scholarly journals Electrophysiological Properties of Crayfish Retinal Photoreceptors

1990 ◽  
Vol 150 (1) ◽  
pp. 111-122
Author(s):  
ARTURO PICONES ◽  
HUGO ARÉCHIGA
Keyword(s):  
Time Course ◽  
Membrane Conductance ◽  
Light Response ◽  
Receptor Potential ◽  
Input Resistance ◽  
Resting Potential ◽  
Electrophysiological Properties ◽  
A Value ◽  
Retinal Photoreceptors ◽  
Conductance Increase

Electrical properties of crayfish retinular photoreceptors were studied in the dark-adapted state and during responses to light. In fully dark-adapted photoreceptors, the resting potential was −49.8±3.3mV and input resistance was 31.3±5.4MΩ (mean±S.E.). The current—voltage relationship showed rectification near the resting potential, with decreased resistance within the depolarizing range. A value of 29.8±5.0kΩcm2 was calculated for specific resistance, and 3.0±0.4μFcm−2 for specific capacitance. Electrotonic analysis showed that the photoreceptor was isopotential. During the light response, membrane conductance increased depending on the stimulus intensity. This relationship was steeper for the conductance change during the initial transient of the receptor potential than during the plateau. A depolarizing afterpotential usually ensued at the end of the light response, concurrent with a residual increased conductance. The time course of the conductance increase during the receptor potential showed two kinetic components, suggesting that at least two distinct membrane processes were involved in its generation.

scholarly journals Shunting Inhibition Does Not Have a Divisive Effect on Firing Rates

1997 ◽  
Vol 9 (5) ◽  
pp. 1001-1013 ◽  
Author(s):  
Gary R. Holt ◽  
Christof Koch
Keyword(s):  
Firing Rate ◽  
Reversal Potential ◽  
Membrane Conductance ◽  
Resting Potential ◽  
Excitatory Postsynaptic Potential ◽  
Firing Rates ◽  
Shunting Inhibition ◽  
A Value ◽  
Inhibitory Conductance ◽  
Conductance Increase

Shunting inhibition, a conductance increase with a reversal potential close to the resting potential of the cell, has been shown to have a divisive effect on subthreshold excitatory postsynaptic potential amplitudes. It has therefore been assumed to have the same divisive effect on firing rates. We show that shunting inhibition actually has a subtractive effecton the firing rate in most circumstances. Averaged over several interspike intervals, the spiking mechanism effectively clamps the somatic membrane potential to a value significantly above the resting potential, so that the current through the shunting conductance is approximately independent of the firing rate. This leads to a subtractive rather than a divisive effect. In addition, at distal synapses, shunting inhibition will also have an approximately subtractive effect if the excitatory conductance is not small compared to the inhibitory conductance. Therefore regulating a cell's passive membrane conductance—for instance, via massive feedback—is not an adequate mechanism for normalizing or scaling its output.

scholarly journals Hyperpolarization of a Barnacle Photoreceptor Membrane following Illumination

1971 ◽  
Vol 57 (6) ◽  
pp. 723-737 ◽  
Author(s):  
H. Koike ◽  
H. Mack Brown ◽  
S. Hagiwara
Keyword(s):  
Membrane Potential ◽  
Time Course ◽  
Membrane Conductance ◽  
Resting Potential ◽  
Photoreceptor Membrane ◽  
Electrogenic Na Pump ◽  
Lateral Ocellus ◽  
Na Ions ◽  
Conductance Increase ◽  
Balanus Eburneus

Membrane potential changes following illumination of a photoreceptor cell in the lateral ocellus of a barnacle (Balanus eburneus) were studied by means of intracellular recording and polarization techniques. Illumination produces a depolarizing response. When the illumination is terminated, the membrane potential temporarily becomes more negative than the resting potential prior to illumination. Although the amplitude of this postillumination hyperpolarization depends upon the intensity as well as the duration of the light pulse, the time course is fairly constant. The hyperpolarization is not associated with any significant membrane conductance increase and is abolished by 10-5 M ouabain. It diminishes when the external Na or K ions are removed. An intracellular injection of Na ions produces a hyperpolarization similar to that following illumination. It is suggested that the postillumination hyperpolarization is produced by an electrogenic Na pump which is activated by the Na influx during illumination.

