Groups Of Neurons Research Articles

Celsr3 drives development and connectivity of the acoustic startle hindbrain circuit.

In the developing brain, groups of neurons organize into functional circuits that direct diverse behaviors. One such behavior is the evolutionarily conserved acoustic startle response, which in zebrafish is mediated by a well-defined hindbrain circuit. While numerous molecular pathways that guide neurons to their synaptic partners have been identified, it is unclear if and to what extent distinct neuron populations in the startle circuit utilize shared molecular pathways to ensure coordinated development. Here, we show that the planar cell polarity (PCP)-associated atypical cadherins Celsr3 and Celsr2, as well as the Celsr binding partner Frizzled 3a/Fzd3a, are critical for axon guidance of two neuron types that form synapses with each other: the command-like neuron Mauthner cells that drive the acoustic startle escape response, and spiral fiber neurons which provide excitatory input to Mauthner cells. We find that Mauthner axon growth towards synaptic targets is vital for Mauthner survival. We also demonstrate that symmetric spiral fiber input to Mauthner cells is critical for escape direction, which is necessary to respond to directional threats. Moreover, we identify distinct roles for Celsr3 and Celsr2, as Celsr3 is required for startle circuit development while Celsr2 is dispensable, though Celsr2 can partially compensate for loss of Celsr3 in Mauthner cells. This contrasts with facial branchiomotor neuron migration in the hindbrain, which requires Celsr2 while we find that Celsr3 is dispensable. Combined, our data uncover critical and distinct roles for individual PCP components during assembly of the acoustic startle hindbrain circuit.

Cellular mechanisms of synchronized rhythmic burst generation in the ventromedial hypothalamus.

The ventromedial hypothalamus (VMH) plays an important role in feeding behavior and control of the sympathetic nervous system (SNS). The VMH includes a group of neurons that exhibit strong synchronized rhythmic burst firing (so-called VMH oscillation). This VMH oscillation is glucose inhibited, responsive to feeding-related peptides, and is functionally coupled to outputs of the SNS. However, the details of its rhythm generation and synchronization mechanisms are unknown. In the present study, we investigated cellular mechanisms of VMH oscillation by means of electrophysiological recordings and calcium imaging in juvenile rat slice preparations including the VMH. In the electrophysiological study, we performed membrane potential recording from neurons in the vicinity of pipettes for field potential recording. We found that the rhythmic bursts in the VMH were preserved in low Ca2+/high Mg2+ synaptic transmission blockade solution. During membrane hyperpolarization by current injection, the action potential was largely inhibited, but fluctuation of the membrane potential remained with a frequency similar to that at resting potential level. The electric VMH oscillation disappeared after application of either a gap junction blocker, carbenoxolone (100µM), or a persistent sodium channel blocker, riluzole (20µM). Membrane potentials and input resistances of rhythmic burst neurons in the VMH were not significantly changed during these manipulations. A calcium imaging study revealed that all VMH cells exhibiting synchronized rhythmic activity detected by intracellular calcium increases were silenced following the application of carbenoxolone. These results suggest that VMH oscillation arises from the activation of persistent sodium channels and coupling via gap junctions.

Deciphering Peripheral Taste Neuron Diversity: Using Genetic Identity to Bridge Taste Bud Innervation Patterns and Functional Responses.

