Modulatory effects of 5-hydroxytryptamine on voltage-activated currents in cultured antennal lobe neurones of the sphinx moth Manduca sexta.

1995 ◽  
Vol 198 (3) ◽  
pp. 613-627 ◽  
Author(s):  
A R Mercer ◽  
J H Hayashi ◽  
J G Hildebrand
Keyword(s):  
Manduca Sexta ◽  
Adult Development ◽  
Antennal Lobe ◽  
Ionic Currents ◽  
Delayed Rectifier ◽  
Patch Clamp Recording ◽  
Whole Cell Patch Clamp ◽  
K Current ◽  
Reversible Reduction

The modulatory effects of 5-hydroxytryptamine (5-HT or serotonin) on voltage-gated currents in central olfactory neurones of the moth Manduca sexta have been examined in vitro using whole-cell patch-clamp recording techniques. Central olfactory neurones were dissociated from the antennal lobes of animals at stage 5 of the 18 stages of metamorphic adult development. The modulatory actions of 5-HT on voltage-activated ionic currents were examined in a subset of morphologically identifiable antennal lobe neurones maintained for 2 weeks in primary cell culture. 5-HT caused reversible reduction of both a rapidly activating A-type K+ current and a relatively slowly activating K+ current resembling a delayed rectifier-type conductance. 5-HT also reduced the magnitude of voltage-activated Ca2+ influx in these cells. The functional significance of 5-HT-modulation of central neurones is discussed.

Dopamine Modulation of Honey Bee (Apis mellifera) Antennal-Lobe Neurons

2006 ◽  
Vol 95 (2) ◽  
pp. 1147-1157 ◽  
Author(s):  
Christopher G. Perk ◽  
Alison R. Mercer
Keyword(s):  
Honey Bee ◽  
Adult Development ◽  
Outward Current ◽  
Pupal Stage ◽  
Ionic Currents ◽  
Delayed Rectifier ◽  
Outward Currents ◽  
Sustained Outward Current ◽  
Dopamine Modulation

Primary olfactory centers [antennal lobes (ALs)] of the honey bee brain are invaded by dopamine (DA)-immunoreactive neurons early in development (pupal stage 3), immediately before a period of rapid growth and compartmentalization of the AL neuropil. Here we examine the modulatory actions of DA on honey bee AL neurons during this period. Voltage-clamp recordings in whole cell configuration were used to determine the effects of DA on ionic currents in AL neurons in vitro from pupal bees at stages 4–6 of the nine stages of metamorphic adult development. In ∼45% of the neurons tested, DA (5–50 × 10−5 M) reduced the amplitude of outward currents in the cells. In addition to a slowly activating, sustained outward current, DA reduced the amplitude of a rapidly activating, transient outward conductance in some cells. Both of the currents modulated by DA could be abolished by the removal of Ca2+ from the external medium or by treatment of cells with charybdotoxin (2 × 10−8 M), a blocker of Ca2+-dependent K+ currents in the cells. Ca2+ currents were not affected by DA, nor were A-type K+ currents ( IA). Results suggest that the delayed rectifier-like current ( IKV) also remains intact in the presence of DA. Taken together, our data indicate that Ca2+-dependent K+ currents are targets of DA modulation in honey bee AL neurons. This study lends support to the hypothesis that DA plays a role in the developing brain of the bee.

Voltage-dependent ionic currents in the ventromedial eclosion hormone neurons of Manduca sexta

1999 ◽  
Vol 202 (17) ◽  
pp. 2371-2383
Author(s):  
R.S. Hewes
Keyword(s):  
Manduca Sexta ◽  
Behavior Pattern ◽  
Ionic Currents ◽  
Peptide Hormone ◽  
Stereotyped Behavior ◽  
Membrane Properties ◽  
Eclosion Hormone ◽  
Whole Cell Patch Clamp ◽  
Voltage Dependent ◽  
K Current

