Characterization of the electroantennogram in Drosophila melanogaster and its use for identifying olfactory capture and transduction mutants

1991 ◽  
Vol 65 (3) ◽  
pp. 702-714 ◽  
Author(s):  
E. Alcorta
Keyword(s):  
Time Constant ◽  
Rise Time ◽  
Time Course ◽  
Electrical Response ◽  
Fall Time ◽  
Stimulus Concentration ◽  
Olfactory Sense ◽  
Kinetics Of ◽  
Drosophila Mutant

1. Amplitude as well as time course of the electroantennogram (EAG) in Drosophila has been used for describing electrical changes produced in the antenna in response to odorous stimulation. 2. Maximal amplitude of response appears to be directly correlated to stimulus concentration but, after achieving a maximum value, is independent of stimulation duration. 3. Rise time and fall time constants have been quantified for describing kinetics of response. The rise time constant decreases, but the fall time constant increases when increasing concentrations of odorant are supplied. 4. Variation among individuals for these EAG parameters is small enough to uncover even partial defects affecting the first sensory step. This fact combined with the possibility of obtaining mutants with defects in any intermediate process producing the electrical response makes the EAG of Drosophila a very useful tool for dissecting the components of the capture and transduction processes in the olfactory sense. 5. This kind of quantitative study of the EAG has been used in a new Drosophila mutant, od A, for localizing peripheral expression of the mutation. od A has been isolated as a behavioral mutant with an abnormally enhanced olfactory response to ethyl acetate. 6. The mutant's EAG in response to this odorant displays a normal amplitude but abnormal kinetics. Rise time as well as fall time show slower kinetics than normal, suggesting some defective step in the capture and transduction process.

Paired-pulse facilitation in the dentate gyrus: a patch-clamp study in rat hippocampus in vitro

1994 ◽  
Vol 72 (1) ◽  
pp. 326-336 ◽  
Author(s):  
M. Andreasen ◽  
J. J. Hablitz
Keyword(s):  
Patch Clamp ◽  
Dentate Gyrus ◽  
Time Constant ◽  
Rise Time ◽  
Time Course ◽  
Nmda Antagonist ◽  
Paired Pulse ◽  
Stimulation Intensity ◽  
Paired Pulse Facilitation ◽  
Epsc Amplitude

1. Whole-cell patch-clamp recordings were used to study paired-pulse facilitation (PPF) of the lateral perforant path input to the dentate gyrus in thin hippocampal slices. 2. Orthodromic stimulation of the lateral perforant pathway evoked a excitatory postsynaptic current (EPSC) with a latency of 3.3 +/- 0.1 ms (mean +/- SE) that fluctuated in amplitude. The EPSC had a rise time (10-90%) of 2.79 +/- 0.06 ms (n = 35) and decayed with a single exponential time course with a time-constant of 9.14 +/- 0.24 ms (n = 35). No correlation was found between the amplitude of the EPSC and the rise time or decay time-constant. The non-N-methyl-D-aspartate (NMDA) antagonist 6-cyano-7-nitroquinoxaline-2,3-dione completely blocked the EPSC whereas the NMDA antagonist D-aminophosphonovaleric acid (APV) had modest effects. 3. When a test (T-)EPSC was preceded at an interval of 100 ms by a conditioning (C-)EPSC, a significant increase in the amplitude of the T-EPSC was seen in 38 out of 44 trials analyzed from a total of 27 granule cells. The average amount of PPF was 35.7 +/- 2.1%. There was no apparent correlation between the amount of PPF and the stimulation intensity or mean amplitude of the C-EPSC. The time course of the facilitated T-EPSC was not significantly different from that of the C-EPSC. 4. No correlation was found between the amplitude of the C-EPSC and that of the T-EPSC. Estimates of quantal content (mcv) were determined by calculating the ratio of the squared averaged EPSC amplitude (from 48 responses) to the variance of these responses (M2/sigma 2) whereas quantal amplitudes (qcv) were estimated by calculating the ratio of the response variance to average EPSC amplitude (sigma 2/M). PPF was found to be associated with an average increase in mcv of 64.8 +/- 7.2% (n = 38) whereas qcv was decreased by 12.1 +/- 3.8%. 5. The time course of PPF was studied by varying the interval between the C- and T-pulse from 10 to 400 ms while keeping the stimulation intensity constant. Maximal facilitation of the T-EPSC was obtained with interpulse intervals < or = 25 ms where the average facilitation amounted to approximately 70% (n = 6). The decline of facilitation was nearly exponential and was no longer evident with intervals > 350 ms.(ABSTRACT TRUNCATED AT 400 WORDS

