Search results for "Synaptic Transmission"
showing 10 items of 178 documents
Interplay between glutamatergic and GABAergic neurotransmission alterations in cognitive and motor impairment in minimal hepatic encephalopathy.
2015
The cognitive and motor alterations in hepatic encephalopathy (HE) are the final result of altered neurotransmission and communication between neurons in neuronal networks and circuits. Different neurotransmitter systems cooperate to modulate cognitive and motor function, with a main role for glutamatergic and GABAergic neurotransmission in different brain areas and neuronal circuits. There is an interplay between glutamatergic and GABAergic neurotransmission alterations in cognitive and motor impairment in HE. This interplay may occur: (a) in different brain areas involved in specific neuronal circuits; (b) in the same brain area through cross-modulation of glutamatergic and GABAergic neur…
Early GABAergic circuitry in the cerebral cortex.
2013
In the cerebral cortex GABAergic signaling plays an important role in regulating early developmental processes, for example, neurogenesis, migration and differentiation. Transient cell populations, namely Cajal-Retzius in the marginal zone and thalamic input receiving subplate neurons, are integrated as active elements in transitory GABAergic circuits. Although immature pyramidal neurons receive GABAergic synaptic inputs already at fetal stages, they are integrated into functional GABAergic circuits only several days later. In consequence, GABAergic synaptic transmission has only a minor influence on spontaneous network activity during early corticogenesis. Concurrent with the gradual devel…
Cellular Mechanisms of Subplate-Driven and Cholinergic Input-Dependent Network Activity in the Neonatal Rat Somatosensory Cortex
2008
Early coordinated network activity promotes the development of cortical structures. Although these early activity patterns have been recently characterized with respect to their developmental, spatial and dynamic properties, the cellular mechanisms by which specific neuronal populations trigger coordinated activity in the neonatal cerebral cortex are still poorly understood. Here we characterize the cellular and molecular processes leading to generation of network activity during early postnatal development. We show that the somatosensory cortex of newborn rats expresses cholinergic-driven calcium transients which are synchronized within the deeply located subplate. Correspondingly, endogen…
Haploinsufficiency of Tsc2 Leads to Hyperexcitability of Medial Prefrontal Cortex via Weakening of Tonic GABAB Receptor-mediated Inhibition.
2020
Abstract Loss-of-function mutation in one of the tumor suppressor genes TSC1 or TSC2 is associated with several neurological and psychiatric diseases, including autism spectrum disorders (ASDs). As an imbalance between excitatory and inhibitory neurotransmission, E/I ratio is believed to contribute to the development of these disorders, we investigated synaptic transmission during the first postnatal month using the Tsc2+/− mouse model. Electrophysiological recordings were performed in acute brain slices of medial prefrontal cortex. E/I ratio at postnatal day (P) 15–19 is increased in Tsc2+/− mice as compared with wildtype (WT). At P25–30, facilitated GABAergic transmission reduces E/I rati…
Topology of synaptic connectivity constrains neuronal stimulus representation, predicting two complementary coding strategies
2022
In motor-related brain regions, movement intention has been successfully decoded from in-vivo spike train by isolating a lower-dimension manifold that the high-dimensional spiking activity is constrained to. The mechanism enforcing this constraint remains unclear, although it has been hypothesized to be implemented by the connectivity of the sampled neurons. We test this idea and explore the interactions between local synaptic connectivity and its ability to encode information in a lower dimensional manifold through simulations of a detailed microcircuit model with realistic sources of noise. We confirm that even in isolation such a model can encode the identity of different stimuli in a lo…
Coincident glutamatergic depolarizations enhance GABAA receptor-dependent Cl- influx in mature and suppress Cl- efflux in immature neurons.
2021
The impact of GABAergic transmission on neuronal excitability depends on the Cl--gradient across membranes. However, the Cl--fluxes through GABAA receptors alter the intracellular Cl- concentration ([Cl-]i) and in turn attenuate GABAergic responses, a process termed ionic plasticity. Recently it has been shown that coincident glutamatergic inputs significantly affect ionic plasticity. Yet how the [Cl-]i changes depend on the properties of glutamatergic inputs and their spatiotemporal relation to GABAergic stimuli is unknown. To investigate this issue, we used compartmental biophysical models of Cl- dynamics simulating either a simple ball-and-stick topology or a reconstructed CA3 neuron. Th…
From the Golgi-Cajal mapping to the transmitter-based characterization of the neuronal networks leading to two modes of brain communication: Wiring a…
2007
After Golgi-Cajal mapped neural circuits, the discovery and mapping of the central monoamine neurons opened up for a new understanding of interneuronal communication by indicating that another form of communication exists. For instance, it was found that dopamine may be released as a prolactin inhibitory factor from the median eminence, indicating an alternative mode of dopamine communication in the brain. Subsequently, the analysis of the locus coeruleus noradrenaline neurons demonstrated a novel type of lower brainstem neuron that monosynaptically and globally innervated the entire CNS. Furthermore, the ascending raphe serotonin neuron systems were found to globally innervate the forebrai…
Pre- and postsynaptic type-1 cannabinoid receptors control the alterations of glutamate transmission in experimental autoimmune encephalomyelitis
2013
Type-1 cannabinoid receptors (CB1R) are important regulators of the neurodegenerative damage in multiple sclerosis (MS) and in experimental autoimmune encephalomyelitis (EAE). In GABAergic striatal neurons, CB1R stimulation exerts protective effects by limiting inflammation-induced potentiation of glutamate-mediated spontaneous excitatory postsynaptic currents (sEPSCs). Here we show that CB1R located on GABAergic or on glutamatergic neurons are differentially involved in the pre- and postsynaptic alterations of sEPSCs caused by EAE in the striatum. After induction of EAE, mice selectively lacking CB1R on GABAergic neurons (GABA-CB1R-KO) showed exacerbated alterations of sEPSC duration in GA…
Neuromuscular junction disassembly and muscle fatigue in mice lacking neurotrophin-4
2001
Neurotrophin-4 (NT-4) is produced by slow muscle fibers in an activity-dependent manner and promotes growth and remodeling of adult motorneuron innervation. However, both muscle fibers and motor neurons express NT-4 receptors, suggesting bidirectional NT-4 signaling at the neuromuscular junction. Mice lacking NT-4 displayed enlarged and fragmented neuromuscular junctions with disassembled postsynaptic acetylcholine receptor (AChR) clusters, reduced AChR binding, and acetylcholinesterase activity. Electromyographic responses, posttetanic potentiation, and action potential amplitude were also significantly reduced in muscle fibers from NT-4 knock-out mice. Slow-twitch soleus muscles from thes…
Evidence that 3 alpha-hydroxy-5 alpha-pregnan-20-one is a physiologically relevant modulator of GABA-ergic neurotransmission.
1991
Abstract 3α-Hydroxy-5α-pregnan-20-one (HPO) is a progesterone metabolite which exhibits narcotic properties at high concentrations by interactions with the receptor for gamma-aminobutyric acid (GABA). The present investigation characterized low-dose effects of HPO on GABA A receptor binding, by determining the allosteric properties of HPO on the in vitro binding of 3 H-muscimol to membrane fractions from the cerebella of ovariectomized rats. A newly developed method for tissue preparation was used to wash out endogenous ligands interfering with the assay. HPO reduced the affinity of 3 H-muscimol to GABA A receptor sites by 52% and enhanced the number of accessible binding sites from 5.5±0.5…