Beyond a Transmission Cable—New Technologies to Reveal the Richness in Axonal Electrophysiology

Journal of Neuroscience, Journal Year: 2024, Volume and Issue: 44(11), P. e1446232023 - e1446232023

Published: March 13, 2024

The axon is a neuronal structure capable of processing, encoding, and transmitting information. This assessment contrasts with limiting, but deeply rooted, perspective where the functions solely as transmission cable somatodendritic activity, sending signals in form stereotypical action potentials. arose, at least partially, because technical difficulties probing axons: their extreme length-to-diameter ratio intricate growth paths preclude study dynamics through traditional techniques. Recent findings are challenging this view revealing much larger repertoire axonal computations. Axons display complex signaling processes structure–function relationships, which can be modulated via diverse activity-dependent mechanisms. Additionally, axons exhibit patterns activity that dramatically different from those corresponding soma. Not surprisingly, many these recent discoveries have been driven by novel technology developments, allow for vitro electrophysiology unprecedented spatiotemporal resolution signal-to-noise ratio. In review, we outline state-of-the-art toolset summarize function it has enabled. We also review increasing microtechnologies controlling guidance which, combination available cutting-edge imaging approaches, potential more controlled high-throughput studies. anticipate adoption new technologies neuroscience community will drive era experimental opportunities physiology consequently, function.

Language: Английский

---

Ex vivo functional characterization of mouse olfactory bulb projection neurons reveals a heterogenous continuum

eNeuro, Journal Year: 2025, Volume and Issue: 12(3), P. ENEURO.0407 - 24.2025

Published: Feb. 4, 2025

Mitral cells (MCs) and tufted (TCs) in the olfactory bulb (OB) act as an input convergence hub transmit information to higher areas. Since first characterized, they have been classed distinct projection neurons based on size location: laminarly arranged MCs with a diameter larger than 20 µm mitral layer (ML) smaller TCs spread across both ML external plexiform layers (EPL). Recent vivo work has shown that these encode complementary information, akin parallel channels other sensory systems. Yet, many ex studies still collapse them into single class, mitral/tufted, when describing their physiological properties impact circuit function. Using immunohistochemistry whole-cell patch-clamp electrophysiology fixed or acute slices from adult mice, we attempted align data test soma size-based classifier of bulbar using passive intrinsic firing properties. We found there is no clear separation between cell types active Rather, heterogeneous continuum three loosely clustered subgroups: EPL, putative ML. These findings illustrate large functional heterogeneity present within OB complement existing literature highlighting how systems preponderant possibly used decode complex information.

Language: Английский

---

Early-life stress differentially affects CA3 synaptic inputs converging on apical and basal dendrites of CA1 pyramidal neurons

Frontiers in Neural Circuits, Journal Year: 2025, Volume and Issue: 19

Published: Feb. 19, 2025

There is evidence that stress factors and negative experiences in early life may affect brain development leading to mental disorders adulthood. At the stage of postnatal ontogenesis, central nervous system has high plasticity, which decreases with maturation. Most likely, this plasticity necessary for establishing synaptic connections between different types neurons, regulating strength individual synapses, ultimately forming properly functioning neuronal networks. The vast majority studies have examined effects early-life (ELS) on gene expression or behavior memory. However, impact ELS functional plastic properties excitatory inhibitory synapses are currently much less understood. Based data obtained a few it been suggested reduces long-term potentiation (LTP) at Schaffer collateral CA1 pyramidal cell Nevertheless, groups reported somewhat contradictory results. In report we show differentially affects LTP CA3 inputs, apical dendrites reduced, while formed by cells basal remains unaffected.

Language: Английский

---

Cross‐strata co‐occurrence of ripples with theta‐frequency oscillations in the hippocampus of foraging rats

The Journal of Physiology, Journal Year: 2024, Volume and Issue: 602(10), P. 2315 - 2341

Published: April 23, 2024

Abstract Brain rhythms have been postulated to play central roles in animal cognition. A prominently reported dichotomy of hippocampal links theta‐frequency oscillations (4–12 Hz) and ripples (120–250 exclusively preparatory consummatory behaviours, respectively. However, because the differential power expression these two signals across strata , such exclusivity requires validation through analyses simultaneous multi‐ recordings. We assessed co‐occurrence with multi‐channel recordings extracellular potentials from foraging rats. detected all ripple events an identified stratum pyramidale (SP) channel. then defined theta epochs based on lacunosum‐moleculare (SLM) or radiatum (SR). found ∼20% (in SP) co‐occur SR/SLM channels, here as ripples. Strikingly, when were instead SP channel, co‐occurrences significantly reduced a progressive reduction along SLM‐SR‐SP axis. Behaviourally, we most occur during immobile periods, comparable exploratory epochs. Furthermore, axis was common periods. Finally, strong theta‐phase preference within fourth quadrant [3π/2 – 2π] associated oscillation. The prevalence expands potential ripple‐frequency span continuum encoding, retrieval consolidation, achieved interactions oscillations. image Key points brain manifests recorded electrical potentials, different frequencies oscillation distinct behavioural states. assigns hippocampus be Our rodent coupled cross‐ provide direct quantitative evidence for occurrence nested These results highlight need analysis pipeline that explicitly accounts specific where individual oscillatory is high, analysing simultaneously data multiple . observations open avenues investigations involving between