Modulation of crayfish retinal sensitivity by 5-hydroxytryptamine

1990 ◽  
Vol 150 (1) ◽  
pp. 123-143 ◽  
Author(s):  
H. Arechiga ◽  
E. Banuelos ◽  
E. Frixione ◽  
A. Picones ◽  
L. Rodriguez-Sosa
Keyword(s):  
Membrane Conductance ◽  
Receptor Potential ◽  
Retinal Sensitivity ◽  
Circadian Cycle ◽  
Dual Effect ◽  
Pigment Granules ◽  
Retinal Photoreceptors ◽  
Low Levels ◽  
Conductance Increase ◽  
Dose Dependent

The responsiveness of crayfish retinal photoreceptors to light was enhanced by exposure to 5-hydroxytryptamine (5-HT), either following injection into whole animals or following topical application to isolated eyestalks or retinas. The effect was measured as an increment in the amplitude of the receptor potential, and was dose-dependent in the range 10(−6)-10(−3) mol l-1 (injected as a 0.1 microliter dose in intact animals). It was more pronounced at low levels of illumination and was reversibly blocked by methysergide. The enhancement was a consequence of a dual effect: (a) retraction of the proximal pigment granules within the photoreceptors, with a corresponding increase in the light-admittance function of the retina; and (b) a direct effect, facilitating a membrane conductance increase which mediated the generation of the receptor potential. A set of axons in the lamina ganglionaris with a 5-HT-like immunoreactivity was found in the vicinity of the photoreceptor axons. 5-HT antagonists were capable of blocking the physiological retraction of pigment granules in photoreceptors at night, suggesting that 5-HT acts as a modulator during the nocturnal phase of the circadian cycle in the crayfish retina.

Is cyclic guanosine monophosphate the internal 'second messenger' for cholinergic actions on central neurons?

1976 ◽  
Vol 54 (2) ◽  
pp. 172-176 ◽  
Author(s):  
K. Krnjević ◽  
E. Puil ◽  
R. Werman
Keyword(s):  
Time Course ◽  
Membrane Conductance ◽  
Cyclic Guanosine Monophosphate ◽  
Guanosine Monophosphate ◽  
Resting Potential ◽  
Electrical Excitability ◽  
Spinal Motoneurons ◽  
Central Neurons ◽  
Intracellular Cgmp ◽  
Post Synaptic Potential

The most consistent effects produced by intracellular injections of guanosine 3′,5′-cyclic monophosphate (cGMP) (but not 5′-guanosine 5′-monophosphate in spinal motoneurons of cats are a rise in membrane conductance, acceleration in time course of spike potentials, and accentuation of the post-spike hyperpolarization. Associated changes in resting potential are smaller, less constant, and more often in the depolarizing than hyperpolarizing direction. cGMP tends to increase electrical excitability but reduces excitatory post-synaptic potential amplitudes. Most of the effects of intracellular cGMP are quite different from, or indeed opposite to, those of either extra- or intracellular applications of acetylcholine and therefore not consistent with the proposal that cGMP is the internal mediator of muscarinic actions.

Posttetanic hyperpolarization produced by electrogenic Na(+)-K+ pump in lizard axons impaled near their motor terminals

1993 ◽  
Vol 70 (5) ◽  
pp. 1874-1884 ◽  
Author(s):  
K. Morita ◽  
G. David ◽  
J. N. Barrett ◽  
E. F. Barrett
Keyword(s):  
Action Potential ◽  
Action Potentials ◽  
Time Course ◽  
Input Resistance ◽  
Peak Amplitude ◽  
Resting Potential ◽  
Tetanic Stimulation ◽  
Train Duration ◽  
Consistent Change ◽  
Nodal Voltage

