iSPNs. Enhancing DLS ACh facilitated L-DOPA-induced turning behavior but not dyskinesia in parkinsonian mice.

CONCLUSIONS

Our results demonstrated that enhancing striatal ACh facilitated the effect of L-DOPA by modulating DA tone. It may challenge the classical hypothesis of a purely competitive interaction between dopaminergic and cholinergic neuromodulation in improving PD motor deficits. Modulating ACh levels within the dopaminergic system may improve striatal DA availability in PD patients.

Neural Network Mechanisms Underlying General Anesthesia: Cortical and Subcortical Nuclei

General anesthesia plays a significant role in modern medicine. However, the precise mechanism of general anesthesia remains unclear, posing a key scientific challenge in anesthesiology. Advances in neuroscience techniques have enabled targeted manipulation of specific neural circuits and the capture of brain-wide neural activity at high resolution. These advances hold promise for elucidating the intricate mechanisms of action of general anesthetics. This review aims to summarize our current understanding of the role of cortical and subcortical nuclei in modulating general anesthesia, providing new evidence of cortico-cortical and thalamocortical networks in relation to anesthesia and consciousness. These insights contribute to a comprehensive understanding of the neural network mechanisms underlying general anesthesia.

Dopamine transmission at D1 and D2 receptors in the nucleus accumbens contributes to the expression of incubation of cocaine craving

Relapse represents a consistent clinical problem for individuals with substance use disorder. In the incubation of craving model of persistent craving and relapse, cue-induced drug seeking progressively intensifies or "incubates" during the first weeks of abstinence from drug self-administration and then remains high for months. Previously, we and others have demonstrated that expression of incubated cocaine craving requires strengthening of excitatory synaptic transmission in the nucleus accumbens core (NAcc). However, despite the importance of dopaminergic signaling in the NAcc for motivated behavior, little is known about the role that dopamine (DA) plays in the incubation of cocaine craving. Here we used fiber photometry to measure DA transients in the NAcc of male and female rats during cue-induced seeking tests conducted in early abstinence from cocaine self-administration, prior to incubation, and late abstinence, after incubation of craving has plateaued. We observed DA transients time-locked to cue-induced responding but their magnitude did not differ significantly when measured during early versus late abstinence seeking tests. Next, we tested for a functional role of these DA transients by injecting DA receptor antagonists into the NAcc just before the cue-induced seeking test. Blockade of either D1 or D2 DA receptors reduced cue-induced cocaine seeking after but not before incubation. We found no main effect of sex or significant interaction of sex with other factors in our experiments. These results suggest that DA contributes to incubated cocaine seeking but the emergence of this role reflects changes in postsynaptic responsiveness to DA rather than presynaptic alterations.

Engineering signalling pathways in mammalian cells

In mammalian cells, signalling pathways orchestrate cellular growth, differentiation and survival, as well as many other processes that are essential for the proper functioning of cells. Here we describe cutting-edge genetic-engineering technologies for the rewiring of signalling networks in mammalian cells. Specifically, we describe the recombination of native pathway components, cross-kingdom pathway transplantation, and the development of de novo signalling within cells and organelles. We also discuss how, by designing signalling pathways, mammalian cells can acquire new properties, such as the capacity for photosynthesis, the ability to detect cancer and senescent cell markers or to synthesize hormones or metabolites in response to chemical or physical stimuli. We also review the applications of mammalian cells in biocomputing. Technologies for engineering signalling pathways in mammalian cells are advancing basic cellular biology, biomedical research and drug discovery.

Molecular Spies in Action: Genetically Encoded Fluorescent Biosensors Light up Cellular Signals

Cellular function is controlled through intricate networks of signals, which lead to the myriad pathways governing cell fate. Fluorescent biosensors have enabled the study of these signaling pathways in living systems across temporal and spatial scales. Over the years there has been an explosion in the number of fluorescent biosensors, as they have become available for numerous targets, utilized across spectral space, and suited for various imaging techniques. To guide users through this extensive biosensor landscape, we discuss critical aspects of fluorescent proteins for consideration in biosensor development, smart tagging strategies, and the historical and recent biosensors of various types, grouped by target, and with a focus on the design and recent applications of these sensors in living systems.

