Mechanisms Determining the Dynamic Range of the Bullfrog Olfactory Receptor Cell

2005 ◽  
Vol 93 (4) ◽  
pp. 1880-1888 ◽  
Author(s):  
Akihiro Tomaru ◽  
Takashi Kurahashi
Keyword(s):  
Olfactory Receptor ◽  
Dynamic Range ◽  
Time Integration ◽  
Firing Frequency ◽  
Current Injection ◽  
Inward Current ◽  
Whole Cell Patch Clamp ◽  
Voltage Clamp Condition ◽  
Clamp Condition ◽  
The Hill

Spike discharges of single olfactory receptor cells (ORCs) were recorded with the whole cell patch-clamp method applied to slice preparation. In parallel, activities of transduction channels were measured under the voltage-clamp condition. When cells were stimulated by odorants, 54 out of 306 cells exhibited inward current responses (10 mM cineole in the puffer pipette). The amplitude of the inward current was dependent on the stimulus period, reflecting the time integration for the stimulus dose, and the relation could be fitted by the Hill equation. Under the current-clamp condition, current injection induced spike discharges. In cells showing repetitive firings, the firing frequency was dependent on the amount of injected current. The relation was fitted by the Michaelis-Menten equation showing saturation. When cells were responsive to the odorant and had abilities to discharge repetitive spikes, the depolarizing responses were accompanied by repetitive spikes. In those cells, the spike frequency was dose-dependent, expressing saturation similar to the result obtained by current injection. Since both transduction channel and spike generative steps expressed saturation in their dose dependences, we explored what step(s) actually determines saturation in ORC signaling processes. By examining dose-response relations of both the current and spikes in the same cells, saturating dose was found to be dependent largely on that of the transduction step. This suggests that the dynamic range is fundamentally determined by the transduction system. In addition, a simple model derived from the nonlinearity of the plasma membrane could explain that a critical level of dynamic range was, at least in part, modified by the membrane nonlinearity.

Activation kinetics of the acetylcholine-gated potassium current in isolated atrial cells

1989 ◽  
Vol 257 (4) ◽  
pp. C646-C650 ◽  
Author(s):  
N. Inomata ◽  
T. Ishihara ◽  
N. Akaike
Keyword(s):  
Latent Period ◽  
Time Lag ◽  
Rapid Change ◽  
External Solution ◽  
Hill Coefficient ◽  
Atrial Cells ◽  
Voltage Clamp Condition ◽  
Concentration Clamp Technique ◽  
Clamp Condition ◽  
The Hill

Processes involved in activation of the acetylcholine (ACh) receptor-operated K+ current (IK) were examined in atrial cells isolated from guinea pig using a "concentration-clamp" technique. This approach allows for the intracellular perfusion and the rapid change of external solution (time constant 4 ms) with cell-attached condition under a single-electrode voltage-clamp condition. The ACh-induced IK increased in a sigmoidal fashion with increasing concentrations of ACh. The Ka value estimated from the concentration-response curve was 3 X 10(-7) M, and the Hill coefficient was 1.0. The activation phase was accelerated not only by increasing the concentration of ACh but also by elevating the temperature. Before activation of the current, there was a brief latent period after the application of ACh. The latent period was shortened considerably with the increase in ACh concentration and in temperature, i.e., 267 +/- 20 ms at 18 degrees C, 98 +/- 11 ms at 26 degrees C, and 44 +/- 6 ms at 37 degrees C for 10(-6) M ACh. These results suggest that the latent period of ACh response seems to be the time lag needed for the activation of K+ channels using remote sensor.

scholarly journals Modulation of High-Voltage Activated Ca2+ Channels in the Rat Periaqueductal Gray Neurons by μ-Type Opioid Agonist

1997 ◽  
Vol 77 (3) ◽  
pp. 1418-1424 ◽  
Author(s):  
Chang-Ju Kim ◽  
Jeong-Seop Rhee ◽  
Norio Akaike
Keyword(s):  
G Proteins ◽  
Opioid Receptor ◽  
High Voltage ◽  
Inhibitory Effect ◽  
Periaqueductal Gray ◽  
Dependent Manner ◽  
Opioid Agonist ◽  
Voltage Clamp Condition ◽  
Voltage Dependent ◽  
Clamp Condition