1. The hyperpolarization that follows tetanic stimulation was recorded intra-axonally from the internodal region of intramuscular myelinated motor axons. 2. The peak amplitude of the posttetanic hyperpolarization (PTH) that followed stimulation at 20-100 Hz for < or = 35 s increased with increasing train duration, reaching a maximum of 22 mV. PTH decayed over a time course that increased from tens to hundreds of seconds with increasing train duration. For a given frequency of stimulation the time integral of PTH was proportional to the number of stimuli in the train, averaging 3-4 mV.s per action potential. 3. Ouabain (0.1-1 mM) and cyanide (1 mM) depolarized the resting potential and abolished PTH. Tetanic stimulation in ouabain was followed by a slowly decaying depolarization (probably due to extra-axonal K+ accumulation) whose magnitude and duration increased as the duration of the train increased. 4. Axonal input resistance showed no consistent change during PTH in normal solution but increased during PTH in the presence of 3 mM Cs+ (which blocks axonal inward rectifier currents). 5. PTH was abolished when bath Na+ was replaced by Li+ or choline. PTH persisted after removal of bath Ca2+ and addition of 2 mM Mn2+. 6. Removal of bath K+ abolished the PTH recorded after brief stimulus trains and greatly reduced the duration of PTH recorded after longer stimulus trains. 7. A brief application of 10 mM K+, which normally depolarizes axons, produced a ouabain-sensitive hyperpolarization in axons bathed in K(+)-free solution. 8. These observations suggest that in these myelinated axons PTH is produced mainly by activation of an electrogenic Na(+)-K(+)-ATPase, rather than by changes in K+ permeability or transmembrane [K+] gradients. This conclusion is supported by calculations showing agreement between estimates of Na+ efflux/impulse based on PTH measurements and estimates of Na+ influx/impulse based on nodal voltage-clamp measurements. Pump activity also appears to contribute to the resting potential. 9. The stimulus intensity required to initiate a propagating action potential increased during PTH but decreased during the posttetanic depolarization recorded in ouabain. Thus changes in axonal excitability after tetanic stimulation correlate with changes in the posttetanic membrane potential. 10. Action potentials that propagated during PTH had a larger peak amplitude and were followed by a larger and longer depolarizing afterpotential than action potentials elicited at the resting potential. This enhancement of the depolarizing afterpotential is consistent with previous reports of an increased superexcitable period after action potentials evoked during PTH.

Electrical properties of oxytocin neurons in organotypic cultures from postnatal rat hypothalamus

1996 ◽  
Vol 76 (4) ◽  
pp. 2772-2785 ◽  
Author(s):  
P. Jourdain ◽  
D. A. Poulain ◽  
D. T. Theodosis ◽  
J. M. Israel
Keyword(s):  
Electrical Properties ◽  
Action Potential ◽  
Glutamate Receptors ◽  
Action Potentials ◽  
Firing Pattern ◽  
Membrane Conductance ◽  
Input Resistance ◽  
Resting Potential ◽  
Organotypic Cultures ◽  
Current Pulses

1. Intracellular recordings were performed on immunocytochemically identified oxytocin (OT) neurons (n = 101) maintained for 2-7 wk in hypothalamic organotypic cultures derived from 4-to 6-day-old rat neonates. The neurons displayed a resting potential of -58.9 +/- 6.8 mV (mean +/- SD, n = 74), an input resistance of 114 +/- 26.8 M omega (n = 66), and a time constant of 9.6 +/- 1.4 ms (n = 57). Voltage-current (V-I) relations, linear at resting potential, showed a pronounced outward rectification when depolarized from hyperpolarized membrane potentials. At these hyperpolarized potentials, depolarizing current pulses induced a delayed action potential. 2. Action potentials had an amplitude of 73.4 +/- 9.7 mV and a duration of 1.9 +/- 0.2 ms. Each action potential was followed by an afterhyperpolarization of 7.9 +/- 2.0 mV in amplitude lasting 61.7 +/- 11.3 ms. The depolarizing phase of action potentials was both Na+ and Ca2+ dependent, whereas repolarization was due to a K+ conductance increase. 3. When Ba2+ was substituted for Ca2+ in the medium, OT neurons displayed prolonged sustained depolarizations. In the presence of tetrodotoxin (TTX), these depolarizations were triggered by depolarizing current pulses and arrested by hyperpolarizing current pulses or by local application of Ca2+, Co2+, Cd2+, No sustained depolarization was obtained when nifedipine was added to the medium. These data suggest that OT cells in organotypic culture possess L-type Ca2+ channels. 4. All OT neurons generated spontaneous action potentials at resting potential. Of 59 neurons, 29 showed a slow, irregular firing pattern (< or = 2.5 spikes/s), 24 generated a fast continuous firing pattern (> or = 2.5 spikes/s), and 6 cells displayed a bursting pattern of activity consisting of alternating periods of spike discharge and quiescence. None of the bursting cells exhibited regenerative endogenous potentials (plateau potentials). On the contrary, in four of these cells, the bursting activity was clearly due to patterned synaptic activity. 5. The cultured OT cells responded to exogenous gamma-aminobutyric acid (GABA) and muscimol with a hyperpolarization and an increase in membrane conductance. These effects still were observed in the presence of TTX, indicating that they were due to direct activation of GABA receptors in the cells. The GABA-induced response was mediated by GABAA receptors because it was blocked by bicuculline, but not by GABAB receptors, because baclofen and hydroxysaclofen had no effect on membrane potential and input resistance. 6. OT neurons responded to exogenous glutamate, quisqualate, and kainate with a depolarization concomitant with an increase in membrane conductance. N-methyl-D-aspartate depolarized the cells in Mg(2+)-free medium. These effects were observed in the presence of TTX, suggesting that OT cells expressed ionotropic glutamate receptors. Trans-(1S,3R)-1-amino-1,3-cyclopentane-dicarboxylic acid and (+/-)-alpha-amino-4-carboxymethylphenylglycine had no effect on OT cells, thus excluding the presence of metabotropic glutamate receptors. 7. Taken together, our observations demonstrate that hypothalamic slice cultures from 4- to 6-day-old rat neonates contain well-differentiated OT neurons that display electrical properties similar to those shown by adult neurons in vitro. Such cultures provide a reliable model to investigate membrane properties of adult OT neurons and a useful means to study the long-term modulation of their electrical behaviour by various agents known to affect OT cells in vivo.