The ventromedial cells (VM cells) of the moth Manduca sexta belong to a peptide hormone signaling hierarchy that directs an episodic and stereotyped behavior pattern, ecdysis. The VM cells respond to declining ecdysteroid titers at the end of the final larval molt with a transcription-dependent decrease in spike threshold and the abrupt release of the previously stockpiled neuropeptide, eclosion hormone (EH). This report describes whole-cell patch-clamp recordings of acutely isolated VM cell somata made to identify membrane currents that may underlie the increase in VM cell excitability during EH release and that may contribute to abrupt peptide release. There were at least three voltage- and time-dependent conductances in the VM cells. The inward current was carried exclusively by a voltage-dependent inward Ca(2+) current (I(Ca)), and the outward currents were a combination of a Ca(2+)-dependent outward K(+) current (I(K(Ca))) and a transient, voltage-dependent outward K(+) current, the A current (I(A)). In current-clamp recordings, the currents present in the acutely isolated somata were sufficient to generate membrane properties similar to those observed in the VM cells in situ. This study represents the first step toward characterization of the mechanisms underlying the abrupt release of EH stores from the VM cells preceding ecdysis.

scholarly journals Probucol-induced hERG Channel Reduction can be Rescued by Matrine and Oxymatrinein vitro

2020 ◽  
Vol 25 (43) ◽  
pp. 4606-4612 ◽  
Author(s):  
Yuan-Qi Shi ◽  
Pan Fan ◽  
Guo-Cui Zhang ◽  
Yu-Hao Zhang ◽  
Ming-Zhu Li ◽  
...  
Keyword(s):  
Action Potential ◽  
Action Potential Duration ◽  
Surface Expression ◽  
Herg Channel ◽  
Delayed Rectifier ◽  
Patch Clamp Recording ◽  
Herg Current ◽  
Factor Specificity ◽  
Lowering Drug

Background: The human ether-a-go-go-related gene (hERG) potassium channel is the rapidly activating component of cardiac delayed rectifier potassium current (IKr), which is a crucial determinant of cardiac repolarization. The reduction of hERG current is commonly believed to cause Long QT Syndrome (LQTs). Probucol, a cholesterol-lowering drug, induces LQTs by inhibiting the expression of the hERG channel. Unfortunately, there is currently no effective therapeutic method to rescue probucol-induced LQTs. Methods: Patch-clamp recording techniques were used to detect the action potential duration (APD) and current of hERG. Western blot was performed to measure the expression levels of proteins. Results: In this study, we demonstrated that 1 μM matrine and oxymatrine could rescue the hERG current and hERG surface expression inhibited by probucol. In addition, matrine and oxymatrine significantly shortened the prolonged action potential duration induced by probucol in neonatal cardiac myocytes. We proposed a novel mechanism underlying the probucol induced decrease in the expression of transcription factor Specificity protein 1 (Sp1), which is an established transactivator of the hERG gene. We also demonstrated that matrine and oxymatrine were able to upregulate Sp1 expression which may be one of the possible mechanisms by which matrine and oxymatrine rescued probucol-induced hERG channel deficiency. Conclusion: Our current results demonstrate that matrine and oxymatrine could rescue probucol-induced hERG deficiency in vitro, which may lead to potentially effective therapeutic drugs for treating acquired LQT2 by probucol in the future.

Voltage-gated currents of rabbit A- and B-type horizontal cells in retinal monolayer cultures

1994 ◽  
Vol 11 (2) ◽  
pp. 369-378 ◽  
Author(s):  
Stefan Löhrke ◽  
Hans-Dieter Hofmann
Keyword(s):  
Single Channel ◽  
Ionic Currents ◽  
Calcium Currents ◽  
Horizontal Cells ◽  
Delayed Rectifier ◽  
Patch Clamp Recording ◽  
Voltage Gated ◽  
Monolayer Cultures ◽  
Inward Currents

AbstractIn monolayer cultures prepared from immature early postnatal rabbit retina, small populations of neurons can be demonstrated to differentiate into apparently mature A- and B-type horizontal cells. Using wholecell, single-channel, patch-clamp recording techniques, we have analyzed the pattern of voltage-gated conductances expressed by mammalian horizontal cells under these conditions. A total of six different voltage-dependent ionic currents were recorded. Tetrodotoxin-sensitive fast sodium inward currents (INa) were found in 81% of the A-type and 90% of the B-type cells. Inward calcium currents could be demonstrated in all cells tested after blockade of other conductances. Two types of outward potassium currents with properties of the 4–aminopyridine-sensitive transient IA and the tetraethylammonium sensitive delayed rectifier IK, respectively, could be characterized in whole-cell recordings. An inward rectifying potassium current (Ianom) typical for horizontal cells was activated in response to hyperpolarizing voltage steps. These types of currents have also been described in dissociated adult horizontal cells from lower vertebrates and cat. With single-channel recordings on inside-out patches excised from B-type cells, an additional Ca2+-dependent current (IK(Ca)) was observed which, so far, has not been described in horizontal cells developing in situ. Our results demonstrate that cultured rabbit horizontal cells express a set of voltage-gated currents which largely, but not completely, corresponds to that described in situ for horizontal cells of other species. The culture system will allow further investigation of developmental and functional aspects of mammalian horizontal cells.

