Reciprocal Synaptic Interactions Between Rod Bipolar Cells and Amacrine Cells in the Rat Retina

1999 ◽  
Vol 81 (6) ◽  
pp. 2923-2936 ◽  
Author(s):  
Espen Hartveit
Keyword(s):  
Nmda Receptor ◽  
Receptor Antagonist ◽  
Transmitter Release ◽  
Amacrine Cells ◽  
Nmda Receptor Antagonist ◽  
Bipolar Cells ◽  
Rat Retina ◽  
Voltage Gated ◽  
Synaptic Interactions ◽  
Rod Bipolar Cells

Reciprocal synaptic interactions between rod bipolar cells and amacrine cells in the rat retina. Reciprocal synaptic transmission between rod bipolar cells and presumed A17 amacrine cells was studied by whole cell voltage-clamp recording of rod bipolar cells in a rat retinal slice preparation. Depolarization of a rod bipolar cell evoked two identifiable types of Ca2+ current, a T-type current that activated at about −70 mV and a current with L-type pharmacology that activated at about −50 mV. Depolarization to greater than or equal to −50 mV also evoked an increase in the frequency of postsynaptic currents (PSCs). The PSCs reversed at ∼ E Cl (the chloride equilibrium potential), followed changes in E Cl, and were blocked by γ-aminobutyric acidA (GABAA) and GABAC receptor antagonists and thus were identified as GABAergic inhibitory PSCs (IPSCs). Bipolar cells with cut axons displayed the T-type current but lacked an L-type current and depolarization-evoked IPSCs. Thus L-type Ca2+ channels are placed strategically at the axon terminals to mediate transmitter release from rod bipolar cells. The IPSCs were blocked by the non- N-methyl-d-aspartate (non-NMDA) receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione, indicating that non-NMDA receptors mediate the feed-forward bipolar-to-amacrine excitation. The NMDA receptor antagonist 3-((RS)-2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid had no consistent effect on the depolarization-evoked IPSCs, indicating that activation of NMDA receptors is not essential for the feedforward excitation. Tetrodotoxin (a blocker of voltage-gated Na+channels) reversibly suppressed the reciprocal response in some cells but not in others, indicating that graded potentials are sufficient for transmitter release from A17 amacrine cells, but suggesting that voltage-gated Na+ channels, under some conditions, can contribute to transmitter release.

Membrane currents evoked by ionotropic glutamate receptor agonists in rod bipolar cells in the rat retinal slice preparation

1996 ◽  
Vol 76 (1) ◽  
pp. 401-422 ◽  
Author(s):  
E. Hartveit
Keyword(s):  
Nmda Receptor ◽  
Plexiform Layer ◽  
Amacrine Cells ◽  
Bipolar Cells ◽  
Inner Plexiform Layer ◽  
Receptor Agonists ◽  
Long Latency ◽  
Glutamate Receptor Agonists ◽  
Conductance Increase ◽  
Rod Bipolar Cells

