Receptor Potential In Response Research Articles

Studies of the Drosophila norpA phototransduction mutant. I. Electrophysiological changes and the offsetting effect of light.

The electrophysiological characteristics of norpAH52, a temperature sensitive phototransduction mutant of Drosophila melanogaster, were studied in vivo. Upon raising the environmental temperature to 33-37 degrees C, mutant flies exhibited time-dependent changes in photoresponses. Initial observations were losses in responsiveness at low light intensities and prolonged receptor potential waveforms. Next, reductions in response amplitudes at higher light intensities occurred, until no responses were obtained. On return to lower temperature the electrophysiological properties recovered in reverse order. Based on these observations we conclude that the primary defect of norpA affects the efficiency of the phototransduction process. Enhanced light exposure could offset the receptor potential changes in norpA. With the temperature sensitive mutant: (1) additional light exposure prolonged the time that responses could be observed at the higher temperature, (2) when 1-s illuminations no longer elicited responses at the higher temperature, 1-min illuminations at the same intensity temporarily restored the ability to obtain 1-s-responses, and (3) light accelerated the restoration of responses on return to lower temperature. Illumination also had an effect on non-temperature sensitive norpA mutants, enabling the production of small photoresponses in norpAH44, a mutant that normally does not exhibit any responses, and improving the low-light-intensity responses of norpAP16. Our study indicates that the PI cycle, which is inhibited in norpA mutants (Yoshioka et al. 1985), is an important light-sensitive positive step or effector in the production of receptor potential responses.

Localized adaptation processes in olfactory sensilla of Saturniid moths

Receptor potentials and nerve impulses were recorded extracellularly from the two olfactory cells innervating most sensilla trichodea on the antenna of male Antheraea polyphemus and Antheraea pemyi moths that respond to two key compounds, the sex pheromone components (E)-6, (Z)-11-hexadecadienyl acetate and (E)-6, (Z)-11-hexadecadienal. Stimulation with the key compound of one receptor cell auto-adapts this cell and also cross-adapts the other cell in the same sensillum but cross-adaptation is weaker than auto-adaptation. Local stimulation experiments demonstrate that sections of the olfactory receptor cell can be selectively adapted as monitored by the receptor potential response. The mechanism of impulse generation can adapt separately from the mechanism generating the receptor potential as indicated by an altered relationship between impulse response and receptor potential. These results demonstrate multiple and distributed adaptation processes in an olfactory bipolar neuron as studied in a time domain of seconds. Cross-adaptation may indicate extracellular alterations caused by excitation of one cell but could also be caused by direct inhibitory action of the stimulus compound.

Receptor potentials of isolated frog muscle spindle evoked by sinusoidal stimulation.

Receptor potentials in response to sinusoidal stimulation have been recorded from isolated muscle spindles of the frog. Sinusoidal displacements of different amplitudes (20-120 micron) and frequencies (0.1-100 Hz) were used. The mean static stretch level was adjusted between resting length (L0) and L0 + 400 micron, so that the amplitude and phase-response characteristics were measured at different operating points. Depending on the amount of static prestretch, there is a well-defined dynamic range, which limits the receptor potential by nonlinear compression of either its positive or negative half-cycle. For each point on the static operating curve there exists a dynamic operating curve with a sigmoidal shape. The range of each dynamic curve is approximately 80 micron, independent of the static displacement, and the maxima of all dynamic curves are the same. Therefore the dynamic curves are not symmetrical about their static operating point. The slope of the steepest portion is 10% of the maximum elicitable receptor potential per 10-micron dynamic displacement. For stimulus frequencies greater than 2 Hz the receptor potential deviates from a sinusoidal waveform, exhibiting a fast depolarization transient during stretch and a prolonged repolarization transient during release of stretch. The steepness of the depolarization transient increases with increasing stimulus frequency, amplitude, and prestretch level. As a result, the interval from trough to peak of the receptor potential shortens to less than 90 degrees instead of half a cycle. The repolarization transient has an exponential decay with a time constant of approximately 40 ms that remains constant during the various stimulus conditions. As a result of this slow decay time, individual receptor potentials summate, so that the response divides into a modulated receptor potential (AC component) and a maintained depolarization (DC component). The amplitude response characteristic of the stationary AC component increases with increasing stimulus frequencies up to a peak at 2 Hz, after which it declines with a slope of -3 dB/octave. Provided large sinusoidal stretches and/or extended prestretch levels are used, this high-frequency decline of the AC component is compensated for by the proportional increase of the DC component, so that the peak depolarization values remain constant from 2 to 100 Hz. Stimulus and response are in phase for stimulus frequencies less than 2 Hz and reverse to phase lag at higher stimulus frequencies.(ABSTRACT TRUNCATED AT 400 WORDS)