scholarly journals Conductance Change Associated with Receptor Potentials of Gustatory Cells in Rat

1971 ◽  
Vol 58 (6) ◽  
pp. 688-699 ◽  
Author(s):  
Masahiro Ozeki
Keyword(s):  
Membrane Conductance ◽  
Receptor Potential ◽  
Cell Types ◽  
Taste Bud ◽  
Resting Potential ◽  
Gustatory Cell ◽  
Long Duration ◽  
Intracellular Microelectrodes ◽  
Chemical Stimuli ◽  
Potential Level

The electrical properties of gustatory cells and cells which do not respond to chemical stimuli in the taste bud of fungiform papillae in rats were studied by means of intracellular microelectrodes. Neither of these cell types showed spike electrogenesis. Gustatory cells showed a depolarization, the receptor potential, associated with an increase in the membrane conductance in response to NaCl, sucrose, and HCl, whereas quinine produced a decrease in the conductance together with an increase in the receptor potential magnitude. The reversal point of the receptor potential in response to NaCl or KCl was close to zero membrane potential, but in the case of quinine it was at a more negative potential level than the resting potential. From these results two receptive processes are postulated in the gustatory cell membrane. When the gustatory cells were stimulated for a long duration by concentrated NaCl or sucrose, receptor potentials showed adaptation with decrease in magnitude, but adaptation of the responses to HCl and quinine were hardly detected. Adaptation of the receptor potential was not correlated with conductance change.

scholarly journals Light Response of a Giant Aplysia Neuron

1973 ◽  
Vol 62 (3) ◽  
pp. 239-254 ◽  
Author(s):  
Arthur M. Brown ◽  
H. Mack Brown
Keyword(s):  
Reversal Potential ◽  
Outward Current ◽  
Membrane Conductance ◽  
Light Response ◽  
Resting Potential ◽  
Neuronal Membrane ◽  
Giant Neuron ◽  
Membrane Hyperpolarization ◽  
Pressure Injection ◽  
External K

Illumination of an Aplysia giant neuron evokes a membrane hyperpolarization which is associated with a membrane conductance increase of 15%. The light response is best elicited at 490 nM: the neuron also has an absorption peak at this wavelength. At the resting potential (-50 to -60 mV) illumination evokes an outward current in a voltage-clamped cell. This current reverses sign very close to EK calculated from direct measurements of internal and external K+ activity. Increases in external K+ concentration shift the reversal potential of the light-evoked response by the same amount as the change in EK. Decreases in external Na+ or Cl- do not affect the response. Therefore, the response is attributed to an increase in K+ conductance. Pressure injection of Ca2+ into this neuron also hyperpolarizes the cell membrane. This effect is also due largely to an increase in K+ conductance. The light response after Ca2+ injection does not appear to be altered. Pressure injection of EGTA abolished or greatly reduced the light response. The effect was reversible. We suggest that light acts upon a single pigment in this neuron, releasing Ca2+ which in turn increases K+ conductance, thereby hyperpolarizing the neuronal membrane.

