scholarly journals The Ventral Photoreceptor Cells of Limulus

1969 ◽  
Vol 54 (3) ◽  
pp. 310-330 ◽  
Author(s):  
Ronald Millecchia ◽  
Alexander Mauro
Keyword(s):  
Receptor Potential ◽  
Photoreceptor Cells ◽  
Regenerative Process ◽  
Resting Potential ◽  
Transient Phase ◽  
External Concentration ◽  
Slow Potential ◽  
Retinular Cells ◽  
Convenient Model ◽  
State Component

The ventral photoreceptors of Limulus polyphemus are unipolar cells with large, ellipsoidal somas located long both "lateral olfactory nerves." As a consequence of their size and location, the cells are easily impaled with microelectrodes. The cells have an average resting potential of -48 mv. The resting potential is a function of the external concentration of K. When the cell is illuminated, it gives rise to the typical "receptor potential" seen in most invertebrate photoreceptors which consists of a transient phase followed by a maintained phase of depolarization. The amplitude of the transient phase depends on both the state of adaptation of the cell and the intensity of the illumination, while the amplitude of the maintained phase depends only on the intensity of the illumination. The over-all size of the receptor potential depends on the external concentration of Na, e.g. in sodium-free seawater the receptor potential is markedly reduced, but not abolished. On the other hand lowering the Ca concentration produces a marked enhancement of both components of the response, but predominantly of the steady-state component. Slow potential fluctuations are seen in the dark-adapted cell when it is illuminated with a low intensity light. A spike-like regenerative process can be evoked by either the receptor potential or a current applied via a microelectrode. No evidence of impulse activity has been found in the axons of these cells. The ventral photoreceptor cell has many properties in common with a variety of retinular cells and therefore should serve as a convenient model of the primary receptor cell in many invertebrate eyes.

scholarly journals Effects of Sodium, Potassium, and Calcium Ions on Slow and Spike Potentials in Single Photoreceptor Cells

1969 ◽  
Vol 53 (5) ◽  
pp. 541-561 ◽  
Author(s):  
Bernard Fulpius ◽  
Fritz Baumann
Keyword(s):  
Ionic Composition ◽  
Receptor Potential ◽  
Photoreceptor Cells ◽  
Resting Potential ◽  
Retinula Cell ◽  
Strong Light ◽  
Bathing Medium ◽  
Rich Solution ◽  
Intracellular Microelectrodes ◽  
Honeybee Drone

The influence of changes in the ionic composition of the bathing medium on responses of the retinula cell of the honeybee drone to light was examined by means of intracellular microelectrodes. The resting potential of the cell was influenced mainly by the concentration of K. The peak of the receptor potential (the transient), which in a normal solution and with strong light approaches zero membrane potential, overshot this level in a K-rich solution. An increase in the concentration of K also raised the level of the steady-state phase of the receptor potential (the plateau). The amplitude of the receptor potential was decreased and the spike potential rapidly abolished when Na was replaced by either sucrose, choline, or Tris. In a Ca-free solution the amplitude of the response and especially that of the plateau, was increased. An increase in Ca had the opposite effects. All these changes were reversible. An attempt was made to interpret the receptor and spike potentials in terms of passive movements of Na and K across the membrane of the retinula cell. The major difficulty encountered was to find an explanation for the persistence of an appreciable fraction of the transient and the plateau in preparations kept up to 12 hr in a solution in which all the Na had been replaced by choline, Tris, or sucrose.

scholarly journals Properties of visual cells in the lateral eye of Limulus in situ: intracellular recordings.

1977 ◽  
Vol 69 (2) ◽  
pp. 203-220 ◽  
Author(s):  
R B Barlow ◽  
E Kaplan
Keyword(s):  
Optic Nerve ◽  
Light Intensity ◽  
Single Photon ◽  
Receptor Potential ◽  
Photoreceptor Cells ◽  
Nerve Fibers ◽  
Potential Fluctuations ◽  
Visual Cells ◽  
Retinular Cells

Two types of potential fluctuations, large and small, recorded intracellularly from photoreceptors in the dark-adapted Limulus eye in situ underlie the dual properties of the impulse discharge of the optic nerve fibers. The small potential fluctuations (SPFs)--the well-known quantum bumps--were normally less than 20 mV in amplitude. The large potential fluctuations (LPFs) were up to 80 mV in amplitude. LPFs appear to be regenerative events triggered by SPFs that enable single photon absorptions in retinular cells to fire off nerve impulses in the eccentric cell. In the dark, SPFs and LPFs occur spontaneously. At low light intensities, LPFs are the major components of the receptor potential. At high intensities, LPFs are suppressed and SPFs become the major components. SPFs and LPFs together enable single photoreceptor cells to encode approximately a 9-log unit range of light intensity. Excising the eye from the animal or cutting off its blood supply generally abolishes LPFs and thereby reduces the range of light intensity coded in the optic nerve discharge.