Innervation density governs crosstalk of GPCR-based norepinephrine and dopamine sensors

GPCR-based fluorescent sensors are widely used to correlate neuromodulatory signaling with brain function. While experiments in transfected cells often reveal selectivity for individual neurotransmitters, sensor specificity in the brain frequently remains uncertain. Pursuing experiments in brain slices and in vivo, we find that norepinephrine and dopamine cross-activate the respective sensors. Non-specific activation occurred when innervation of the cross-reacting transmitter was high, and silencing of specific innervation was indispensable for interpreting sensor fluorescence.

L-DOPA Promotes Functional Proliferation Through GPR143, Specific L-DOPA Receptor of Astrocytes

l-3,4-Dihydroxyphenylalanine (levodopa and L-DOPA in this text), alongside dopamine, boasts high biocompatibility, prompting industrial demand for its use as a coating material. Indeed, the effectiveness of L-DOPA is steadily rising as it serves as an oral therapeutic agent for neurodegenerative brain diseases, particularly Parkinson's disease (PD). However, the effects of L-DOPA on the growth and function of astrocytes, the main glial cells, and the most numerous glial cells in the brain, are unknown. Here, we investigated whether L-DOPA is possible as a coating material on cover glass and polystyrene for rat primary astrocytes. The coating state of L-DOPA on the cover glass and polystyrene was characterized by X-ray photoelectron spectroscopy (XPS) and static water contact angle (WCA). Interestingly, L-DOPA coated on the cover glass promoted the proliferation of astrocytes but not neurons. Furthermore, L-DOPA coated on the cover glass, as opposed to polystyrene, facilitated the proliferation of the astrocytes. The astrocytes grown on L-DOPA-coated cover glasses exhibited functional receptor-activated Ca2+ transients through the activation of protease-activated receptor subtype 1 (PAR-1), recognized as an astrocytic functional marker. However, cover glass coated with 0, 500, 1000, 2000, and 4000 μg/mL L-DOPA maintained astrocyte viability, while supplementation with 500 and 1000 μM L-DOPA significantly decreased astrocyte viability. This suggests that treatments with free 500 and 1000 μM L-DOPA significantly reduced the number of astrocytes. Both Pimozide, an inhibitor of G protein-coupled receptor 143 (GPR143), also known as Ocular albinism type 1 (OA1), and CCG2046, an inhibitor of regulator of G protein signaling 4 (RGS4), reduced the viability of astrocytes on cover glass coated with L-DOPA compared to astrocytes on cover glass coated with poly-d-lysine (PDL). This suggests that L-DOPA promotes astrocyte proliferation through activation of the GPR143 signaling pathway. These findings imply that L-DOPA proliferates functional astrocytes through the activation of GPR143. These results are the first report that L-DOPA coating cover glass proliferates rat primary astrocytes with the activation of GPR143. The discovery that levodopa enhances cell adhesion can significantly influence research in multiple ways. It provides insights into cell behavior, disease mechanisms, and potential therapeutic applications in tissue engineering and regenerative medicine. Additionally, it offers opportunities to explore novel approaches for improving cell-based therapies and tissue regeneration. Overall, this finding opens up new avenues for research, with broad implications across various scientific fields.

Microplasma-induced in situ rapid synthesis of CoSe nanosphere@N-doped polymeric carbon dots derived from ZIF-67 for highly sensitive dopamine detection

BACKGROUND

Designing a fast and sensitive electrochemical sensing platform to achieve selective quantitative detection of dopamine (DA) is a great challenge. Combining transition metal selenides (TMSs) with a variety of conductive carbonaceous materials is one of the effective strategies to improve the electrocatalytic activity of TMSs. However, most of the reported preparation methods of TMSs/carbon-based composite nanomaterials need to be annealed at a high temperature for a long time, which does not meet the requirements of sustainable development. Therefore, it is of great significance to explore an energy-efficient and fast method to prepare these compounds.

RESULTS

In this work, CoSe nanosphere@nitrogen-doped polymeric carbon dots are rapid prepared using ZIF precursor by simple dielectric barrier discharge (DBD) microplasma-induced on carbon cloth (CoSe NSs@N-PCDs/CC) for the first time. Owing to the fact that CoSe can promote rapid proton transfer, N-CDs has a high specific surface area, rich functional groups and electrical conductivity, this electrode exhibits highly sensitive non-enzymatic electrochemical sensing performance for DA detection. The linear range and detection limit are 0.1 μM-50 μM and 40.2 nM, respectively, and it have been successfully applied to the determination of DA levels in real human serum samples. Theoretical DFT calculations show that the most efficient interaction with DA on the surface of CoSe (101) can promote electrochemical reactions and catalyze DA oxidation.

