Biology subjects

Leao, R.

Publications and source records attributed to Leao, R..

6 recordsLinked to original sources

bioRxiv2024

Layer 5 Martinotti cell activation reduces pyramidal cell population plasticity and improves fine motor function

During motor activity and motor learning, pyramidal cells in the motor cortex receive inputs from local interneurons as well as deeper structures. Layer 5 pyramidal cells in the primary motor cortex then feed commands to spinal circuits for motor execution. The genetic ablation of layer 5 Chrna2 Martinotti cells, which selectively target pyramidal tract pyramidal cells, resulted in disturbed fine motor functions. Using calcium imaging combined with chemogenetics, we show that activation of layer 5 Chrna2 Martinotti cells during training increases pyramidal cell tuning, changes responses temporal patterns and decreases assembly reconfiguration, while not affecting motor learning success rates. However, in mice that had already learned a reach-and-grasp (prehension) task, Chrna2 Martinotti cell activation resulted in improved prehension and increased power in low theta and high gamma bands of local field potentials in the motor cortex. This work indicates that activation of Chrna2 Martinotti cells reduces pyramidal cell assembly plasticity during learning, possibly facilitating already acquired motor skills.

neuroscience↗

bioRxiv2023

5-MeO-DMT induces sleep-like LFP spectral signatures in the hippocampus and prefrontal cortex of awake rats

5-methoxy-N,N-dimethyltryptamine (5-MeO-DMT) is a potent classical psychedelic known to induce changes in locomotion, behaviour, and sleep in rodents. However, there is limited knowledge regarding its acute neurophysiological effects. Local field potentials (LFPs) are commonly used as a proxy for neural activity, but previous studies investigating psychedelics have been hindered by confounding effects of behavioural changes and anaesthesia, which alter these signals. To address this gap, we investigated acute LFP changes in the hippocampus (HP) and medial prefrontal cortex (mPFC) of freely behaving rats, following 5-MeO-DMT administration. 5-MeO-DMT led to an increase of delta power and a decrease of theta power in the HP LFPs, which could not be accounted for by changes in locomotion. Furthermore, we observed a dose-dependent reduction in slow (20-50 Hz) and mid (50-100Hz) gamma power, as well as in theta phase modulation, even after controlling for the effects of speed and theta power. State map analysis of the spectral profile of awake behaviour induced by 5-MeO-DMT revealed similarities to electrophysiological states observed during slow-wave sleep (SWS) and rapid-eye-movement (REM) sleep. Our findings suggest that the psychoactive effects of classical psychedelics are associated with the integration of waking behaviours with sleep-like spectral patterns in LFPs.

neuroscience↗

bioRxiv2021

Laser Capture Microdissection optimization for high-quality RNA in mouse brain tissue

Laser Capture Microdissection (LCM) is a method that allows to select and dissecting specific structures, cell populations, or even single cells from different types of tissue to extract DNA, RNA, or proteins. It is easy to perform and precise, avoiding unwanted signals from irrelevant cells, because gene expression may be affected by a bulk of heterogeneous material in a sample. However, despite its efficiency, several steps can affect the sample RNA integrity. In comparison to DNA, RNA is a much more unstable molecule and represents a challenge in the LCM method. Here we describe an optimized protocol to provide good concentration and high-quality RNA in specific structures, such as Dentate Gyrus and CA1 in the hippocampus, basolateral amygdala and anterior cingulate cortex of mouse brain tissue.

neuroscience↗

bioRxiv2021

Neuroimmune-glial cells interactions elevate the kynurenine metabolic pathway to sustain neuropathic pain

Neuropathic pain is triggered by injury to the somatosensory system, and is one of the most important types of chronic pain. Nevertheless, critical pathophysiological mechanisms that maintain neuropathic pain are poorly understood. Here, we show that neuropathic pain is abrogated when the kynurenine metabolic pathway (KYNPATH) initiated by the enzyme indoleamine 2,3-dioxygenase (IDO) is ablated pharmacologically or genetically. Mechanistically, it was found that IDO upregulation in dendritic cells that accumulate in the dorsal root leptomeninges led to increased levels of kynurenine (Kyn) in the spinal cord, where Kyn is metabolized by astrocytes-expressed kynurenine-3-monooxygenase into a pro-nociceptive metabolite 3-hydroxykynurenine. In conclusion, these data reveal a novel role for KYNPATH as an important factor maintaining neuropathic pain during neuroimmune-glia cells interactions. This novel paradigm offers potential new targets for drug development against this type of chronic pain.

neuroscience↗

bioRxiv2018

A voltage-dependent depolarization induced by low external glucose in neurons of the nucleus of the tractus solitarius of rats: interaction with KATP channels regulated by external glucose.