Intensity and frequency characteristics of pacinian corpuscles. II. Receptor potentials.

Intensity characteristics that relate receptor- (generator) potential amplitude to vibration amplitude and frequency characteristics that relate either the stimulus intensity required for a criterion response or the phase angle between the stimulus and the receptor potential to vibration frequency have been obtained from isolated pacinian corpuscles removed from cat mesentery. The intensity characteristics of signal-averaged receptor potentials in response to sinusoidal displacements were found to be linear at low stimulus levels and to saturate at higher ones. At the higher levels, an asymmetric full-wave rectification was often found, the degree of which varied among receptors. The receptor-potential waveforms showed a time-dependent hysteresis in response to every stimulus cycle at moderate and high stimulus levels. An average intensity characteristic is given. The measured amplitude-frequency characteristics for a constant magnitude of the receptor potential below the neural spike threshold were found to be U-shaped functions. The averaged (n = 7) amplitude-frequency characteristic generated at a constant criterion response had a best frequency of 370 Hz and a bandwidth of Q3 dB equal to 0.8. The phase-frequency characteristics of the receptor potentials below spike threshold exhibited two populations of responses. Both populations underwent phase changes of about 300 degrees as the vibration frequency was increased from 20 Hz to 1.0 kHz but were separated by 180 degrees. An average (n = 8) phase-frequency characteristic is shown. For a constant neural firing rate, the relationship between receptor-potential amplitude and stimulus frequency was also U-shaped. Several qualitative physiological models are presented in relation to previously reported anatomical evidence (14, 18, 19, 32, 45). For the intensity domain, it is suggested that the cytoplasmic extensions that protrude from the unmyelinated portion of the corpuscle axon into the hemilamellar clefts are responsible for the asymmetric full-wave rectification and the response polarity in the phase-frequency characteristics. It is the asymmetric full-wave rectification and consequent receptor-potential waveforms that produce the 2 spikes/stimulus cycle plateaus in the characteristics relating firing rate to stimulus intensity described in the preceding paper (5). An additional model, based on the recovery of spike threshold, suggests how the plateaus in the firing rate-intensity characteristics (5) are produced. For the frequency domain, three filters in cascade can account for the frequency characteristic obtained with a constant firing rate criterion (see Ref. 5).(ABSTRACT TRUNCATED AT 400 WORDS)

Responses of isolated Golgi tendon organs of cat to sinusoidal stretch.

1. Receptor potential and tension have been recorded from isolated Golgi tendon organs in response to sinusoidal stretch. Responses depended on amplitude and frequency of stretch and on the initial (resting) tension of the preparation. 2. Both tension and receptor potential behaved as power functions of stretch amplitude over most of the range corresponding to physiological tendon strains. However, for very small stretch amplitudes (less than 8 microns), a more linear response was seen. Those characteristics of responses that depended on stretch amplitude behaved similarly at all frequencies examined. 3. Frequency dependence of tension was slight. Its character, a gradual monotonic increase in response with increasing stretch frequency and a constant phase lead of a few degrees, did not change over the examined frequency range from 0.12 to 80 Hz. In contrast, receptor potential displayed a marked frequency dependence, increasing rapidly with increasing frequency of stretch in the range from approximately 1 to 20 Hz, then slowly declining as frequency was further increased. 4. Changes in initial tension of the preparation produced marked parallel changes in the amplitude dependence of tension and receptor potential. Frequency response was not significantly affected. 5. By comparing tension and receptor potential responses, the relative contributions of mechanical and electrical properties of the receptor to the sensory transduction process was examined. The present results suggest that in tendon organs the observed nonlinear dependence on amplitude of stretch originates primarily in the mechanical stage of transduction. Dynamic sensitivity, however, seems largely attributable to ionic processes within the sensory terminal membranes.