SIGNIFICANCE

Using ZIF as precursor, CoSe NSs@N-PCDs/CC electrochemical electrode was synthesized in situ by simple and energy-saving DBD microplasma. CoSe NSs can effectively prevent the aggregation of function-rich N-PCDs and significantly improve the electrocatalytic activity of the composite. The mechanism of high selectivity of CoSe NSs@N-PCDs/CC electrode to DA was studied by DFT calculation. This work provides a new idea for the fast and green synthesis of transition metal and carbon-based nanomaterials by microplasma.

INTERSPECIES ORGANOIDS REVEAL HUMAN-SPECIFIC MOLECULAR FEATURES OF DOPAMINERGIC NEURON DEVELOPMENT AND VULNERABILITY

The disproportionate expansion of telencephalic structures during human evolution involved tradeoffs that imposed greater connectivity and metabolic demands on midbrain dopaminergic neurons. Despite the central role of dopaminergic neurons in human-enriched disorders, molecular specializations associated with human-specific features and vulnerabilities of the dopaminergic system remain unexplored. Here, we establish a phylogeny-in-a-dish approach to examine gene regulatory evolution by differentiating pools of human, chimpanzee, orangutan, and macaque pluripotent stem cells into ventral midbrain organoids capable of forming long-range projections, spontaneous activity, and dopamine release. We identify human-specific gene expression changes related to axonal transport of mitochondria and reactive oxygen species buffering and candidate cis- and trans-regulatory mechanisms underlying gene expression divergence. Our findings are consistent with a model of evolved neuroprotection in response to tradeoffs related to brain expansion and could contribute to the discovery of therapeutic targets and strategies for treating disorders involving the dopaminergic system.

Dynamic overrepresentation of accumbal cues in food- and opioid-seeking rats after prenatal THC exposure

The increasing prevalence of cannabis use during pregnancy has raised medical concerns, primarily related to Δ9-tetrahydrocannabinol (THC), which readily crosses the placenta and affects fetal brain development. Previous research has identified dopaminergic alterations related to maternal THC consumption. However, the consequences that prenatal cannabis exposure (PCE) has on striatum-based processing during reward pursuit have not been determined. Here, we characterize PCE rats during food or opioid-maintained reward seeking. We find that the supramotivational phenotype of PCE rats is independent of value-based processing and is instead related to augmented reinforcing efficiency of opioid rewards. Our findings reveal that prenatal THC exposure leads to increased cue-evoked dopamine responses and an overrepresentation of effort-driven striatal encoding patterns. Recapitulating clinical findings, drug-related PCE adaptations were more pronounced in males, who showed increased vulnerability for relapse. Collectively, these findings indicate that prenatal THC exposure in male rats engenders a pronounced neurodevelopmental susceptibility to addiction-like disorders.

The interhemispheric amygdala-accumbens circuit encodes negative valence in mice

The structurally symmetric mammalian brain hemispheres are interconnected by commissural axons across the midline. However, the functions of interhemispheric connectivity remain largely unknown. We found that in mice, transection of the anterior commissure (AC), which connects the rostroventral forebrain, impaired avoidant behaviors. The basolateral amygdala (BLA) in the mouse projects to the contralateral nucleus accumbens (NAc) through the AC, independent of its ipsilateral projections. Aversive stimuli activated contralateral BLA-NAc projections. Positive stimuli, however, activated ipsilateral projections. Selective activation of contralateral BLA-NAc projections activated D2-positive medium spiny neurons (D2-MSNs), reduced NAc dopamine levels, and caused aversion, whereas selective activation of ipsilateral BLA-NAc projections activated D1-MSNs, increased NAc dopamine levels, and induced reward. The contralateral BLA-AC-NAc pathway is crucial for encoding negative valence, demonstrating distinct functions of intra- and interhemispheric circuits in brain physiology.