Plateau Potentials in Developing Antennal-Lobe Neurons of the Moth, Manduca sexta

2005 ◽  
Vol 93 (4) ◽  
pp. 1949-1958 ◽  
Author(s):  
A. R. Mercer ◽  
P. Kloppenburg ◽  
J. G. Hildebrand
Keyword(s):  
Electrical Activity ◽  
Manduca Sexta ◽  
Antennal Lobe ◽  
Membrane Properties ◽  
Plateau Potentials ◽  
Extracellular Medium ◽  
Threshold Phenomena ◽  
Plateau State ◽  
Developing Neurons

Using whole cell recordings from antennal-lobe (AL) neurons in vitro and in situ, in semi-intact brain preparations, we examined membrane properties that contribute to electrical activity exhibited by developing neurons in primary olfactory centers of the brain of the sphinx moth, Manduca sexta. This activity is characterized by prolonged periods of membrane depolarization that resemble plateau potentials. The presence of plateau potential–generating mechanisms was confirmed using a series of tests established earlier. Brief depolarizing current pulses could be used to trigger a plateau state. Once triggered, plateau potentials could be terminated by brief pulses of hyperpolarizing current. Both triggering and terminating of firing states were threshold phenomena, and both conditions resulted in all-or-none responses. Rebound excitation from prolonged hyperpolarizing pulses could also be used to generate plateau potentials in some cells. These neurons were found to express a hyperpolarization-activated inward current. Neither the generation nor the maintenance of plateau potentials was affected by removal of Na+ ions from the extracellular medium or by blockade of Na+ currents with TTX. However, blocking of Ca2+ currents with Cd2+ (5 × 10−4 M) inhibited the generation of plateau potentials, indicating that, in Manduca AL neurons, plateau potentials depend on Ca2+. Examining Ca2+ currents in isolation revealed that activation of these currents occurs in the absence of experimentally applied depolarizing stimuli. Our results suggest that this activity underlies the generation of plateau potentials and characteristic bursts of electrical activity in developing AL neurons of M. sexta.

scholarly journals Morphine-induced synaptic plasticity in the VTA is reversed by HDAC inhibition

2016 ◽  
Vol 116 (3) ◽  
pp. 1093-1103 ◽  
Author(s):  
Michael E. Authement ◽  
Ludovic D. Langlois ◽  
Haifa Kassis ◽  
Shawn Gouty ◽  
Matthieu Dacher ◽  
...  
Keyword(s):  
Behavioral Plasticity ◽  
Drugs Of Abuse ◽  
Patch Clamp Recording ◽  
Whole Cell Patch Clamp ◽  
Synaptic Changes ◽  
Induced Changes ◽  
And Behavior ◽  
H3 Acetylation

Dopamine (DA) dysfunction originating from the ventral tegmental area (VTA) occurs as a result of synaptic abnormalities following consumption of drugs of abuse and underlies behavioral plasticity associated with drug abuse. Drugs of abuse can cause changes in gene expression through epigenetic mechanisms in the brain that underlie some of the lasting neuroplasticity and behavior associated with addiction. Here we investigated the function of histone acetylation and histone deacetylase (HDAC)2 in the VTA in recovery of morphine-induced synaptic modifications following a single in vivo exposure to morphine. Using a combination of immunohistochemistry, Western blot, and whole cell patch-clamp recording in rat midbrain slices, we show that morphine increased HDAC2 activity in VTA DA neurons and reduced histone H3 acetylation at lysine 9 (Ac-H3K9) in the VTA 24 h after the injection. Morphine-induced synaptic changes at glutamatergic synapses involved endocannabinoid signaling to reduce GABAergic synaptic strength onto VTA DA neurons. Both plasticities were recovered by in vitro incubation of midbrain slices with a class I-specific HDAC inhibitor (HDACi), CI-994, through an increase in acetylation of histone H3K9. Interestingly, HDACi incubation also increased levels of Ac-H3K9 and triggered GABAergic and glutamatergic plasticities in DA neurons of saline-treated rats. Our results suggest that acute morphine-induced changes in VTA DA activity and synaptic transmission engage HDAC2 activity locally in the VTA to maintain synaptic modifications through histone hypoacetylation.