Receptor potentials of lizard hair cells with free-standing stereocilia: responses to acoustic clicks.

Receptor potentials of single hair cells in the free-standing region of the basilar papilla of the anaesthetized alligator lizard were measured intracellularly with micropipettes. Stimuli were primarily acoustic pulses (clicks) delivered to the tympanic membrane. The receptor potential was independent of click repetition rate for the range 10-150 clicks/s. This property is presumed to be the basis of the rate independence of the extracellular cochlear microphonic potential. The receptor potential wave-form consisted of a fast oscillatory component (or oscillation) superimposed on a usually positive (depolarizing) slow component. Reversal of the stimulus polarity resulted in a reversal of the polarity of the oscillations; the polarity of the slow component remained unchanged. The relative magnitudes of the two components depended on click level. At the higher click levels the magnitudes of the slow and oscillatory components were comparable. The relation of the receptor potential to the stimulus was non-linear; the peak-to-peak magnitude of the receptor potential increased less than proportionately with increasing sound-pressure level, and reversal of the stimulus polarity did not result in a reversal of the receptor potential. The receptor-potential magnitude for high-level clicks ranged from 1-13 mV peak-to-peak with an average value of 3.5 mV. At the lower click levels the magnitude of the slow component was much smaller than that of the oscillatory component. The relation of the receptor potential to the acoustic stimulus approached that of a linear system, the magnitude of the receptor potential became approximately proportional to the sound-pressure level, and reversal of the stimulus polarity resulted in approximate reversal of the receptor potential. For low-level stimuli the frequency of the oscillations of the receptor potential in response to clicks was approximately equal to the frequency of maximal a.c. response to tones. Apparently, both phenomena reflect the frequency selectivity of the processes generating the receptor potential. The frequency of oscillations in the click response varied from one cell to another (range of 1.0-2.2 kHz in this study). The results are qualitatively consistent with a model (Weiss, Mulroy & Altmann, 1974) that contains a linear, band-pass filter followed by a rectifier followed by a low-pass filter.

Cochlear inner hair cells: effects of transient asphyxia on intracellular potentials.

Intracellular potentials were recorded from inner hair cells in the guinea pig cochlea. Transient asphyxia was induced by interrupting respiration for brief periods. Asphyxia caused a hyperpolarization of the resting membrane potential (resting Em). The hyperpolarization averaged 2.9 mV for 30 s asphyxias and 5.7 mV for 45 s asphyxias. The membrane potential recovered quickly after normal ventilation was resumed. Asphyxia also induced a rapid and profound decrease of the d.c. receptor potential in response to moderate intensity tone bursts at the characteristic frequency of the inner hair cell. At maximal depression, the receptor potential was reduced about 60% for a 30 s asphyxia and 100% for a 45 s asphyxia. The receptor potential recovered slowly after normal ventilation was resumed. A similar percent reduction and time course of recovery were observed for the a.c. receptor potential. In recordings from the same animals, the round window compound action potential (CAP) was as severely depressed by asphyxia as the hair cell receptor potentials. The time course of recovery for the CAP was similar to the slow recovery of the d.c. receptor potential. In contrast, the round window cochlear microphonics (CM) and the endolymphatic potential (EP) were affected less by asphyxia and recovered quickly after ventilation was resumed. Frequency tuning curves (FTCs) for the d.c. receptor potential were measured during the period of maximal receptor potential depression. These FTCs showed decreased tip sensitivity and a decrease in sharpness of tuning, as measured by the Q10. These changes were fully reversible. Low frequency (tail) segments of the FTCs were much less affected by asphyxia. The inner hair cell FTC changes during asphyxia were compared with neural FTC changes reported by other investigators. The similarities lead us to the conclusion that the inner hair cell and the auditory neural response to sound are equally sensitive to asphyxia.

An analysis of receptor potential and tension of isolated cat muscle spindles in response to sinusoidal stretch.

