Control of the Subthalamic Innervation of the Rat Globus Pallidus by D2/3 and D4 Dopamine Receptors

2006 ◽  
Vol 96 (6) ◽  
pp. 2877-2888 ◽  
Author(s):  
Adán Hernández ◽  
Osvaldo Ibáñez-Sandoval ◽  
Arturo Sierra ◽  
René Valdiosera ◽  
Dagoberto Tapia ◽  
...  
Keyword(s):  
Globus Pallidus ◽  
Receptor Agonist ◽  
Brain Slices ◽  
Mean Amplitude ◽  
Patch Clamp Technique ◽  
Antidromic Activation ◽  
Whole Cell Patch Clamp ◽  
Presynaptic Site ◽  
Site Of Action

The effects of activating dopaminergic D2/3 and D4 receptors during activation of the subthalamic projection to the globus pallidus (GP) were explored in rat brain slices using the whole cell patch-clamp technique. Byocitin labeling and both orthodromic and antidromic activation demonstrated the integrity of some subthalamopallidal connections in in vitro parasagittal brain slices. Excitatory postsynaptic currents (EPSCs) that could be blocked by CNQX and AP5 were evoked onto pallidal neurons by local field stimulation of the subthalamopallidal pathway in the presence of bicuculline. Bath application of dopamine and quinpirole, a dopaminergic D2-class receptor agonist, reduced evoked EPSCs by about 35%. This effect was only partially blocked by sulpiride, a D2/3 receptor antagonist. The sulpiride-sensitive reduction of the subthalamopallidal EPSC was associated with an increase in the paired-pulse ratio (PPR) and a reduction in the frequency but not the mean amplitude of spontaneous EPSCs (sEPSCs), indicative of a presynaptic site of action, which was confirmed by variance–mean analysis. The sulpiride-resistant EPSC reduction was mimicked by PD 168,077 and blocked by L-745,870, selective D4 receptor agonist and antagonist, respectively, suggesting the involvement of D4 receptors. The reduction of EPSCs produced by PD 168,077 was not accompanied by changes in PPR or the frequency of sEPSCs; however, it was accompanied by a reduction in mean sEPSC amplitude, indicative of a postsynaptic site of action. These results show that dopamine modulates subthalamopallidal excitation by presynaptic D2/3 and postsynaptic D4 receptors. The importance of this modulation is discussed.

scholarly journals Regulation of Inhibitory Synapses by Presynaptic D4 Dopamine Receptors in Thalamus

2010 ◽  
Vol 104 (5) ◽  
pp. 2757-2765 ◽  
Author(s):  
Gubbi Govindaiah ◽  
Tongfei Wang ◽  
Martha U. Gillette ◽  
Shane R. Crandall ◽  
Charles L. Cox
Keyword(s):  
Substantia Nigra ◽  
Globus Pallidus ◽  
Receptor Agonist ◽  
Receptor Activation ◽  
Substantia Nigra Pars Compacta ◽  
Inhibitory Synapses ◽  
Reticular Nucleus ◽  
Postsynaptic Currents ◽  
Presynaptic Site ◽  
Site Of Action