Electrophysiological response to thyrotropin-releasing hormone of rat lactotrophs in primary culture

1990 ◽  
Vol 258 (2) ◽  
pp. E311-E319 ◽  
Author(s):  
P. Sartor ◽  
L. Dufy-Barbe ◽  
J. B. Corcuff ◽  
A. Taupignon ◽  
B. Dufy
Keyword(s):  
Primary Culture ◽  
Input Resistance ◽  
Thyrotropin Releasing Hormone ◽  
Female Rats ◽  
Resting Potential ◽  
Pituitary Cells ◽  
Releasing Hormone ◽  
Electrophysiological Properties ◽  
L Cells ◽  
D Cells

The response of rat pituitary cells to thyrotropin-releasing hormone (TRH) in primary culture was studied in the whole-cell configuration with the patch-clamp technique. Prolactin (PRL)-containing cells were identified in the culture with a peroxidase-antiperoxidase immunocytochemical method. The cells were cultured from the pituitaries of diestrous (D) and lactating (L) female rats. Membrane electrophysiological properties (resting potential and input resistance) of pituitary cells in primary culture varied widely. Under the recording conditions reported here, the mean resting potential of lactotrophs was about -30 mV. There were spontaneous fluctuations in membrane resting potential (10-15 mV) as well as of membrane input resistance, making these parameters difficult to evaluate accurately. Most of the cells exhibited spontaneous firing activity that was shown to be mainly calcium-dependent. There was no difference between L and D cells in resting membrane electrophysiological properties. TRH (10(-7) M) induced a transient hyperpolarization of the membrane similar to that previously described in the GH3 clonal pituitary cell line. Voltage-clamp studies showed that this hyperpolarization resulted from activation of an outward current, the reversal potential of which ranged from -48 to -86.5 mV. Experimental manipulations of the ionic composition of internal and external recording media suggested that both K+ and Cl- were involved. This hyperpolarizing response was observed both in D and L cells, although L cells had larger and faster responses than D cells. This observation may be of physiological significance because lactotrophs have been reported to exist in various subtypes.

scholarly journals Electrophysiological properties of isolated photoreceptors from the eye of Lima scabra.

1991 ◽  
Vol 97 (1) ◽  
pp. 17-34 ◽  
Author(s):  
E Nasi
Keyword(s):  
Light Adaptation ◽  
Sea Water ◽  
Bright Light ◽  
Receptor Potential ◽  
Input Resistance ◽  
Photoreceptor Cells ◽  
Continuous Illumination ◽  
Moderate Intensity ◽  
Electrophysiological Properties ◽  
Voltage Dependent

Photoreceptor cells were enzymatically dissociated from the eye of the file clam, Lima scabra. Micrographs of solitary cells reveal a villous rhabdomeric lobe, a smooth soma, and a heavily pigmented intermediate region. Membrane voltage recordings using patch electrodes show resting potentials around -60 mV. Input resistance ranges from 300 M omega to greater than 1 G omega, while membrane capacitance is of the order of 50-70 pF. In darkness, quantum bumps occur spontaneously and their frequency can be increased by dim continuous illumination in a fashion graded with light intensity. Stimulation with flashes of light produces a depolarizing photoresponse which is usually followed by a transient hyperpolarization if the stimulus is sufficiently intense. Changing the membrane potential with current-clamp causes the early phase to invert around +10 mV, while the hyperpolarizing dip disappears around -80 mV. With bright light, the biphasic response is followed by an additional depolarizing wave, often accompanied by a burst of action potentials. Both Na and Ca ions are required in the extracellular solution for normal photoexcitation: the response to flashes of moderate intensity is greatly degraded either when Na is replaced with Tris, or when Ca is substituted with Mg. By contrast, quantum bumps elicited by dim, sustained light are not affected by Ca removal, but they are markedly suppressed in a reversible way in 0 Na sea water. It was concluded that the generation of the receptor potential is primarily dependent on Na ions, whereas Ca is probably involved in a voltage-dependent process that shapes the photoresponse. Light adaptation by repetitive flashes leads to a decrease of the depolarizing phase and a concomitant enhancement of the hyperpolarizing dip, eventually resulting in a purely hyperpolarizing photoresponse. Dark adaptation restores the original biphasic shape of the photoresponse.

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