scholarly journals TRP and the PDZ Protein, Inad, Form the Core Complex Required for Retention of the Signalplex in Drosophila Photoreceptor Cells

2000 ◽  
Vol 150 (6) ◽  
pp. 1411-1422 ◽  
Author(s):  
Hong-Sheng Li ◽  
Craig Montell
Keyword(s):  
Transient Receptor Potential ◽  
Direct Interaction ◽  
Light Response ◽  
Receptor Potential ◽  
Photoreceptor Cells ◽  
Macromolecular Complex ◽  
Pdz Domains ◽  
The Core ◽  
Transient Receptor ◽  
Drosophila Photoreceptor

The light response in Drosophila photoreceptor cells is mediated by a series of proteins that assemble into a macromolecular complex referred to as the signalplex. The central player in the signalplex is inactivation no afterpotential D (INAD), a protein consisting of a tandem array of five PDZ domains. At least seven proteins bind INAD, including the transient receptor potential (TRP) channel, which depends on INAD for localization to the phototransducing organelle, the rhabdomere. However, the determinants required for localization of INAD are not known. In this work, we showed that INAD was required for retention rather than targeting of TRP to the rhabdomeres. In addition, we demonstrated that TRP bound to INAD through the COOH terminus, and this interaction was required for localization of INAD. Other proteins that depend on INAD for localization, phospholipase C and protein kinase C, also mislocalized. However, elimination of any other member of the signalplex had no impact on the spatial distribution of INAD. A direct interaction between TRP and INAD did not appear to have a role in the photoresponse independent of localization of multiple signaling components. Rather, the primary function of the TRP/ INAD complex is to form the core unit required for localization of the signalplex to the rhabdomeres.

An electrically evoked slow potential of the frog's retina. II. Identification with PII component of electroretinogram

1975 ◽  
Vol 38 (1) ◽  
pp. 198-209 ◽  
Author(s):  
R. W. Knighton
Keyword(s):  
Electrical Current ◽  
Photoreceptor Cells ◽  
Slow Potential ◽  
Synaptic Terminals ◽  
Electrical Stimuli ◽  
Retinal Response

1. To show conclusively that the electrically evoked retinal response (EERG) is in fact an electrically evoked component of the usual ERG, it is necessary to show that the two responses have the same intraretinal pattern of current generators. A method for determining when two responses have the same origin has been developed. This method utilizes measurements from a single microelectrode penetrating the retina. 2. The method was sensitive enough to detect differences in the origins of two responses when they were present. 3. The EERG had the same intraretinal origin as the PII component of the ERG, and thus is the PII component evoked by electricity rather than by light. 4. The hypothesis that electrical stimuli act on the synaptic terminals of the photoreceptor cells predicts that electrical current will evoke components of the ERG. The fact that the EERG is an electrically evoked component of the ERG fulfills that prediction.

scholarly journals Receptor-mediated activation of recombinant Trpl expressed in Sf9 insect cells

1995 ◽  
Vol 305 (2) ◽  
pp. 605-611 ◽  
Author(s):  
Y Hu ◽  
W P Schilling
Keyword(s):  
Photoreceptor Cell ◽  
Receptor Potential ◽  
Photoreceptor Cells ◽  
Sharp Contrast ◽  
Membrane Receptors ◽  
Cation Channels ◽  
Sf9 Cells ◽  
Baculovirus Expression ◽  
Baculovirus Expression Vector ◽  
Stimulation Of