Voltage Dependence of the Glycine Receptor–Channel Kinetics in the Zebrafish Hindbrain

1999 ◽  
Vol 82 (5) ◽  
pp. 2120-2129 ◽  
Author(s):  
Pascal Legendre
Keyword(s):  
Time Constant ◽  
Rise Time ◽  
Time Course ◽  
Voltage Dependence ◽  
Good Description ◽  
Glycine Receptor ◽  
Relative Amplitude ◽  
Time Constants ◽  
Low Concentration ◽  
Voltage Dependent

Electrophysiological recordings of outside-out patches to fast-flow applications of glycine were made on patches derived from the Mauthner cells of the 50-h-old zebrafish larva. As for glycinergic miniature inhibitory postsynaptic currents (mIPSCs), depolarizing the patch produced a broadening of the transient outside-out current evoked by short applications (1 ms) of a saturating concentration of glycine (3 mM). When the outside-out patch was depolarized from −50 to +20 mV, the peak current varied linearly with voltage. A 1-ms application of 3 mM glycine evoked currents that activated rapidly and deactivated biexponentially with time constants of ≈5 and ≈30 ms (holding potential of −50 mV). These two decay time constants were increased by depolarization. The fast deactivation time constant increased e-fold per 95 mV. The relative amplitude of the two decay components did not significantly vary with voltage. The fast component represented 64.2 ± 2.8% of the total current at −50 mV and 54.1 ± 10% at +20 mV. The 20–80% rise time of these responses did not show any voltage dependence, suggesting that the opening rate constant is insensitive to voltage. The 20–80% rise time was 0.2 ms at −70 mV and 0.22 ms at +20 mV. Responses evoked by 100–200 ms application of a low concentration of glycine (0.1 mM) had a biphasic rising phase reflecting the complex gating behavior of the glycine receptor. The time constant of these two components and their relative amplitude did not change with voltage, suggesting that modal shifts in the glycine-activated channel gating mode are not sensitive to the membrane potential. Using a Markov model to simulate glycine receptor gating behavior, we were able to mimic the voltage-dependent change in the deactivation time course of the responses evoked by 1-ms application of 3 mM glycine. This kinetics model incorporates voltage-dependent closing rate constants. It provides a good description of the time course of the onset of responses evoked by the application of a low concentration of glycine at all membrane potentials tested.

scholarly journals Delays in inactivation development and activation kinetics in myxicola giant axons.

1982 ◽  
Vol 80 (1) ◽  
pp. 83-102 ◽  
Author(s):  
L Goldman ◽  
J L Kenyon
Keyword(s):  
Time Constant ◽  
Time Course ◽  
Series Resistance ◽  
Activation Kinetics ◽  
Time To Peak ◽  
Exponential Decline ◽  
Na Inactivation ◽  
The Difference ◽  
True Property ◽  
Kinetics Of