Peripheral taste neurons exhibit functional, genetic, and morphological diversity, yet understanding how or if these attributes combine into taste neuron types remains unclear. In this study, we used male and female mice to relate taste bud innervation patterns to the function of a subset of proenkephalin-expressing (Penk+) taste neurons. We found that taste arbors (the portion of the axon within the taste bud) stemming from Penk+ neurons displayed diverse branching patterns and lacked stereotypical endings. The range in complexity observed for individual taste arbors from Penk+ neurons mirrored the entire population, suggesting that taste arbor morphologies are not primarily regulated by neuron type. Notably, the distinguishing feature of arbors from Penk+ neurons was their propensity to come within 110 nm (in apposition with) different types of taste-transducing cells within the taste bud. This finding is contrary to the expectation of genetically defined taste neuron types that functionally represent a single stimulus. Consistently, further investigation of Penk+ neuron function revealed that they are more likely to respond to innately aversive stimuli -sour, bitter and high salt concentrations - as compared to the full taste population. Penk+ neurons are less likely to respond to non-aversive stimuli -sucrose, umami, and low salt- compared to the full population. Our data support the presence of a genetically defined neuron type in the geniculate ganglion that is responsive to innately aversive stimuli. This implies that genetic expression might categorize peripheral taste neurons into hedonic groups, rather than simply identifying neurons that respond to a single stimulus.Significance Statement Peripheral taste neuron coding has been heavily debated. Our study delves into this issue by leveraging genetic expression in a specific neuron subset to relate peripheral innervation patterns to functional taste responses. We examined a taste neuron type that appears to be in apposition with multiple taste-transducing cell types and responds to innately aversive concentrations of sour, bitter, and high NaCl stimuli. These collective observations suggest that genetic markers can delineate groups of neurons sharing similar hedonic responses rather than categorizing neurons solely based on individual taste qualities.

Neuropeptide-dependent spike time precision and plasticity in circadian output neurons.

Circadian rhythms influence various physiological and behavioral processes such as sleep-wake cycles, hormone secretion, and metabolism. Circadian output neurons are a group of neurons that receive input from the central circadian clock located in the suprachiasmatic nucleus of the mammalian brain and transmit timing information to different regions of the brain and body, coordinating the circadian rhythms of various physiological processes. In Drosophila , an important set of circadian output neurons are called pars intercerebralis (PI) neurons, which receive input from specific clock neurons called DN1. These neurons can further be subdivided into functionally and anatomically distinctive anterior (DN1a) and posterior (DN1p) clusters. The neuropeptide diuretic hormones 31 (Dh31) and 44 (Dh44) are the insect neuropeptides known to activate PI neurons to control activity rhythms. However, the neurophysiological basis of how Dh31 and Dh44 affect circadian clock neural coding mechanisms underlying sleep in Drosophila is not well understood. Here, we identify Dh31/Dh44-dependent spike time precision and plasticity in PI neurons. We find that the application of synthesized Dh31 and Dh44 affects membrane potential dynamics of PI neurons in the precise timing of the neuronal firing through their synergistic interaction, possibly mediated by calcium-activated potassium channel conductance. Further, we characterize that Dh31/Dh44 enhances postsynaptic potentials in PI neurons. Together, these results suggest multiplexed neuropeptide-dependent spike time precision and plasticity as circadian clock neural coding mechanisms underlying sleep in Drosophila .

Investigating Mechanically Activated Currents from Trigeminal Neurons of Non-Human Primates.

Pain sensation has predominantly mechanical modalities in many pain conditions. Mechanically activated (MA) ion channels on sensory neurons underly responsiveness to mechanical stimuli. The study aimed to address gaps in knowledge regarding MA current properties in higher order species such as non-human primates (NHP; common marmosets), and characterization of MA currents in trigeminal (TG) neuronal subtypes. We employed patch clamp electrophysiology and immunohistochemistry (IHC) to associate MA current types to different marmoset TG neuronal groups. TG neurons were grouped according to presumed marker expression, action potential (AP) width, characteristic AP features, after-hyperpolarization parameters, presence/absence of AP trains and transient outward currents, and responses to mechanical stimuli. Marmoset TG were clustered into 5 C-fiber and 5 A-fiber neuronal groups. The C1 group likely represent non-peptidergic C-nociceptors, the C2-C4 groups resembles peptidergic C-nociceptors, while the C5 group could be either cold-nociceptors or C-low-threshold-mechanoreceptors (C-LTMR). Among C-fiber neurons only C4 were mechanically responsive. The A1 and A2 groups are likely A-nociceptors, while the A3-A5 groups probably denote different subtypes of A-low-threshold-mechanoreceptors (A-LTMRs). Among A-fiber neurons only A1 was mechanically unresponsive. IHC data was correlated with electrophysiology results and estimates that NHP TG has ∼25% peptidergic C-nociceptors, ∼20% non-peptidergic C-nociceptors, ∼30% A-nociceptors, ∼5% C-LTMR, and ∼20% A-LTMR. Overall, marmoset TG neuronal subtypes and their associated MA currents have common and unique properties compared to previously reported data. Findings from this study could be the basis for investigation on MA current sensitizations and mechanical hypersensitivity during head and neck pain conditions.