The Drosophila proteins, Trp and Trpl, are suggested to be cation channels responsible for depolarization of the receptor potential associated with stimulation of insect photoreceptor cells by light. Consistent with this hypothesis, we recently showed that recombinant Trpl forms Ca(2+)- and Ba(2+)-permeable non-selective cation channels when expressed in Sf9 cells using the baculovirus expression vector. As Trpl may be activated in the photoreceptor cell after stimulation of phospholipase C, we hypothesized that a similar regulation of recombinant Trpl may be observed in the Sf9 cell after activation of heterologous membrane receptors linked to Ca(2+)-signal-transduction pathways. To test this hypothesis, Ca2+ signalling was examined in Fura-2-loaded Sf9 cells infected with baculovirus containing cDNA for the M5 muscarinic receptor alone (M5 cells) or in cells co-infected with both M5 and Trpl-containing baculoviruses (M5-Trpl cells). Addition of carbachol (100 microM) to M5 cells produced an increase in cytosolic free Ca2+ concentration ([Ca2+]i) (mean +/- S.D.; n = 17) from 101 +/- 20 to 762 +/- 178 nM which declined to a sustained elevated level of 384 +/- 102 nM after 3 min. The sustained component was eliminated by removal of extracellular Ca2+ or by addition of La3+ or Gd3+ (10 microM). In M5-Trpl cells, basal [Ca2+]i increased as a function of time after infection. To evaluate the contribution of Ca2+ influx to the overall profile observed, Ba2+, a Ca2+ surrogate that is not a substrate for the Ca2+ pump, was used. The increase in basal [Ca2+]i seen in M5-Trpl cells was associated with an increase in basal Ba2+ influx. Addition of carbachol to M5-Trpl cells at 30-36 h after infection produced a large increase in [Ca2+]i to a sustained value of 677 +/- 143 nM. This change in [Ca2+]i was (1) blocked by atropine, (2) attenuated in the absence of extracellular Ca2+, and (3) relatively insensitive to La3+, but blocked by Gd3+ in the 0.1-1 mM range. In the presence of 10 microM Gd3+ to block the endogenous-receptor-mediated Ca(2+)-influx in M5-Trpl cells. In sharp contrast increase in Ba2+ influx in M5-Trpl cells. In sharp contrast, neither Ca2+ nor Ba2+ influx through Trpl was affected by thapsigargin, a selective inhibitor of the endoplasmic reticulum Ca(2+)-ATPase pump.(ABSTRACT TRUNCATED AT 400 WORDS)

Photoreceptor cells with unusual functional properties on the ventral nerve of Limulus

1999 ◽  
Vol 16 (6) ◽  
pp. 1191-1197 ◽  
Author(s):  
KÁROLY NAGY ◽  
MARLIES DORLÖCHTER ◽  
SVENJA KLÄSEN ◽  
DANNY STEINBUSCH
Keyword(s):  
Time Course ◽  
Single Photon ◽  
Receptor Potential ◽  
Photoreceptor Cells ◽  
Light Sensitivity ◽  
Atpase Inhibitor ◽  
Decay Kinetics ◽  
Normal Cells ◽  
Inward Current ◽  
Low Efficiency

Normal photoreceptor cells on the ventral nerve of Limulus respond to a moderately intense flash with a large receptor potential or current. Occasionally, cells are found in which the same flash evokes only a small receptor potential or current. Our investigations reveal physiological reasons for the poor light sensitivity in these “unusual cells.” In unusual cells prolonged illumination with intense light evokes a step-like inward current with an amplitude of some nanoamperes, but without a large transient peak. The current appears to be summed up of single photon responses with amplitudes smaller than about 50 pA. Their time course is similar to that of small single photon responses forming the so-called macroscopic C1 component in normal cells. The macroscopic current evoked by an intense flash has slow activation and deactivation kinetics and reaches a saturated amplitude of about 4–5 nanoamperes. The light-intensity dependence of the current evoked by flashes or by prolonged illumination has a slope of about 1 in log–log plots. The decay kinetics of the current is similar to that of the C1 component measured in normal cells after the block of the C2 component. Occasionally, the step-like current is superposed by large standard bumps. These bumps are blocked by the Ca2+-ATPase inhibitor cyclopiazonic acid, while the sustained inward current persists. We conclude that in unusual cells the light-activated current is identical to the C1 component of normal cells. The phospholipase C pathway that in normal cells presumably gives rise to the C2 component functions only with a low efficiency in unusual cells.

Interactions of membrane potential and cations in regulation of ciliary activity in Paramecium

1976 ◽  
Vol 65 (2) ◽  
pp. 427-448
Author(s):  
H. Machemer
Keyword(s):  
Membrane Potential ◽  
High Frequency ◽  
Resting Potential ◽  
Ciliary Activity ◽  
Frequency Increase ◽  
External Concentration ◽  
Membrane Hyperpolarization ◽  
Ciliary Beating ◽  
Fixed Membrane ◽  
K Concentration