Na inactivation was studied in Myxicola (two-pulse procedure, 6-ms gap between conditioning and test pulses). Inactivation developed with an initial delay (range 130-817 microseconds) followed by a simple exponential decline (time constant tau c). Delays (deviations from a simple exponential) are seen only for brief conditioning pulses were gNa is slightly activated. Hodgkin-Huxley kinetics with series resistance, Rs, predict deviations from a simple exponential only for conditioning pulses that substantially activate gNa. Reducing INa fivefold (Tris substitution) had no effect on either tau c or delay. Delay in not generated by Rs or by contamination from activation development. The slowest time constant in Na tails is approximately 1 ms (Goldman and Hahin, 1978) and the gap was 6 ms. Shortening the gap to 2 ms had no effect on either tau c or delay. Delay is a true property of the channel. Delay decreased with more positive conditioning potentials, and also decreased approximately proportionally with time to peak gNa during the conditioning pulse, as expected for sequentially coupled activation and inactivation. In a few cases the difference between Na current values for brief conditioning pulses and the tau c exponential could be measured. Difference values decayed exponentially with time constant tau m. The inactivation time course is described by a model that assumes a process with the kinetics of gNa activation as a precursor to inactivation.

scholarly journals Kinetics of oxygen consumption after a single flash of light in photoreceptors of the drone (Apis mellifera).

1982 ◽  
Vol 80 (1) ◽  
pp. 19-55 ◽  
Author(s):  
M Tsacopoulos ◽  
S Poitry
Keyword(s):  
Oxygen Consumption ◽  
Time Constant ◽  
Time Course ◽  
Sodium Pump ◽  
Fourier Transforms ◽  
Recovery Phase ◽  
Peak Amplitude ◽  
Single Flash ◽  
High Concentrations ◽  
Kinetics Of

The time course of the rate of oxygen consumption (QO2) after a single flash of light has been measured in 300-micrometers slices of drone retina at 22 degrees C. To measure delta QO2(t), the change in QO2 from its level in darkness, the transients of the partial pressure of O2 (PO2) were recorded with O2 microelectrodes simultaneously in two sites in the slice and delta QO2 was calculated by a computer using Fourier transforms. After a 40-ms flash of intense light, delta QO2, reached a peak of 40 microliters O2/g.min and then declined exponentially to the baseline with a time constant tau 1 = 4.96 +/- 0.49 s (SD, n = 10). The rising phase was characterized by a time constant tau 2 = 1.90 +/- 0.35 s (SD, n = 10). The peak amplitude of delta QO2 increased linearly with the log of the light intensity. Replacement of Na+ by choline, known to decrease greatly the light-induced transmembrane current, caused a 63% decrease of delta QO2. With these changes, however, the kinetics of delta QO2 (t) were unchanged. This suggest that the recovery phase is rate-limited by a single reaction with apparent first-order kinetics. Evidence is provided that suggests that this reaction may be the working of the sodium pump. Exposure of the retina to high concentrations of ouabain or strophanthidin (inhibitors of the sodium pump) reduced the peak amplitude of delta QO2 by approximately 80% and increased tau 1. The increase of tau 1 was an exponential function of the time of exposure to the cardioactive steroids. Hence, it seems likely that the greatest part of delta QO2 is used for the working of the pump, whose activity is the mechanism underlying the rate constant of the descending limb of delta QO2 (t).

scholarly journals Kinetics of intramembrane charge movement and sodium current in frog node of Ranvier.

1982 ◽  
Vol 79 (4) ◽  
pp. 571-602 ◽  
Author(s):  
J M Dubois ◽  
M F Schneider
Keyword(s):  
Time Constant ◽  
Time Course ◽  
Sodium Current ◽  
Node Of Ranvier ◽  
Charge Movement ◽  
Intramembrane Charge Movement ◽  
Time Courses ◽  
Charge Movements ◽  
Kinetics Of ◽  
Microsecond Pulse