scholarly journals Functional and Pharmacological Evaluation of a Novel SCN2A Variant Linked to Early-onset Epilepsy

2020 ◽  
Author(s):  
Scott K. Adney ◽  
John J. Millichap ◽  
Jean-Marc DeKeyser ◽  
Tatiana Abramova ◽  
Christopher H. Thompson ◽  
...  
Keyword(s):  
Drug Response ◽  
Time Course ◽  
Voltage Dependence ◽  
De Novo ◽  
Patch Clamp Recording ◽  
Variants Of Unknown Significance ◽  
Whole Cell Patch Clamp ◽  
Genetic Features ◽  
Resurgent Current

ABSTRACTObjectiveWe identified a novel de novo SCN2A variant (M1879T) associated with infantile-onset epilepsy that responded dramatically to sodium channel blocker antiepileptic drugs. We analyzed the functional and pharmacological consequences of this variant to establish pathogenicity, and to correlate genotype with phenotype and clinical drug response.MethodsThe clinical and genetic features of an infant boy with epilepsy are presented. We investigated the effect of the variant using heterologously expressed recombinant human NaV1.2 channels. We performed whole-cell patch clamp recording to determine the functional consequences and response to carbamazepine.ResultsThe M1879T variant caused disturbances in channel inactivation including substantially depolarized voltage-dependence of inactivation, slower time course of inactivation, and enhanced resurgent current that collectively represent a gain-of-function. Carbamazepine partially normalized the voltage-dependence of inactivation and produced use-dependent block of the variant channel at high pulsing frequencies. Carbamazepine also suppresses resurgent current conducted by M1879T channels, but this effect was explained primarily by reducing the peak transient current. Molecular modeling suggests that the M1879T variant disrupts contacts with nearby residues in the C-terminal domain of the channel.InterpretationOur study demonstrates the value of conducting functional analyses of SCN2A variants of unknown significance to establish pathogenicity and genotype-phenotype correlations. We also show concordance of in vitro pharmacology using heterologous cells with the drug response observed clinically in a case of SCN2A-associated epilepsy.

In Vitro Properties of Neurons in the Rat Pretectal Nucleus of the Optic Tract

2007 ◽  
Vol 97 (5) ◽  
pp. 3574-3584 ◽  
Author(s):  
N. Prochnow ◽  
P. Lee ◽  
W. C. Hall ◽  
M. Schmidt
Keyword(s):  
Fluorescent Dyes ◽  
Optic Tract ◽  
Cell Populations ◽  
Patch Clamp Recording ◽  
Visual Activity ◽  
Optokinetic Reflex ◽  
Whole Cell Patch Clamp ◽  
Pretectal Nucleus ◽  
Efferent Projections

The nucleus of the optic tract (NOT) has been implicated in the initiation of the optokinetic reflex (OKR) and in the modulation of visual activity during saccades. The present experiments demonstrate that these two functions are served by separate cell populations that can be distinguished by differences in both their cellular physiology and their efferent projections. We compared the response properties of NOT cells in rats using target-directed whole cell patch-clamp recording in vitro. To identify the cells at the time of the recording experiments, they were prelabeled by retrograde axonal transport of WGA-apo-HRP-gold (15 nm), which was injected into their primary projection targets, either the ipsilateral superior colliculus (iSC), or the contralateral NOT (cNOT), or the ipsilateral inferior olive (iIO). Retrograde labeling after injections in single animals of either WGA-apo-HRP-gold with different particle sizes (10 and 20 nm) or two different fluorescent dyes distinguished two NOT cell populations. One projects to both the iSC and cNOT. These cells are spontaneously active in vitro and respond to intracellular depolarizations with temporally regular tonic firing. The other population projects to the iIO and consists of cells that show no spontaneous activity, respond phasically to intracellular depolarization, and show irregular firing patterns. We propose that the spontaneously active pathway to iSC and cNOT is involved in modulating the level of visual activity during saccades and that the phasically active pathway to iIO provides a short-latency relay from the retina to premotor mechanisms involved in reducing retinal slip.