1. With the use of the whole cell voltage-clamp technique, I have recorded the current responses to ionotropic glutamate receptor agonists of rod bipolar cells in vertical slices of rat retina. Rod bipolar cells constitute a single population of cells and were visualized by infrared differential interference contrast video microscopy. They were targeted by the position of their cell bodies in the inner nuclear layer and, after recording, were visualized in their entirety by labeling with the fluorescent dye Lucifer yellow, which was included in the recording pipette. To study current-voltage relationships of evoked currents, voltage-gated potassium currents were blocked by including Cs+ and tetraethylammonium+ in the recording pipette. 2. Pressure application of the non-N-methyl-D-aspartate (non-NMDA) receptor agonists kainate and (S)-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) from puffer pipettes evoked a long-latency conductance increase selective for chloride ions. When the intracellular chloride concentration was increased, the reversal potential changed, corresponding to the change in equilibrium potential for chloride. The response was evoked in the presence of 5 mM Co2+ and nominally O mM Ca2+ in the extracellular solution, presumably blocking all external Ca2(+)-dependent release of neurotransmitter. 3. The long latency of kainate-evoked currents in bipolar cells contrasted with the short-latency currents evoked by gamma-aminobutyric acid (GABA) and glycine in rod bipolar cells and by kainate in amacrine cells. 4. Application of NMDA evoked no response in rod bipolar cells. 5. Coapplication of AMPA with cyclothiazide, a blocker of agonist-evoked desensitization of AMPA receptors, enhanced the conductance increase compared with application of AMPA alone. Coapplication of the non-NMDA receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione blocked the response to kainate and AMPA, indicating that the response was mediated by conventional ionotropic glutamate receptors. 6. The conductance increase evoked by non-NMDA receptor agonists could not be blocked by a combination of 100 microM picrotoxin and 10 microM strychnine. Application of the GABAC receptor antagonist 3-aminopropyl (methyl)phosphinic acid (3-APMPA) strongly reduced the response, and coapplication of 500 microM 3-APMPA and 100 microM picrotoxin completely blocked the response. These results suggested that the conductance increase evoked by non-NMDA receptor agonists was mediated by release of GABA and activation of GABAC receptors, and most likely also GABAA receptors, on rod bipolar cells. 7. Kainate responses like those described above could not be evoked in bipolar cells in which the axon had been cut somewhere along its passage to the inner plexiform layer during the slicing procedure. This suggests that the response was dependent on the integrity of the axon terminal in the inner plexiform layer, known to receive GABAergic synaptic input from amacrine cells. 8. The results indicate that ionotropic glutamate receptors are not involved in mediating synaptic input from photoreceptors to rod bipolar cells and that an unconventional mechanism of GABA release from amacrine cells might operate in the inner plexiform layer.

Voltage- and transmitter-gated currents in isolated rod bipolar cells of rat retina

1990 ◽  
Vol 63 (4) ◽  
pp. 860-876 ◽  
Author(s):  
A. Karschin ◽  
H. Wassle
Keyword(s):  
Ion Channels ◽  
Outward Current ◽  
Amacrine Cells ◽  
Bipolar Cells ◽  
Similar Distribution ◽  
Isolated Cells ◽  
Membrane Hyperpolarization ◽  
Rat Retina ◽  
Inward Current ◽  
Rod Bipolar Cells

1. Bipolar cells were isolated from adult rat retinas after enzymatic and mechanical treatment. The cells could be unequivocally identified from their morphology because of high retention of their axon and dendritic processes after isolation. 2. Protein kinase C (PKC) immunoreactivity performed on sections of the rat retina labeled rod bipolar cells and a few amacrine cells. Virtually all bipolar cells in the dissociates expressed PKC immunoreactivity and were, therefore, rod bipolar cells. 3. Rod bipolar cells were examined with the tight-seal whole-cell and excised-patch recording techniques. Resting potentials of the isolated cells recorded under current-clamp conditions showed a broad unimodal distribution around -37 mV. 4. Membrane depolarization from a holding potential of -90 mV resulted in an outward current. A fast sodium inward current was not observed. Membrane hyperpolarization from a holding potential of -40 mV activated an inwardly rectifying current. 5. gamma-Aminobutyric acid (GABA) and glycine, the putative retinal neurotransmitters that mediate the bipolar cells' receptive field surround in vivo, activated chloride conductances in almost all isolated bipolar cells. GABA- and glycine-evoked currents were both desensitizing and could be antagonized by the classical blockers bicuculline, picrotoxin, and strychnine, respectively. 6. Pressure application of the drugs from fine microcapillaries to various parts of the isolated cells suggests a high GABA sensitivity at the axonal endings compared with either the somatic or dendritic region. A similar distribution was not found for glycine. On the contrary, glycine-induced single-channel events with main conductances of 52 and 34 pS were recorded from membrane patches excised from the cells' somata. 7. Conductances induced by glutamate and several excitatory amino acid agonists were observed in a number of the cells. Application of the glutamate agonist 2-amino-4-phosphonobutyric acid (APB) induced an inward current at negative holding potentials associated with the opening of ion channels. In only 5 of 93 cells, APB closed ion channels, leading to a decrease in membrane conductance.

