scholarly journals Characterization of the chemosensitive response of individual solitary complex neurons from adult rats

2009 ◽  
Vol 296 (3) ◽  
pp. R763-R773 ◽  
Author(s):  
Nicole L. Nichols ◽  
Daniel K. Mulkey ◽  
Katherine A. Wilkinson ◽  
Frank L. Powell ◽  
Jay B. Dean ◽  
...  
Keyword(s):  
Steady State ◽  
Firing Rate ◽  
Hypercapnic Acidosis ◽  
Neonatal Rats ◽  
Patch Clamp Technique ◽  
Adult Rats ◽  
Whole Cell Patch Clamp ◽  
Patch Pipette ◽  
Solitary Complex

We studied the CO2/H+-chemosensitive responses of individual solitary complex (SC) neurons from adult rats by simultaneously measuring the intracellular pH (pHi) and electrical responses to hypercapnic acidosis (HA). SC neurons were recorded using the blind whole cell patch-clamp technique and loading the soma with the pH-sensitive dye pyranine through the patch pipette. We found that SC neurons from adult rats have a lower steady-state pHi than SC neurons from neonatal rats. In the presence of chemical and electrical synaptic blockade, adult SC neurons have firing rate responses to HA (percentage of neurons activated or inhibited and the magnitude of response as determined by the chemosensitivity index) that are similar to SC neurons from neonatal rats. They also have a typical response to isohydric hypercapnia, including decreased ΔpHi, followed by pHi recovery, and increased firing rate. Thus, the chemosensitive response of SC neurons from adults is similar to the chemosensitive response of SC neurons from neonatal rats. Because our findings for adults are similar to previously reported values for neurons from neonatal rats, we conclude that intrinsic chemosensitivity is established early in development for SC neurons and is maintained throughout adulthood.

Characterization of voltage-dependent calcium currents in mouse motoneurons

1992 ◽  
Vol 68 (1) ◽  
pp. 85-92 ◽  
Author(s):  
M. Mynlieff ◽  
K. G. Beam
Keyword(s):  
Voltage Dependence ◽  
Low Voltage ◽  
Calcium Currents ◽  
Patch Clamp Technique ◽  
Maximal Amplitude ◽  
Time To Peak ◽  
Whole Cell Patch Clamp ◽  
Voltage Dependent ◽  
Channel Currents

1. Calcium channel currents were measured with the whole-cell patch clamp technique in cultured, identified mouse motoneurons. Three components of current were operationally defined on the basis of voltage dependence, kinetics, and pharmacology. 2. Test potentials to -50 mV or greater (10 mM external Ca2+) elicited a low-voltage activated T-type current that was transient (decaying to baseline in less than 200 ms) and had a relatively slow time to peak (20-50 ms). A 1-s prepulse to -45 mV produced approximately half-maximal inactivation of this T current. 3. Two high-voltage activated (HVA) components of current (1 transient and 1 sustained) were activated by test potentials to -20 mV or greater (10 mM external Ca2+). A 1-s prepulse to -35 mV produced approximately half-maximal inactivation of the transient component without affecting the sustained component. 4. When Ba2+ was substituted for Ca2+ as the charge carrier, activation of the HVA components was shifted in the hyperpolarizing direction, and the relative amplitude of the transient HVA component was reduced. 5. Amiloride (1-2 mM) caused a reversible, partial block of the T current without affecting the HVA components. 6. The dihydropyridine agonist isopropyl 4-(2,1,3-benzoxadiazol-4-yl)-1,4-dihydro-2,6-dimethyl-5-nitro-3- pyridine-carboxylate [(+)-SDZ 202-791, 100 nM-1 microM)] shifted the activation of the sustained component of HVA current to more negative potentials and increased its maximal amplitude. Additionally, (+)-SDZ 202-791 caused the appearance of a slowed component of tail current.(ABSTRACT TRUNCATED AT 250 WORDS)

Opposing effects of coupled and uncoupled NOS activity on the Na+-K+ pump in cardiac myocytes

2008 ◽  
Vol 294 (2) ◽  
pp. C572-C578 ◽  
Author(s):  
C. N. White ◽  
E. J. Hamilton ◽  
A. Garcia ◽  
D. Wang ◽  
K. K. M. Chia ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Superoxide Dismutase ◽  
Cardiac Myocytes ◽  
Pump Current ◽  
No Synthase ◽  
Patch Clamp Technique ◽  
Whole Cell Patch Clamp ◽  
Patch Pipette ◽  
Pump Activity ◽  
Opposing Effects