Dopamine (DA) receptors are the principal targets of drugs used in the treatment of schizophrenia. Among the five DA receptor subtypes, the D4 subtype is of particular interest because of the relatively high affinity of the atypical neuropleptic clozapine for D4 compared with D2 receptors. GABA-containing neurons in the thalamic reticular nucleus (TRN) and globus pallidus (GP) express D4 receptors. TRN neurons receive GABAergic afferents from globus pallidus (GP), substantia nigra pars reticulata (SNr), and basal forebrain as well as neighboring TRN neuron collaterals. In addition, TRN receives dopaminergic innervations from substantia nigra pars compacta (SNc); however, the role of D4 receptors in neuronal signaling at inhibitory synapses is unknown. Using whole cell recordings from in vitro pallido-thalamic slices, we demonstrate that DA selectively suppresses GABAA receptor-mediated inhibitory postsynaptic currents (IPSCs) evoked by GP stimulation. The D2-like receptor (D2,3,4) agonist, quinpirole, and selective D4 receptor agonist, PD168077, mimicked the actions of DA. The suppressive actions of DA and its agonists were associated with alterations in paired pulse ratio and a decrease in the frequency of miniature IPSCs, suggesting a presynaptic site of action. GABAA receptor agonist, muscimol, induced postsynaptic currents in TRN neurons were unaltered by DA or quinpirole, consistent with the presynaptic site of action. Finally, DA agonists did not alter intra-TRN inhibitory signaling. Our data demonstrate that the activation of presynaptic D4 receptors regulates GABA release from GP efferents but not TRN collaterals. This novel and selective action of D4 receptor activation on GP-mediated inhibition may provide insight to potential functional significance of atypical antipsychotic agents. These findings suggest a potential heightened TRN neuron activity in certain neurological conditions, such as schizophrenia and attention deficit hyperactive disorders.

Voltage-dependent stimulation of the Na+-K+ pump by insulin in rabbit cardiac myocytes

2000 ◽  
Vol 278 (3) ◽  
pp. C546-C553 ◽  
Author(s):  
Peter S. Hansen ◽  
Kerrie A. Buhagiar ◽  
David F. Gray ◽  
Helge H. Rasmussen
Keyword(s):  
Protein Phosphatase ◽  
Ventricular Myocytes ◽  
Pump Current ◽  
Phosphatidylinositol 3 Kinase ◽  
Patch Clamp Technique ◽  
Membrane Pump ◽  
Whole Cell Patch Clamp ◽  
Voltage Dependent ◽  
Phosphatase 2A

Insulin enhances Na+-K+ pump activity in various noncardiac tissues. We examined whether insulin exposure in vitro regulates Na+-K+ pump function in rabbit ventricular myocytes. Pump current ( I p) was measured using the whole-cell patch-clamp technique at test potentials ( V ms) from −100 to +60 mV. When the Na+ concentration in the patch pipette ([Na]pip) was 10 mM, insulin caused a V m-dependent increase in I p. The increase was ∼70% when V m was at near physiological diastolic potentials. This effect persisted after elimination of extracellular voltage-dependent steps and when K+ and K+-congeners were excluded from the patch pipettes. When [Na]pip was 80 mM, causing near-maximal pump stimulation, insulin had no effect, suggesting that it did not cause an increase in membrane pump density. Effects of tyrphostin A25, wortmannin, okadaic acid, or bisindolylmaleimide I in pipette solutions suggested that the insulin-induced increase in I p involved activation of tyrosine kinase, phosphatidylinositol 3-kinase, and protein phosphatase 1, whereas protein phosphatase 2A and protein kinase C were not involved.

Dietary cholesterol affects Na+-K+ pump function in rabbit cardiac myocytes

1997 ◽  
Vol 272 (4) ◽  
pp. H1680-H1689 ◽  
Author(s):  
D. F. Gray ◽  
P. S. Hansen ◽  
M. M. Doohan ◽  
L. C. Hool ◽  
H. H. Rasmussen
Keyword(s):  
Cardiac Myocytes ◽  
Serum Cholesterol ◽  
Dietary Cholesterol ◽  
Membrane Cholesterol ◽  
Patch Clamp Technique ◽  
Apparent Affinity ◽  
Pump Function ◽  
Whole Cell Patch Clamp