Highly Sensitive and Biocompatible Microsensor for Selective Dynamic Monitoring of Dopamine in Rat Brain

Highly selective and sensitive in vivo neurotransmitter dynamic monitoring of the central nervous system has long been a challenging endeavor. Here, an implantable and biocompatible microsensor with excellent performances was reported by electrodepositing poly(3,4-ethylenedioxythiophene)-electrochemically reduced graphene oxide (PEDOT-ERGO) nanocomposites and poly(tannic acid) (pTA) sequentially on the carbon fiber electrode (CFE) surface, and its feasibility in in vivo electrochemical sensing applications were demonstrated. Due to the synergistic electrocatalytic effect of PEDOT-ERGO nanocomposites with the negative-charged pTA on dopamine (DA) redox reaction, the microsensor exhibits high detection sensitivities of 1.1 and 0.37 nA μM-1 in the detection ranges of 0.02-0.5 and 0.5-20 μM with a low limit of detection of 9.2 nM. Also, the microsensor shows excellent selectivity, good sensing stability, repeatability, and reproducibility. In addition, the highly hydrophilic and negative-charged pTA inhibits the nonspecific adsorption of hydrophobic proteins, which endows the microsensor with good antifouling ability. Moreover, DA dynamics in rat brain were successfully monitored in real time, and the selective sensing ability of the microsensor in vivo was also demonstrated. The present study provides a new method for selective dynamics monitoring of DA in the brain, which would help to better understand the pathological and physiological functions of DA.

Applications of functional neurotransmitter release imaging with genetically encoded sensors in psychiatric research

Psychiatric research encompasses diverse methodologies to understand the complex interplay between neurochemistry and behavior in mental health disorders. Despite significant advancements in pharmacological interventions, there remains a critical gap in understanding the precise functional changes underlying psychiatric conditions and the mechanisms of action of therapeutic agents. Genetically encoded sensors have emerged as powerful tools to address these challenges by enabling real-time monitoring of neurochemical dynamics in specific neuronal populations. This prospective explores the utility of neurotransmitter binding genetically encoded sensors in uncovering the nature of neuronal dysregulation underpinning mental illness, assessing the impact of pharmaceutical interventions, and facilitating the discovery of novel treatments.

Mechanisms of neuromodulatory volume transmission

A wealth of neuromodulatory transmitters regulate synaptic circuits in the brain. Their mode of signaling, often called volume transmission, differs from classical synaptic transmission in important ways. In synaptic transmission, vesicles rapidly fuse in response to action potentials and release their transmitter content. The transmitters are then sensed by nearby receptors on select target cells with minimal delay. Signal transmission is restricted to synaptic contacts and typically occurs within ~1 ms. Volume transmission doesn't rely on synaptic contact sites and is the main mode of monoamines and neuropeptides, important neuromodulators in the brain. It is less precise than synaptic transmission, and the underlying molecular mechanisms and spatiotemporal scales are often not well understood. Here, we review literature on mechanisms of volume transmission and raise scientific questions that should be addressed in the years ahead. We define five domains by which volume transmission systems can differ from synaptic transmission and from one another. These domains are (1) innervation patterns and firing properties, (2) transmitter synthesis and loading into different types of vesicles, (3) architecture and distribution of release sites, (4) transmitter diffusion, degradation, and reuptake, and (5) receptor types and their positioning on target cells. We discuss these five domains for dopamine, a well-studied monoamine, and then compare the literature on dopamine with that on norepinephrine and serotonin. We include assessments of neuropeptide signaling and of central acetylcholine transmission. Through this review, we provide a molecular and cellular framework for volume transmission. This mechanistic knowledge is essential to define how neuromodulatory systems control behavior in health and disease and to understand how they are modulated by medical treatments and by drugs of abuse.

Reductions of Grin2a in adolescent dopamine neurons confers aberrant salience and related psychosis phenotype

Psychosis is a hallmark of schizophrenia. It typically emerges in late adolescence and is associated with dopamine abnormalities and aberrant salience. Most genes associated with schizophrenia risk involve ubiquitous targets that may not explain delayed emergence of dopaminergic disruptions. This includes GRIN2A, the gene encoding the GluN2A subunit of the NMDA receptor. Both common and rare variants of GRIN2A are considered genetic risk factors for schizophrenia diagnosis. We find that Grin2a knockout in dopamine neurons during adolescence is sufficient to produce a behavioral phenotype that mirrors aspects of psychosis. These include disruptions in effort optimization, salience attribution, and ability to utilize feedback to guide behavior. We also find a selective effect of this manipulation on dopamine release during prediction error signaling. These data provide mechanistic insight into how variants of GRIN2A may lead to the latent presentation of aberrant salience and abnormalities in dopamine dynamics. This etiologically relevant model may aid future discovery of course altering treatments for schizophrenia.