scholarly journals Cholecystokinin-like immunoreactive amacrine cells in the rat retina

2002 ◽  
Vol 19 (4) ◽  
pp. 531-540 ◽  
Author(s):  
SALLY I. FIRTH ◽  
CAROLINA VARELA ◽  
PEDRO DE LA VILLA ◽  
DAVID W. MARSHAK
Keyword(s):  
Cellular Localization ◽  
Plexiform Layer ◽  
Amacrine Cells ◽  
Cell Types ◽  
Bipolar Cells ◽  
Peripheral Retina ◽  
Inner Plexiform Layer ◽  
Rat Retina ◽  
Rats And Mice ◽  
Rod Bipolar Cells

High levels of endogenous cholecystokinin (CCK) are present in the rat retina (Eskay & Beinfeld, 1982), but the cellular localization and physiological actions of CCK in the rat retina are uncertain. The goals of this study were to characterize the cells containing CCK, identify cell types that interact with CCK cells, and investigate the effects of CCK on rod bipolar cells. Rat retinas were labeled with antibody to gastrin-CCK (gCCK) using standard immunofluorescence techniques. Patch-clamp methods were used to record from dissociated rod bipolar cells from rats and mice. Gastrin-CCK immunoreactive (-IR) axons were evenly distributed throughout the retina in stratum 5 of the inner plexiform layer of the rat retina. However, the gCCK-IR somata were only detected in the ganglion cell layer in the peripheral retina. The gCCK-IR cells contained glutamate decarboxylase, and some of them also contained immunoreactive substance P. Labeled axons contacted PKC-IR rod bipolar cells, and recoverin-IR ON-cone bipolar cells. CCK-octapeptide inhibits GABAC but not GABAA mediated currents in dissociated rod bipolar cells.

Functional Organization of Cone Bipolar Cells in the Rat Retina

1997 ◽  
Vol 77 (4) ◽  
pp. 1716-1730 ◽  
Author(s):  
Espen Hartveit
Keyword(s):  
Receptor Antagonist ◽  
Functional Organization ◽  
Amacrine Cells ◽  
Bipolar Cells ◽  
Short Latency ◽  
Rat Retina ◽  
Long Latency ◽  
Aii Amacrine Cells ◽  
Aii Amacrine ◽  
Cone Bipolar Cells

Hartveit, Espen. Functional organization of cone bipolar cells in the rat retina. J. Neurophysiol. 77: 1716–1730, 1997. The responses of cone bipolar cells in slices of rat retina to ionotropic glutamate receptor agonists were recorded with the whole cell voltage-clamp technique in the presence of 5 mM Co2+ and nominally 0 mM Ca2+ extracellularly. Application of the non- N-methyl-d-aspartate (non-NMDA) receptor agonists kainate and (S)-α-amino-3-hydroxy-5-methyl-4-isoxazolepropionate had a series of effects on cone bipolar cells (types 1–9), and the different cell types could be classified as on- or off-type cells according to which type(s) of responses they displayed. First, direct responses were observed in cell types 1–4 as short-latency inward currents at −70 mV with reversal potentials ( E revs) close to 0 mV, characteristic of nonselective cation channels. Second, some cells, among types 5–9, did not display short-latency inward currents to kainate at −70 mV. Other type 5–8 cells displayed short-latency kainate responses, but the currents could not be reversed ( E rev of +40 mV or greater). I suggest that these responses are conveyed to the cone bipolar cells through gap junctions, most likely with AII amacrine cells. The lack of reversal is likely due to a substantial voltage drop across the gap junctions resulting in an inadequate voltage control of AII amacrine cells when the recording pipette is on the cone bipolar cell. Kainate responses recorded directly from AII amacrine cells had E rev ∼ 0 mV. Third, long-latency indirect responses selective for chloride ions ( E rev ∼ chloride equilibrium potential) were observed in many cone bipolar cells during longer-lasting application of kainate. The long-latency response component was suppressed by coapplication of the γ-aminobutyric acid-A (GABAA) receptor antagonist picrotoxin and the GABAC receptor antagonist 3-aminopropyl(methyl)phosphinic acid. This long-latency component was absent in axotomized bipolar cells, suggesting that it was due to external Ca2+-independent release of GABA onto the axon terminals of the cone bipolar cells. All kainate-evoked response components were blocked by the non-NMDA receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione. Application of NMDA evoked no response in cone bipolar cells. These results suggest that cone bipolar cells types 1–4 are off cone bipolar cells, whereas cone bipolar cells types 5–9 are on cone bipolar cells.