The brain demands constant supply of glucose-derived energy for cell metabolism and survival, and brain hypoglycemia may compromise synaptic functions. The brainstem nucleus of the tractus solitarius (NTS) is an integrative center for autonomic counterregulatory responses to hypoglycemia, and recent evidences have demonstrated that NTS neurons can also sense fluctuations in glucose levels in the extracellular milieu. Glucose-sensing neurons rely on glucose metabolism to respond to changes in glucose availability, but the ionic mechanisms underlying the low-glucose sensitivity are not well elucidated in NTS neurons. Therefore, this work aimed to investigate the effect of low extracellular glucose (0.5 mM) on the electrophysiological properties of NTS neurons of rats, by whole-cell patch-clamp. We showed that in NTS neurons maintained in 5 mM extracellular glucose, low glucose induces a depolarization in most neurons, which was correlated with membrane potential, decreased with depolarization. ATP-sensitive potassium (KATP) channels contribute to the hyperpolarized resting membrane potential (RMP) of NTS neurons, and blockage of KATP channels produced depolarization of the membrane and occludes the effect of low glucose, thus acting as modulators of low-glucose sensing in NTS neurons. However, this effect is caused by depolarization, since membrane hyperpolarization after KATP blockage restores the effect of low glucose. Additionally, we demonstrated that the incubation of NTS neurons in high glucose (10 mM) prior to recordings leads to more depolarized RMP in these neurons, what contributes to increase the number of neurons unresponsive to a low-glucose challenge, possibly via depolarization by inhibition of KATP channels following increased amounts of high glucose-derived intracellular ATP. We conclude that NTS neurons depolarize the membrane in response to the application of a low-glucose solution, but this effect is occluded by membrane depolarization triggered by KATP blockage. This suggests a homeostatic regulation of the membrane potential by glucose.

physiology↗

bioRxiv2016

THE CREATION OF A NEGATIVE SLOPE CONDUCTANCE REGION BY THE ACTIVATION OF THE PERSISTENT SODIUM CURRENT PROLONGS NEAR-THRESHOLD SYNAPTIC POTENTIALS

A change of the input resistance (Rin) of the neuron involves a change in the membrane conductances by opening and closing of ion channels. In passive membranes, i.e., membranes with only linear leak conductances, the increase or decrease of these conductances leads to a decrease or increase of the Rin and the membrane time constant ({tau}m). However, the presence of subthreshold voltage dependent currents can produce non-linear effects generating deviations from this relationship, especially the contradictory effect of negative conductances, as produced by the sodium-persistent current (INaP), on the Rin. In this work we aimed to analyze experimentally and theoretically the impact of the negative conductance produced by INaP on Rin. Experiments of whole-cell patch-clamp conducted in CA1 hippocampus pyramidal cells from brain slices showed a paradoxical voltage-dependent decrease of the Rin and the {tau}m in subthreshold membrane potentials close to the firing threshold after the perfusion with TTX, which inhibits INaP. This effect is postulated to be a result of the negative slope conductance in the subthreshold region produced by this conductance. The analysis of the experimental data, together with simulations found that the slope conductance of INaP is negative for subthreshold membrane potentials and its magnitude is voltage dependent in the same range observed for the voltage-dependence of Rin and {tau}m. The injection of an artificial INaP using dynamic-clamp in the presence of TTX restored the Rin and {tau}m to its original values. Additionally the injection of an artificial leak current with a negative conductance in the presence of TTX restored the Rin and {tau}m as the artificial Inap did. On the other hand, the injection of an artificial leak current with a positive conductance in the presence of TTX had no effect on the Rin and {tau}m. We conclude that INaP increases the Rin and {tau}m by the negative slope conductance observed in its non-monotonic I-V relationship. These results demonstrate that the effect of Inap on Rin and {tau}m is stronger in potentials near the firing threshold, which could potentiate the temporal summation of the EPSPs increasing their temporal integration and facilitating action potential firing. Because of its negative slope conductance, INaP is more effective in increasing excitability near threshold than a depolarizing leak current.

biophysics↗