12502 Bdnf Production by Kiss1 Neurons Acts in a Sexually Dependent Way to Control Sexual Development and Energy Balance in Female and Male Mice

Abstract Disclosure: A.M. Zanesco: None. D. Cabral: None. J. Ferreira: None. F. Valdivieso-Rivera: None. A.L. Carvalho: None. N. Mendes: None. C. Sponton: None. R. Frazao: None. L.A. Velloso: None. The hypothalamus is a key region in the central nervous system that controls different functions such as energy balance, thermogenesis, and reproduction. Kiss1 neurons integrate two distinct neuronal pathways, reproduction, and energy balance, both essential to species survival and maintenance. Recent studies, identify that the Brain-derived neurotrophic factor, BDNF produced by neurons and astrocytes in the hypothalamus is essential to control homeostatic and hedonic feeding by acting in specific groups of hypothalamic neurons. No studies showed the action of BDNF produced in the arcuate nucleus (ARC) of the hypothalamus. Using single-cell RNA sequencing analysis of data obtained from mice hypothalamus reveals that Kiss1 neurons express BDNF and we confirmed this result by immunofluorescence assay. Curiously, there is more expression of BDNF in the female hypothalamus compared with the male hypothalamus. But, when we selected specifically the BDNF produced by KISS1 neurons, this difference disappears. Based on that, we used a Cre-loxP approach to selectively knockout BDNF in Kiss1 neurons and identify the changes in sexual development and energy balance in female and male mice. All experiments were approved by the Animal Use Ethics Committee of UNICAMP (CEUA: 5591-1/2020 and CIBio 04/2021). All female and male mice were evaluated daily to identify their sexual development. We identified no changes in metabolic parameters, such as body weight and adiposity in male and female mice fed on a chow diet. Additionally, BDNF ablation in Kiss1 neurons (BDNF-KO) leaded to a premature vaginal opening, a decreased in uterus and ovary weight, and compromises the regular cyclicity of the estrus cycle in females. No difference was found in the sexual development of male mice, indicating that this effect is sexually dependent. Based on the fact that BDNF produced in VMH and DMH acts as anorexigenic effects, and Kiss1 neurons integrate the neuronal pathway responsible for energy balance, we decided to investigate the effects of BDNF ablation in Kiss1 neurons in female and male mice fed on high-fat diet. Interestingly, male mice without BDNF production in Kiss neurons were protected from obesity development compared with wild-type mice, both fed on a high-fat diet. When they were fed on a chow diet, male BDNF-KO mice, exhibited hyperphagia compared to control mice, showing a disruption in control of food intake and body weight maintenance. No differences were identified in body weight gain, food intake, and adiposity in BDNF-KO female mice. Based on that, we conclude that BDNF produced by Kiss1 exerts different functions in male and female mice. In females, it is more related to sexual development, and males in control of energy balance. This is the first research showing the BDNF production by Kiss1 neurons and its dimorphism effects on male and female mice. Presentation: 6/2/2024

Ticagrelor-related dyspnea beyond adenosine: Insights into retrotrapezoid hyperactivity

Ticagrelor, a P2Y12 receptor antagonist, has been demonstrated to induce dyspnea, which is not associated with cardiac or pulmonary alterations, or metabolic disturbances. The attribution of ticagrelor-related dyspnea to excess adenosine has been widely proposed, yet is not supported by experimental data. In this paper, we put forth a novel hypothesis that the hyperactivity of the retrotrapezoid nucleus, a group of ventral medullary neurons involved in respiratory modulation, is the underlying cause of ticagrelor-related dyspnea. This hypothesis offers a theoretical resolution to the discrepancies and controversies present in previous theories.

