Currents in the Synaptic Terminals of Barnacle Photoreceptors

Stuart, Ann E.; Hayashi, Jon H.; Moore, John W.; Davis, Roger T.

doi:10.1007/978-1-4613-2307-5_28

Cited by 10 publications

(15 citation statements)

References 14 publications

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“…These data are in agreement with other studies showing that in insects, histamine is inactivated either through oxidation to imidazole-4-acetic acid or via N-acetylation to N-acetylhistamine (Gustafsson and Plym Forshell, 1964;Huggins and Woodruff, 1968;Reite, 1972;Elias and Evans, 1983). Similarly, in barnacles, most of the histamine taken up is not metabolized (Stuart and Mekeel, 1990). In Aplysia, y-glutamylhistamine is the primary metabolite (Weinreich, 1979).…”

Section: Histamine Uptake and Metabolismsupporting

confidence: 92%

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Histamine: A Neurotransmitter Candidate for Drosophila Photoreceptors

Sarthy

1991

Journal of Neurochemistry

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Recent experimental evidence suggests that histamine might be the synaptic transmitter used by invertebrate photoreceptors. In the present study, we have examined whether histamine is a transmitter candidate for Drosophila photoreceptors. Our findings are as follows: (a) Large amounts of histamine are synthesized by wild-type heads, whereas heads from the eye-deficient mutants, eyes absent and sine oculis, show reduced histamine synthesis. (b) Histidine decarboxylase activity is approximately 10-fold higher in extracts of normal heads compared with that in the mutants. (c) Histamine taken up by fly heads is metabolized into N-acetylhistamine and imidazole-4-acetic acid. (d) Immunostaining of normal and sevenless heads with histamine-specific antisera demonstrates that histamine is present in photoreceptors R1-6 and R8. (e) Histamine synthesized from exogenously supplied [3H]histidine can be released by depolarization with 50 mM K+, and the release is Ca2+ dependent. These observations strongly suggest that histamine is a major neurotransmitter used by Drosophila photoreceptors.

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Section: Histamine Uptake and Metabolismsupporting

confidence: 92%

“…Recently, Stuart and Mekeel ( 1990) reported uptake of histamine into terminals when photoreceptors were stimulated with flashing light. It is interesting that this uptake was reduced when the histamine antagonist pyrilamine was present.…”

Section: Histamine Uptake and Metabolismmentioning

confidence: 99%

Histamine: A Neurotransmitter Candidate for Drosophila Photoreceptors

Sarthy

1991

Journal of Neurochemistry

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“…Precedent exists for calcium channels with different activation voltages even in the same preparation (Dunlap & Fischbach, 1981;Carbone & Lux, 1984;Nowycky, Fox & Tsien, 1984). Indeed we have observed calcium currents to activate in the region of the dark resting potential and to reach a maximum at about -40 mV when the receptor's voltage is held at the dark resting level of -60 mV (Stuart, Hayashi, Moore & Davis, 1985). In contrast, calcium currents at squid synapse activate around -40 mV and reach a maximum at about -10 mV (Smith, Augustine & Charlton, 1985).…”

Section: Transmission Of Small Presynaptic Voltage Changesmentioning

confidence: 93%

Adaptation in the input‐output relation of the synapse made by the barnacle's photoreceptor.

Hayashi¹,

Moore²,

Stuart³

1985

The Journal of Physiology

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SUMMARY1. A study was made of synaptic transmission between the four median photoreceptors ofthe giant barnacle (Balanus nubilus) and their post-synaptic cells (I-cells). Simultaneous intracellular recordings were made from the presynaptic terminal region of a photoreceptor and from the soma of an I-cell.2. The photoreceptor's membrane potential provided feed-back to bath electrodes that passed current into the receptors' axons, permitting the voltage to be controlled at the point of arborization of their presynaptic terminals. Simultaneous recordings from a second photoreceptor showed that its voltage tracked the first.3.Step depolarizations of the receptors from their dark resting potential (about -60 mV) caused hyperpolarizations of the I-cell that reached a peak, then decayed to a plateau value. The amplitude of the I-cell's response grew with presynaptic depolarizations, saturating at presynaptic values 10-20 mV depolarized from dark rest.

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“…Finally, the synaptic current is indeed a problem, of such magnitude when the terminals are bathed in normal external Ca 2+ (20 mM) that it causes a loss of voltage control (Stuart et al, 1986). Although we used lower concentrations of Ca 2+ in the present experiments, we do not know how well voltage is controlled at the release sites themselves.…”

Section: Factors Affecting the Value Of The Clamped Voltage In The Arbormentioning

confidence: 98%

Currents in the presynaptic terminal arbors of barnacle photoreceptors

Hayashi

Stuart

1993

Vis Neurosci

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We have described the currents flowing across the presynaptic membranes of the four median photoreceptors of the giant barnacle, Balanus nubilus, using a quasi-voltage clamp arrangement. Membrane potential, measured in the terminal region of one photoreceptor, was controlled in all four terminals by feedback current supplied through the nerve containing the photoreceptors' axons. The [Ca 2+ ] o in the saline was reduced to decrease the Ca 2+ current, enabling better voltage control, and tetraethylammonium ion (TEA, 20 mM) was added to block a fast voltage-dependent K + conductance.Depolarizing voltage steps from the resting potential in the dark (-60 mV) evoked slow, inward Ca 2+ -dependent currents which could be blocked by Co 2+ , Mg 2+ , or Cd 2+ . The Ca 2+ currents were followed by large outward currents that persisted for many seconds after the offset of moderate or large pulses. These tail currents increased in magnitude and duration with pulse duration and reversed at about -80 mV, consistent with previous evidence for a Ca 2+ -activated K + conductance in this membrane. When the Ca 2+ -activated outward current was reduced to zero by increasing the [K + ] o so as to set E K at -20 mV, and then stepping the voltage to this value, the step evoked a steady inward Ca 2+ current. Thus, the Ca 2+ current did not show voltage-or Ca 2+ -dependent inactivation. When Ba 2+ was substituted for Ca 2+ , 500-ms depolarizing steps evoked steady inward currents but no outward currents. In any given experiment, the activation voltage of the Ca 2+ or Ba 2+ current did not depend on holding potential.At the barnacle photoreceptor's synapse, the postsynaptic cell adapts to maintained presynaptic voltage by a mechanism that is not understood. We conclude that neither Ca 2+ current inactivation nor a shift in activation voltage with holding potential can account for this adaptation.

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Currents in the Synaptic Terminals of Barnacle Photoreceptors

Cited by 10 publications

References 14 publications

Histamine: A Neurotransmitter Candidate for Drosophila Photoreceptors

Histamine: A Neurotransmitter Candidate for Drosophila Photoreceptors

Adaptation in the input‐output relation of the synapse made by the barnacle's photoreceptor.

Currents in the presynaptic terminal arbors of barnacle photoreceptors

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