Pharmacological delivery of nitric oxide (NO) stimulates the cardiac Na+-K+ pump. However, effects of NO synthesized by NO synthase (NOS) often differ from the effects of NO delivered pharmacologically. In addition, NOS can become “uncoupled” and preferentially synthesize O2·−, which often has opposing effects to NO. We tested the hypothesis that NOS-synthesized NO stimulates Na+-K+ pump activity, and uncoupling of NOS inhibits it. To image NO, we loaded isolated rabbit cardiac myocytes with 4,5-diaminofluorescein-2 diacetate (DAF-2 DA) and measured fluorescence with confocal microscopy. l-Arginine (l-Arg; 500 μmol/l) increased DAF-2 DA fluorescence by 51% compared with control ( n = 8; P < 0.05). We used the whole cell patch-clamp technique to measure electrogenic Na+-K+ pump current ( Ip). Mean Ip of 0.35 ± 0.03 pA/pF ( n = 44) was increased to 0.48 ± 0.03 pA/pF ( n = 7, P < 0.05) by 10 μmol/l l-Arg in pipette solutions. This increase was abolished by NOS inhibition with radicicol or by NO-activated guanylyl cyclase inhibition with 1 H-[1,2,4]oxadiazole[4,3-a]quinoxalin-1-one. We next examined the effect of uncoupling NOS using paraquat. Paraquat (1 mmol/l) induced a 51% increase in the fluorescence intensity of O2·−-sensitive dye dihydroethidium compared with control ( n = 9; P < 0.05). To examine the functional effects of uncoupling, we measured Ip with 100 μmol/l paraquat included in patch pipette solutions. This decreased Ip to 0.28 ± 0.03 pA/pF ( n = 12; P < 0.001). The paraquat-induced pump inhibition was abolished by superoxide dismutase (in pipette solutions). We conclude that NOS-mediated NO synthesis stimulates the Na+-K+ pump, whereas uncoupling of NOS causes O2·−-mediated pump inhibition.

scholarly journals The calcium-independent transient outward potassium current in isolated ferret right ventricular myocytes. II. Closed state reverse use-dependent block by 4-aminopyridine.

1993 ◽  
Vol 101 (4) ◽  
pp. 603-626 ◽  
Author(s):  
D L Campbell ◽  
Y Qu ◽  
R L Rasmusson ◽  
H C Strauss
Keyword(s):  
Steady State ◽  
Right Ventricular ◽  
Ventricular Myocytes ◽  
Patch Clamp Technique ◽  
Time Constants ◽  
Closed State ◽  
Whole Cell Patch Clamp ◽  
Dependent Behavior ◽  
Steady State Inactivation ◽  
K Current

Block of the calcium-independent transient outward K+ current, I(to), by 4-aminopyridine (4-AP) was studied in ferret right ventricular myocytes using the whole cell patch clamp technique. 4-AP reduces I(to) through a closed state blocking mechanism displaying "reverse use-dependent" behavior that was inferred from: (a) development of tonic block at hyperpolarized potentials; (b) inhibition of development of tonic block at depolarized potentials; (c) appearance of "crossover phenomena" in which the peak current is delayed in the presence of 4-AP at depolarized potentials; (d) relief of block at depolarized potentials which is concentration dependent and parallels steady-state inactivation for low 4-AP concentrations (V1/2 approximately -10 mV in 0.1 mM 4-AP) and steady-state activation at higher concentrations (V1/2 = +7 mV in 1 mM 4-AP, +15 mV in 10 mM 4-AP); and (e) reassociation of 4-AP at hyperpolarized potentials. No evidence for interaction of 4-AP with either the open or inactivated state of the I(to) channel was obtained from measurements of kinetics of recovery and deactivation in the presence of 0.5-1.0 mM 4-AP. At hyperpolarized potentials (-30 to -90 mV) 10 mM 4-AP associates slowly (time constants ranging from approximately 800 to 1,300 ms) with the closed states of the channel (apparent Kd approximately 0.2 mM). From -90 to -20 mV the affinity of the I(to) channel for 4-AP appears to be voltage insensitive; however, at depolarized potentials (+20 to +100 mV) 4-AP dissociates with time constants ranging from approximately 350 to 150 ms. Consequently, the properties of 4-AP binding to the I(to) channel undergo a transition in the range of potentials over which channel activation and inactivation occurs (-30 to +20 mV). We propose a closed state model of I(to) channel gating and 4-AP binding kinetics, in which 4-AP binds to three closed states. In this model 4-AP has a progressively lower affinity as the channel approaches the open state, but has no intrinsic voltage dependence of binding.