The Neuroanatomy of Induced Pluripotent Stem Cells: In Vitro Models of Subcortical Nuclei in Neurodegenerative Disorders.

Neuromodulatory subcortical systems (NSSs) are monoaminergic and cholinergic neuronal groups that are markedly and precociously involved in the pathogenesis of many neurodegenerative disorders (NDDs), including Parkinson's and Alzheimer's diseases. In humans, although many tools have been developed to infer information on these nuclei, encompassing neuroimaging and neurophysiological methods, a detailed and specific direct evaluation of their cellular features in vivo has been difficult to obtain until recent years. The development of induced pluripotent stem cell (iPSC) models has allowed research to deeply delve into the cellular and molecular biology of NSS neurons. In fact, iPSCs can be produced easily and non-invasively from patients' fibroblasts or circulating blood monocytes, by de-differentiating those cells using specific protocols, and then be re-differentiated towards neural phenotypes, which may reproduce the specific features of the correspondent brain neurons (including NSS ones) from the same patient. In this review, we summarized findings obtained in the field of NDDs using iPSCs, with the aim to understand how reliably these might represent in vitro models of NSS. We found that most of the current literature in the field of iPSCs and NSSs in NDDs has focused on midbrain dopaminergic neurons in Parkinson's disease, providing interesting results on cellular pathophysiology and even leading to the first human autologous transplantation. Differentiation protocols for noradrenergic, cholinergic, and serotoninergic neurons have also been recently defined and published. Thus, it might be expected that in the near future, this approach could extend to other NSSs and other NDDs.

Spatio-temporal mechanisms of consolidation, recall and reconsolidation in reward-related memory trace.

The formation of memories is a complex, multi-scale phenomenon, especially when it involves integration of information from various brain systems. We have investigated the differences between a novel and consolidated association of spatial cues and amphetamine administration, using an in situ hybridisation method to track the short-term dynamics during the recall testing. We have found that remote recall group involves smaller, but more consolidated groups of neurons, which is consistent with their specialisation. By employing machine learning analysis, we have shown this pattern is especially pronounced in the VTA; furthermore, we also uncovered significant activity patterns in retrosplenial and prefrontal cortices, as well as in the DG and CA3 subfields of the hippocampus. The behavioural propensity towards the associated localisation appears to be driven by the nucleus accumbens, however, further modulated by a trio of the amygdala, VTA and hippocampus, as the trained association is confronted with test experience. Moreover, chemogenetic analysis revealed central amygdala as critical for linking appetitive emotional states with spatial contexts. These results show that memory mechanisms must be modelled considering individual differences in motivation, as well as covering dynamics of the process.

Concept and location neurons in the human brain provide the ‘what’ and ‘where’ in memory formation

Our brains create new memories by capturing the ‘who/what’, ‘where’ and ‘when’ of everyday experiences. On a neuronal level, mechanisms facilitating a successful transfer into episodic memory are still unclear. We investigated this by measuring single neuron activity in the human medial temporal lobe during encoding of item-location associations. While previous research has found predictive effects in population activity in human MTL structures, we could attribute such effects to two specialized sub-groups of neurons: concept cells in the hippocampus, amygdala and entorhinal cortex (EC), and a second group of parahippocampal location-selective neurons. In both item- and location-selective populations, firing rates were significantly higher during successfully encoded trials. These findings are in line with theories of hippocampal indexing, since selective index neurons may act as pointers to neocortical representations. Overall, activation of distinct populations of neurons could directly support the connection of the ‘what’ and ‘where’ of episodic memory.

State of the Art in Sub-Phenotyping Midbrain Dopamine Neurons.

