scholarly journals SK Current, Expressed During the Development and Regeneration of Chick Hair Cells, Contributes to the Patterning of Spontaneous Action Potentials

2022 ◽  
Vol 15 ◽  
Author(s):  
Snezana Levic
Keyword(s):  
Electrical Activity ◽  
Hair Cells ◽  
Action Potentials ◽  
Functional Expression ◽  
Basilar Papilla ◽  
Spontaneous Electrical Activity ◽  
Intracellular Ca ◽  
Spontaneous Action ◽  
Spontaneous Action Potentials

Chick hair cells display calcium (Ca2+)-sensitive spontaneous action potentials during development and regeneration. The role of this activity is unclear but thought to be involved in establishing proper synaptic connections and tonotopic maps, both of which are instrumental to normal hearing. Using an electrophysiological approach, this work investigated the functional expression of Ca2+-sensitive potassium [IK(Ca)] currents and their role in spontaneous electrical activity in the developing and regenerating hair cells (HCs) in the chick basilar papilla. The main IK(Ca) in developing and regenerating chick HCs is an SK current, based on its sensitivity to apamin. Analysis of the functional expression of SK current showed that most dramatic changes occurred between E8 and E16. Specifically, there is a developmental downregulation of the SK current after E16. The SK current gating was very sensitive to the availability of intracellular Ca2+ but showed very little sensitivity to T-type voltage-gated Ca2+ channels, which are one of the hallmarks of developing and regenerating hair cells. Additionally, apamin reduced the frequency of spontaneous electrical activity in HCs, suggesting that SK current participates in patterning the spontaneous electrical activity of HCs.

scholarly journals Expression and functions of N-type Cav2.2 and T-type Cav3.1 channels in rat vasopressin neurons under normotonic conditions

2020 ◽  
Vol 70 (1) ◽  
Author(s):  
Kaori Sato-Numata ◽  
Tomohiro Numata ◽  
Yoichi Ueta ◽  
Yasunobu Okada
Keyword(s):  
Action Potentials ◽  
Functional Expression ◽  
Flufenamic Acid ◽  
Action Potential Generation ◽  
Potential Generation ◽  
Firing Activity ◽  
Plasma Osmolarity ◽  
Spontaneous Action ◽  
Vasopressin Neurons ◽  
Spontaneous Action Potentials

Abstract Arginine vasopressin (AVP) neurons play essential roles in sensing the change in systemic osmolarity and regulating AVP release from their neuronal terminals to maintain the plasma osmolarity. AVP exocytosis depends on the Ca2+ entry via voltage-gated Ca2+ channels (VGCCs) in AVP neurons. In this study, suppression by siRNA-mediated knockdown and pharmacological sensitivity of VGCC currents evidenced molecular and functional expression of N-type Cav2.2 and T-type Cav3.1 in AVP neurons under normotonic conditions. Also, both the Cav2.2 and Cav3.1 currents were found to be sensitive to flufenamic acid (FFA). TTX-insensitive spontaneous action potentials were suppressed by FFA and T-type VGCC blocker Ni2+. However, Cav2.2-selective ω-conotoxin GVIA failed to suppress the firing activity. Taken together, it is concluded that Cav2.2 and Cav3.1 are molecularly and functionally expressed and both are sensitive to FFA in unstimulated rat AVP neurons. Also, it is suggested that Cav3.1 is primarily involved in their action potential generation.

scholarly journals Cholinergic efferent synaptic transmission regulates the maturation of auditory hair cell ribbon synapses

Open Biology ◽  
2013 ◽  
Vol 3 (11) ◽  
pp. 130163 ◽  
Author(s):  
Stuart L. Johnson ◽  
Carolina Wedemeyer ◽  
Douglas E. Vetter ◽  
Roberto Adachi ◽  
Matthew C. Holley ◽  
...  
Keyword(s):  
Electrical Activity ◽  
Action Potentials ◽  
Cell Development ◽  
Sensory Cells ◽  
Inhibitory Input ◽  
Efferent System ◽  
Ribbon Synapses ◽  
Functional Maturation ◽  
Spontaneous Action ◽  
Spontaneous Action Potentials

Spontaneous electrical activity generated by developing sensory cells and neurons is crucial for the maturation of neural circuits. The full maturation of mammalian auditory inner hair cells (IHCs) depends on patterns of spontaneous action potentials during a ‘critical period’ of development. The intrinsic spiking activity of IHCs can be modulated by inhibitory input from cholinergic efferent fibres descending from the brainstem, which transiently innervate immature IHCs. However, it remains unknown whether this transient efferent input to developing IHCs is required for their functional maturation. We used a mouse model that lacks the α9-nicotinic acetylcholine receptor subunit (α9nAChR) in IHCs and another lacking synaptotagmin-2 in the efferent terminals to remove or reduce efferent input to IHCs, respectively. We found that the efferent system is required for the developmental linearization of the Ca 2+ -sensitivity of vesicle fusion at IHC ribbon synapses, without affecting their general cell development. This provides the first direct evidence that the efferent system, by modulating IHC electrical activity, is required for the maturation of the IHC synaptic machinery. The central control of sensory cell development is unique among sensory systems.