Kim, Chang-Ju, Jeong-Seop Rhee, and Norio Akaike. Modulation of high-voltage activated Ca2+ channels in the rat periaqueductal gray neurons by μ-type opioid agonist. J. Neurophysiol. 77: 1418–1424, 1997. The effect of μ-type opioid receptor agonist, D-Ala2,N-MePhe4,Gly5-ol-enkephalin (DAMGO), on high-voltage-activated (HVA) Ca2+ channels in the dissociated rat periaqueductal gray (PAG) neurons was investigated by the use of nystatin-perforated patch recording mode under voltage-clamp condition. Among 118 PAG neurons tested, the HVA Ca2+ channels of 38 neurons (32%) were inhibited by DAMGO (DAMGO-sensitive cells), and the other 80 neurons (68%) were not affected by DAMGO (DAMGO-insensitive cells). The N-, P-, L-, Q-, and R-type Ca2+ channel components in DAMGO-insensitive cells shared 26.9, 37.1, 22.3, 7.9, and 5.8%, respectively, of the total Ca2+ channel current. The channel components of DAMGO-sensitive cells were 45.6, 25.7, 21.7, 4.6, and 2.4%, respectively. The HVA Ca2+ current of DAMGO-sensitive neurons was inhibited by DAMGO in a concentration-, time-, and voltage-dependent manner. Application of ω-conotoxin-GVIA occluded the inhibitory effect of DAMGO ∼70%. So, HVA Ca2+ channels inhibited by DAMGO were mainly the N-type Ca2+ channels. The inhibitory effect of DAMGO on HVA Ca2+ channels was prevented almost completely by the pretreatment of pertussis toxin (PTX) for 8–10 h, suggesting that DAMGO modulation on N-type Ca2+ channels in rat PAG neurons is mediated by PTX-sensitive G proteins. These results indicate that μ-type opioid receptor modulates N-type HVA Ca2+ channels via PTX-sensitive G proteins in PAG neurons of rats.

Multiple Effects of Serotonin and Acetylcholine on Hyperpolarization-Activated Inward Current in Locomotor Activity-Related Neurons in Cfos-EGFP Mice

2010 ◽  
Vol 104 (1) ◽  
pp. 366-381 ◽  
Author(s):  
Yue Dai ◽  
Larry M. Jordan
Keyword(s):  
Spinal Cord ◽  
Motor System ◽  
Reversal Potential ◽  
Rhythmic Activity ◽  
Maximal Conductance ◽  
Inward Current ◽  
Spinal Interneurons ◽  
Whole Cell Patch Clamp ◽  
Activation Rate ◽  
Maximal Activation

Hyperpolarization-activated inward current ( Ih) has been shown to be involved in production of bursting during various forms of rhythmic activity. However, details of Ih in spinal interneurons related to locomotion remain unknown. Using Cfos-EGFP transgenic mice (P6–P12) we are able to target the spinal interneurons activated by locomotion. Following a locomotor task, whole cell patch-clamp recordings were obtained from ventral EGFP+ neurons in spinal cord slices (T13–L4, 200–250 μm). Ih was found in 51% of EGFP+ neurons ( n = 149) with almost even distribution in lamina VII (51%), VIII (47%), and X (55%). Ih could be blocked by ZD7288 (10–20 μM) or cesium (1–1.5 mM) but was insensitive to barium (2–2.5 mM). Ih activated at −80.1 ± 9.2 mV with half-maximal activation −95.5 ± 13.3 mV, activation rate 10.0 ± 3.2 mV, time constant 745 ± 501 ms, maximal conductance 1.0 ± 0.7 nS, and reversal potential −34.3 ± 3.6 mV. 5-HT (15–20 μM) and ACh (20–30 μM) produced variable effects on Ih. 5-HT increased Ih in 43% of EGFP+ neurons ( n = 37), decreased Ih in 24%, and had no effect on Ih in 33% of the neurons. ACh decreased Ih in 67% of EGFP+ neurons ( n = 18) with unchanged Ih in 33% of the neurons. This study characterizes the Ih in locomotor-related interneurons and is the first to demonstrate the variable effects of 5-HT and ACh on Ih in rodent spinal interneurons. The finding of 5-HT and ACh-induced reduction of Ih in EGFP+ neurons suggests a novel mechanism that the motor system could use to limit the participation of certain neurons in locomotion.

