Biology subjects

Ranjbar-Slamloo, Y.

Publications and source records attributed to Ranjbar-Slamloo, Y..

4 recordsLinked to original sources

bioRxiv2024

Diversity of ancestral brainstem noradrenergic neurons across species and multiple biological factors

The brainstem cell group, locus coeruleus (LC), is present across vertebrates and influences cardiorespiratory, metabolic, immune, and cognitive functions by activating in two putatively distinct firing patterns. Yet, the degree to which the LC firing rates and patterns are homogenous across species has never been assessed due to inherently limited sample sizes. To remedy this, we pooled cross-species data from 20 laboratories to show that firing rates differ across species and are modulated by sex, age, and type of in vitro or in vivo preparation. Contrary to the prevailing dual-mode firing pattern schema, we observed patterns spread across a low-dimensional manifold, with subregions enriched for specific biological factors and neurodegenerative disease models. Our findings show considerable diversity in an ancestral vertebrate neuromodulatory system.

neuroscience↗

bioRxiv2021

Locus Coeruleus Stimulation Affects response Adaptation in the Somatosensory Cortex of Whisker-to-barrel Touch System

Stimulus-driven responses in the cortex reduce due to prior exposure to sensory stimuli, a phenomenon called sensory adaptation. Depression of synaptic supplies and afterhyperpolarization (AHP) following each action potential are the main proposed mechanisms for adaptation. In vitro studies have shown that the neuronal adaptation in the barrel cortex depends on slow AHPs. Such AHPs can be affected by neuromodulators, such as noradrenaline. This evidence suggests that Locus Coeruleus (LC) noradrenergic system may reduce sensory adaptation through this cellular mechanism. We proposed that LC stimulation before whisker deflection can affect the degree of adaptation in the barrel cortex, depending on the nature of noradrenergic interactions in the barrel cortex. We coupled adapted or non-adapted whisker deflections with LC phasic stimulation with a 400 ms interval. A 50ms sinusoidal vibration was applied to the whisker immediately before the test deflection. Neuronal activity was recorded from the barrel cortex (BC) in a urethane anesthetized rat. We quantified the effect of LC stimulation on the degree of adaptation in BC; a lower adaptation index shows lower adaptation. Our result showed that LC stimulation significantly modulated adapted response in 30 % of units with insignificant modulation on the adaptor or non-adapted response. This modulation was in two directions; adaptation decreased in 5 % of units and increased in 25 % of units. In addition to LC modulation on adaptor response in the level of individual units, adaptor response was lower modulated in around 70 % of units, on average. This modulation was not correlated by LC modulation on non-adapted response. Although sensory adaptation in BC was attenuate by LC stimulation in the majority of units, there was a limited number of units that showed significant modulation.

neuroscience↗

bioRxiv2020

Loss of the Er81 Transcription Factor in Cholinergic Cells Alters Striatal Activity and Habit Formation

The finely-tuned activity of cholinergic interneurons (CINs) in the striatum is key for motor control, learning, and habit formation. Yet, the molecular mechanisms that determine their unique functional properties remain poorly explored. Using a combination of genetic and biochemical assays, in vitro and in vivo physiological characterisation, we report that selective ablation of the Er81 transcription factor leads to prominent changes in CIN molecular, morphological and electrophysiological features. In particular, the lack of Er81 amplifies intrinsic delayed-rectifier and hyperpolarization-activated currents, which subsequently alters the tonic and phasic activity of CINs. We further demonstrate that these alterations enhance their pause and time-locked responses to sensorimotor inputs in awake mice. Finally, this study reveals an Er81-dependent developmental mechanism in CINs essential for habit formation in adult mice. Highlights- The Er81 transcription factor is expressed in striatal cholinergic interneurons (CINs) - Conditional deletion of Er81 alters key molecular, morphological and electrophysiological properties of CINs in adult mice - Deletion of Er81 reduces the intrinsic excitability of CINs by upregulating delayed rectifier and hyperpolarization-activated currents - Deletion of Er81 alters in vivo striatal activity and habit formation

neuroscience↗

bioRxiv2018

Diverse tuning underlies sparse activity in L2/3 vibrissal cortex of awake mice

It is widely reported that superficial layers of the somatosensory cortex exhibit sparse firing. This sparseness could reflect weak feedforward sensory inputs that are not sufficient to generate action potentials in these layers. Alternatively, sparseness might reflect tuning to unknown or higher-level complex features that are not fully explored in the stimulus space. Here, we examined these hypotheses by applying a range of vibrotactile and manual vibrissal stimuli in awake, head-fixed mice while performing loose-seal cell-attached recordings from the vibrissal primary somatosensory (vS1) cortex. A high-velocity stimulus delivered by a piezo-electric actuator evoked activity in a small fraction of regular spiking supragranular neurons (29%) in awake condition. However, a majority of the supragranular regular spiking neurons (84%) were driven by manual stimulation of whiskers. Our results suggest that most neurons in the superficial layers of vS1 cortex contribute to coding in awake conditions when neurons may encounter their preferred feature(s) during whisker-object interactions.

neuroscience↗