In isolated cat muscle spindles the receptor potential responses of primary and secondary endings as well as tension responses to sinusoidal length changes in the steady state have been analysed. 1. At a given stimulus frequency, receptor potential per unit length change (receptor potential gain) in both primary and secondary endings is constant when displacement is less than about 10 micrometer. With larger stretches, receptor potential gain decreases approximately as a power function of displacement, the gain of primary endings decreasing more rapidly with increasing displacement than that of secondary endings. Tension per unit length change (tension gain) shows a similar constant range above which it also decreases as a power function of displacement. 2. In spite of the large reduction in gain at high displacement amplitudes, response wave forms remained essentially sinusoidal. The gain reduction results principally from a displacement-dependent non-linearity which has a rapid onset and slow decay. 3. Receptor potential and tension responses to small amplitude sinusoidal stretch depend, in a parallel manner, on the initial length of the preparation. 4. Both receptor potential and tension responses are highly dependent on frequency of sinusoidal stretch. In primary endings receptor potential gain increased as a power function of frequency over the range 0 . 01 to about 40 Hz, above which frequency the gain decreased; phase advance remained relatively constant up to 10 Hz then decreased to become a phase lag at higher frequency. In secondary endings receptor potential gain remained fairly constant between 0 . 01 and 1 Hz then rose as a power function of frequency but less steeply than in primary endings. 3. The possible mechanisms underlying these findings are discussed.

Responses of primary and secondary endings of isolated mammalian muscle spindles to sinusoidal length changes.

1. Responses of primary and secondary endings of isolated cat spindles to sinusoidal length changes have been recorded before and after block of impulse activity by tetrodotoxin. 2. Primary endings may discharge with each cycle of sinusoidal stretch at 25-50 Hz, with stretch amplitudes applied to the spindle poles as small as 1 micron. Thresholds are higher at lower frequencies. 3. In primary endings, amplitude of the receptor potential varies with frequency and magnitude of sinusoidal stretch. At a given stretch amplitude, the receptor-potential response increases markedly between 1 and 10 Hz. At a fixed frequency, for example, at Hz, the response to graded amplitude of sinusoidal stretch is highly nonlinear, sensitivity decreasing with large amplitudes. 4. Secondary endings show a much higher threshold than primary endings to sinusoidal stretch. Thus, at 25 Hz, secondary endings required stretch amplitudes of 50-100 micron to evoke discharge. Relatively large amplitudes of stretch were also required to evoked detectable receptor potentials. Over the range studied, the receptor potential varied more linearly with stretch amplitude in secondary than in primary endings.

Olfactory response in excitable protoplasmic droplet and internodal cell of Nitella.

IN higher vertebrates, olfactory reception takes place at the receptor cell in the olfactory epithelium. The elicitation of neural responses caused by odorants is not restricted to the olfactory organs; other excitable systems (for example, the trigeminal nerve and vomeronasal organ of the tortoise1,2, ganglion cell3 of Helix and contact chemoreceptor of the fly4) are also to respond to odorants. Excitable membranes in general probably respond to odorants, and the processes of olfactory reception and of excitation of a membrane must be closely related. The interaction between odorants and an excitable membrane which is basic to the molecular process of olfactory stimulation, has not been investigated with this relationship in mind, because of the small size of the olfactory cells and of the excitable systems mentioned. This factor has prevented the recording of the intracellular receptor potential in response to odorants. To clarify the physicochemical mechanism underlying the olfactory reception, we have therefore used the protoplasmic droplet and internodal cell of Nitella to investigate the effect of odorants on the electrical properties of an excitable membrane. Apart from its size, the protoplasmic droplet has the advantage of having a functional membrane contiguous with the external solution5–7.

