Biology subjects

Galliano, E.

Publications and source records attributed to Galliano, E..

7 recordsLinked to original sources

bioRxiv2025

A low-cost and open-source olfactometer to precisely deliver single odours and odour mixtures

Despite its profound influence on human emotion and memory, and its critical importance in animal behaviour, olfaction has historically been understudied compared to other sensory modalities. Contributing to this relative neglect may be challenges inherent to odour delivery: unlike visual or auditory stimuli, odorants must be vaporised, transported, and actively cleared, requiring specialised equipment and creating temporal delays and contamination risks. While commercial olfactometers provide reliable solutions, they can be expensive and, due to proprietary software, may be difficult to customise. Existing custom designs, though excellent, often require specialized technical skills and/or access to engineering workshops. Thus, to help widen access to well-controlled odour delivery, we developed a low-cost, fully open-source olfactometer that can be assembled without specialised facilities or engineering skills and customised according to experimental needs. Our design prioritises affordability, accessibility, and versatility while maintaining temporal precision and stimulus control across applications from rodent behaviour to human psychophysics. This methods articles provides full design specifications, assembly details, and behavioural validation across both rodents and humans with the aim of reducing barriers and enabling more laboratories to study this crucial sensory system.

neuroscience↗

bioRxiv2024

Neuronal plasticity at puberty in hypothalamic neurons controlling fertility in female mice

Puberty is a critical transition period to achieve fertility and reproductive capacity in all mammalian species. At puberty, the hypothalamic-pituitary-gonadal (HPG) is activated by neuroendocrine changes in the brain. Central to this are Kiss1 neurons that produce kisspeptin, a neuropeptide which is a potent stimulator of gonadotropin releasing hormone (GnRH) secretion. Kiss1 neurons in the arcuate region of the hypothalamus (Kiss1ARC) increase pulsatile secretion of GnRH at puberty. Other developmental maturational changes in the brain are often accompanied by neuronal plasticity changes but this has not been studied in Kiss1 neurons. Electrophysiological characterisation of Kiss1ARC neurons from female mice shows that these neurons undergo profound intrinsic plasticity at puberty with a critical window between 3 and 4 weeks. Immature Kiss1ARC neurons cannot sustain depolarisation-evoked firing for even 500 ms and instead fire a brief burst of high frequency spikes before falling silent. This would make them unsuitable for the sustained activity that is needed to activate GnRH neurons and trigger LH secretion in the HPG axis. After puberty, sustained firing can be maintained, which endows post-puberty Kiss1ARC neurons with a mature physiological phenotype that is amenable to neuropeptide modulation for generation of burst firing and pulsatile release of kisspeptin. There is a corresponding decrease in the threshold for action potential initiation, a more hyperpolarised post-spike trough and a larger medium after-hyperpolarisation (mAHP). Gene expression analysis showed a significant decrease in Scn2a (Nav1.2 channel), Kcnq2 (Kv7.2 channel) and Lrrc55 (BK channel auxiliary {gamma}3-subunit) expression and an increase in Hcn1 (hyperpolarization activated cyclic nucleotide-gated potassium channel) expression which may contribute to the observed electrophysiological changes. Ovariectomy and {beta}-estradiol replacement defined a window of estrogen-dependent plasticity of action potential firing at puberty, such that post-puberty Kiss1ARC neurons achieve a mature physiological phenotype for activation of the HPG axis.

neuroscience↗

bioRxiv2024

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

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

neuroscience↗

bioRxiv2023

Deprivation-induced plasticity in the early central circuits of the rodent visual, auditory, and olfactory systems: a systematic review and meta-analysis of the literature

Activity-dependent neuronal plasticity is crucial for animals to adapt to dynamic sensory environments. Traditionally, research on activity dependent-plasticity has used sensory deprivation approaches in animal models, and it has focused on its effects in primary sensory cortices. However, emerging evidence emphasizes the importance of activity-dependent plasticity both in the sensory organs and in sub-cortical regions where cranial nerves relay information to the brain. Additionally, a critical question arises: do different sensory modalities share common cellular mechanisms for deprivation-induced plasticity at these central entry-points? Furthermore, does the duration of deprivation correlate with specific plasticity mechanisms? This study aims to systematically review and meta-analyse research papers that investigated visual, auditory, or olfactory deprivation in rodents. Specifically, it explores the consequences of sensory deprivation in homologous regions at the first central synapse after the cranial nerve: vision--lateral geniculate nucleus and superior colliculus; audition-- ventral and dorsal cochlear nucleus; olfaction--olfactory bulb. The systematic search yielded 91 research papers (39 vision, 22 audition, 30 olfaction), revealing significant heterogeneity in publication trends, experimental methods of inducing deprivation, measures of deprivation-induced plasticity, and reporting, across the three sensory modalities. Nevertheless, despite these methodological differences, commonalities emerged when correlating the plasticity mechanisms with the duration of the sensory deprivation. Following short-term deprivations (up to 1 day) all three systems showed reduced activity levels and increased disinhibition. Medium-term deprivation (1 day to a week) induced greater glial involvement and synaptic remodelling. Long-term deprivation (over a week) predominantly led to macroscopic structural changes including tissue shrinkage and apoptosis. These findings underscore the importance of standardizing methodologies and reporting practices. Additionally, they highlight the value of cross-modals synthesis for understanding how the nervous system, including peripheral, pre-cortical, and cortical areas, respond to and compensate for sensory inputs loss.