Developmental Changes in the Electrophysiological Properties and Response Characteristics of Manduca Antennal-Lobe Neurons

2002 ◽  
Vol 87 (6) ◽  
pp. 2650-2663 ◽  
Author(s):  
Alison R. Mercer ◽  
John G. Hildebrand
Keyword(s):  
Adult Development ◽  
Action Potentials ◽  
Antennal Lobe ◽  
Electrical Excitability ◽  
Whole Cell ◽  
Electrophysiological Properties ◽  
Response Characteristics ◽  
Cell Current ◽  
Whole Cell Current

Using whole cell patch-clamp recordings, we have examined changes in the electrophysiological properties and response characteristics of antennal lobe (AL) neurons associated with the metamorphic adult development of the sphinx moth, Manduca sexta. Whole cell current profiles and electrical excitability were examined in dispersed AL neurons in vitro, and in medial-group AL neurons in situ in semi-intact brain preparations. Around stages 2–4 of the 18 stages of metamorphic adult development, whole cell current profiles were dominated by large outward (K+) currents. Calcium-dependent action potentials could be elicited at this stage, but only a small percentage of cells exhibited sodium spikes. From stages 3 to 10, there was a rapid increase in the proportion of AL neurons exhibiting rapidly activating, transient sodium currents, and many cells in vitro exhibited spontaneous bursts of spike activity at this time. As development progressed, action-potential waveforms became shorter in duration and larger in amplitude. Cell-type–specific differences in the prevalence of spontaneous activity, and in the electrophysiological properties and response characteristics of AL neurons, were most apparent late in metamorphosis. While removal of antennal sensory input to the ALs early (stage 1–2) in metamorphosis had no detectable effect on the development of cell excitability, a significantly higher percentage of neurons in vitro from stage 4 pupae exhibited sodium-based action potentials following the addition of serotonin to the culture medium. Characteristic forms of electrical excitability in developing Manduca AL neurons, and their modulation by serotonin, seem likely to play a central role in the functional development of the ALs.

scholarly journals High Efficacy by GAL-021: A Known Intravenous Peripheral Chemoreceptor Modulator that Suppresses BKCa-Channel Activity and Inhibits IK(M) or Ih

Biomolecules ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 188
Author(s):  
Te-Ling Lu ◽  
Zi-Han Gao ◽  
Shih-Wei Li ◽  
Sheng-Nan Wu
Keyword(s):  
Ionic Currents ◽  
Gh3 Cells ◽  
Delayed Rectifier ◽  
Bkca Channel ◽  
Dependent Manner ◽  
Channel Activity ◽  
Bkca Channels ◽  
Cationic Current ◽  
K Current ◽  
Change In Mean

GAL-021 has recently been developed as a novel breathing control modulator. However, modifications of ionic currents produced by this agent remain uncertain, although its efficacy in suppressing the activity of big-conductance Ca2+-activated K+ (BKCa) channels has been reported. In pituitary tumor (GH3) cells, we found that the presence of GAL-021 decreased the amplitude of macroscopic Ca2+-activated K+ current (IK(Ca)) in a concentration-dependent manner with an effective IC50 of 2.33 μM. GAL-021-mediated reduction of IK(Ca) was reversed by subsequent application of verteporfin or ionomycin; however, it was not by that of diazoxide. In inside-out current recordings, the addition of GAL-021 to the bath markedly decreased the open-state probability of BKCa channels. This agent also resulted in a rightward shift in voltage dependence of the activation curve of BKCa channels; however, neither the gating charge of the curve nor single-channel conductance of the channel was changed. There was an evident lengthening of the mean closed time of BKCa channels in the presence of GAL-021, with no change in mean open time. The GAL-021 addition also suppressed M-type K+ current with an effective IC50 of 3.75 μM; however, its presence did not alter the amplitude of erg-mediated K+ current, or mildly suppressed delayed-rectifier K+ current. GAL-021 at a concentration of 30 μM could also suppress hyperpolarization-activated cationic current. In HEK293T cells expressing α-hSlo, the addition of GAL-021 was also able to suppress the BKCa-channel open probabilities, and GAL-021-mediated suppression of BKCa-channel activity was attenuated by further addition of BMS-191011. Collectively, the GAL-021 effects presented herein do not exclusively act on BKCa channels and these modifications on ionic currents exert significant influence on the functional activities of electrically excitable cells occurring in vivo.

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