Biology subjects

Galvan, E. J.

Publications and source records attributed to Galvan, E. J..

4 recordsLinked to original sources

bioRxiv2025

Layer V Neocortical Neurons From Individuals With Drug-Resistant Epilepsy Show Multiple Synaptic Alterations but Lack Somatic Hyperexcitability

Although neuronal hyperexcitability is the primary mechanism underlying seizure activity in epilepsy, little is known about how different neuronal mechanisms at different organizational levels contribute to network hyperexcitability in the human epileptic brain. In this study, we determined a series of cellular and synaptic properties of layer V pyramidal neurons from neocortical tissue of patients with drug-resistant epilepsy that may contribute the hyperexcitable state associated with epilepsy. Using the whole cell, patch-clamp technique, and extracellular recordings, we determined the passive and active electrophysiological properties of layer V pyramidal neurons with regular spiking phenotypes from temporal, parietal, and frontal neocortices surgically resected from individuals with drug-resistant epilepsy. Also, the glutamatergic strength, the synchronicity between presynaptic volleys and field excitatory postsynaptic potentials, and short-term, frequency-dependent plasticity were determined at the synaptic level. Lastly, biocytin-filled pyramidal neurons were used to perform post hoc digital reconstructions and morphometric analyses. The collected data revealed that pyramidal neurons exhibit minimal spontaneous activity, similar resting membrane potentials, and input resistance values among the temporal, parietal, and frontal neocortices. Although frontal neurons were more hyperexcitable than temporal and parietal neurons, the firing output was comparable to that previously observed in non-pathological human tissue. The digital reconstructions confirmed the identity of pyramidal neurons and revealed alterations in dendritic complexity. In contrast, the analyses of the extracellular recordings uncovered significant desynchronization between presynaptic excitability and postsynaptic activity and loss of short-term depression in response to repetitive stimulation within the gamma range (30 Hz). Our data suggest that neocortical layer V pyramidal neurons from individuals with drug-resistant epilepsy are not necessarily hyperexcitable at the somatic level. Instead, synaptic alterations, such as synaptic desynchronization and a loss of frequency-dependent short-term depression may significantly contribute to the hyperexcitable state observed during seizure activity.

neuroscience↗

bioRxiv2024

D1-like receptor activation rescues hippocampal synaptic plasticity and cognitive impairments in the MK-801 schizophrenia model.

Schizophrenia is a disorder with a higher cognitive decline in early adulthood, causing impaired retention of episodic memories. However, the physiological and behavioral functions that underlie cognitive deficits with a potential mechanism to ameliorate and improve cognitive performance are unknown. In this study, we used the MK-801 neurodevelopmental schizophrenia-like model. Rats were divided into two groups: one received MK-801, and the other received saline for five consecutive days (7-11 postnatal days, PND). Using extracellular field recordings in acute hippocampal slices and the Barnes maze task, we evaluated synaptic plasticity late-LTP and spatial memory in freely moving animals in early adolescence and young adulthood. Next, we examined D1-like activation as a mechanism to ameliorate cognitive impairments. Our results suggest that MK-801 neonatal treatment induces impairment in late-LTP expression and deficits in spatial memory retrieval in early adolescence that is maintained until young adulthood. Furthermore, we found that activation of D1-like dopamine receptors ameliorates the impairments and promotes a robust expression of late-LTP and an improved performance in the Barnes maze task, suggesting a novel and potential therapeutic role in treating cognitive impairments in schizophrenia. Highlights- MK-801 Schizophrenia model induces impairment in Late-LTP at early adolescence and young developmental stage. - Barnes maze recall phase is impaired in the MK-801 Schizophrenia model. - The activation of D1-like receptors promotes recovery and induction of the - Late-LTP in the MK-801 schizophrenia model in adolescent and young adult rats. - Activation of D1-like dopamine receptors improves behavioral performance in the MK-801 schizophrenia model in adolescent and young adult rats. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=127 SRC="FIGDIR/small/599791v1_ufig1.gif" ALT="Figure 1"> View larger version (20K): org.highwire.dtl.DTLVardef@e258e7org.highwire.dtl.DTLVardef@3ab481org.highwire.dtl.DTLVardef@20aa4dorg.highwire.dtl.DTLVardef@8cc518_HPS_FORMAT_FIGEXP M_FIG C_FIG Disturbances in episodic memories are observed in patients with schizophrenia and rodent models. Still, the hippocampal physiological substrates with a potential rescue mechanism related to consolidation of memories have not been elucidated. Here, in vitro electrophysiology and in vivo Barnes maze task are used at two ages in the MK-801 neurodevelopmental schizophrenia-like model. We observed a loss of hippocampal late-LTP and impaired recall phase, and the activation of dopamine D1-like receptors attenuated the impairments with a rescue of both late-LTP and recall phase, suggesting an important role of D1-like receptors activity for episodic memory in schizophrenia.

