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Hippocampus Feb 2014GABAergic inhibitory interneurons control fundamental aspects of neuronal network function. Their functional roles are assumed to be defined by the identity of their...
GABAergic inhibitory interneurons control fundamental aspects of neuronal network function. Their functional roles are assumed to be defined by the identity of their input synapses, the architecture of their dendritic tree, the passive and active membrane properties and finally the nature of their postsynaptic targets. Indeed, interneurons display a high degree of morphological and physiological heterogeneity. However, whether their morphological and physiological characteristics are correlated and whether interneuron diversity can be described by a continuum of GABAergic cell types or by distinct classes has remained unclear. Here we perform a detailed morphological and physiological characterization of GABAergic cells in the dentate gyrus, the input region of the hippocampus. To achieve an unbiased and efficient sampling and classification we used knock-in mice expressing the enhanced green fluorescent protein (eGFP) in glutamate decarboxylase 67 (GAD67)-positive neurons and performed cluster analysis. We identified five interneuron classes, each of them characterized by a distinct set of anatomical and physiological parameters. Cross-correlation analysis further revealed a direct relation between morphological and physiological properties indicating that dentate gyrus interneurons fall into functionally distinct classes which may differentially control neuronal network activity.
Topics: Animals; Animals, Newborn; Bicuculline; Calbindin 2; Calbindins; Cluster Analysis; Dentate Gyrus; Electric Stimulation; Excitatory Amino Acid Antagonists; GABA-A Receptor Antagonists; Glutamate Decarboxylase; Green Fluorescent Proteins; In Vitro Techniques; Interneurons; Kynurenic Acid; Membrane Potentials; Mice; Mice, Inbred C57BL; Mice, Transgenic
PubMed: 24108530
DOI: 10.1002/hipo.22214 -
Physiological Reports Mar 2017The aim of this study was to evaluate the effects of two gamma-amino butyric acid (GABA)a receptor antagonists on motor behavioral tasks in a pharmacological model of...
The aim of this study was to evaluate the effects of two gamma-amino butyric acid (GABA)a receptor antagonists on motor behavioral tasks in a pharmacological model of Parkinson disease (PD) in rodents. Ninety-six Swiss mice received intraperitoneal injection of Haloperidol (1 mg/kg) to block dopaminergic receptors. GABAa receptors antagonists Bicuculline (1 and 5 mg/kg) and Flumazenil (3 and 6 mg/kg) were used for the assessment of the interaction among these neurotransmitters, in this PD model. The motor behavior of the animals was evaluated in the catalepsy test (30, 60, and 90 min after drugs application), through open field test (after 60 min) and trough functional gait assessment (after 60 min). Both Bicuculline and Flumazenil were able to partially reverse catalepsy induced by Haloperidol. In the open field test, Haloperidol reduced the number of horizontal and vertical exploration of the animals, which was not reversed trough application of GABAa antagonists. Furthermore, the functional gait assessment was not sensitive enough to detect motor changes in this animal model of PD. There is an interaction between dopamine and GABA in the basal ganglia and the blocking GABAa receptors may have therapeutic potential in the treatment of PD.
Topics: Animals; Behavior, Animal; Bicuculline; Disease Models, Animal; Flumazenil; GABA-A Receptor Antagonists; Gait; Mice; Motor Activity; Parkinsonian Disorders
PubMed: 28351968
DOI: 10.14814/phy2.13081 -
Neuroscience Feb 2017Self-organized criticality (SoC), a spontaneous dynamic state established and maintained in networks of moderate complexity, is a universal characteristic of neural...