Intramembrane charge movement (Q) and sodium current (INa) were monitored in isolated voltage-clamped frog nodes of Ranvier, ON charge movements (QON) for pulses from the holding potential (-100 mV) to potentials V less than or equal to 0 mV followed single exponential time courses, whereas two exponentials were found for pulses to V greater than or equal to 20 mV. The voltage dependence of both QON and its time constant tauON indicated that the two ON components resolved at V greater than or equal to 20 mV were also present, though not resolvable, for pulses to V less than or equal to 0 mV. OFF charge movements (QOFF) monitored at various potentials were well described by single exponentials. When QOFF was monitored at -30 or -40 mV after a 200-microsecond pulse to +20 mV and QON was monitored at the same potential using pulses directly from -100 mV, tauON/tauOFF = 2.5 +/- 0.3. At a set OFF potential (-90 to -70 mV), tauOFF first increased with increasing duration tON of the preceding pulse to a given potential (0 to +30 mV) and then decreased with further increases in tON. The declining phase of tauOFF followed a time course similar to that of the decline in QOFF with tON. For the same pulse protocol, the OFF time constant tauNa for INA also first increased with tON but then remained constant over the tON interval during which tauOFF and QOFF were declining. After 200- or 300-microsecond pulses to +20, +20, or +50 mV, tauOFF/tauNa at -70 to -90 mV was 1.2 +/- 0.1. Similar tauOFF/tauNa ratios were predicted by channel models having three identical charged gating particles that can rapidly and reversibly form an immobile dimer or trimer after independently crossing the membrane from their OFF to their ON locations.

Use of Knockout Mice Reveals Involvement of M2-Muscarinic Receptors in Control of the Kinetics of Acetylcholine Release

2003 ◽  
Vol 89 (4) ◽  
pp. 1954-1967 ◽  
Author(s):  
I. Slutsky ◽  
J. Wess ◽  
J. Gomeza ◽  
J. Dudel ◽  
I. Parnas ◽  
...  
Keyword(s):  
Muscarinic Receptors ◽  
Knockout Mice ◽  
Rise Time ◽  
Time Course ◽  
Acetylcholine Release ◽  
Frog Neuromuscular Junction ◽  
Quantal Content ◽  
Experimental Treatments ◽  
Kinetics Of ◽  
M2 Muscarinic Receptors

We have previously suggested that presynaptic M2-muscarinic receptors (M2R) are involved in the control of the time course of evoked acetylcholine release in the frog neuromuscular junction. The availability of knockout mice lacking functional M2R (M2-KO) enabled us to address this issue in a more direct way. Using the phrenic diaphragm preparation, we show that in wild-type (WT) mice experimental manipulations known to affect Ca2+ entry and removal, greatly affected the amount of acetylcholine released (quantal content). However, the time course of release remained unaltered under all these experimental treatments. On the other hand, in the M2-KO mice, similar experimental treatments affected both the quantal content and the time course of release. In general, a larger quantal content was accompanied by a longer duration of release. Similarly, the rise time of the postsynaptic current produced by axon stimulation was sensitive to changes in [Ca2+]o or [Mg2+]o in M2-KO mice but not in WT mice. Measurements of Ca2+ currents revealed that the shorter rise time of the postsynaptic current seen in high [Mg2+]o in M2-KO mice was not produced by a shorter wave of the presynaptic Ca2+ current. These results support our earlier findings and provide direct evidence for the major role that presynaptic M2-muscarinic receptors play in the control of the time course of evoked acetylcholine release under physiological conditions.

scholarly journals Development and Characterization of a Gene Expression Reporter System for Clostridium acetobutylicumATCC 824

1999 ◽  
Vol 65 (9) ◽  
pp. 3793-3799 ◽  
Author(s):  
Seshu B. Tummala ◽  
Neil E. Welker ◽  
Eleftherios T. Papoutsakis
Keyword(s):  
Gene Expression ◽  
Reporter Gene ◽  
Time Course ◽  
Specific Activity ◽  
Reporter System ◽  
Inhibit Protein Synthesis ◽  
Acetoacetate Decarboxylase ◽  
The Stability ◽  
Kinetics Of