Abstract 17193: Inhibiting Late Sodium Current Attenuates Isoproterenol-Induced Transient Inward Current and Delayed Afterdepolarizations in Ventricular Myocytes

Circulation ◽  
2015 ◽  
Vol 132 (suppl_3) ◽  
Author(s):  
Yejia Song ◽  
Nesrine El-Bizri ◽  
Sridharan Rajamani ◽  
Luiz Belardinelli
Keyword(s):  
Ventricular Myocytes ◽  
Sodium Current ◽  
Selective Inhibition ◽  
Adrenergic Stimulation ◽  
Patch Clamp Technique ◽  
Cardiac Tissues ◽  
Inward Current ◽  
Transient Inward Current ◽  
Whole Cell Patch Clamp ◽  
Series Of Experiments

Introduction: The β-adrenergic agonist isoproterenol (ISO) is known to induce the arrhythmogenic transient inward current (I Ti ) and delayed afterdepolarization (DAD) via a stimulation of L-type Ca 2+ current. Recent studies found that ISO-induced DADs in cardiac tissues are inhibited by GS967, a selective blocker of the late Na + current (I NaL ). Thus, we hypothesize that I NaL contributes to the actions of ISO, and selective inhibition of this current will reduce ISO-induced I Ti and DADs. Methods: Transmembrane currents and action potentials of rabbit and guinea pig (GP) ventricular myocytes were recorded using the whole-cell patch-clamp technique. ISO (0.1 μM), GS967 (1 μM) and the Na + channel blocker tetrodotoxin (TTX, 3 μM) were used in the experiments. Results: In rabbit myocytes, application of ISO caused an increase in the amplitude of I NaL from -0.10±0.03 to -0.32±0.04 pA/pF (n = 17, p < 0.05). The ISO-stimulated I NaL was inhibited by GS967 and TTX. In one series of experiments, ISO increased the I NaL from -0.14±0.04 to -0.35±0.06 pA/pF, and GS967 applied in the presence of ISO reduced the current to -0.14±0.03 pA/pF (n = 9, p < 0.05). In another series of experiments, the amplitude of I NaL was increased by ISO from -0.17±0.08 to -0.41±0.09 pA/pF, and was decreased to -0.09±0.08 pA/pF when TTX was applied with ISO (n = 5, p < 0.05). Application of ISO also induced I Ti and DADs. GS967 applied in the presence of ISO inhibited the amplitude of I Ti by 52±6%, from -1.79±0.30 to -0.87±0.16 pA/pF (n = 8, p < 0.05). Consistent with the inhibition of I Ti , GS967 suppressed the amplitude of ISO-induced DADs by 56±12%, from 6.54±1.59 to 3.22±1.27 mV (n = 5, p < 0.05). Similarly, in GP myocytes ISO-induced I Ti and DADs were decreased by GS967 from -1.14±0.21 to -0.73±0.16 pA/pF (n = 7, p < 0.05) and from 7.16±0.59 to 4.67±0.24 mV (n = 5, p < 0.05), respectively. Conclusions: An increased I NaL is likely to contribute to the proarrhythmic effects of ISO in cardiac myocytes. GS967 significantly attenuated ISO-induced I NaL , I Ti and DADs, suggesting that inhibiting this current could be an effective strategy to antagonize the arrhythmogenic actions of β-adrenergic stimulation.

Persistence of the olfactory receptor current in a wide variety of extracellular environments

1996 ◽  
Vol 75 (4) ◽  
pp. 1386-1391 ◽  
Author(s):  
S. J. Kleene ◽  
R. Y. Pun
Keyword(s):  
Olfactory Receptor ◽  
Rana Pipiens ◽  
Olfactory Receptor Neurons ◽  
Resting Potential ◽  
Induced Current ◽  
Olfactory Cilia ◽  
Inward Current ◽  
Cyclic Monophosphate ◽  
Cationic Current ◽  
Receptor Neurons

We measured the current activated by cytoplasmic adenosine 3':5'-cyclic monophosphate (cAMP) in olfactory cilia from the frog Rana pipiens. The odorant-induced current in frog olfactory receptor neurons was also measured for comparison. In both cases, recordings were performed near the neuronal resting potential in a variety of extracellular bath solutions. 2. In Ca(2+)-free baths, cAMP activated an inward current in excised olfactory cilia that was carried entirely by cations. As extracellular Ca2+ was increased, the cationic current decreased while a second current, carried by C1-, increased. Total cAMP-activated current decreased with increasing extracellular CA2+. When external Na+ but not Ca2+ was eliminated, only the C1- component of the current persisted. When external Na+ and Ca2+ were both removed, there was no cAMP-activated current. 3. In receptor neurons, the total odorant-induced receptor current varied in a similar way with the extracellular ionic environment. Under conditions favoring the anionic receptor current, the response amplitude decreased and the latency increased. 4. It is known that olfactory receptor currents persist in a wide variety of extracellular environments. This persistence can be sufficiently explained by the balance between cationic and anionic currents demonstrated here.