Dopaminergic neurons in the ventral tegmental area (VTA) and the substantia nigra pars compacta (SNpc) comprise around 75% of all dopaminergic neurons in the human brain. While both groups of dopaminergic neurons are in close proximity in the midbrain and partially overlap, development, function, and impairments in these two classes of neurons are highly diverse. The molecular and cellular mechanisms underlying these differences are not yet fully understood, but research over the past decade has highlighted the need to differentiate between these two classes of dopaminergic neurons during their development and in the mature brain. This differentiation is crucial not only for understanding fundamental circuitry formation in the brain but also for developing therapies targeted to specific dopaminergic neuron classes without affecting others. In this review, we summarize the state of the art in our understanding of the differences between the dopaminergic neurons of the VTA and the SNpc, such as anatomy, structure, morphology, output and input, electrophysiology, development, and disorders, and discuss the current technologies and methods available for studying these two classes of dopaminergic neurons, highlighting their advantages, limitations, and the necessary improvements required to achieve more-precise therapeutic interventions.

Targeted Treatment Strategies for Mitochondria Dysfunction: Correlation with Neurological Disorders.

Mitochondria are an essential intracellular organelle for medication targeting and delivery since they seem to create energy and conduct many other cellular tasks, and mitochondrial dysfunctions and malfunctions lead to many illnesses. Many initiatives have been taken to detect, diagnose, and image mitochondrial abnormalities, and to transport and accumulate medicines precisely to mitochondria, all because of special mitochondrial aspects of the pathophysiology of cancer. In addition to the negative membrane potential and paradoxical mitochondrial dynamics, they include high temperatures, high levels of reactive oxygen species, high levels of glutathione, and high temperatures. Neurodegenerative diseases represent a broad spectrum of debilitating illnesses. They are linked to the loss of certain groups of neurons based on an individual's physiology or anatomy. The mitochondria in a cell are generally accepted as the authority with respect to ATP production. Disruption of this system is linked to several cellular physiological issues. The development of neurodegenerative disorders has been linked to mitochondrial malfunction, according to pathophysiological studies. There seems to be substantial evidence connecting mitochondrial dysfunction and oxidative stress to the development of neurodegenerative disorders. It has been extensively observed that mitochondrial malfunction triggers autophagy, which plays a role in neurodegenerative disorders. In addition, excitotoxicity and mitochondrial dysfunction have been linked to the development of neurodegenerative disorders. The pathophysiology of neurodegenerative illnesses has been linked to increased apoptosis and necrosis, as well as mitochondrial malfunction. A variety of synthetic and natural treatments have shown efficacy in treating neurodegenerative illnesses caused by mitochondrial failure. Neurodegenerative illnesses can be effectively treated with existing drugs that target mitochondria, although their precise formulations are poorly understood. Therefore, there is an immediate need to focus on creating drug delivery methods specifically targeted at mitochondria in the treatment and diagnosis of neurodegenerative disorders.

A new hybrid learning control system for robots based on spiking neural networks

This paper presents a new hybrid learning and control method that can tune their parameters based on reinforcement learning. In the new proposed method, nonlinear controllers are considered multi-input multi-output functions and then the functions are replaced with SNNs with reinforcement learning algorithms. Dopamine-modulated spike-timing-dependent plasticity (STDP) is used for reinforcement learning and manipulating the synaptic weights between the input and output of neuronal groups (for parameter adjustment). Details of the method are presented and some case studies are done on nonlinear controllers such as Fractional Order PID (FOPID) and Feedback Linearization. The structure and the dynamic equations for learning are presented, and the proposed algorithm is tested on robots and results are compared with other works. Moreover, to demonstrate the effectiveness of SNNFOPID, we conducted rigorous testing on a variety of systems including a two-wheel mobile robot, a double inverted pendulum, and a four-link manipulator robot. The results revealed impressively low errors of 0.01 m, 0.03 rad, and 0.03 rad for each system, respectively. The method is tested on another controller named Feedback Linearization, which provides acceptable results. Results show that the new method has better performance in terms of Integral Absolute Error (IAE) and is highly useful in hardware implementation due to its low energy consumption, high speed, and accuracy. The duration necessary for achieving full and stable proficiency in the control of various robotic systems using SNNFOPD, and SNNFL on an Asus Core i5 system within Simulink’s Simscape environment is as follows:– Two-link robot manipulator with SNNFOPID: 19.85656 hours– Two-link robot manipulator with SNNFL: 0.45828 hours– Double inverted pendulum with SNNFOPID: 3.455 hours– Mobile robot with SNNFOPID: 3.71948 hours– Four-link robot manipulator with SNNFOPID: 16.6789 hours.This method can be generalized to other controllers and systems like robots.