ABSTRACT A gene expression reporter system (pHT3) for Clostridium acetobutylicum ATCC 824 was developed by using thelacZ gene from Thermoanaerobacterium thermosulfurogenes EM1 as the reporter gene. In order to test the reporter system, promoters of three key metabolic pathway genes,ptb (coding for phosphotransbutyrylase), thl(coding for thiolase), and adc (coding for acetoacetate decarboxylase), were cloned upstream of the reporter gene in pHT3 in order to construct vectors pHT4, pHT5, and pHTA, respectively. Detection of β-galactosidase activity in time course studies performed with strains ATCC 824(pHT4), ATCC 824(pHT5), and ATCC 824(pHTA) demonstrated that the reporter gene produced a functional β-galactosidase in C. acetobutylicum. In addition, time course studies revealed differences in the β-galactosidase specific activity profiles of strains ATCC 824(pHT4), ATCC 824(pHT5), and ATCC 824(pHTA), suggesting that the reporter system developed in this study is able to effectively distinguish between different promoters. The stability of the β-galactosidase produced by the reporter gene was also examined with strains ATCC 824(pHT4) and ATCC 824(pHT5) by using chloramphenicol treatment to inhibit protein synthesis. The data indicated that the β-galactosidase produced by the lacZgene from T. thermosulfurogenes EM1 was stable in the exponential phase of growth. In pH-controlled fermentations of ATCC 824(pHT4), the kinetics of β-galactosidase formation from theptb promoter and phosphotransbutyrylase formation from its own autologous promoter were found to be similar.

Kinetics of activation of the potassium conductance in the squid giant axon

1988 ◽  
Vol 232 (1269) ◽  
pp. 375-394 ◽  
Keyword(s):  
Time Constant ◽  
Potassium Current ◽  
Time Course ◽  
Potassium Conductance ◽  
Giant Axon ◽  
Squid Giant Axon ◽  
A Value ◽  
Initial Rise ◽  
Principal Effect ◽  
Kinetics Of

A quantitative re-investigation of the time course of the initial rise of the potassium current in voltage-clamped squid giant axons is described. The n 4 law of the Hodgkin–Huxley equations was found to be well obeyed only for the smallest test pulses, and for larger ones a good fit of the inflected rise required use of the expression (1 – exp {– t / ז n 1 }) X –1 (1 – exp { – t / ז n 2 }), where both of the time constants and the power X varied with the size of the test pulse. Application of a negative prepulse produced a delay in the rise resulting mainly from an increase of X from a value of about 3 at –70 mV to 8 at –250 mV, while ז n 1 remained constant and ז n 2 was nearly doubled. The process responsible for generating this delay was switched on with a time constant of 8 ms at 4°C, which fell to about 1 ms at 15°C. Analysis of the inward tail currents at the end of a voltage-clamp pulse showed that there was a substantial external accumulation of potassium owing to the restriction of its diffusion out of the Schwann cell space, which, when duly allowed for, roughly doubled the calculated value of the potassium conductance. Computations suggested that the principal effect of such a build-up of [K] o would be to reduce the fitted values of ז n 1 and ז n 2 to two-thirds or even half their true sizes, while the power X would generally be little changed; but it would not affect the necessity to introduce a second time constant, nor would it invalidate our findings on the effect of negative prepulses.

scholarly journals Kinetics of Turn-offs of Frog Rod Phototransduction Cascade

2008 ◽  
Vol 132 (5) ◽  
pp. 587-604 ◽  
Author(s):  
Luba A. Astakhova ◽  
Michael L. Firsov ◽  
Victor I. Govardovskii
Keyword(s):  
Time Constant ◽  
Dark Current ◽  
Main Part ◽  
Time Course ◽  
Light Adaptation ◽  
Key Factors ◽  
Time Courses ◽  
Kinetics Of ◽  
Phototransduction Cascade ◽  
Effect Of Light