Molecular and circuit determinants in the globus pallidus mediating control of cocaine-induced behavioral plasticity

The globus pallidus externus (GPe) is a central component of the basal ganglia circuit that acts as a gatekeeper of cocaine-induced behavioral plasticity. However, the molecular and circuit mechanisms underlying this function are unknown. Here, we show that GPe parvalbumin-positive (GPePV) cells mediate cocaine responses by selectively modulating ventral tegmental area dopamine (VTADA) cells projecting to the dorsomedial striatum (DMS). Interestingly, GPePV cell activity in cocaine-naive mice is correlated with behavioral responses following cocaine, effectively predicting cocaine sensitivity. Expression of the voltage-gated potassium channels KCNQ3 and KCNQ5 that control intrinsic cellular excitability following cocaine was downregulated, contributing to the elevation in GPePV cell excitability. Acutely activating channels containing KCNQ3 and/or KCNQ5 using the small molecule carnosic acid, a key psychoactive component of Salvia rosmarinus (rosemary) extract, reduced GPePV cell excitability and impaired cocaine reward, sensitization, and volitional cocaine intake, indicating its therapeutic potential to counteract psychostimulant use disorder.

Wakefulness Induced by TAAR1 Partial Agonism in Mice Is Mediated Through Dopaminergic Neurotransmission

Trace amine-associated receptor 1 (TAAR1) is a negative regulator of dopamine (DA) release. The partial TAAR1 agonist RO5263397 promotes wakefulness and suppresses NREM and REM sleep in rodents and non-human primates. We tested the hypothesis that the TAAR1-mediated effects on sleep/wake regulation were due, in part, to DA release. Male C57BL6/J mice (n = 8) were intraperitoneally administered the D1R antagonist SCH23390, the D2R antagonist eticlopride, a combination of D1R + D2R antagonists, or saline at ZT5.5, followed 30 min later by RO5263397 or vehicle per os. EEG, EMG, subcutaneous temperature, and activity were recorded across the 8 treatments and sleep architecture was analyzed for 6 h post-dosing. As described previously, RO5263397 increased wakefulness and delayed NREM and REM sleep onset. D1, D2, and D1 + D2 pretreatment reduced RO5263397-induced wakefulness for 1-2 h after dosing but only the D1 antagonist significantly reduced the TAAR1-mediated increase in NREM latency. Neither the D1 nor the D2 antagonist affected the TAAR1-mediated suppression of REM sleep. These results suggest that, whereas the TAAR1 effects on wakefulness are mediated, in part, through the D2R, D1R activation plays a role in reversing the TAAR1-mediated increase in NREM sleep latency. In contrast, the TAAR1-mediated suppression of REM sleep appears not to involve D1R or D2R mechanisms.

Wideband ratiometric measurement of tonic and phasic dopamine release in the striatum

Reward learning, cognition, and motivation are supported by changes in neurotransmitter levels across multiple timescales. Current measurement technologies for various neuromodulators (such as dopamine and serotonin) do not bridge timescales of fluctuations, limiting the ability to define the behavioral significance, regulation, and relationship between fast (phasic) and slow (tonic) dynamics. To help resolve longstanding debates about the behavioral significance of dopamine across timescales, we developed a novel quantification strategy, augmenting extensively used carbon-fiber Fast Scan Cyclic Voltammetry (FSCV). We iteratively engineered the FSCV scan sequence to rapidly modify electrode sensitivity within a sampling window and applied ratiometric analysis for wideband dopamine measurement. This allowed us to selectively eliminate artifacts unrelated to electrochemical detection (i.e., baseline drift), overcoming previous limitations that precluded wideband dopamine detection from milliseconds to hours. We extensively characterize this approach in vitro, validate performance in vivo with simultaneous microdialysis, and deploy this technique to measure wideband dopamine changes across striatal regions under pharmacological, optogenetic, and behavioral manipulations. We demonstrate that our approach can extend to additional analytes, including serotonin and pH, providing a robust platform to assess the contributions of multi-timescale neuromodulator fluctuations to cognition, learning, and motivation.