An Infralimbic Cortex Neuronal Ensemble Encoded During Learning Attenuates Fear Generalization Expression.

Generalization allows for experience to flexibly guide behavior when conditions change. A basic physical unit of memory storage and expression in the brain are sparse, distributed groups of neurons known as ensembles (i.e., the engram). The infralimbic (IL) subregion of the ventral medial prefrontal cortex plays a key role in modulating conditioned defensive responses. How IL neuronal ensembles established during learning contribute to generalized responses is unknown. In this set of experiments, generalization was tested in male and female mice by presenting a novel, ambiguous, tone generalization stimulus following Pavlovian defensive (fear) conditioning. The first experiment was designed to test a role for IL in generalization using chemogenetic manipulations. Results show IL bidirectionally regulates defensive behavior. IL silencing promotes a switch in defensive state from vigilant scanning to generalized freezing, while IL stimulation reduces freezing in favor of scanning. Leveraging activity-dependent tagging technology (ArcCreERT2 x eYFP system), a neuronal ensemble, preferentially located in IL superficial layer 2/3, was associated with the generalization stimulus. Remarkably, in the identical discrete location, fewer reactivated neurons were associated with the generalization stimulus at the remote timepoint (30 days) following learning. When an IL neuronal ensemble established during learning was selectively chemogenetically silenced, generalization increased. Conversely, IL neuronal ensemble stimulation reduced generalization. Overall, these data identify a crucial role for IL in suppressing generalized responses. Further, we uncover an IL neuronal ensemble, formed during learning, functions to later attenuate the expression of generalization in the presence of ambiguous threat stimuli.

The recovery of parabolic avalanches in spatially subsampled neuronal networks at criticality

Scaling relationships are key in characterizing complex systems at criticality. In the brain, they are evident in neuronal avalanches—scale-invariant cascades of neuronal activity quantified by power laws. Avalanches manifest at the cellular level as cascades of neuronal groups that fire action potentials simultaneously. Such spatiotemporal synchronization is vital to theories on brain function yet avalanche synchronization is often underestimated when only a fraction of neurons is observed. Here, we investigate biases from fractional sampling within a balanced network of excitatory and inhibitory neurons with all-to-all connectivity and critical branching process dynamics. We focus on how mean avalanche size scales with avalanche duration. For parabolic avalanches, this scaling is quadratic, quantified by the scaling exponent, χ = 2, reflecting rapid spatial expansion of simultaneous neuronal firing over short durations. However, in networks sampled fractionally, χ is significantly lower. We demonstrate that applying temporal coarse-graining and increasing a minimum threshold for coincident firing restores χ = 2, even when as few as 0.1% of neurons are sampled. This correction crucially depends on the network being critical and fails for near sub- and supercritical branching dynamics. Using cellular 2-photon imaging, our approach robustly identifies χ = 2 over a wide parameter regime in ongoing neuronal activity from frontal cortex of awake mice. In contrast, the common ‘crackling noise’ approach fails to determine χ under similar sampling conditions at criticality. Our findings overcome scaling bias from fractional sampling and demonstrate rapid, spatiotemporal synchronization of neuronal assemblies consistent with scale-invariant, parabolic avalanches at criticality.

Inhibitory circuits generate rhythms for leg movements during Drosophila grooming.

Limbs execute diverse actions coordinated by the nervous system through multiple motor programs. The basic architecture of motor neurons that activate muscles that articulate joints for antagonistic flexion and extension movements is conserved from flies to vertebrates. While excitatory premotor circuits are expected to establish sets of leg motor neurons that work together, our study uncovered a new instructive role for inhibitory circuits: their ability to generate rhythmic leg movements. Using electron microscopy data for the Drosophila nerve cord, we categorized ~120 GABAergic inhibitory neurons from the 13A and 13B hemi-lineages into classes based on similarities in morphology and connectivity. By mapping their synaptic partners, we uncovered pathways for inhibiting specific groups of motor neurons, disinhibiting antagonistic counterparts, and inducing alternation between flexion and extension. We tested the function of specific inhibitory neurons through optogenetic activation and silencing, using an in-depth ethological analysis of leg movements during grooming. We combined anatomy and behavior analysis findings to construct a computational model that can reproduce major aspects of the observed behavior, confirming the sufficiency of these premotor inhibitory circuits to generate rhythms.