Properties of cAMP-dependent and Ca(2+)-dependent whole cell Cl- conductances in rat epididymal cells

1993 ◽  
Vol 264 (4) ◽  
pp. C794-C802 ◽  
Author(s):  
S. J. Huang ◽  
W. O. Fu ◽  
Y. W. Chung ◽  
T. S. Zhou ◽  
P. Y. Wong
Keyword(s):  
Cystic Fibrosis ◽  
Transmembrane Conductance Regulator ◽  
Transmembrane Conductance ◽  
Whole Cell ◽  
Cyclic Monophosphate ◽  
Cation Current ◽  
Whole Cell Patch Clamp ◽  
Current Voltage ◽  
Clamp Condition ◽  
Cl Conductance

Single rat epididymal cell studied under whole cell patch-clamp condition responded to 8-(4-chlorophenylthio)-adenosine 3',5'-cyclic monophosphate (CPT-cAMP) (500 microM) and to ionomycin (1 microM) by an increase in whole cell conductance. A major part of the stimulated current was carried by Cl-, although a small part was due to nonselective cation current. After elimination of the cation current component by using impermeant cation, the cells revealed different Cl- conductance properties in response to adenosine 3',5'-cyclic monophosphate (cAMP) and ionomycin. The cAMP-stimulated Cl- conductance was independent of time and voltage and showed a linear current-voltage relationship. The anion permselectivity was NO3- > Br- > Cl- approximately I- >> SO(4)2-. The ionomycin-stimulated Cl- conductance showed marked time and voltage dependency. In contrast to the cAMP-induced anion permselectivity, the ionomycin-induced anion permselectivity was I- > Br- approximately NO3- > Cl- >> SO(4)2-. These results indicate that the epididymal epithelial cells exhibit different Cl- conductances sensitive to cAMP and Ca2+. The cAMP-activated conductance has properties resembling the type associated with the cystic fibrosis transmembrane conductance regulator found in cystic fibrosis-affected epithelia. This finding supports the notion that the epididymis is a cystic fibrosis epithelium.

Local Excitatory Circuits in the Intermediate Gray Layer of the Superior Colliculus

1999 ◽  
Vol 81 (3) ◽  
pp. 1424-1427 ◽  
Author(s):  
Diana L. Pettit ◽  
Matthew C. Helms ◽  
Psyche Lee ◽  
George J. Augustine ◽  
William C. Hall
Keyword(s):  
Superior Colliculus ◽  
Intermediate Layer ◽  
Tree Shrew ◽  
Patch Clamp Recording ◽  
Inward Current ◽  
Whole Cell Patch Clamp ◽  
Synaptic Interactions ◽  
Layer Neuron ◽  
Inward Currents ◽  
Synaptic Responses

Local excitatory circuits in the intermediate gray layer of the superior colliculus. We have used photostimulation and whole cell patch-clamp recording techniques to examine local synaptic interactions in slices from the superior colliculus of the tree shrew. Uncaging glutamate 10–75 μm from the somata of neurons in the intermediate gray layer elicited a long-lasting inward current, due to direct activation of glutamate receptors on these neurons, and brief inward currents caused by activation of presynaptic neurons. The synaptic responses occurred as individual currents or as clusters that lasted up to several hundred milliseconds. Excitatory synaptic responses, which reversed at membrane potentials near 0 mV, could be evoked by uncaging glutamate anywhere within 75 μm of an intermediate layer neuron. Our results indicate the presence of extensive local excitatory circuits in the intermediate layer of the superior colliculus and support the hypothesis that such intrinsic circuitry contributes to the development of presaccadic command bursts.

scholarly journals Differential Interactions of Na+ Channel Toxins with T-type Ca2+ Channels

2008 ◽  
Vol 132 (1) ◽  
pp. 101-113 ◽  
Author(s):  
Hui Sun ◽  
Diego Varela ◽  
Denis Chartier ◽  
Peter C. Ruben ◽  
Stanley Nattel ◽  
...  
Keyword(s):  
Ventricular Myocytes ◽  
Low Voltage ◽  
Parallel Evolution ◽  
Na Channel ◽  
Patch Clamp Technique ◽  
Hek 293 ◽  
Inward Current ◽  
Whole Cell Patch Clamp ◽  
The Right ◽  
Ca2 Channels