Language: Английский

---

A method to analyze gene expression profiles from hippocampal neurons electrophysiologically recorded in vivo

Frontiers in Neuroscience, Journal Year: 2024, Volume and Issue: 18

Published: April 17, 2024

Hippocampal pyramidal neurons exhibit diverse spike patterns and gene expression profiles. However, their relationships with single are not fully understood. In this study, we designed an electrophysiology-based experimental procedure to identify profiles using RNA sequencing of hippocampal whose were recorded in living mice. This technique involves a sequence experiments consisting

Language: Английский

---

Unveiling the cell biology of hippocampal neurons with dendritic axon origin

The Journal of Cell Biology, Journal Year: 2024, Volume and Issue: 224(1)

Published: Sept. 24, 2024

In mammalian axon-carrying–dendrite (AcD) neurons, the axon emanates from a basal dendrite, instead of soma, to create privileged route for action potential generation at initial segment (AIS). However, it is unclear how such unusual morphology established and whether structure function AIS in AcD neurons are preserved. By using dissociated hippocampal cultures as model, we show that development can occur prior synaptogenesis independently vivo environment. A single precursor neurite first gives rise then AcD. The possesses similar cytoskeletal architecture soma-derived similarly functions trafficking barrier retain axon-specific molecular composition. does not undergo homeostatic plasticity, contains lesser cisternal organelles, receives fewer inhibitory inputs. Our findings reveal insights into neuron biology underscore structural differences based on onset.

Language: Английский

---

Excitatory neurons in stratum radiatum provide an alternative pathway for excitation flow that escapes perisomatic inhibition

Published: March 5, 2024

For over half a century, it has been postulated that the internal excitatory circuit in hippocampus consists of three relay stations. Excitation arrives from entorhinal cortex to DG granule cells, is transmitted through mossy fibers CA3 pyramidal and then Schaffer collaterals CA1 neurons. In all structures (DG, CA1), activity neurons involved synaptic transmission excitation are under control inhibitory basket recruited into network via feed-forward feed-back excitation. However, late 90s “stratum radiatum giant cells” were described as novel type neuron with anatomical features cells. Since then, role these cells hippocampal circuitry not well understood. Here, using optogenetic electrophysiological techniques we characterized functional location within network. We show that: (i) main drive stratum (ExN R ) comes collaterals; (ii) field, ExN directly connected local but provide massive efficient input parvalbumin positive (PV+) interneurons; (iii) reciprocally innervated by bistratified inhibited backet (iv) efficiency PV+ interneurons sufficient for single action potential trigger inhibition downstream Taken together, our data shows constitute an alternative pathway avoids burden perisomatic inhibition.

Language: Английский

---

A dendrite is a dendrite is a dendrite? Dendritic signal integration beyond the “antenna” model

Pflügers Archiv - European Journal of Physiology, Journal Year: 2024, Volume and Issue: unknown

Published: Aug. 9, 2024

Neurons in central nervous systems receive multiple synaptic inputs and transform them into a largely standardized output to their target cells-the action potential. A simplified model posits that signals are integrated by linear summation passive propagation towards the axon initial segment, where threshold for spike generation is either crossed or not. However, lines of research during past decades have shown signal integration individual neurons much more complex, with important functional consequences at cellular, network, behavioral-cognitive level. The interplay between concomitant excitatory inhibitory postsynaptic potentials depends strongly on relative timing localization respective synapses. In addition, dendrites contain voltage-dependent conductances, which allow scaling potentials, non-linear input processing, compartmentalization signals. Together, these features enable rich variety single-neuron computations, including operations plasticity. Hence, we revise over-simplified messages from textbooks use computational models like integrate-and-fire some caution. This concept article summarizes most mechanisms dendritic highlights recent developments field.

Language: Английский

---

Influence of early-life stress on hippocampal synaptic and network properties

Frontiers in Neural Circuits, Journal Year: 2024, Volume and Issue: 18

Published: Dec. 19, 2024

According to the World Health Organization, number of people suffering from depressive disorders worldwide is approaching 350 million. The consequences include considerable worsening quality life, which frequently leads social isolation. One key factors may cause depression in adulthood early life stress, particular, insufficient maternal care during infancy. Studies performed with children raised orphanages have shown that long-term complete absence (chronic stress) vulnerability emotional disorders, including depression, adulthood. All above dictates need for a deep understanding mechanisms pathogenicity stress neurogenesis. Therefore, experienced stages development are actively studied animal models. A large body evidence has accumulated indicating stress-induced changes gene expression and behavioral However, connection between molecular biology neurons complex behavior runs through synaptic connections linking these into neural networks. In turn, coordinated activity neuronal ensembles, achieved by balance excitation inhibition, basis behavior. Unfortunately, effect on interactions remains poorly understood.

Language: Английский

---

Novel aspects of signal processing in lamina I

Neuropharmacology, Journal Year: 2024, Volume and Issue: 247, P. 109858 - 109858

Published: Jan. 28, 2024

The most superficial layer of the spinal dorsal horn, lamina I, is a key element nociceptive processing system. It contains different types projection neurons (PNs) and local-circuit (LCNs) whose functional roles in signal are poorly understood. This article reviews recent progress elucidating novel anatomical features physiological properties I PNs LCNs revealed by whole-cell recordings ex vivo cord. part Special Issue on "Ukrainian Neuroscience".

Language: Английский

---