Self-organized criticality (SoC), a spontaneous dynamic state established and maintained in networks of moderate complexity, is a universal characteristic of neural systems. Such systems produce cascades of spontaneous activity that are typically characterized by power-law distributions and rich, stable spatiotemporal patterns (i.e., neuronal avalanches). Since the dynamics of the critical state confer advantages in information processing within neuronal networks, it is of great interest to determine how criticality emerges during development. One possible mechanism is developmental, and includes axonal elongation during synaptogenesis and subsequent synaptic pruning in combination with the maturation of GABAergic inhibition (i.e., the integration then fragmentation process). Because experimental evidence for this mechanism remains inconclusive, we studied the developmental variation of neuronal avalanches in dissociated cortical neurons using high-density complementary metal-oxide semiconductor (CMOS) microelectrode arrays (MEAs). The spontaneous activities of nine cultures were monitored using CMOS MEAs from 4 to 30days in vitro (DIV) at single-cell spatial resolution. While cells were immature, cultures demonstrated random-like patterns of activity and an exponential avalanche size distribution; this distribution was followed by a bimodal distribution, and finally a power-law-like distribution. The bimodal distribution was associated with a large-scale avalanche with a homogeneous spatiotemporal pattern, while the subsequent power-law distribution was associated with diverse patterns. These results suggest that the SoC emerges through a two-step process: the integration process accompanying the characteristic large-scale avalanche and the fragmentation process associated with diverse middle-size avalanches.
Topics: 6-Cyano-7-nitroquinoxaline-2,3-dione; Action Potentials; Animals; Bicuculline; Cells, Cultured; Central Nervous System Agents; Cerebral Cortex; Cortical Synchronization; Microelectrodes; Neurons; Rats, Wistar
PubMed: 27915209
DOI: 10.1016/j.neuroscience.2016.11.031 -
Toxicological Sciences : An Official... Mar 2019Early life exposures to environmental contaminants are implicated in the pathogenesis of many neurodevelopmental disorders (NDDs). These disorders often display sex...
Early life exposures to environmental contaminants are implicated in the pathogenesis of many neurodevelopmental disorders (NDDs). These disorders often display sex biases, but whether environmental neurotoxicants act in a sex-dependent manner to modify neurodevelopment is largely unknown. Since altered dendritic morphology is associated with many NDDs, we tested the hypothesis that male and female primary mouse neurons are differentially susceptible to the dendrite-promoting activity of 2,2',3,5',6-pentachlorobiphenyl (PCB 95). Hippocampal and cortical neuron-glia co-cultures were exposed to vehicle (0.1% dimethylsulfoxide) or PCB 95 (100 fM-1 μM) from day in vitro 7-9. As determined by Sholl analysis, PCB 95-enhanced dendritic growth in female but not male hippocampal and cortical neurons. In contrast, both male and female neurons responded to bicuculline with increased dendritic complexity. Detailed morphometric analyses confirmed that PCB 95 effects on the number and length of primary and nonprimary dendrites varied depending on sex, brain region and PCB concentration, and that female neurons responded more consistently with increased dendritic growth and at lower concentrations of PCB 95 than their male counterparts. Exposure to PCB 95 did not alter cell viability or the ratio of neurons to glia in cultures of either sex. These results demonstrate that cultured female mouse hippocampal and cortical neurons are more sensitive than male neurons to the dendrite-promoting activity of PCB 95, and suggest that mechanisms underlying PCB 95-induced dendritic growth are sex-dependent. These data highlight the importance of sex in neuronal responses to environmental neurotoxicants.
Topics: Animals; Astrocytes; Bicuculline; Cell Survival; Cerebral Cortex; Coculture Techniques; Dendrites; Female; Hippocampus; Mice; Mice, Inbred C57BL; Neuronal Plasticity; Neurons; Polychlorinated Biphenyls; Primary Cell Culture; Sex Factors
PubMed: 30395321
DOI: 10.1093/toxsci/kfy277 -
Acta Neurobiologiae Experimentalis 2000The effects of bicuculline methiodide administration into ventromedial hypothalamus (15 ng per site, bilaterally) on fear behavior and monoamines (NA, DA, 5-HT) and GABA...