Light and dopamine impact two circadian neurons to promote morning wakefulness

In both mammals and flies, circadian brain neurons orchestrate physiological oscillations and behaviors like wake and sleep-these neurons can be subdivided by morphology and by gene expression patterns. Recent single-cell sequencing studies identified 17 Drosophila circadian neuron groups. One of these includes only two lateral neurons (LNs), which are marked by the expression of the neuropeptide ion transport peptide (ITP). Although these two ITP+ LNs have long been grouped with five other circadian evening activity cells, inhibiting the two neurons alone strongly reduces morning activity, indicating that they also have a prominent morning function. As dopamine signaling promotes activity in Drosophila, like in mammals, we considered that dopamine might influence this morning activity function. Moreover, the ITP+ LNs express higher mRNA levels than other LNs of the type 1-like dopamine receptor Dop1R1. Consistent with the importance of Dop1R1, cell-specific CRISPR-Cas9 mutagenesis of this receptor in the two ITP+ LNs renders flies significantly less active in the morning, and exvivo live imaging shows Dop1R1-dependent cyclic AMP (cAMP) responses to dopamine in these two neurons. Notably, the response is more robust in the morning, reflecting higher morning Dop1R1 mRNA levels in the two neurons. As mRNA levels are not elevated in constant darkness, this suggests light-dependent upregulation of morning Dop1R1 transcript levels. Taken together with the enhanced morning cAMP response to dopamine, the data indicate how light and dopamine promote morning wakefulness in flies, mimicking the important effect of light on morning wakefulness in humans.

Enhanced Neurotransmitter Detection with Biorecognition Element-Functionalized Organic Electrochemical Transistors

The United States National Academies of Science and Engineering have issued a grand challenge to “reverse-engineer the brain”. Addressing this challenge requires a more complete understanding of how connections between individual neurons and groups of neurons are formed and maintained, as well as a more thorough elucidation of the signaling processes that drive neural network optimization. However, to achieve these goals, it is first necessary to develop the appropriate fundamental tools and protocols for adaptive biointerfacing, bottom-up neuroscience, and neuromodulation.To address this challenge, our research team has developed neurotransmitter-specific biosensors based on organic electrochemical transistors (OECT), which are electrolyte-gated devices that permit large signal amplification, ionic-to-electronic signal transduction, and controllable variable resistance. Given that their porous channel materials enable volumetric interaction with the adjacent electrolyte, OECT offer increased detection sensitivity compared to other electrolyte-gated devices such as field-effect transistors (FET). Although these OECT devices have demonstrated utility in a wide range of applications, from neuromorphic computing to bioelectronic devices, they are still in an early stage of development.We report enhanced electrochemical sensing of dopamine, mediated by functionalizing the OECT gate electrode with dopamine-specific biorecognition elements (BRE, i.e., aptamers). To optimize these devices, our team tested a variety of electrode functionalization approaches (e.g. alkane-thiol or silane chemistry, layer-by-layer, and covalent modification). The operational principle of BRE-functionalized OECT gate electrode biosensing is based on changes in gate electrode surface potential caused by target-binding to the BRE. When the target binds to the BRE, the event alters the capacitance at the surface of the functionalized gate electrode. The change in surface potential at the gate electrode shifts the applied potential on the OECT channel, which alters the doping state of the OECT channel. The channel materials are mixed ionic/electronic conductors, so changes in the doping state of the channel will directly affect the transconductance of the channel, which alters the OECT transfer characteristic and thereby permits sensing. The large transconductance of the OECT channel allows small changes in doping state to amplify the signal caused by binding of the target to the surface-attached BRE.In this study, we directly compare the dopamine biosensing performance of BRE-functionalized gold electrodes tested in two different sensing configurations:(i) traditional amperometric biosensor with a BRE-functionalized working electrode(ii) OECT with BRE-functionalized gate electrodeWe confirm the operational principles outlined above, and quantitatively assess the biosensing performance through a variety of analytical and electroanalytical techniques, such as cyclic voltammetry, open-circuit potentiometry, electrochemical impedance spectroscopy (EIS), square-wave and differential pulse voltammetry (DPV), and electrochemical quartz crystal microbalance (EQCM). We also compare the observed concentration-dependent changes in OECT transfer characteristics to the changes predicted by a theoretical analysis of surface potential.Finally, we will present the steps we have taken to implement these devices within organ-on-a-chip systems, both for traditional neurotransmitter biosensing and to demonstrate the utility of our devices for studying the formation and longitudinal evolution of neural networks within in vitro neuronal colonies.

