The mechanism of ethanol action on midbrain dopaminergic neuron firing: a dynamic-clamp study of the role of Ih and GABAergic synaptic integration

2011 ◽  
Vol 106 (4) ◽  
pp. 1901-1922 ◽  
Author(s):  
Takashi Tateno ◽  
Hugh P. C. Robinson
Keyword(s):  
Hcn Channels ◽  
Dynamic Clamp ◽  
Gabaergic Interneurons ◽  
Channel Current ◽  
Midbrain Dopaminergic Neuron ◽  
Rebound Spiking ◽  
Perforated Patch Clamp ◽  
Clamp Study

Hyperpolarization-activated and cyclic nucleotide-gated (HCN) channels are expressed in dopaminergic (DA) neurons of the ventral tegmental area (VTA) as well as in DA and GABAergic neurons of the substantia nigra (SN). The excitation of DA neurons induced by ethanol has been proposed to result from its enhancing HCN channel current, Ih. Using perforated patch-clamp recordings in rat midbrain slices, we isolated Ih in these neurons by voltage clamp. We showed that ethanol reversibly increased the amplitude and accelerated the activation kinetics of Ih and caused a depolarizing shift in its voltage dependence. Using dynamic-clamp conductance injection, we injected artificial Ih and fluctuating GABAergic synaptic conductance inputs into neurons following block of intrinsic Ih. This demonstrated directly a major role of Ih in promoting rebound spiking following phasic inhibition, which was enhanced as the kinetics and amplitude of Ih were changed in the manner induced by ethanol. Similar effects of ethanol were observed on Ih and firing rate in non-DA, putatively GABAergic interneurons, indicating that in addition to its direct effects on firing, ethanol will produce large changes in the inhibition and disinhibition (via GABAergic interneurons) converging on DA neurons. Thus the overall effects of ethanol on firing of DA cells of the VTA and SN in vivo, and hence on phasic dopamine release in the striatum, appear to be determined substantially by its action on Ih in both DA cells and GABAergic interneurons.

scholarly journals Deficiency of intellectual disability-related gene Brpf1 reduced inhibitory neurotransmission and Map2k7 expression in GABAergic interneurons

2021 ◽  
Author(s):  
Jingli Cao ◽  
Weiwei Xian ◽  
Maierdan Palihati ◽  
Yu Zhu ◽  
Guoxiang Wang ◽  
...  
Keyword(s):  
Intellectual Disability ◽  
Dendritic Morphology ◽  
Gabaergic Interneurons ◽  
Related Gene ◽  
Inhibitory Neurotransmission ◽  
Whole Cell Patch Clamp ◽  
Developmental Niche ◽  
And Function

AbstractIntellectual disability is closely related to impaired GABA neurotransmission. Brpf1 was specifically expressed in medial ganglionic eminence (MGE), a developmental niche of GABAergic interneurons, and patients with BRPF1 mutations were mentally retarded. To test its role in development and function of MGE-derived GABAergic interneurons, we performed immunofluorescence staining, whole-cell patch-clamp, MGE transplantation and mRNA-Seq to understand its effect on neuronal differentiation, dendritic morphology, electrophysiology, migration and gene regulation, using mouse MGE-derived GABAergic interneurons infected with AAV-shBrpf1. We found a decreasing trend on parvalbumin+ interneuron differentiation. Moreover, increased firing threshold, decreased number of evoked APs, and a reduced amplitude of mIPSCs were observed before any significant change of MAP2+ dendritic morphology and in vivo migration appeared. Finally, mRNA-Seq analysis revealed that genes related to neurodevelopment and synaptic transmission such as Map2k7 were dysregulated. Our results demonstrated a key role of Brpf1 in inhibitory neurotransmission and related gene expression of GABAergic interneurons.

Disruption of GABAA Receptors on GABAergic Interneurons Leads to Increased Oscillatory Power in the Olfactory Bulb Network

2001 ◽  
Vol 86 (6) ◽  
pp. 2823-2833 ◽  
Author(s):  
Zoltan Nusser ◽  
Leslie M. Kay ◽  
Gilles Laurent ◽  
Gregg E. Homanics ◽  
Istvan Mody
Keyword(s):  
Olfactory Bulb ◽  
Granule Cells ◽  
Fold Increase ◽  
Network Activity ◽  
Gabaergic Interneurons ◽  
Synaptic Inhibition ◽  
Principal Cells ◽  
Network Oscillations