The effects of bicuculline methiodide administration into ventromedial hypothalamus (15 ng per site, bilaterally) on fear behavior and monoamines (NA, DA, 5-HT) and GABA in structures of the brain defensive system (hypothalamus, midbrain gray matter, amygdala, hippocampus and frontal cortex) were studied. Fear behavior was examined in the modified version of light-dark transition test. The time out from the illuminated compartment of chamber, the time spent there and number of returns to the illuminated compartment was measured. Additionally motor activity, i.e., number of crossings and rearings in dark as well as in the illuminated part of compartment, was registered. Blockade of GABAA receptors in the ventromedial hypothalamus resulted in increased fear behavior, i.e. decrease of time out from illuminated compartment and decrease of the time spent there. Motor behavior remained unchanged. HPLC analysis showed reduction of GABA concentration in all investigated brain structures. An increase of NA concentration in all examined structures with exception of the hypothalamus without effect on MHPG/NA was observed as well. Dopamine level remained unchanged, but DOPAC/DA ratio increased in all structures, except frontal cortex. Also HVA/DA ratio increased in the hypothalamus and midbrain. 5-HT concentration increased only in midbrain, 5-HIAA increased in midbrain and in frontal cortex, and 5-HIAA/5-HT ratio increased only in frontal cortex. These results indicate that GABA-ergic and monoaminergic systems remain in functional interactions and that these interactions may play an important role in the neurochemical regulation of fear behavior. The possible mechanism of GABA--monoaminergic interactions is discussed.
Topics: Animals; Bicuculline; Biogenic Monoamines; Brain Chemistry; Fear; GABA Antagonists; Male; Microinjections; Rats; Rats, Wistar; Ventromedial Hypothalamic Nucleus; gamma-Aminobutyric Acid
PubMed: 11016075
DOI: 10.55782/ane-2000-1351 -
British Journal of Pharmacology Mar 19831 The effects of gamma-aminobutyric acid (GABA) and related substances were examined in guinea-pig ileum longitudinal muscle.2 GABA at doses ranging from 10(-7) M to 3 x...
1 The effects of gamma-aminobutyric acid (GABA) and related substances were examined in guinea-pig ileum longitudinal muscle.2 GABA at doses ranging from 10(-7) M to 3 x 10(-6) M elicited a relaxation while at higher doses (3 x 10(-6) M - 10(-4) M), as previously described, it caused a contraction followed by relaxation.3 GABA-induced relaxation was bicuculline-insensitive, was mimicked by (-)-baclofen but not by homotaurine and muscimol. The effect of baclofen was stereospecific. GABA- and (-)-baclofen-induced relaxations were dose-dependent and their ED(50) values were similar. A specific cross-desensitization occurred between GABA and (-)-baclofen.4 The bicuculline-insensitive relaxation induced by GABA and (-)-baclofen was prevented by tetrodotoxin and hyoscine but not by phentolamine plus propranolol, naloxone or theophylline.5 In preparations in which the muscle tone was raised by histamine or prostaglandin F(2alpha), GABA and (-)-baclofen induced relaxation to the same extent as before increasing the tone. If the tone was raised by DMPP, a greater bicuculline-insensitive relaxation occurred.6 Contraction caused by GABA was bicuculline-sensitive and was mimicked by homotaurine and muscimol. Contraction was dose-dependent and muscimol was about three times more potent than GABA or homotaurine. A specific cross-desensitization occurred between the contractile effects of GABA and those of homotaurine or muscimol.7 Bicuculline competitively antagonized the contractile effects of GABA, homotaurine and muscimol and gave closely similar pA(2) values. The slope of the Schild plot for the above drugs was near 1, confirming the competitive nature of the antagonism.8 The bicuculline-sensitive contraction induced by GABA, homotaurine and muscimol was abolished by tetrodotoxin and was non-competitively antagonized by hyoscine, while it was unaffected by hexamethonium, mepyramine and methysergide.9 It is concluded that two receptors mediate the GABA effects in guinea-pig ileum: a bicuculline-sensitive GABA(A) receptor, which elicits contraction through an excitatory action on cholinergic post-ganglionic neurones; and a bicuculline-insensitive GABA(B) receptor which causes relaxation through an inhibitory presynaptic action on cholinergic post-ganglionic neurones. We confirm that GABA, homotaurine and muscimol are GABA(A) agonists, while GABA and (-)-baclofen are GABA(B) agonists.
Topics: Animals; Baclofen; Bicuculline; Guinea Pigs; Ileum; In Vitro Techniques; Male; Muscimol; Muscle Contraction; Muscle, Smooth; Receptors, Cell Surface; Receptors, GABA-A; Taurine; gamma-Aminobutyric Acid
PubMed: 6301600
DOI: 10.1111/j.1476-5381.1983.tb08807.x -
Journal of Neurophysiology Sep 2012While a substantial literature demonstrates the effect of differential experience on development of mammalian sensory cortices and plasticity of adult motor cortex,...