neuroscience↗

bioRxiv2023

Characterization of Identified Dopaminergic Neurons in the Mouse Olfactory Bulb and Midbrain

Dopaminergic (DA) neurons play pivotal roles in diverse brain functions, spanning movement, reward processing, and sensory perception. DA neurons are most abundant in the midbrain (Substantia Nigra pars compacta, SNC, and Ventral Tegmental Area, VTA) and the olfactory bulb (OB) in the forebrain. Interestingly, a subtype of OB DA neurons is capable of regenerating throughout life, while a second class is exclusively born during embryonic development. Emerging evidence in SNC and VTA also indicates substantial heterogeneity in terms of morphology, connectivity, and function. To further investigate this heterogeneity and directly compare form and function of midbrain and forebrain DA neurons, we performed immunohistochemistry and whole-cell patch-clamp recordings in ex vivo brain slices from juvenile DAT-tdTomato mice. After confirming the penetrance and specificity of the dopamine transporter (DAT) Cre line, we compared soma shape, passive membrane properties, voltage sags and action potential firing across midbrain and forebrain DA subtypes. We found that each DA subgroup within midbrain and forebrain was highly heterogeneous, and that DA neurons across the two brain areas are also substantially different. These findings complement previous work in rats as well as gene expression and in vivo datasets, further questioning the existence of a single "dopaminergic" neuronal phenotype.

neuroscience↗

bioRxiv2020

Brief sensory deprivation triggers cell type-specific structural and functional plasticity in olfactory bulb neurons

Can alterations in experience trigger different plastic modifications in neuronal structure and function, and if so, how do they integrate at the cellular level? To address this question, we interrogated circuitry in the mouse olfactory bulb responsible for the earliest steps in odour processing. We induced experience-dependent plasticity in mice by blocking one nostril for a day, a minimally-invasive manipulation which leaves the sensory organ undamaged and is akin to the natural transient blockage suffered during common mild rhinal infections. We found that such brief sensory deprivation produced structural and functional plasticity in one highly specialised bulbar cell type: axon-bearing dopaminergic neurons in the glomerular layer. After 24h naris occlusion, the axon initial segment (AIS) in bulbar dopaminergic neurons became significantly shorter, a structural modification that was also associated with a decrease in intrinsic excitability. These effects were specific to the AIS-positive dopaminergic subpopulation, because no experience-dependent alterations in intrinsic excitability were observed in AIS-negative dopaminergic cells. Moreover, 24h naris occlusion produced no structural changes at the AIS of bulbar excitatory neurons - mitral/tufted and external tufted cells - nor did it alter their intrinsic excitability. By targeting excitability in one specialised dopaminergic subpopulation, experience-dependent plasticity in early olfactory networks might act to fine-tune sensory processing in the face of continually fluctuating inputs.

neuroscience↗

bioRxiv2017

Embryonic and postnatal neurogenesis produce functionally distinct subclasses of dopaminergic neuron

Most neurogenesis in the mammalian brain is completed embryonically, but in certain areas the production of neurons continues throughout postnatal life. The functional properties of mature postnatally-generated neurons often match those of their embryonically-produced counterparts. However, we show here that in the olfactory bulb (OB), embryonic and postnatal neurogenesis produce functionally distinct subpopulations of dopaminergic (DA) neurons. We define two subclasses of OB DA neuron by the presence or absence of a key subcellular specialisation: the axon initial segment (AIS). Large AIS-positive axon-bearing DA neurons are exclusively produced during early embryonic stages, leaving small anaxonic AIS-negative cells as the only DA subtype generated via adult neurogenesis. These populations are functionally distinct: large DA cells are more excitable, yet display weaker and - for certain long-latency or inhibitory events - more broadly-tuned responses to odorant stimuli. Embryonic and postnatal neurogenesis can therefore generate distinct neuronal subclasses, placing important constraints on the functional roles of adult-born neurons in sensory processing.

neuroscience↗