The time course of the light-induced activity of phototrandsuction effector enzyme cGMP-phosphodiesterase (PDE) is shaped by kinetics of rhodopsin and transducin shut-offs. The two processes are among the key factors that set the speed and sensitivity of the photoresponse and whose regulation contributes to light adaptation. The aim of this study was to determine time courses of flash-induced PDE activity in frog rods that were dark adapted or subjected to nonsaturating steady background illumination. PDE activity was computed from the responses recorded from solitary rods with the suction pipette technique in Ca2+-clamping solution. A flash applied in the dark-adapted state elicits a wave of PDE activity whose rising and decaying phases have characteristic times near 0.5 and 2 seconds, respectively. Nonsaturating steady background shortens both phases roughly to the same extent. The acceleration may exceed fivefold at the backgrounds that suppress ≈70% of the dark current. The time constant of the process that controls the recovery from super-saturating flashes (so-called dominant time constant) is adaptation independent and, hence, cannot be attributed to either of the processes that shape the main part of the PDE wave. We hypothesize that the dominant time constant in frog rods characterizes arrestin binding to rhodopsin partially inactivated by phosphorylation. A mathematical model of the cascade that considers two-stage rhodopsin quenching and transducin inactivation can mimic experimental PDE activity quite well. The effect of light adaptation on the PDE kinetics can be reproduced in the model by concomitant acceleration on both rhodopsin phosphorylation and transducin turn-off, but not by accelerated arrestin binding. This suggests that not only rhodopsin but also transducin shut-off is under adaptation control.

Monte Carlo simulation of fast excitatory synaptic transmission at a hippocampal synapse

1996 ◽  
Vol 75 (2) ◽  
pp. 597-608 ◽  
Author(s):  
L. M. Wahl ◽  
C. Pouzat ◽  
K. J. Stratford
Keyword(s):  
Diffusion Coefficient ◽  
Synaptic Transmission ◽  
Time Constant ◽  
Rise Time ◽  
Room Temperature ◽  
Time Course ◽  
Synaptic Cleft ◽  
Open Probability ◽  
Peak Response ◽  
Postsynaptic Receptors

1. A simulation of fast excitatory synaptic transmission at a hippocampal synapse is presented. Individual neurotransmitter molecules are followed as they diffuse through the synaptic cleft and interact with the postsynaptic receptors. The ability of the model to reproduce published results of patch-clamp experiments on CA3 pyramidal cells is illustrated; parameters of the model that affect the time course and variability of the excitatory postsynaptic current (EPSC) are then investigated. 2. To simulate an EPSC, we release 4,000 neurotransmitter molecules simultaneously from a point source centered 15 nm above a rectangular grid of 14 x 14 postsynaptic receptors. The simulated EPSC at room temperature has a 10-90% rise time of 0.28 ms and a peak open probability of 0.27, and decays with a time constant of 2.33 ms, comparing well with values in the literature. 3. To simulate changes in temperature, we use a 10 degrees temperature coefficient (Q10) for diffusion of 1.3 and apply a Q10 of 3.0 to all the rate constants of the kinetic scheme. At 37 degrees C, the 10-90 rise time is 0.07 ms, the peak open probability is 0.56, and the decay time constant is 0.70 ms. The coefficient of variation (CV) at the peak of the EPSC is 9.4% at room temperature; at 37 degrees C, the CV at the peak drops to 6.6%. 4. We use the diffusion coefficient of glutamine, 7.6 x 10(-6) cm2/s, to model the random movement of glutamate molecules in the synaptic cleft. Slower rates of diffusion increase the peak response and slow the time course of decay of the EPSC. 5. Random variations in release site position have little effect on the time course of the average EPSC or on the CV of the peak response. We simulate a dose-response curve for the effects of releasing between 100 and 7,500 neurotransmitter molecules per vesicle. The half-maximal response occurs for 1,740 molecules. For a simulation with 100 postsynaptic receptors and a diffusion coefficient of 2.0 x 10(-6) cm2/s, 4,000 molecules approaches a saturating dose. 6. Changes to the width of the synaptic cleft, or to the number and spacing of the postsynaptic receptors, have marked effects on the peak height of the simulated EPSC. 7. We extend the model to include a spherical vesicle (50 nm diam) connected to the synaptic cleft by a cylindrical pore 15 nm long. Neurotransmitter molecules are randomly distributed within the vesicle and allowed to diffuse into the synaptic cleft through the pore, which opens to its full diameter in one time step. We find that the pore must open to a diameter of > or = 7 nm within 1 microsecond in order to match the time courses of EPSCs in the literature.

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