While a substantial literature demonstrates the effect of differential experience on development of mammalian sensory cortices and plasticity of adult motor cortex, characterization of differential experience on the functional development of motor cortex is meager. We first determined when forelimb movement representations (motor maps) could be detected in rats during postnatal development and then whether their motor map expression could be altered with rearing in an enriched environment consisting of group housing and novel toys or skilled learning by training on the single pellet reaching task. All offspring had high-resolution intracortical microstimulation (ICMS)-derived motor maps using methodologies previously optimized for the adult rat. First, cortical GABA-mediated inhibition was depressed by bicuculline infusion directly into layer V of motor cortex and ICMS-responsive points were first reliably detected on postnatal day (PND) 13. Without relying on bicuculline disinhibition of cortex, motor maps emerged on PND 35 and then increased in size until PND 60 and had progressively lower movement thresholds. Second, environmental enrichment did not affect initial detection of responsive points and motor maps in non-bicuculline-treated pups on PND 35. However, motor maps were larger on PND 45 in enriched rat pups relative to pups in the standard housing condition. Rats in both conditions had similar map sizes on PNDs 60, 75, and 90. Third, reach training in rat pups resulted in an internal reorganization of the map in the hemisphere contralateral, but not ipsilateral, to the trained forelimb. The map reorganization was expressed as proportionately more distal (digit and wrist) representations on PND 45. Our data indicate that both environmental enrichment and skilled reach training experience can differentially modify expression of motor maps during development.
Topics: Age Factors; Animals; Animals, Newborn; Bicuculline; Brain Mapping; Electric Stimulation; Female; Forelimb; GABA-A Receptor Antagonists; Learning; Male; Motor Cortex; Movement; Psychomotor Performance; Rats; Rats, Long-Evans
PubMed: 22723681
DOI: 10.1152/jn.01045.2011 -
PloS One 2013Preconditioning is defined as a range of stimuli that allow cells to withstand subsequent anaerobic and other deleterious conditions. While cell protection under...
Preconditioning is defined as a range of stimuli that allow cells to withstand subsequent anaerobic and other deleterious conditions. While cell protection under preconditioning is well established, this paper investigates the influence of neuroprotective preconditioning drugs, 4-aminopyridine and bicuculline (4-AP/bic), on synaptic communication across a broad network of in vitro rat cortical neurons. Using a permutation test, we evaluated cross-correlations of extracellular spiking activity across all pairs of recording electrodes on a 64-channel multielectrode array. The resulting functional connectivity maps were analyzed in terms of their graph-theoretic properties. A small-world effect was found, characterized by a functional network with high clustering coefficient and short average path length. Twenty-four hours after exposure to 4-AP/bic, small-world properties were comparable to control cultures that were not treated with the drug. Four hours following drug washout, however, the density of functional connections increased, while path length decreased and clustering coefficient increased. These alterations in functional connectivity were maintained at four days post-washout, suggesting that 4-AP/bic preconditioning leads to long-term effects on functional networks of cortical neurons. Because of their influence on communication efficiency in neuronal networks, alterations in small-world properties hold implications for information processing in brain systems. The observed relationship between density, path length, and clustering coefficient is captured by a phenomenological model where connections are added randomly within a spatially-embedded network. Taken together, results provide information regarding functional consequences of drug therapies that are overlooked in traditional viability studies and present the first investigation of functional networks under neuroprotective preconditioning.
Topics: 4-Aminopyridine; Animals; Bicuculline; Brain; Brain Mapping; Electroencephalography; Nerve Net; Neural Pathways; Neurons; Neuroprotective Agents; Rats
PubMed: 23349901
DOI: 10.1371/journal.pone.0054478 -
The Journal of Neuroscience : the... Feb 2020The ongoing activity of prefrontal neurons after a stimulus has disappeared is considered a neuronal correlate of working memory. It depends on the delicate but poorly...