Physicochemical studies of taste reception. I. Model membrane simulating taste receptor potential in response to stimuli of salts, acids and distilled water

A Millipore filter paper impregnanted with the lipids extracted from bovine tongue epithelium was used as a model for the taste receptor membrane and the membrane potentials arisen between two solutions across the membrane were measured under the presence of salts, acids and distilled water as taste stimuli. The changes in the membrane potential induced by these stimuli paralleled closely the taste receptor potentials observed intracellularly with living taste cells or taste never responses as shown in the following. 1. 1. Various salts carrying a common species of anion (NaCl, KCl, NH 4CL and CaCl 2) at a given concentration induced a different magnitude of potential deflections, while sodium salts carrying different species of anion (NaF, NaCl, NaBr and NaI) induced a practically identical potential deflection. The relationship between the magnitude of the potential deflection and the NaCl concentration followed the taste equation. The potential deflection induced by the application of a given concentration of NaCl was independent of pH in a wide range of pH between 3 and 12. 2. 2. A treatment of the membrane with FeCl 3 brought about a reversal of the polarity of the steady potential. An application of NaCl to the FeCl 3-treated membrane induced a variation of the potential deflection with a polarity opposite to that normally displayed. 3. 3. The relations between pH and the magnitude of the potential deflection induced by HCl and acetic acid closely resemble those derived from th taste nerve responses. 4. 4. The model membrane showed potential deflections corresponding to the “water response”; an application of distilled water to the membrane adapted with tap water, Ringer solution, CaCl 2 or NaCl solution brought about a potential deflection as if a high concentration of chemicals were applied to the membrane.

Physicochemical studies of taste reception. II. Possible mechanism of generation of taste receptor potential induced by salt stimuli

This paper discusses the origin of the membrane potential in the model membrane which simulates taste receptor potentials in response to the electrolyte stimuli, on the basis of the results obtained with the model membrane and with the liposomes made of the same lipids as used for the model membrane. 1. 1. The electric resistance of the model membrane was almost independent of the external salt concentration. A sandwiched membrane in which a platinum plate was placed between two sheets of the model membrane produced potential deflections similar to those observed with a sheet of the model membrane. 2. 2. The ζ-potential of liposomes was measured under the presence of various concentrations of the salts (NaCl, KCl, CaCl 2 and MgCl 2). The relationship between the change in the ζ-potential and the NaCl concentration followed the taste equation proposed by Beidler (Beidler, L. M. (1954) J. Gen. Physiol. 38, 133–139). However, the surface charge density of liposomes calculated from the ζ-potential data did not increase with increase of salt concentration, which implied that the increase of the ζ-potential is not attributed to the Langmuir type adsorption of Na + on the anionic sites on the liposomes surface. An application of 2 : 1 type electrolytes (CaCl 2 and MgCl 2) reversed the sign of the surface charge when the salt concentration exceeded about 30 mM. 3. 3. FeCl 3 produced a large positive change in the ζ-potential due to the binding of Fe 3+ to the liposome surface. An application of NaCl to Fe 3+-bound liposomes led to a decrease in the ζ-potential with an increase of the NaCl concentration. On the basis of the above results, it was proposed that taste stimulation with salt stimuli is initiated by a change in the phase boundary potential at the microvilli membrane in taste cells.

Bioelectric Basis of Behavior in Protozoa

Locomotor responses of ciliate protozoans to external stimuli primarily depend on changes in ciliary motion evoked by the stimuli. Certain regions of the protozoan cell produce a receptor potential in response to stimulation. The receptor potential electrotronically spreads to the entire cell membrane and generates an overall electric response due to the electrical excitability of the general membrane. The ionic mechanisms for electrogensis are basically identical to those in nerves, muscles, and receptors of metazoan organisms. The ionic movements across the membrane associated with the electrogensis modify directly and/or indirectly the concentration of certain cations within the cell. The catonic concentration change brings about a modification of the contractile activity of cilia, which in turn results in a change in the ciliary movements. Cilia on different locations of the cell have intrinsically ionic concentrations. This fact, together with the morphological specialization of cilia in different locations on the cell, contributes to the complexity and adaptiveness of locomotor responses found in the ciliated protozoa.

Derivation of a Quantitative Kinetic Model for a Visual Pigment from Observations of Early Receptor Potential

A "complete" and quantitative kinetic model for the states and transitions of the barnacle visual pigment in situ has been constructed from intracellular recordings of the early receptor potential responses to long light pulses. The model involves two stable and four thermolabile states and 10 photochemical, thermal, and metabolic transitions among them. The existence of each state and transition is demonstrated by qualitative examination of the response resulting from a carefully chosen experimental paradigm (combination of intensity, duration, and wavelength of adaptation and stimulation). Quantitative examination of the same responses determines all of the model transition rates, but only puts constraints on the state dipole moments. The latter are determined, and the former refined, by quantitative comparison of the predictions of the complete model with the responses to a set of paradigms chosen to involve as many states and transitions as possible. The fact that good fits can be obtained to these responses without further modification of the model supports its completeness.