Alterations in membrane cholesterol induced in vitro can alter Na+-K+ pump function. Because dietary cholesterol can influence membrane cholesterol in vivo, we examined if dietary cholesterol is a determinant of Na+-K+ pump function. Rabbits were fed cholesterol-supplemented diets for 1-4 wk. Cardiac myocytes were then isolated, and Na+-K+ pump currents (Ip) were measured using the whole cell patch-clamp technique. When the Na+ concentration in the patch pipettes ([Na]pip) was 10 mM, a modest diet-induced increase in serum cholesterol was associated with stimulation of Ip; large increases in serum cholesterol were associated with inhibition. There was no effect of modest or large increases in serum cholesterol on Ip when [Na]pip was 80 mM. The [Na]pip-Ip relationship determined using seven different levels of [Na]pip from 0 to 80 mM indicated that a modest increase in serum cholesterol increased the apparent affinity of the pump for cytoplasmic Na+. In contrast, dietary cholesterol had no effect on the apparent affinity of the pump for extracellular K+. We conclude that cholesterol intake influences the sarcolemmal Na+-K+ pump. This may have clinical implications for cardiovascular function.

scholarly journals Deep brain stimulation: increasing efficiency by alternative waveforms

2016 ◽  
Vol 2 (1) ◽  
pp. 145-148 ◽  
Author(s):  
Katerina Argiti ◽  
Kevin Joseph ◽  
Soheil Mottaghi ◽  
Thomas J. Feuerstein ◽  
Ulrich G. Hofmann
Keyword(s):  
Deep Brain Stimulation ◽  
Brain Stimulation ◽  
Brain Slices ◽  
Pyramidal Cells ◽  
High Frequency Stimulation ◽  
Whole Cell Patch Clamp ◽  
Frequency Stimulation ◽  
Patch Clamp Electrophysiology ◽  
Deep Brain

AbstractDeep brain stimulation (DBS) is based on the effect of high frequency stimulation (HFS) in neuronal tissue. As a therapy option for patients suffering from e.g. Parkinson’s disease, DBS has been used for decades. Despite the widespread use, the effect of HFS on neurons is not fully investigated. Improving the stimulation efficiency und specificity could increase the efficiency of the INS (internal neuronal stimulator) as well as potentially reduce unwanted side effects. The effect of HFS on the GABAergic system was quantified using whole cell patch clamp electrophysiology during HFS stimulation in cortical human brain slices in vitro. Rectangular, sine, sawtooth and triangular waveforms were applied extracellularly. Since HFS has been hypothesized to increase the activity of the axons of GABAergic interneurons, a decrease in activity can be observed in the pyramidal cells that the interneurons project to. By isolating the incoming non- GABAergic events, we can filter out only the GABAA currents which can be verified using a GABAA antagonist. The results show that all the waveforms effectively increase the GABAA currents. The triangle waveform causes the highest significant increase in the activity which further increases over time after the stimulation was turned off.

scholarly journals A Ba2+-Sensitive K+ Current Contributes to the Resting Membrane Potential of Neurons in Rat Suprachiasmatic Nucleus

2002 ◽  
Vol 88 (2) ◽  
pp. 869-878 ◽  
Author(s):  
Marcel de Jeu ◽  
Alwin Geurtsen ◽  
Cyriel Pennartz
Keyword(s):  
Membrane Potential ◽  
Suprachiasmatic Nucleus ◽  
Voltage Dependence ◽  
Brain Slices ◽  
Resting Potential ◽  
Resting Membrane Potential ◽  
Delayed Rectifier ◽  
Patch Clamp Technique ◽  
M Current ◽  
Whole Cell Patch Clamp