The ongoing activity of prefrontal neurons after a stimulus has disappeared is considered a neuronal correlate of working memory. It depends on the delicate but poorly understood interplay between excitatory glutamatergic and inhibitory GABAergic receptor effects. We administered the NMDA receptor antagonist MK-801 and the GABA(A) receptor antagonist bicuculline methiodide while recording cellular activity in PFC of male rhesus monkeys performing a delayed decision task requiring working memory. The blockade of GABA(A) receptors strongly improved the selectivity of the neurons' delay activity, causing an increase in signal-to-noise ratio during working memory periods as well as an enhancement of the neurons' coding selectivity. The blockade of NMDA receptors resulted in a slight enhancement of selectivity and encoding capacity of the neurons. Our findings emphasize the delicate and more complex than expected interplay of excitatory and inhibitory transmitter systems in modulating working memory coding in prefrontal circuits. Ongoing delay activity of prefrontal neurons constitutes a neuronal correlate of working memory. However, how this delay activity is generated by the delicate interplay of synaptic excitation and inhibition is unknown. We probed the effects of excitatory neurotransmitter glutamate and inhibitory neurotransmitter GABA in regulating delay activity in rhesus monkeys performing a delayed decision task requiring working memory. Surprisingly, the blockade of both glutamatergic NMDA and GABA(A) receptors improved neuronal selectivity of delay activity, causing an increase in neuronal signal-to-noise ratio. Moreover, individual neurons were similarly affected by blockade of both receptors. This emphasizes the delicate and more complex than expected interplay of excitatory and inhibitory transmitter systems in modulating working memory coding in prefrontal circuits.
Topics: Action Potentials; Animals; Bicuculline; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; GABA-A Receptor Antagonists; GABAergic Neurons; Glutamic Acid; Macaca mulatta; Male; Memory, Short-Term; Mental Recall; Neurons; Pattern Recognition, Visual; Photic Stimulation; Prefrontal Cortex; Psychomotor Performance; Receptors, GABA-A; Receptors, N-Methyl-D-Aspartate
PubMed: 31911457
DOI: 10.1523/JNEUROSCI.2009-19.2019 -
The Journal of Neuroscience : the... Oct 1995Seventeen rat GABAA receptor subtypes were transiently expressed in the human embryonic kidney 293 cell line from alpha 1, alpha 2, alpha 3, alpha 5, or alpha 6 variants...
Seventeen rat GABAA receptor subtypes were transiently expressed in the human embryonic kidney 293 cell line from alpha 1, alpha 2, alpha 3, alpha 5, or alpha 6 variants with any of the three beta subunits and gamma 2S or gamma 3. We obtained fingerprints in the form of subtype characteristic concentration-response curves of 35S-TBPS binding to GABA and the GABAA antagonists SR 95531 and bicuculline. alpha 3 beta 3 gamma 2S/3 and alpha 5 beta 3 gamma 2S/3 containing receptors effectively recognized 35S-TBPS but not when beta 3 was replaced by the beta 1 or beta 2 subunit. This indicates a specific interaction of alpha and beta variants to form high-affinity 35S-TBPS binding sites. At low levels GABA allosterically increased 35S-TBPS binding to all receptors with the concentration and magnitude depending on the subunit combination. Exchange of the beta variant did not alter the concentration-response curves for alpha 1 and alpha 6 containing receptors but did so for alpha 2 containing receptors. alpha 2 beta 3 gamma 3 receptors displayed strong GABA-induced stimulation of 35S-TBPS binding, whereas binding to alpha 2 beta 3 gamma 3 receptors was marginally increased. SR 95531 and bicuculline decreased 35S-TBPS binding to all gamma 3 containing receptors. In addition, bicuculline was effective on alpha 1 beta x gamma 2 receptors. SR 95531 was threefold more potent than bicuculline in reversing GABA-induced modulation of 35S-TBPS binding in most receptor types, but was 30-fold more potent on alpha 2 beta 1 gamma 3 and alpha 6 beta 1 gamma 2S receptors.(ABSTRACT TRUNCATED AT 250 WORDS)
Topics: Animals; Bicuculline; Bridged Bicyclo Compounds, Heterocyclic; Cell Line; Embryo, Mammalian; GABA Antagonists; Humans; Kidney; Pyridazines; Rats; Receptors, GABA-A; Recombination, Genetic; gamma-Aminobutyric Acid
PubMed: 7472452
DOI: 10.1523/JNEUROSCI.15-10-06957.1995