animal behavior and cognition↗

bioRxiv2024

The bidirectional role of GABAA and GABAB receptors during the differentiation process of neural precursor cells of thesubventricular zone

The intricate process of neuronal differentiation integrates multiple signals to induce transcriptional, morphological, and electrophysiological changes that reshape the properties of neural precursor cells during their maturation and migration process. An increasing number of neurotransmitters and biomolecules have been identified that serve as molecular signals that trigger and guide this process. In this sense, taurine, a sulfur-containing, non-essential amino acid widely expressed in the mammal brain, modulates the neuronal differentiation process. In this study, we describe the effect of taurine acting via the ionotropic GABAA receptor and the metabotropic GABAB receptor on the neuronal differentiation and electrophysiological properties of precursor cells derived from the subventricular zone of the mouse brain. Taurine stimulates the number of neurites and favors the dendritic complexity of the neural precursor cells, accompanied by changes in the somatic input resistance and the strength of inward and outward membranal currents. At the pharmacological level, the blockade of GABAA receptors inhibits these effects, whereas the stimulation of GABAB receptors has no positive effects on the taurine-mediated differentiation process. Strikingly, the blockade of the GABAB receptor with CGP533737 stimulates neurite outgrowth, dendritic complexity, and membranal current kinetics of neural precursor cells. The effects of taurine on the differentiation process involve Ca2+ mobilization and the activation of intracellular signaling cascades since chelation of intracellular calcium with BAPTA-AM, and inhibition of the CaMKII, ERK1/2, and Src kinase inhibits the neurite outgrowth of neural precursor cells of the subventricular zone.

neuroscience↗

bioRxiv2024

Maternal Immune Activation Alters Temporal Precision of Spike Generation of CA1 Pyramidal Neurons by Unbalancing GABAergic Inhibition in the Offspring

Maternal immune activation (MIA) represents a risk factor for neuropsychiatric disorders associated with neurodevelopmental alterations. A growing body of evidence from rodents and non-human primates shows that MIA induced by viral or bacterial infections results in several neurobiological alterations in the offspring. These changes may play an important role in the pathophysiology of psychiatric disorders like schizophrenia and autism spectrum disorders, whose clinical features include impairments in cognitive processing and social performance. Such alterations are causally associated with the maternal inflammatory response to infection rather than with the infection itself. Previously, we reported that CA1 pyramidal neurons of mice exposed to MIA exhibit increased excitability accompanied by a reduction in dendritic complexity. However, potential alterations in cellular and synaptic rules that shape the neuronal computational properties of the offspring remain to be determined. In this study, using mice as subjects, we identified a series of cellular and synaptic alterations endured by CA1 pyramidal neurons of the dorsal hippocampus in a lipopolysaccharide-induced MIA model. Our data provide evidence that MIA reshapes the excitation-inhibition balance by decreasing the perisomatic GABAergic inhibition impinging on CA1 pyramidal neurons. These alterations yield a dysregulated amplification of the temporal and spatial synaptic integration. In addition, MIA-exposed offspring displayed social and anxiety-like abnormalities. Collectively, these findings contribute to the understanding of the cellular and synaptic alterations underlying the behavioral symptoms present in neurodevelopmental disorders associated with MIA. HighlightsO_LILPS injection during pregnancy (MIA) increases cytokine production and decreases litter size. C_LIO_LIMIA increases the temporal summation of EPSPs in hippocampal neurons. C_LIO_LIMIA alters spatial summation and increases the probability of action potential discharge. C_LIO_LIMIA alters the inhibitory/excitatory balance of CA1 pyramidal cells. C_LIO_LIMIA alters the expression of GAD-positive interneurons. C_LIO_LIMIA alters the performance of several behavioral tests in offspring. C_LI

neuroscience↗