A Ba2+-sensitive K+ current was studied in neurons of the suprachiasmatic nucleus (SCN) using the whole cell patch-clamp technique in acutely prepared brain slices. This Ba2+-sensitive K+ current was found in approximately 90% of the SCN neurons and was uniformly distributed across the SCN. Current-clamp studies revealed that Ba2+ (500 μM) reversibly depolarized the membrane potential by 6.7 ± 1.3 mV ( n = 22) and concomitantly Ba2+ induced an increase in the spontaneous firing rate of 0.8 ± 0.2 Hz ( n = 12). The Ba2+-evoked depolarizations did not depend on firing activity or spike dependent synaptic transmission. No significant day/night difference in the hyperpolarizing contribution to the resting membrane potential of the present Ba2+-sensitive current was observed. Voltage-clamp experiments showed that Ba2+ (500 μM) reduced a fast-activating, voltage-dependent K+ current. This current was activated at levels below firing threshold and exhibited outward rectification. The Ba2+-sensitive K+ current was strongly reduced by tetraethylammonium (TEA; 20 and 60 mM) but was insensitive to 4-aminopyridine (4-AP; 5 mM) and quinine (100 μM). A component of Ba2+-sensitive K+ current remaining in the presence of TEA exhibited no clear voltage dependence and is less likely to contribute to the resting membrane potential. The voltage dependence, kinetics and pharmacological properties of the Ba2+- and TEA-sensitive K+ current make it unlikely that this current is a delayed rectifier, Ca2+-activated K+ current, ATP-sensitive K+ current, M-current or K+ inward rectifier. Our data are consistent with the Ba2+- and TEA-sensitive K+ current in SCN neurons being an outward rectifying K+ current of a novel identity or belonging to a known family of K+ channels with related properties. Regardless of its precise molecular identity, the current appears to exert a significant hyperpolarizing effect on the resting potential of SCN neurons.

Reduction of Spontaneous Inhibitory Synaptic Activity in Experimental Heterotopic Gray Matter

2003 ◽  
Vol 89 (1) ◽  
pp. 150-158 ◽  
Author(s):  
Huan-Xin Chen ◽  
Steven N. Roper
Keyword(s):  
Gray Matter ◽  
Pyramidal Neurons ◽  
Strong Association ◽  
In Utero ◽  
Synaptic Activity ◽  
Patch Clamp Technique ◽  
Whole Cell Patch Clamp ◽  
And Function ◽  
Neuronal Heterotopia

Neuronal heterotopia has a strong association with epilepsy, but the mechanisms that underlie this relationship are largely unknown. We have utilized the in utero irradiated rat model to study circuit abnormalities in experimentally induced subcortical heterotopic gray matter. Spontaneous and miniature inhibitory (IPSCs) and excitatory (EPSCs) postsynaptic currents were recorded from visualized heterotopic pyramidal neurons in in vitro hemispheric slices and compared with control neocortical pyramidal neurons using the whole cell patch-clamp technique. The frequency of spontaneous and miniature IPSCs was significantly reduced in pyramidal neurons from heterotopic cortex. Amplitude and kinetics of IPSCs were not different between the two groups. Spontaneous and miniature EPSCs were not different between the two groups. Short-term synaptic plasticity of stimulus-evoked EPSCs showed depression in heterotopic neurons and facilitation in control pyramidal neurons. This study shows a selective impairment of the GABAergic circuitry in experimental heterotopic gray matter. We have reported similar findings in normotopic dysplastic cortex from this model. Taken together, these studies demonstrate a pervasive defect in inhibition throughout the cortex of irradiated rats with cortical dysplasia and neuronal heterotopia. This may have important implications regarding cortical development and function following in utero injuries.

Inhibitory Synaptic Transmission Differs in Mouse Type A and B Medial Vestibular Nucleus Neurons In Vitro

2006 ◽  
Vol 95 (5) ◽  
pp. 3208-3218 ◽  
Author(s):  
Aaron J. Camp ◽  
Robert J. Callister ◽  
Alan M. Brichta
Keyword(s):  
Synaptic Transmission ◽  
Vestibular Nucleus ◽  
Type A ◽  
Mean Amplitude ◽  
Medial Vestibular Nucleus ◽  
Type B ◽  
Inhibitory Synaptic Transmission ◽  
Relative Contribution ◽  
Whole Cell Patch Clamp