Role of sexually dimorphic oxytocin receptor-expressing neurons in the anteroventral periventricular nucleus on maternal behavior.

Oxytocin is a neuropeptide produced by magnocellular neurosecretory neurons located primarily in the supraoptic nucleus and paraventricular nucleus of the hypothalamus. The long axons of these neurons project to the neurohypophysis where oxytocin is released into the general circulation in response to the physiological demands. Oxytocin plays critical roles in female reproductive physiology, specifically in uterine contraction during labor and milk ejection while nursing. Oxytocin is also called "the love hormone" due to its modulatory roles in prosocial behaviors, including social recognition, maternal behavior, and pair bonding. Oxytocin influences behaviors by binding to oxytocin receptors (OXTR) located in various parts of the brain. Previously, we discovered a group of estrogen-dependent OXTR neurons that is exclusively present in the anteroventral periventricular nucleus (AVPV) of females but not of males. The female-specific expression of OXTR in the AVPV is a rare case of neurochemically-demonstrated, all-or-none sexual dimorphism in the brain. In this review, the cellular characterization and functional significance of the sexually dimorphic OXTR neurons in the AVPV as well as the clinical implications of the research will be discussed.

A Detailed Re-Examination of the Period Gene Rescue Experiments Shows That Four to Six Cryptochrome-Positive Posterior Dorsal Clock Neurons (DN1p) of Drosophila melanogaster Can Control Morning and Evening Activity.

Animal circadian clocks play a crucial role in regulating behavioral adaptations to daily environmental changes. The fruit fly Drosophila melanogaster exhibits 2 prominent peaks of activity in the morning and evening, known as morning (M) and evening (E) peaks. These peaks are controlled by 2 distinct circadian oscillators located in separate groups of clock neurons in the brain. To investigate the clock neurons responsible for the M and E peaks, a cell-specific gene expression system, the GAL4-UAS system, has been commonly employed. In this study, we re-examined the two-oscillator model for the M and E peaks of Drosophila by utilizing more than 50 Gal4 lines in conjunction with the UAS-period16 line, which enables the restoration of the clock function in specific cells in the period (per) null mutant background. Previous studies have indicated that the group of small ventrolateral neurons (s-LNv) is responsible for controlling the M peak, while the other group, consisting of the 5th ventrolateral neuron (5th LNv) and the three cryptochrome (CRY)-positive dorsolateral neurons (LNd), is responsible for the E peak. Furthermore, the group of posterior dorsal neurons 1 (DN1p) is thought to also contain M and E oscillators. In this study, we found that Gal4 lines directed at the same clock neuron groups can lead to different results, underscoring the fact that activity patterns are influenced by many factors. Nevertheless, we were able to confirm previous findings that the entire network of circadian clock neurons controls M and E peaks, with the lateral neurons playing a dominant role. In addition, we demonstrate that 4 to 6 CRY-positive DN1p cells are sufficient to generate M and E peaks in light-dark cycles and complex free-running rhythms in constant darkness. Ultimately, our detailed screening could serve as a catalog to choose the best Gal4 lines that can be used to rescue per in specific clock neurons.