Two types of voltage-dependent Ca2+ channels have been identified in heart: high (ICaL) and low (ICaT) voltage-activated Ca2+ channels. In guinea pig ventricular myocytes, low voltage–activated inward current consists of ICaT and a tetrodotoxin (TTX)-sensitive ICa component (ICa(TTX)). In this study, we reexamined the nature of low-threshold ICa in dog atrium, as well as whether it is affected by Na+ channel toxins. Ca2+ currents were recorded using the whole-cell patch clamp technique. In the absence of external Na+, a transient inward current activated near −50 mV, peaked at −30 mV, and reversed around +40 mV (HP = −90 mV). It was unaffected by 30 μM TTX or micromolar concentrations of external Na+, but was inhibited by 50 μM Ni2+ (by ∼90%) or 5 μM mibefradil (by ∼50%), consistent with the reported properties of ICaT. Addition of 30 μM TTX in the presence of Ni2+ increased the current approximately fourfold (41% of control), and shifted the dose–response curve of Ni2+ block to the right (IC50 from 7.6 to 30 μM). Saxitoxin (STX) at 1 μM abolished the current left in 50 μM Ni2+. In the absence of Ni2+, STX potently blocked ICaT (EC50 = 185 nM) and modestly reduced ICaL (EC50 = 1.6 μM). While TTX produced no direct effect on ICaT elicited by expression of hCaV3.1 and hCaV3.2 in HEK-293 cells, it significantly attenuated the block of this current by Ni2+ (IC50 increased to 550 μM Ni2+ for CaV3.1 and 15 μM Ni2+ for CaV3.2); in contrast, 30 μM TTX directly inhibited hCaV3.3-induced ICaT and the addition of 750 μM Ni2+ to the TTX-containing medium led to greater block of the current that was not significantly different than that produced by Ni2+ alone. 1 μM STX directly inhibited CaV3.1-, CaV3.2-, and CaV3.3-mediated ICaT but did not enhance the ability of Ni2+ to block these currents. These findings provide important new implications for our understanding of structure–function relationships of ICaT in heart, and further extend the hypothesis of a parallel evolution of Na+ and Ca2+ channels from an ancestor with common structural motifs.

External ATP-induced changes in [Ca2+]i and membrane currents in mammalian atrial myocytes

1991 ◽  
Vol 260 (4) ◽  
pp. C673-C680 ◽  
Author(s):  
Y. Hirano ◽  
S. Abe ◽  
T. Sawanobori ◽  
M. Hiraoka
Keyword(s):  
Digital Imaging ◽  
Calcium Concentration ◽  
Transient Increase ◽  
P2 Receptor ◽  
Atrial Myocytes ◽  
Whole Cell ◽  
Inward Current ◽  
Whole Cell Patch Clamp ◽  
Induced Changes ◽  
Whole Cell Recordings

Fura-2 fluorescent digital-imaging microscopy and whole cell patch-clamp recordings were used to study the effects of externally applied ATP on atrial myocytes isolated from rabbit and guinea pig hearts. Application of 100 microM ATP elicited a transient increase in intracellular calcium concentration ([Ca2+]i), which was not suppressed by theophylline, whereas adenosine and ADP failed to evoke the response. The Ca2+ transients were suppressed by the application of Co2+, Ni2+, or verapamil and by the removal of extracellular Ca2+, indicating that the inflow of external Ca2+ is necessary to evoke the response. The Ca2+ transient was suppressed also by ryanodine, suggesting that the mobilization of intracellular Ca2+ is another important factor. In the whole cell recordings, ATP induced a transient depolarization of the membrane potential due to the activation of a rapidly desensitizing inward current which persisted in the presence of Co2+, Ni2+, verapamil, or ryanodine. These results indicate that in mammalian atrial myocytes, ATP evoked transient increase in [Ca2+]i via P2-receptor, through the release of internally stored Ca2+ associated with the inflow of external Ca2+. This response seemed to be triggered mainly by the influx of Ca2+ through L-type Ca2+ channel activated by membrane depolarization, which was caused by the ATP-induced inward current.

Sign in / Sign up

Export Citation Format

Share Document