Fast inhibitory synaptic transmission in the medial vestibular nucleus (MVN) is mediated by GABAA receptors (GABAARs) and glycine receptors (GlyRs). To assess their relative contribution to inhibition in the MVN, we recorded miniature inhibitory postsynaptic currents (mIPSCs) in physiologically characterized type A and type B MVN neurons. Transverse brain stem slices were prepared from mice (3–8 wk old), and whole cell patch-clamp recordings were obtained from visualized MVN neurons (CsCl internal; Vm = –70 mV; 23°C). In 81 MVN neurons, 69% received exclusively GABAAergic inputs, 6% exclusively glycinergic inputs, and 25% received both types of mIPSCs. The mean amplitude of GABAAR-mediated mIPSCs was smaller than those mediated by GlyRs (22.6 ± 1.8 vs. 35.3 ± 5.3 pA). The rise time and decay time constants of GABAAR- versus GlyR-mediated mIPSCs were slower (1.3 ± 0.1 vs. 0.9 ± 0.1 ms and 10.5 ± 0.3 vs. 4.7 ± 0.3 ms, respectively). Comparison of type A ( n = 20) and type B ( n = 32) neurons showed that type A neurons received almost exclusively GABAAergic inhibitory inputs, whereas type B neurons received GABAAergic inputs, glycinergic inputs, or both. Intracellular labeling in a subset of MVN neurons showed that morphology was not related to a MVN neuron's inhibitory profile ( n = 15), or whether it was classified as type A or B ( n = 29). Together, these findings indicate that both GABA and glycine contribute to inhibitory synaptic processing in MVN neurons, although GABA dominates and there is a difference in the distribution of GABAA and Gly receptors between type A and type B MVN neurons.

Ketogenic Diet in a Hippocampal Slice

2016 ◽  
Author(s):  
Masahito Kawamura
Keyword(s):  
Ketogenic Diet ◽  
Hippocampal Slice ◽  
Ketone Bodies ◽  
Hippocampal Slices ◽  
Patch Clamp Technique ◽  
Ketogenic Diets ◽  
Whole Cell Patch Clamp ◽  
Electrophysiological Recordings

The hippocampus is thought to be a good experimental model for investigating epileptogenesis in and/or antiepileptic therapy for temporal lobe epilepsy. The hippocampus is also a useful target for researching the ketogenic diet. This chapter focuses on electrophysiological recordings using hippocampal slices and introduces their use for studying the anticonvulsant effects underlying ketogenic diets. The major difficulty in using hippocampal slices is the inability to precisely reproduce the in vivo condition of ketogenic diet feeding in this in vitro preparation. Three different approaches are reported to reproduce diet effects in the hippocampal slices: (1) direct application of ketone bodies, (2) mimicking the ketogenic diet condition with whole-cell patch-clamp technique, and (3) hippocampal slices from ketogenic diet–fed animals. Significant results have been found with each of these methods. These three approaches are useful tools to elucidate the underlying anticonvulsant mechanisms of the ketogenic diet.

Activation of GABAA Receptors in Subthalamic Neurons In Vitro: Properties of Native Receptors and Inhibition Mechanisms

2001 ◽  
Vol 86 (1) ◽  
pp. 75-85 ◽  
Author(s):  
Jérôme Baufreton ◽  
Maurice Garret ◽  
Sandra Dovero ◽  
Bernard Dufy ◽  
Bernard Bioulac ◽  
...  
Keyword(s):  
Motor Behavior ◽  
Brain Slices ◽  
Structural Features ◽  
Burst Firing ◽  
Patch Clamp Technique ◽  
Whole Cell ◽  
Recombinant Receptors ◽  
Firing Mode ◽  
Subthalamic Neurons