Dopamine release plateau and outcome signals in dorsal striatum contrast with classic reinforcement learning formulations

We recorded dopamine release signals in centromedial and centrolateral sectors of the striatum as mice learned consecutive versions of visual cue-outcome conditioning tasks. Dopamine release responses differed for the centromedial and centrolateral sites. In neither sector could these be accounted for by classic reinforcement learning alone as classically applied to the activity of nigral dopamine-containing neurons. Medially, cue responses ranged from initial sharp peaks to modulated plateau responses; outcome (reward) responses during cue conditioning were minimal or, initially, negative. At centrolateral sites, by contrast, strong, transient dopamine release responses occurred at both cue and outcome. Prolonged, plateau release responses to cues emerged in both regions when discriminative behavioral responses became required. At most sites, we found no evidence for a transition from outcome signaling to cue signaling, a hallmark of temporal difference reinforcement learning as applied to midbrain dopaminergic neuronal activity. These findings delineate a reshaping of striatal dopamine release activity during learning and suggest that current views of reward prediction error encoding need review to accommodate distinct learning-related spatial and temporal patterns of striatal dopamine release in the dorsal striatum.

Dopamine-modified hyaluronic acid (DA-HA) as a novel dopamine-mimetics with minimal autoxidation and cytotoxicity

Dopamine-modified hyaluronic acid (DA-HA) has been initially developed as an efficient coating and adhesion material for industrial uses. However, the biological activity and safety of DA-HA in the brain have not been explored yet. Here, we report a series of evidence that DA-HA exhibits similar functionality as dopamine (DA), but with much lower toxicity arising from autoxidation. DA-HA shows very little autoxidation even after 48-h incubation. This is profoundly different from DA and its derivatives including l-DOPA, which all induce severe neuronal death after pre-autoxidation, indicating that autoxidation is the cause of neuronal death. Furthermore, in vivo injection of DA-HA induces significantly lower toxicity compared to 6-OHDA, a well-known oxidized and toxic form of DA, and alleviates the apomorphine-induced rotational behavior in the 6-OHDA animal model of Parkinson's disease. Our study proposes that DA-HA with DA-like functionalities and minimal toxicity has a great potential to treat DA-related disease.

Fluorescence sensing probe based on functionalized mesoporous MOFs for non-invasive and detection of dopamine in human fluids

Abnormal amount of dopamine (DA) in human body is closely relate to various diseases, such as Parkinson's disease, pheochromocytoma. Real-time monitoring DA is crucial for disease warning, diagnosis and treatment. Currently, most methods rely on invasive blood testing for detecting DA, which is only completed with the aid of the medical staffs in hospitals. Herein, a non-invasive fluorescence visual strategy is developed for the real-time monitoring DA, based on luminescent nanoparticles and modified mesoporous zeolite imidazole framework (ZIF-8-NH2) dodecahedrons. During the reaction process, DA is enriched through the spatial configuration of ZIF-8-NH2 and hydrogen bonding effect. The luminescence of Cr3+-doped zinc gallate (ZnGa2O4:Cr3+, ZGC) is inhibited by the photo-induced electron transfer (PET) mechanism to realize sensitively detecting DA. The intelligent sensing platform based on the designed fluorescence probe and color recognition system is structured for real-time detection of DA in urine. Furthermore, a skin-fitting hydrogel patch is prepared by combining a fluorescent probe with chitosan, which enables sensitive and accurate detection of DA in sweat without the complex sample pretreatment. The non-invasive fluorescence detection method provides an effective strategy for quantitatively monitoring DA in human fluids.

Mapping multi-regional functional connectivity of astrocyte-neuronal networks during behaviors

Significance

Diverse behaviors rely on coordinated activity and multi-regional functional connectivity within astrocyte-neuronal networks. However, current techniques for simultaneously measuring astrocytic and neuronal activities across multiple brain regions during behaviors remain limited.

Aim

We propose a multi-fiber solution that can simultaneously record activities of astrocyte-neuronal networks across multiple regions during behaviors.