scholarly journals Transient outwardly rectifying A currents are involved in the firing rate response to altered CO2 in chemosensitive locus coeruleus neurons from neonatal rats

2013 ◽  
Vol 305 (7) ◽  
pp. R780-R792 ◽  
Author(s):  
Ke-Yong Li ◽  
Robert W. Putnam
Keyword(s):  
Firing Rate ◽  
Locus Coeruleus ◽  
Intracellular Ph ◽  
Membrane Depolarization ◽  
Extracellular Ph ◽  
Transient Current ◽  
Hypercapnic Acidosis ◽  
Neonatal Rats ◽  
Maximal Amplitude ◽  
A Current

The effect of hypercapnia on outwardly rectifying currents was examined in locus coeruleus (LC) neurons in slices from neonatal rats [postnatal day 3 (P3)–P15]. Two outwardly rectifying currents [4-aminopyridine (4-AP)-sensitive transient current and tetraethyl ammonium (TEA)-sensitive sustained current] were found in LC neurons. 4-AP induced a membrane depolarization of 3.6 ± 0.6 mV ( n = 4), while TEA induced a smaller membrane depolarization of 1.2 ± 0.3 mV ( n = 4). Hypercapnic acidosis (HA) inhibited both currents. The maximal amplitude of the TEA-sensitive current was reduced by 52.1 ± 4.5% ( n = 5) in 15% CO2 [extracellular pH (pHo) 7.00, intracellular pH (pHi) 6.96]. The maximal amplitude of the 4-AP-sensitive current was reduced by 34.5 ± 3.0% ( n = 6) in 15% CO2 (pHo 7.00, pHi 6.96), by 29.4 ± 6.8% ( n = 6) in 10% CO2 (pHo 7.15, pHi 7.14), and increased by 29.0 ± 6.4% ( n = 6) in 2.5% CO2 (pHo 7.75, pHi 7.35). 4-AP completely blocked hypercapnia-induced increased firing rate, but TEA did not affect it. When LC neurons were exposed to HA with either pHo or pHi constant, the 4-AP-sensitive current was inhibited. The data show that the 4-AP-sensitive current (likely an A current) is inhibited by decreases in either pHo or pHi. The change of the A current by various levels of CO2 is correlated with the change in firing rate induced by CO2, implicating the 4-AP-sensitive current in chemosensitive signaling in LC neurons.

scholarly journals The calcium-independent transient outward potassium current in isolated ferret right ventricular myocytes. I. Basic characterization and kinetic analysis.

1993 ◽  
Vol 101 (4) ◽  
pp. 571-601 ◽  
Author(s):  
D L Campbell ◽  
R L Rasmusson ◽  
Y Qu ◽  
H C Strauss
Keyword(s):  
Steady State ◽  
Ventricular Myocytes ◽  
Nonlinear Least Squares ◽  
Patch Clamp Technique ◽  
Time Constants ◽  
Whole Cell Patch Clamp ◽  
Voltage Dependent ◽  
Steady State Inactivation ◽  
K Current ◽  
Necessary And Sufficient

Enzymatically isolated myocytes from ferret right ventricles (12-16 wk, male) were studied using the whole cell patch clamp technique. The macroscopic properties of a transient outward K+ current I(to) were quantified. I(to) is selective for K+, with a PNa/PK of 0.082. Activation of I(to) is a voltage-dependent process, with both activation and inactivation being independent of Na+ or Ca2+ influx. Steady-state inactivation is well described by a single Boltzmann relationship (V1/2 = -13.5 mV; k = 5.6 mV). Substantial inactivation can occur during a subthreshold depolarization without any measurable macroscopic current. Both development of and recovery from inactivation are well described by single exponential processes. Ensemble averages of single I(to) channel currents recorded in cell-attached patches reproduce macroscopic I(to) and indicate that inactivation is complete at depolarized potentials. The overall inactivation/recovery time constant curve has a bell-shaped potential dependence that peaks between -10 and -20 mV, with time constants (22 degrees C) ranging from 23 ms (-90 mV) to 304 ms (-10 mV). Steady-state activation displays a sigmoidal dependence on membrane potential, with a net aggregate half-activation potential of +22.5 mV. Activation kinetics (0 to +70 mV, 22 degrees C) are rapid, with I(to) peaking in approximately 5-15 ms at +50 mV. Experiments conducted at reduced temperatures (12 degrees C) demonstrate that activation occurs with a time delay. A nonlinear least-squares analysis indicates that three closed kinetic states are necessary and sufficient to model activation. Derived time constants of activation (22 degrees C) ranged from 10 ms (+10 mV) to 2 ms (+70 mV). Within the framework of Hodgkin-Huxley formalism, Ito gating can be described using an a3i formulation.