Effect of a polarizing current on receptor potential of the isolated frog muscle spindle

The effect of a polarizing current on electrical activity of the isolated frog muscle spindle was studied. A depolarizing current increased the frequency and reduced the amplitude of afferent spike activity, both spontaneous and evoked by mechanical stimulation. A hyperpolarizing current produced the opposite effect. The amplitude of the receptor potential in response to a mechanical stimulus varied as a linear function of the intensity of the polarizing current

The actions of tetrodotoxin, procaine, and acetylcholine on gustatory receptions in frog and rat.

1) The effects of tetrodotoxin (TTX), procaine and acetylcholine choline (ACh) were investigated both the recording the receptor potential in gustatory cells by measuring and the integrated response of their afferent nerves in rats and frogs.3) TTX (10-6 g/ml) did not induce electrical responses in the gustatory cells of frog and rat or in chorda tympani nerve of rat and glossopharyngeal nerve of frog, nor did it suppress the generation of the receptor potential in response to gustatory stimuli. Procaine (0.1 or 0.5 %) also had no effect on the receptive process in the rat. However, in the frog the magnitude of the integrated response of the nerve in response to NaCl and CaCl2 was depressed after the tongue had been soaked in TTX.3) ACh (10-4 g/ml) did not elicit electrical response in the gustatory cell and the nerve of the rat. In the frog, 10-3 g/ml ACh did not produce any immediate response in gustatory cell but the magnitude of integrated response of the nerve to NaCl was modified after the tongue had been soaked in ACh for some time.4) It was suggested that the penetration of solutions from the tongue surface might hardly occur into the space surrounding the gustatory cell bodies of the rat, while in the frog occur in some extent.

Conductance Change Associated with Receptor Potentials of Gustatory Cells in Rat

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.

Olfactory unit potentials and receptor potential responses of Lucilia sericata.

ARTICLESOlfactory unit potentials and receptor potential responses of Lucilia sericataRE KayRE KayPublished Online:01 May 1971https://doi.org/10.1152/ajplegacy.1971.220.5.1481MoreSectionsPDF (2 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformation Cited ByChemoreception: The Significance of Receptor NumbersCoacervate-like Membrane Structures and Olfactory TransductionActa Physiologica Scandinavica, Vol. 99, No. 2Single Sensillum responses in the male mothAdoxophyes orana (F.v.R.) to female sex pheromone components and their geometrical isomersJournal of comparative physiology, Vol. 121, No. 2Structural and functional aspects of sense organs on the maxillary palps of Calliphora vicinaJournal of Insect Physiology, Vol. 22, No. 6 More from this issue > Volume 220Issue 5May 1971Pages 1481-1487 Copyright & PermissionsCopyright © 1971 by American Physiological Societyhttps://doi.org/10.1152/ajplegacy.1971.220.5.1481PubMed5574668History Published online 1 May 1971 Published in print 1 May 1971 Metrics

Reversal of Photoreceptor Polarity Recorded during the Graded Receptor Potential Response to Light in the Eye of Limulus

Intracellular electrodes were inserted into single photoreceptor units of the excised lateral eye of Limulus, and preparations were selected from which graded receptor potentials of relatively large amplitude could be recorded in response to light stimuli. The experimental data indicated that the graded receptor potential does not arise solely from a collapse of the resting membrane potential of the sensory cells of the eye, since a reversal of polarity of the photoreceptor unit could be demonstrated when the eye was stimulated by light. In the recovery period following stimulation, characteristic changes in the so-called resting potential were recorded. It is suggested that these changes in the so-called resting membrane potential are electrical signs of recovery processes occurring in the photoreceptor, because the potential changes were recorded when the eye was in darkness and because the magnitudes of the potential changes were a predictable function of the intensity and duration parameters of the preceding light stimulus.