Photodynamic Alteration of Sodium Currents in Lobster Axons

Pooler, John P.

doi:10.1085/jgp.60.4.367

Cited by 45 publications

(51 citation statements)

References 29 publications

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“…10A, B) such that the extent of phototoxic damage differs throughout the preparation. Species variations could also account for differences in phototoxicity in heart and axons as implied by the single cell experiments on Sepia (Chalazonitis, 1964) and lobster nerves (Pooler, 1972).…”

Section: Discussionmentioning

confidence: 99%

Optical probes of membrane potential in heart muscle.

Morad¹,

Salama²

1979

The Journal of Physiology

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SUMMARY1. The fluorescent dye Merocyanine-540 and the two weakly fluorescent dyes Merocyanine-rhodanine and Merocyanine-oxazolone are shown to respond as optical probes of membrane potential in heart muscle.2. In frog hearts stained with Merocyanine-540, the absorption at 540 nm decreases by 0-1-1.0% and increases at 570nm by 0.01-0.5% during the action potential. With either a 540 or a 570 nm excitation wave-length, the fluorescence increases by 1-2 %. The time course of all three optical measurements follows the kinetics of the action potential. 3. Merocyanine-rhodanine exhibits potential-dependent optical responses through a 0-5 % decrease in absorption at 750 nm, and Merocyanine-oxazolone has a 1I0 % decrease in absorption at 720 nm. Their optical responses have a signal-to-noise ratio of 100/1 and 500/1, respectively. 4. The action spectrum of Merocyanine-rhodanine is triphasic in frog heart with an increase in transmittance from 780 to 700, a decrease from 700 to 600, and an increase from 600 to 450 nm. Merocyanine-oxazolone shows only increases in transmittance during membrane depolarization.5. The optical responses of these probes are linear with respect to changes in membrane potential.6. Pharmacological agents or ionic interventions do not alter the membrane potential sensitivity of 7. Rapid spectrophotometric measurements at various phases of the action potential indicate that the potential dependent optical signals of Merocyanine-540 are produced by changes in amplitude of fluorescence and absorption bands. The lack of wave-length displacement as a function of membrane potential, i.e. electrochromism, is not the mechanism governing the voltage sensitivity of Merocyanine-540.8. The data suggest that these Merocyanine dyes bind to the plasma membrane and serve as linear optical probes of membrane potential in heart muscle.

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Section: Discussionmentioning

confidence: 99%

Optical probes of membrane potential in heart muscle.

Morad¹,

Salama²

1979

The Journal of Physiology

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“…The dye solution was then replaced with sea water that had been bubbled with nitrogen gas. The deoxygenation effectively eliminated the photodynamic damage to the axon (Arvanitaki & Chalazonitis, 1961 ;Pooler, 1972) that would have occurred with some dyes. With dyes that were only slightly soluble in sea water, Pluronic F-127 (BASF Wyandotte Corp., Wyandotte, Michigan), a high molecular-weight surfactant polyol, was included in the dye solution, using the following procedure.…”

Section: Methodsmentioning

confidence: 99%

Changes in axon fluorescence during activity: Molecular probes of membrane potential

et al. 1974

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Summary. The fluorescence of dyes added to squid giant axons was studied during action potentials and voltage-clamp steps. One goal was to find fluorescence changes related to the increases in membrane conductance that underlie propagation. A second goal was to find large changes in fluorescence that would allow optical monitoring of membrane potential in neurons and other cells. Attempts were made to measure fluorescence changes using over 300 different fluorescent molecules and positive results were obtained with more than half of these. No evidence was found that would relate any of the fluorescence changes to the increases in membrane conductance that accompany depolarization; most, instead, were correlated with the changes in membrane potential. The fluorescence changes of several dyes were relatively large; the largest changes during an action potential were 10 -3 of the resting intensity. They could be measured with a signal-to-noise ratio of better than 10:1 in a single sweep.Changes in the fluorescence of molecules added to axons have been studied in an effort to learn about alterations in membrane structure that occur during excitation (Tasaki, Carnay &Watanabe, 1969;Cohen, Landowne, Shrivastav &Ritchie, 1970; Conti, Tasaki &Wanke, 1971). Although it was suggested that ANS and TNS fluorescence changes were related to increases in membrane conductance, our experiments (Davila, Cohen, Salzberg &Shrivastav, 1974) indicated that these fluorescence changes were, in fact, potential dependent. With the hope that other dyes would provide information about the structural basis of the conductance

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“…Photodynamic damage (12,25) was the factor limiting the duration offluorescence experiments. Therefore, no more than four trials were averaged in these experiments.…”

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confidence: 99%

Simultaneous optical measurements of electrical activity from multiple sites on processes of cultured neurons.

Grinvald¹,

Ross²,

Farber³

1981

Proc. Natl. Acad. Sci. U.S.A.

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Optical methods using changes in fluorescence and absorption ofvoltage-sensitive dyes were developed to record electrical activity from processes of nerve cells grown in monolayer culture. For transmission measurements, a merocyanine dye was discovered that was more sensitive than others previously tested on cultured neurons. Action potentials from the somata of these cells were detected without averaging, with a signal-to-noise ratio of 20:1. With this dye, electrical responses were simultaneously recorded from many points along the arborization of neuroblastoma cells by using a 10 x 10 array ofphotodiodes positioned in the microscope image plane. Frequently different processes had different shapes of electrical responses, suggesting regional specializations. Fluorescence measurements with an oxonol dye proved to be more sensitive than transmission measurements, particularly when recording from small processes. By changing the position of the cell relative to a laser microbeam while recording electrically from the cell body, it was possible to monitor the membrane potential in the cell body and in the process simultaneously. From the delay in reponse in the process, a lower limit for the mean conduction velocity of 0.2-0.6 m/sec was found for 2-to 7-,um processes. The mean space constants of processes were estimated by comparing the amplitudes of passive voltage responses in the cell body and growth cone. A lower limit of400-950 ,um was obtained for 4-to 7-,um processes. Many questions in neurobiology require an understanding of the regional properties ofneurons. For example, the integration of multiple synaptic inputs by single nerve cells requires a knowledge ofthe passive and active electrical membrane properties ofthe dendritic branches, soma, and axon (1-4); the space constants of each of the processes and the location and nature of specialized segments with localized excitability must be determined. Also, the role that given ions play in the regulation of neuronal development requires knowledge of the electrical properties of the developing neurites (5). Yet, the electrical events in the growth cone are not known.,Nerve cells maintained in tissue culture offer a simplified system for studying these electrical parameters, yet these questions are difficult to approach by current techniques because it is hard to record intracellularly from small processes. Extracellular recording from small processes ofcultured neurons has been reported (6-8). However, this technique is inadequate when studying graded potentials or regional variations in the form of the action potential (9, 10). Furthermore, simultaneous measurements of events in different regions within one neuron are very hard with classical recording methods. Some of the limitations inherent in these methods were recently discussed (10).Optical methods for measuring membrane potential by using voltage-sensitive dyes have been developed by Cohen and coworkers (11)(12)(13)(14) and by Waggoner (15) and colleagues. These dyes act as molecular transdu...

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Photodynamic Alteration of Sodium Currents in Lobster Axons

Cited by 45 publications

References 29 publications

Optical probes of membrane potential in heart muscle.

Optical probes of membrane potential in heart muscle.

Changes in axon fluorescence during activity: Molecular probes of membrane potential

Simultaneous optical measurements of electrical activity from multiple sites on processes of cultured neurons.

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