scholarly journals Substance P Differentially Modulates Firing Rate of Solitary Complex (SC) Neurons from Control and Chronic Hypoxia-Adapted Adult Rats

PLoS ONE ◽  
2014 ◽  
Vol 9 (2) ◽  
pp. e88161 ◽  
Author(s):  
Nicole L. Nichols ◽  
Frank L. Powell ◽  
Jay B. Dean ◽  
Robert W. Putnam
Keyword(s):  
Substance P ◽  
Firing Rate ◽  
Chronic Hypoxia ◽  
Adult Rats ◽  
Solitary Complex

scholarly journals Curcumin Activates Vagal Afferent Neurons Through the Modulation of Ion Channels via α7 nAChR

2019 ◽  
Vol 14 (8) ◽  
pp. 1934578X1987373
Author(s):  
Simiao Qiao ◽  
Yannong Dou ◽  
Huijuan Hu ◽  
Yue Dai
Keyword(s):  
Potassium Currents ◽  
Underlying Mechanism ◽  
Electrophysiological Recording ◽  
Patch Clamp Technique ◽  
Α7 Nicotinic Acetylcholine Receptor ◽  
Adult Rats ◽  
Whole Cell Patch Clamp ◽  
Α7 Nachr ◽  
Specific Antagonist ◽  
Channel Currents

Curcumin, a plant polyphenol, has been previously reported to attenuate collagen-induced arthritis in rats by modulating the function of the cholinergic system, but the underlying mechanism remains to be identified. In this study, primary nodose ganglion (NG) neurons were prepared from the adult rats and the electrophysiological recording was performed using the whole-cell patch clamp technique. Curcumin was shown to reduce total potassium currents and A-type currents, without significant effect on the activation or inactivation of potassium channels. Moreover, curcumin selectively enhanced tetrodotoxin-sensitive (TTX-S) sodium channel currents. These effects could be abolished by methyllycaconitine citrate (specific antagonist of α7 nACh receptor). Interestingly, curcumin did not modulate TTX-resistant (TTX-R) or calcium channels. These results suggest that curcumin increases the excitability of NG neurons by decreasing potassium currents and increasing TTX-S sodium currents via α7 nicotinic acetylcholine receptor (nAchR).

scholarly journals Spike Frequency Adaptation and Neocortical Rhythms

2002 ◽  
Vol 88 (2) ◽  
pp. 761-770 ◽  
Author(s):  
Galit Fuhrmann ◽  
Henry Markram ◽  
Misha Tsodyks
Keyword(s):  
Firing Rate ◽  
Pyramidal Neurons ◽  
Spike Frequency ◽  
Spike Frequency Adaptation ◽  
Patch Clamp Technique ◽  
Response Characteristics ◽  
Frequency Adaptation ◽  
Whole Cell Patch Clamp ◽  
The Mean

Spike-frequency adaptation in neocortical pyramidal neurons was examined using the whole cell patch-clamp technique and a phenomenological model of neuronal activity. Noisy current was injected to reproduce the irregular firing typically observed under in vivo conditions. The response was quantified by computing the poststimulus histogram (PSTH). To simulate the spiking activity of a pyramidal neuron, we considered an integrate-and-fire model to which an adaptation current was added. A simplified model for the mean firing rate of an adapting neuron under noisy conditions is also presented. The mean firing rate model provides a good fit to both experimental and simulation PSTHs and may therefore be used to study the response characteristics of adapting neurons to various input currents. The models enable identification of the relevant parameters of adaptation that determine the shape of the PSTH and allow the computation of the response to any change in injected current. The results suggest that spike frequency adaptation determines a preferred frequency of stimulation for which the phase delay of a neuron's activity relative to an oscillatory input is zero. Simulations show that the preferred frequency of single neurons dictates the frequency of emergent population rhythms in large networks of adapting neurons. Adaptation could therefore be one of the crucial factors in setting the frequency of population rhythms in the neocortex.