Role of K+ Channels in Frequency Regulation of Spontaneous Action Potentials in Rat Pituitary GH3 Cells

2003 ◽  
Vol 78 (5) ◽  
pp. 260-269 ◽  
Author(s):  
Suk-Ho Lee ◽  
Eun Hae Lee ◽  
Shin Young Ryu ◽  
Hyewhon Rhim ◽  
Hye-Jung Baek ◽  
...  
Keyword(s):  
Action Potentials ◽  
Frequency Regulation ◽  
Rat Pituitary ◽  
Spontaneous Action ◽  
Spontaneous Action Potentials

Spontaneous electrical rhythmicity and the role of the sarcoplasmic reticulum in the excitability of guinea pig gallbladder smooth muscle cells

2006 ◽  
Vol 290 (4) ◽  
pp. G655-G664 ◽  
Author(s):  
Onesmo B. Balemba ◽  
Matthew J. Salter ◽  
Thomas J. Heppner ◽  
Adrian D. Bonev ◽  
Mark T. Nelson ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Sarcoplasmic Reticulum ◽  
Action Potentials ◽  
Cyclopiazonic Acid ◽  
Cellular Mechanisms ◽  
Voltage Dependent ◽  
Spontaneous Action ◽  
Potential Activity ◽  
Spontaneous Action Potentials

Spontaneous action potentials and Ca2+ transients were investigated in intact gallbladder preparations to determine how electrical events propagate and the cellular mechanisms that modulate these events. Rhythmic phasic contractions were preceded by Ca2+ flashes that were either focal (limited to one or a few bundles), multifocal (occurring asynchronously in several bundles), or global (simultaneous flashes throughout the field). Ca2+ flashes and action potentials were abolished by inhibiting sarcoplasmic reticulum (SR) Ca2+ release via inositol (1,4,5)-trisphosphate [Ins(1,4,5)P3] channels with 2-aminoethoxydiphenyl borate and xestospongin C or by inhibiting voltage-dependent Ca2+ channels (VDCCs) with nifedipine or diltiazem or nisoldipine. Inhibiting ryanodine channels with ryanodine caused multiple spikes superimposed upon plateaus of action potentials and extended quiescent periods. Depletion of SR Ca2+ stores with thapsigargin or cyclopiazonic acid increased the frequency and duration of Ca2+ flashes and action potentials. Acetylcholine, carbachol, or cholecystokinin increased synchronized and increased the frequency of Ca2+ flashes and action potentials. The phospholipase C (PLC) inhibitor U-73122 did not affect Ca2+ flash or action potential activity but inhibited the excitatory effects of acetylcholine on these events. These results indicate that Ca2+ flashes correspond to action potentials and that rhythmic excitation in the gallbladder is multifocal among gallbladder smooth muscle bundles and can be synchronized by excitatory agonists. These events do not depend on PLC activation, but agonist stimulation involves activation of PLC. Generation of these events depends on Ca2+ entry via VDCCs and on Ca2+ mobilization from the SR via Ins(1,4,5)P3 channels.

Regional differences in the role of the Ca2+ and Na+ currents in pacemaker activity in the sinoatrial node

1997 ◽  
Vol 272 (6) ◽  
pp. H2793-H2806 ◽  
Author(s):  
I. Kodama ◽  
M. R. Nikmaram ◽  
M. R. Boyett ◽  
R. Suzuki ◽  
H. Honjo ◽  
...  
Keyword(s):  
Action Potentials ◽  
Regional Differences ◽  
Sinoatrial Node ◽  
Pacemaker Activity ◽  
Na Current ◽  
Na Currents ◽  
Spontaneous Action ◽  
Spontaneous Action Potentials ◽  
Rabbit Sinoatrial Node

The effect of block of the L-type Ca2+ current by 2 microM nifedipine and of the Na+ current by 20 microM tetrodotoxin on the center (normally the leading pacemaker site) and periphery (latent pacemaker tissue) of the rabbit sinoatrial node was investigated. Spontaneous action potentials were recorded with microelectrodes from either an isolated right atrium containing the whole node or small balls of tissue (approximately 0.3-0.4 mm in diameter) from different regions of the node. Nifedipine abolished the action potential in the center, but not usually in the periphery, in both the intact sinoatrial node and the small balls. Tetrodotoxin had no effect, on electrical activity in small balls from the center, but it decreased the takeoff potential and upstroke velocity and slowed the spontaneous activity (by 49 +/- 10%; n = 11) in small balls from the periphery. It is concluded that whereas the L-type Ca2- current plays an obligatory role in pacemaking in the center, the Na+ current plays a major role in pacemaking in the periphery.