Synchronized neural activity is believed to be essential for many CNS functions, including neuronal development, sensory perception, and memory formation. In several brain areas GABAA receptor–mediated synaptic inhibition is thought to be important for the generation of synchronous network activity. We have used GABAA receptor β3 subunit deficient mice (β3−/−) to study the role of GABAergic inhibition in the generation of network oscillations in the olfactory bulb (OB) and to reveal the role of such oscillations in olfaction. The expression of functional GABAA receptors was drastically reduced (>93%) in β3−/− granule cells, the local inhibitory interneurons of the OB. This was revealed by a large reduction of muscimol-evoked whole-cell current and the total current mediated by spontaneous, miniature inhibitory postsynaptic currents (mIPSCs). In β3−/− mitral/tufted cells (principal cells), there was a two-fold increase in mIPSC amplitudes without any significant change in their kinetics or frequency. In parallel with the altered inhibition, there was a significant increase in the amplitude of theta (80% increase) and gamma (178% increase) frequency oscillations in β3−/− OBs recorded in vivo from freely moving mice. In odor discrimination tests, we found β3−/− mice to be initially the same as, but better with experience than β3+/+ mice in distinguishing closely related monomolecular alcohols. However, β3−/− mice were initially better and then worse with practice than control mice in distinguishing closely related mixtures of alcohols. Our results indicate that the disruption of GABAAreceptor–mediated synaptic inhibition of GABAergic interneurons and the augmentation of IPSCs in principal cells result in increased network oscillations in the OB with complex effects on olfactory discrimination, which can be explained by an increase in the size or effective power of oscillating neural cell assemblies among the mitral cells of β3−/− mice.

scholarly journals Rational design of a mutation to investigate the role of the brain protein TRIP8b in limiting the cAMP response of HCN channels in neurons

2020 ◽  
Vol 152 (9) ◽  
Author(s):  
Alessandro Porro ◽  
Anna Binda ◽  
Matteo Pisoni ◽  
Chiara Donadoni ◽  
Ilaria Rivolta ◽  
...  
Keyword(s):  
Cortical Neurons ◽  
Rational Design ◽  
Regulatory Subunit ◽  
Hcn Channels ◽  
Subcellular Targeting ◽  
Mutant Channel ◽  
Channel Trafficking ◽  
Starting Point

TRIP8b (tetratricopeptide repeat–containing Rab8b-interacting protein) is the neuronal regulatory subunit of HCN channels, a family of voltage-dependent cation channels also modulated by direct cAMP binding. TRIP8b interacts with the C-terminal region of HCN channels and controls both channel trafficking and gating. The association of HCN channels with TRIP8b is required for the correct expression and subcellular targeting of the channel protein in vivo. TRIP8b controls HCN gating by interacting with the cyclic nucleotide-binding domain (CNBD) and competing for cAMP binding. Detailed structural knowledge of the complex between TRIP8b and CNBD was used as a starting point to engineer a mutant channel, whose gating is controlled by cAMP, but not by TRIP8b, while leaving TRIP8b-dependent regulation of channel trafficking unaltered. We found two-point mutations (N/A and C/D) in the loop connecting the CNBD to the C-linker (N-bundle loop) that, when combined, strongly reduce the binding of TRIP8b to CNBD, leaving cAMP affinity unaltered both in isolated CNBD and in the full-length protein. Proof-of-principle experiments performed in cultured cortical neurons confirm that the mutant channel provides a genetic tool for dissecting the two effects of TRIP8b (gating versus trafficking). This will allow the study of the functional role of the TRIP8b antagonism of cAMP binding, a thus far poorly investigated aspect of HCN physiology in neurons.

scholarly journals Deficiency of intellectual disability-related gene Brpf1 reduced inhibitory neurotransmission in MGE-derived GABAergic interneurons

2021 ◽  
Author(s):  
Jingli Cao ◽  
Weiwei Xian ◽  
Maierdan Palihati ◽  
Yu Zhu ◽  
Guoxiang Wang ◽  
...  
Keyword(s):  
Intellectual Disability ◽  
Dendritic Morphology ◽  
Gabaergic Interneurons ◽  
Related Gene ◽  
Migration Ability ◽  
Inhibitory Neurotransmission ◽  
Whole Cell Patch Clamp ◽  
And Function

Abstract Intellectual disability is closely related to impaired GABA neurotransmission. Brpf1 was specifically expressed in medial ganglionic eminence (MGE), a developmental niche of GABAergic interneurons, and patients with BRPF1 mutations showed intellectual disability. To test its role in development and function of MGE-derived GABAergic interneurons, we performed immunofluorescence staining, whole-cell patch-clamp, MGE transplantation and mRNA-Seq to understand its effect on neuronal differentiation, dendritic morphology, electrophysiology, migration and gene regulation, using mouse MGE-derived GABAergic interneurons infected with AAV-shBrpf1. The results showed that Brpf1 knockdown had a decreasing trend, although not significant, on the differentiation of GABAergic interneurons into parvalbumin+ interneurons. Moreover, increased firing threshold, decreased number of evoked action potentials, and a reduced amplitude of miniature inhibitory postsynaptic currents were observed before any significant change of MAP2+ dendritic morphology and in vivo migration ability appeared. Finally, mRNA-Seq analysis revealed that genes related to neurodevelopment and synaptic transmission such as Map2k7 were dysregulated. Our results demonstrated a key role of Brpf1 in inhibitory neurotransmission and related gene expression of GABAergic interneurons.