The subthalamic nucleus (STN) influences the output of the basal ganglia, thereby interfering with motor behavior. The main inputs to the STN are GABAergic. We characterized the GABAA receptors expressed in the STN and investigated the response of subthalamic neurons to the activation of GABAA receptors. Cell-attached and whole cell recordings were made from rat brain slices using the patch-clamp technique. The newly identified ε subunit confers atypical pharmacological properties on recombinant receptors, which are insensitive to barbiturates and benzodiazepines. We tested the hypothesis that native subthalamic GABAAreceptors contain ε proteins. Applications of increasing concentrations of muscimol, a selective GABAAagonist, induced Cl− and HCO[Formula: see text]currents with an EC50 of 5 μM. Currents induced by muscimol were fully blocked by the GABAAreceptor antagonists, bicuculline and picrotoxin. They were strongly potentiated by the barbiturate, pentobarbital (+190%), and by the benzodiazepines, diazepam (+197%) and flunitrazepam (+199%). Spontaneous inhibitory postsynaptic currents were also significantly enhanced by flunitrazepam. Furthermore, immunohistological experiments with an ε subunit-specific antibody showed that the ε protein was not expressed within the STN. Native subthalamic GABAA receptors did not, therefore, display pharmacological or structural properties consistent with receptors comprising ε. Burst firing is a hallmark of Parkinson's disease. Half of the subthalamic neurons have the intrinsic capacity of switching from regular-firing to burst-firing mode when hyperpolarized by current injection. This raises the possibility that activation of GABAA receptors might trigger the switch. Statistical analysis of spiking activity established that 90% of intact neurons in vitro were in single-spike firing mode, whereas 10% were in burst-firing mode. Muscimol reversibly stopped recurrent electrical activity in all intact neurons. In neurons held in whole cell configuration, membrane potential hyperpolarized by −10 mV whilst input resistance decreased by 50%, indicating powerful membrane shunting. Muscimol never induced burst firing, even in neurons that exhibited the capacity of switching from regular- to burst-firing mode. These molecular and functional data indicate that native subthalamic GABAA receptors do not contain the ε protein and activation of GABAA receptors induces membrane shunting, which is essential for firing inhibition but prevents switching to burst-firing. They suggest that the STN, like many other parts of the brain, has the physiological and structural features of the widely expressed GABAA receptors consisting of αβγ subunits.

scholarly journals Diterpene Lipo-Alkaloids with Selective Activities on Cardiac K+ Channels

Planta Medica ◽  
2017 ◽  
Vol 83 (17) ◽  
pp. 1321-1328 ◽  
Author(s):  
Tivadar Kiss ◽  
Botond Borcsa ◽  
Péter Orvos ◽  
László Tálosi ◽  
Judit Hohmann ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Ion Channels ◽  
Patch Clamp Technique ◽  
Diterpene Alkaloids ◽  
Girk Channels ◽  
Vast Number ◽  
K Channels ◽  
Whole Cell Patch Clamp ◽  
Girk Channel

Abstract Aconitum diterpene alkaloids are known for their remarkable toxicity, which is due to their effect on ion channels. Activation of voltage-gated Na+ channels is the major cause of their cardiotoxicity, however, influence on K+ channels may also play a role in the overall effect.Here we report the synthesis of a series of lipo-alkaloids, including four new compounds, based on the 14-benzoylaconine structure, which is the core of a vast number of diterpene alkaloids naturally occurring in Aconitum species. The activities of these compounds were measured in vitro on K+ ion channels using the whole-cell patch-clamp technique. Structure-activity analysis was carried out based on the data of 51 compounds (32 genuine diterpene alkaloids, 5 fatty acids, and 14 lipo-alkaloids). Depending on their substitution, these compounds exert different activities on GIRK (G protein-coupled inwardly-rectifying potassium channel) and hERG (human ether-à-go-go-related gene) channels. Fatty acids and diterpene alkaloids show lower activity on the GIRK channel than lipo-alkaloids. Lipo-alkaloids also have less pronounced hERG inhibitory activity compared to the cardiotoxic aconitine. Considering the GIRK/hERG selectivity as an indicator of perspective therapeutic applicability, lipo-alkaloids are significantly more selective than the genuine diterpene alkaloids. 14-Benzoyl-8-O-eicosa-8Z,11Z,14Z-trienoate and 14-benzoyl-8-O-eicosa-11Z,14Z,17Z-trienoate are strong and selective inhibitors of GIRK channels, thus, they are promising subjects for further studies to develop diterpene alkaloid-based antiarrhythmic pharmacons.

Sign in / Sign up

Export Citation Format

Share Document