Na+ Dependence and the Role of Glutamate Receptors and Na+ Channels in Ion Fluxes During Hypoxia of Rat Hippocampal Slices

2000 ◽  
Vol 84 (4) ◽  
pp. 1869-1880 ◽  
Author(s):  
Michael Müller ◽  
George G. Somjen
Keyword(s):  
Nmda Receptor ◽  
Receptor Antagonist ◽  
Glutamate Receptors ◽  
Pyramidal Neurons ◽  
Hippocampal Slices ◽  
Nmda Receptor Antagonist ◽  
Tissue Slices ◽  
Glutamate Antagonists ◽  
Voltage Gated ◽  
Current Flows

Spreading depression (SD) as well as hypoxia-induced SD-like depolarization in forebrain gray matter are characterized by near complete depolarization of neurons. The biophysical mechanism of the depolarization is not known. Earlier we reported that simultaneous pharmacological blockade of all known major Na+ and Ca2+ channels prevents hypoxic SD. We now recorded extracellular voltage, Na+, and K+concentrations and the intracellular potential of individual CA1 pyramidal neurons during hypoxia of rat hippocampal tissue slices after substituting Na+ in the bath by an impermeant cation, or in the presence of channel blocking drugs applied individually and in combination. Reducing extracellular Na+ concentration [Na+]o to 90 mM postponed the hypoxia-induced extracellular DC-potential deflection (Δ V o) and reduced its amplitude, and it also postponed the SD-like depolarization of neurons. After lowering [Na+]o to 25 mM, SD-like Δ V o became very small, indicating that an influx of Na+ is required for SD; influx of Ca2+ ions alone is not sufficient. We then asked whether the SD-related Na+ current flows through glutamate-controlled and/or through voltage-gated Na+channels. Administration of either the non- N-methyl-d-aspartate (NMDA) receptor antagonist 6,7-dinitroquinoxaline-2,3-dione (DNQX), or the NMDA receptor antagonist (±)-3-(2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid (CPP) postponed the hypoxic Δ V o and depressed its amplitude but the effect of the combined administration of these two drugs was not greater than that of either alone. During the early phase of hypoxia, before SD onset, [K+]oincreased faster and reached a much higher level in the presence of glutamate antagonists than in their absence. The [K+]o level reached at the height of hypoxic SD was, however, not affected. When TTX was added to DNQX and CPP, SD was prevented in half the trials. When SD did occur, it was greatly delayed, yet eventually neurons depolarized to the same extent as in normal solution. The SD-related sudden drop in [Na+]o was depressed by only 19% in the presence of the three drugs, indicating that Na+ can flow into cells through pathways other than ionotropic glutamate receptors and TTX-sensitive Na+ channels. We conclude that, when they are functional, glutamate-receptor-mediated and voltage-gated Na+ currents are the major generators of the self-regenerative rapid depolarization, but in their absence other pathways can sometimes take their place. The final level of SD-like depolarization is determined by positive feedback and not by the number of channels available. A schematic flow chart of the events generating hypoxic SD is discussed.

Sign in / Sign up

Export Citation Format

Share Document