In Vivo Dynamic Clamp Study of Ih in the Mouse Inferior Colliculus

2010 ◽  
Vol 104 (2) ◽  
pp. 940-948 ◽  
Author(s):  
A. P. Nagtegaal ◽  
J.G.G. Borst
Keyword(s):  
Membrane Potential ◽  
Inferior Colliculus ◽  
Single Cells ◽  
Membrane Resistance ◽  
Resting Membrane Potential ◽  
Dynamic Clamp ◽  
Small Contribution ◽  
Functional Relevance ◽  
Rebound Spiking

Approximately half of the cells in the mouse inferior colliculus have the hyperpolarization-activated mixed cation current Ih, yet little is known about its functional relevance in vivo. We therefore studied its contribution to the processing of sound information in single cells by making in vivo whole cell recordings from the inferior colliculus (IC) of young-adult anesthetized C57Bl/6 mice. Following pharmacological block of the endogenous channels, a dynamic clamp approach allowed us to study the responses to current injections or auditory stimuli in the presence and absence of Ih within the same neuron, thus avoiding network or developmental effects. The presence of Ih changed basic cellular properties, including depolarizing the resting membrane potential and decreasing resting membrane resistance. Sound-evoked excitatory postsynaptic potentials were smaller but at the same time reached a more positive membrane potential when Ih was present. With Ih, a subset of cells showed rebound spiking following hyperpolarizing current injection. Its presence also changed more complex cellular properties. It decreased temporal summation in response to both hyperpolarizing and depolarizing repetitive current stimuli, and resulted in small changes in the cycle-averaged membrane potential during sinusoidal amplitude modulated (SAM) tones. Furthermore, Ih minimally decreased the response to a tone following a depolarization, an effect that may make a small contribution to forward masking. Our results thus suggest that previously observed differences in IC cells are a mixture of direct effects of Ih and indirect effects due to the change in membrane potential or effects due to the co-expression with other channels.

scholarly journals Loss of HCN2 in Dorsal Hippocampus of Young Adult Mice Induces Specific Apoptosis of the CA1 Pyramidal Neuron Layer

2021 ◽  
Vol 22 (13) ◽  
pp. 6699
Author(s):  
Matthias Deutsch ◽  
Carina Stegmayr ◽  
Sabine Balfanz ◽  
Arnd Baumann
Keyword(s):  
Young Adult ◽  
Hippocampal Neurons ◽  
Dorsal Hippocampus ◽  
Proper Function ◽  
Hcn Channels ◽  
Knock Down ◽  
Ion Conducting

Neurons inevitably rely on a proper repertoire and distribution of membrane-bound ion‑conducting channels. Among these proteins, the family of hyperpolarization-activated and cyclic nucleotide-gated (HCN) channels possesses unique properties giving rise to the corresponding Ih-current that contributes to various aspects of neural signaling. In mammals, four genes (hcn1-4) encode subunits of HCN channels. These subunits can assemble as hetero- or homotetrameric ion-conducting channels. In order to elaborate on the specific role of the HCN2 subunit in shaping electrical properties of neurons, we applied an Adeno-associated virus (AAV)-mediated, RNAi-based knock-down strategy of hcn2 gene expression both in vitro and in vivo. Electrophysiological measurements showed that HCN2 subunit knock-down resulted in specific yet anticipated changes in Ih-current properties in primary hippocampal neurons and, in addition, corroborated that the HCN2 subunit participates in postsynaptic signal integration. To further address the role of the HCN2 subunit in vivo, we injected recombinant (r)AAVs into the dorsal hippocampus of young adult male mice. Behavioral and biochemical analyses were conducted to assess the contribution of HCN2-containing channels in shaping hippocampal network properties. Surprisingly, knock-down of hcn2 expression resulted in a severe degeneration of the CA1 pyramidal cell layer, which did not occur in mice injected with control rAAV constructs. This finding might pinpoint to a vital and yet unknown contribution of HCN2 channels in establishing or maintaining the proper function of CA1 pyramidal neurons of the dorsal hippocampus.

Mitochondrial matrix calcium ions regulate energy production in myocardium: A cytochemical study

1990 ◽  
Vol 48 (2) ◽  
pp. 166-167
Author(s):  
W.A. Jacob ◽  
R. Hertsens ◽  
A. Van Bogaert ◽  
M. De Smet
Keyword(s):  
Energy Metabolism ◽  
Calcium Ions ◽  
Energy Production ◽  
Regulation Of Respiration ◽  
Free Calcium ◽  
Mitochondrial Matrix ◽  
Cytochemical Study ◽  
Nmr Techniques

In the past most studies of the control of energy metabolism focus on the role of the phosphorylation potential ATP/ADP.Pi on the regulation of respiration. Studies using NMR techniques have demonstrated that the concentrations of these compounds for oxidation phosphorylation do not change appreciably throughout the cardiac cycle and during increases in cardiac work. Hence regulation of energy production by calcium ions, present in the mitochondrial matrix, has been the object of a number of recent studies.Three exclusively intramitochondnal dehydrogenases are key enzymes for the regulation of oxidative metabolism. They are activated by calcium ions in the low micromolar range. Since, however, earlier estimates of the intramitochondnal calcium, based on equilibrium thermodynamic considerations, were in the millimolar range, a physiological correlation was not evident. The introduction of calcium-sensitive probes fura-2 and indo-1 made monitoring of free calcium during changing energy metabolism possible. These studies were performed on isolated mitochondria and extrapolation to the in vivo situation is more or less speculative.

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