Approach

We employed cell-specific dual-color genetically encoded calcium indicators (GECIs) and multi-fiber photometry to simultaneously measure astrocytic and neuronal Ca2+ transients across multiple brain regions in freely behaving animals.

Results

Our findings demonstrate that both movements and sensory stimuli induce synchronized and highly correlated Ca2+ transients in astrocytes and neurons of freely behaving mice. In addition, we recorded astrocytic and neuronal Ca2+ transients from multiple brain regions during mouse behaviors. Our observations reveal heightened synchronization of astrocytic and neuronal Ca2+ transients across different brain regions during movements or sensory stimuli, indicating enhanced functional connectivity within brain-wide astrocyte-neuronal networks.

Conclusions

Multi-fiber photometry, combined with cell-specific dual-color GECIs, represents a powerful approach for investigating astrocytic and neuronal activities across different brain regions during behaviors. This technique serves as a versatile tool for analyzing the multi-regional functional connectivity map of astrocyte-neuronal networks associated with specific behaviors.

Dopamine dynamics in nucleus accumbens across reward-based learning of goal-directed whisker-to-lick sensorimotor transformations in mice

The synaptic and neuronal circuit mechanisms underlying reward-based learning remain to be fully determined. In the mammalian brain, dopamine release in nucleus accumbens is thought to contribute importantly to reward signals for learning and promoting synaptic plasticity. Here, through longitudinal fiber photometry of a genetically-encoded fluorescent sensor, we investigated dopamine signals in the nucleus accumbens of thirsty head-restrained mice as they learned to lick a liquid reward spout in response to single deflections of the C2 whisker across varying reward contingencies. Reward delivery triggered by well-timed licking drove fast transient dopamine increases in nucleus accumbens. On the other hand, unrewarded licking was overall associated with reduced dopamine sensor fluorescence, especially in trials where reward was unexpectedly omitted. The dopamine reward signal upon liquid delivery decreased within individual sessions as mice became sated. As mice learned to lick the reward spout in response to whisker deflection, a fast transient sensory-evoked dopamine signal developed, correlating with the learning of the whisker detection task across consecutive training days, as well as within single learning sessions. The well-defined behavioral paradigm involving a unitary stimulus of a single whisker as a reward-predicting cue along with precisely quantified licking allows untangling of sensory, motor and reward-related dopamine signals and how they evolve across the learning of whisker-dependent goal-directed sensorimotor transformations. Our longitudinal measurements of dopamine dynamics across reward-based learning are overall consistent with the hypothesis that dopamine could play an important role as a reward signal for reinforcement learning.

Neuromodulator and neuropeptide sensors and probes for precise circuit interrogation in vivo

To determine how neuronal circuits encode and drive behavior, it is often necessary to measure and manipulate different aspects of neurochemical signaling in awake animals. Optogenetics and calcium sensors have paved the way for these types of studies, allowing for the perturbation and readout of spiking activity within genetically defined cell types. However, these methods lack the ability to further disentangle the roles of individual neuromodulator and neuropeptides on circuits and behavior. We review recent advances in chemical biology tools that enable precise spatiotemporal monitoring and control over individual neuroeffectors and their receptors in vivo. We also highlight discoveries enabled by such tools, revealing how these molecules signal across different timescales to drive learning, orchestrate behavioral changes, and modulate circuit activity.

3D model for human glia conversion into subtype-specific neurons, including dopamine neurons

Two-dimensional neuronal cultures have a limited ability to recapitulate the in vivo environment of the brain. Here, we introduce a three-dimensional in vitro model for human glia-to-neuron conversion, surpassing the spatial and temporal constrains of two-dimensional cultures. Focused on direct conversion to induced dopamine neurons (iDANs) relevant to Parkinson disease, the model generates functionally mature iDANs in 2 weeks and allows long-term survival. As proof of concept, we use single-nucleus RNA sequencing and molecular lineage tracing during iDAN generation and find that all glial subtypes generate neurons and that conversion relies on the coordinated expression of three neural conversion factors. We also show the formation of mature and functional iDANs over time. The model facilitates molecular investigations of the conversion process to enhance understanding of conversion outcomes and offers a system for in vitro reprogramming studies aimed at advancing alternative therapeutic strategies in the diseased brain.