scholarly journals Spontaneous action potentials in retinal horizontal cells of goldfish (Carassius auratus) are dependent upon L-type Ca2+ channels and ryanodine receptors

2019 ◽  
Vol 122 (6) ◽  
pp. 2284-2293 ◽  
Author(s):  
Michael W. Country ◽  
Benjamin F. N. Campbell ◽  
Michael G. Jonz
Keyword(s):  
Action Potentials ◽  
Carassius Auratus ◽  
Ryanodine Receptors ◽  
Horizontal Cells ◽  
Outer Retina ◽  
Current Clamp ◽  
Goldfish Carassius Auratus ◽  
Intracellular Ca ◽  
Spontaneous Action ◽  
Spontaneous Action Potentials

Horizontal cells (HCs) are interneurons of the outer retina that undergo graded changes in membrane potential during the light response and provide feedback to photoreceptors. We characterized spontaneous Ca2+-based action potentials (APs) in isolated goldfish ( Carassius auratus) HCs with electrophysiological and intracellular imaging techniques. Transient changes in intracellular Ca2+ concentration ([Ca2+]i) were observed with fura-2 and were abolished by removal of extracellular Ca2+ or by inhibition of Ca2+ channels by 50 µM Cd2+ or 100 µM nifedipine. Inhibition of Ca2+ release from stores with 20 µM ryanodine or 50 µM dantrolene abolished Ca2+ transients and increased baseline [Ca2+]i. This increased baseline was prevented by blocking L-type Ca2+ channels with nifedipine, suggesting that Ca2+-induced Ca2+ release from stores may be needed to inactivate membrane Ca2+ channels. Caffeine (3 mM) increased the frequency of Ca2+ transients, and the store-operated channel antagonist 2-aminoethyldiphenylborinate (100 μM) counteracted this effect. APs were detected with voltage-sensitive dye imaging (FluoVolt) and current-clamp electrophysiology. In current-clamp recordings, regenerative APs were abolished by removal of extracellular Ca2+ or in the presence of 5 mM Co2+ or 100 µM nifedipine, and APs were amplified with 15 mM Ba2+. Collectively, our data suggest that during APs Ca2+ enters through L-type Ca2+ channels and that Ca2+ stores (gated by ryanodine receptors) contribute to the rise in [Ca2+]i. This work may lead to further understanding of the possible role APs have in vision, such as transitioning from light to darkness or modulating feedback from HCs to photoreceptors. NEW & NOTEWORTHY Horizontal cells (HCs) are interneurons of the outer retina that provide inhibitory feedback onto photoreceptors. HCs respond to light via graded changes in membrane potential. We characterized spontaneous action potentials in HCs from goldfish and linked action potential generation to a rise in intracellular Ca2+ via plasma membrane channels and ryanodine receptors. Action potentials may play a role in vision, such as transitioning from light to darkness, or in modulating feedback from HCs to photoreceptors.

cAMP suppresses CA2+-dependent electrical activity of airway smooth muscle induced by TEA

1987 ◽  
Vol 62 (1) ◽  
pp. 175-179 ◽  
Author(s):  
I. S. Richards ◽  
J. Ousterhout ◽  
N. Sperelakis ◽  
C. G. Murlas
Keyword(s):  
Smooth Muscle ◽  
Electrical Activity ◽  
Airway Smooth Muscle ◽  
Action Potentials ◽  
Resting Membrane Potential ◽  
Airway Smooth Muscle Cells ◽  
Cyclic Monophosphate ◽  
Spontaneous Action ◽  
Intracellular Microelectrodes ◽  
Spontaneous Action Potentials

Using intracellular microelectrodes, we investigated whether exogenous dibutyryl adenosine 3 ′,5′-cyclic monophosphate (DBcAMP) or forskolin influenced the electrical effects of tetraethylammonium (TEA) on canine tracheal smooth muscle. We found that 20 mM TEA depolarized airway smooth muscle cells from a resting membrane potential (Em) of -59 +/- 4 mV (mean +/- SD) to -45 +/- 2 mV and caused spontaneous action potentials (AP's) to develop, which were 33 +/- 2 mV in amplitude. These were totally abolished in 0 Ca2+ solution. DBcAMP (1 mM) suppressed the development of this TEA-induced electrical activity and the phasic contractions electrically coupled to it. DBcAMP had no significant effect on Em in the absence of TEA however. Forskolin (1 microM) produced similar effects. Our findings suggest that Ca2+ is the principal ion responsible for the inward current associated with the TEA-induced AP's in airway smooth muscle, and that adenosine 3′,5′-cyclic monophosphate may suppress the electrogenesis of this current.

Sign in / Sign up

Export Citation Format

Share Document