Ciliary activity in Paramecium was investigated in different external solutions using techniques of voltage clamp and high frequency cinematography. An increase in the external concentration of K, Ca or Mg ions decreased the resting potential. It had no effect on ciliary activity. When the membrane potential was fixed, an increase in external Ca or Mg and, to a lesser extent, an increase in K concentration, raised the frequency of normal beating or decreased the frequency of reversed beating of the cilia. Similar effects resulted from membrane hyperpolarization with constant ionic conditions. Increase in concentration of Ca, but not of Mg or K, enhanced hyperpolarization-induced augmentation of ciliary frequency. Increase in Ca concentration also specifically augmented the delayed increase in inward current during rapid hyperpolarizing clamp. The results support the view that [Ca]i regulates the frequency and direction of ciliary beating. It is suggested that the insensitivity of the ciliary motor system to elevations of the external concentrations of ions results from compensation of their effects on [Ca]i. Depolarization itself appears to increase [Ca]i while elevation of the external ion concentrations at a fixed membrane potential appears to decrease [Ca]i.

Ionic mechanisms of phototransduction in photoreceptor cells from the epistellar body of the octopus eledone cirrhosa

1999 ◽  
Vol 202 (8) ◽  
pp. 977-986
Author(s):  
C.S. Cobb ◽  
R. Williamson
Keyword(s):  
Time Course ◽  
Sea Water ◽  
Light Flash ◽  
Receptor Potential ◽  
Photoreceptor Cells ◽  
Evoked Response ◽  
Na Channel ◽  
External Application ◽  
Ionic Mechanisms ◽  
Potential Activity

Intracellular recordings were made from extraocular photoreceptor cells within isolated epistellar bodies of the lesser or northern octopus Eledone cirrhosa. The cells had resting potentials around −41+/−5 mV (mean +/− s.d., N=60) and showed light-flash-induced membrane depolarisation. The evoked response to a brief light flash consisted of a transient peak depolarisation, followed by a plateau component. The magnitude of the light-induced peak depolarisation response was decreased by bathing the epistellar body in artificial sea water (ASW) low in Na+, where choline+ replaced Na+, or by passing steady depolarising current. Replacement of external Na+ by Li+ had no effect on the light-stimulated response. The external application of the Na+ channel blocker tetrodotoxin (3 micromol l-1) increased the light-evoked response, but this was accompanied by a loss of action potential activity. The amplitude and duration of the response to a light flash was increased by bathing the epistellar body in ASW low in Ca2+, or in ASW containing 10 mmol l-1 Co2+, and after intracellular microinjection of the Ca2+ buffer EGTA. Intracellular microinjection of Ca2+ or inositol 1,4,5-trisphosphate, or external application of the phospholipase C inhibitor U-73122, had no apparent effect on the light-evoked response. These results are consistent with the interpretation that (1) the majority of the light-induced inward current is carried by Na+, probably via a non-selective cation channel, and (2) an increase in the intracellular free Ca2+ concentration, mediated by the phototransduction process, is involved in regulating the light-induced inward photocurrent and thus, in effect, determines the amplitude, time course and sensitivity of the receptor potential.

scholarly journals Electrophysiology of the Insect Dorsal Ocellus

1961 ◽  
Vol 44 (3) ◽  
pp. 605-627 ◽  
Author(s):  
Philip Ruck
Keyword(s):  
Cell Layer ◽  
Receptor Cell ◽  
Photoreceptor Cells ◽  
Nerve Fibers ◽  
Spontaneous Discharge ◽  
Generator Potential ◽  
Nerve Impulses ◽  
Potential Component ◽  
Ocellar Nerve ◽  
State Component

Dorsal ocelli are small cup-like organs containing a layer of photoreceptor cells, the short axons of which synapse at the base of the cup with dendritic terminals of ocellar nerve fibers. The ocellar ERG of dragonflies, recorded from the surface of the receptor cell layer and from the long lateral ocellar nerve, contains four components. Component 1 is a depolarizing sensory generator potential which originates in the distal ends of the receptor cells and evokes component 2. Component 2 is believed to be a depolarizing response of the receptor axons. It evokes a hyperpolarizing postsynaptic potential, component 3, which originates in the dendritic terminals of the ocellar nerve fibers. Ocellar nerve fibers in dragonflies are spontaneously active, discharging afferent nerve impulses (component 4) in the dark-adapted state. Component 3 inhibits this discharge. The ERG of the cockroach ocellus is similar. The main differences are that component 3 is not as conspicuous as in the dragonflies and that in most cases ocellar nerve impulses appear only as a brief burst at "off." In one preparation a spontaneous discharge of nerve impulses was observed. As in the dragonflies, this was inhibited by illumination.

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