scholarly journals Response of membrane potential and intracellular pH to hypercapnia in neurons and astrocytes from rat retrotrapezoid nucleus

2005 ◽  
Vol 289 (3) ◽  
pp. R851-R861 ◽  
Author(s):  
Nick A. Ritucci ◽  
Joseph S. Erlichman ◽  
J. C. Leiter ◽  
Robert W. Putnam
Keyword(s):  
Firing Rate ◽  
Brain Slices ◽  
Hypercapnic Acidosis ◽  
Neonatal Rats ◽  
Intracellular Acidification ◽  
Extracellular Acidification ◽  
Retrotrapezoid Nucleus ◽  
Distinct Area ◽  
Constant Ph ◽  
Sensitivity Changes

We compared the response to hypercapnia (10%) in neurons and astrocytes among a distinct area of the retrotrapezoid nucleus (RTN), the mediocaudal RTN (mcRTN), and more intermediate and rostral RTN areas (irRTN) in medullary brain slices from neonatal rats. Hypercapnic acidosis (HA) caused pHo to decline from 7.45 to 7.15 and a maintained intracellular acidification of 0.15 ± 0.02 pH unit in 90% of neurons from both areas ( n = 16). HA excited 44% of mcRTN (7/16) and 38% of irRTN neurons (6/16), increasing firing rate by 167 ± 75% (chemosensitivity index, CI, 256 ± 72%) and 310 ± 93% (CI 292 ± 50%), respectively. These responses did not vary throughout neonatal development. We compared the responses of mcRTN neurons to HA (decreased pHi and pHo) and isohydric hypercapnia (IH; decreased pHi with constant pHo). Neurons excited by HA (firing rate increased 156 ± 46%; n = 5) were similarly excited by IH (firing rate increased 167 ± 38%; n = 5). In astrocytes from both RTN areas, HA caused a maintained intracellular acidification of 0.17 ± 0.02 pH unit ( n = 6) and a depolarization of 5 ± 1 mV ( n = 12). In summary, many neurons (42%) from the RTN are highly responsive (CI 248%) to HA; this may reflect both synaptically driven and intrinsic mechanisms of CO2 sensitivity. Changes of pHi are more significant than changes of pHo in chemosensory signaling in RTN neurons. Finally, the lack of pHi regulation in response to HA suggests that astrocytes do not enhance extracellular acidification during hypercapnia in the RTN.

Electrophysiological characterization of a motilin agonist, GM611, on rabbit duodenal smooth muscle

1996 ◽  
Vol 271 (6) ◽  
pp. G1003-G1016
Author(s):  
K. Yamada ◽  
S. Chen ◽  
N. A. Abdullah ◽  
M. Tanaka ◽  
Y. Ito ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Patch Clamp ◽  
Monovalent Cation ◽  
Patch Clamp Technique ◽  
Spike Amplitude ◽  
Whole Cell Patch Clamp ◽  
Voltage Dependent ◽  
Potential Recording ◽  
Electrophysiological Characterization

Effects of motilin and a newly synthesized erythromycin derivative, GM611, on membrane potential and currents of rabbit duodenal smooth muscle have been investigated by intracellular potential recording and whole cell patch-clamp technique and compared with results from contractile experiments. Motilin and GM611 (0.01-100 nM) dose dependently produced slowly sustained depolarizations (half-maximal effective dose = 0.15 and 3.9 nM for motilin and GM611, respectively) but exhibited biphasic effects on spike activities superimposed on slow waves. With small depolarizations, the number of spike discharges increased, whereas larger depolarizations markedly reduced spike amplitude. Motilin-induced (or GM611-induced) depolarization appeared to be associated with the activation of monovalent cation-selective channels, and the reduction in the spike amplitude appeared mainly to be associated with inhibition of voltage-dependent Ca2+ channels. Furthermore, data from patch-clamp experiments suggested that Ca2+ release occurred from heparin-sensitive internal stores upon stimulation of motilin receptors by these agonists. Possible implications of these electrophysiological effects in motilin- or GM611-induced tonic and phasic contractions have been discussed.

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