On bipolar cell responses in the teleost retina are generated by two distinct mechanisms

1996 ◽  
Vol 76 (6) ◽  
pp. 3842-3849 ◽  
Author(s):  
G. B. Grant ◽  
J. E. Dowling
Keyword(s):  
Lucifer Yellow ◽  
Reversal Potential ◽  
Chloride Ions ◽  
Bipolar Cells ◽  
Equilibrium Potential ◽  
Perforated Patch ◽  
Cell Responses ◽  
Patch Pipette ◽  
Teleost Retina ◽  
Local Superfusion

1. ON Bipolar cells were recorded in slices obtained from hybrid bass retinas. Cells were identified as bipolar cells by position in the slice, by characteristic voltage- and ligand-gated currents, and by filling with the fluorescent dye Lucifer yellow. Cells were recorded with the use of either whole cell or perforated-patch techniques. Standard electrophysiological protocols were used. Drugs were applied by puffing and by local superfusion. 2. Application of exogenous glutamate to ON bipolar cells generated two characteristic responses. One effect of glutamate was to open a conductance with a reversal potential close to the chloride equilibrium potential. The other effect of glutamate was to close a conductance with a reversal potential near 0 mV. These two effects of glutamate on ON bipolar cells match the effects of light described previously with the use of intracellular recordings. Thus the effects of glutamate that we report here appear to underlie the rod and cone inputs to these cells. 3. Many of the ON bipolar cells recorded demonstrated both classes of responses to glutamate. To isolate the two responses, 500 microM glutamate was first applied, and then glutamate in the presence of 5 microM 2-amino-4-phosphonobutyric acid (APB). APB specifically blocks the effects of glutamate on the putative roddriven glutamate receptor (the glutamate-elicited conductance decrease), allowing us to study in isolation the effects of glutamate on the cone component, the glutamate-activated chloride current (IGlu). 4. By isolating IGlu as described above, and taking advantage of the fact that amphotericin-perforated-patch recordings limit the diffusion of chloride ions between the patch pipette and the cell body, we found the physiological reversal potential of IGlu to be -58.9 +/- 7.7 (SD) mV. 5. Both the putative rod- and cone-mediated glutamatergic inputs to these bipolar cells could be activated by driving the photoreceptors with puffs of potassium. The currents recorded with this technique were very similar to those seen with direct application of glutamate.

Properties of GABA-activated whole-cell currents in bipolar cells of the rat retina

1990 ◽  
Vol 4 (4) ◽  
pp. 349-357 ◽  
Author(s):  
Hermes H. Yeh ◽  
Maria B. Lee ◽  
Jane E. Cheun
Keyword(s):  
Reversal Potential ◽  
Cell Voltage ◽  
Bipolar Cells ◽  
Whole Cell ◽  
Rat Retina ◽  
Enzymatic Dissociation ◽  
Adult Rat ◽  
Cell Responses ◽  
Conductance Increase ◽  
Distinct Morphology

AbstractThis paper describes experiments on GABA-activated whole-cell membrane currents in bipolar cells freshly isolated from the adult rat retina. The main goal was to determine whether bipolar cell responses to GABA could be resolved in terms of mediation by the GABAA receptor, the GABAB receptor, or both. Bipolar cells were isolated by gentle enzymatic dissociation and identified by their distinct morphology. GABA agonists and antagonists were applied focally by pressure and the resultant currents were recorded under whole-cell voltage clamp. In all bipolar cells tested, GABA (0.1–100 μM) induced a monophasic response associated with a conductance increase (IGABA). The shift in reversal potential for IGABA as a function of pipet [CI] paralleled that predicted based on the Nernst equation for Cl−. IGABA was mimicked by muscimol (5–20 μM) and antagonized by bicuculline (20–100 μM). Baclofen (0.1–1.0 mM) produced no apparent conductance change. “Hot spots” of sensitivity to GABA which might be associated with regions of synaptic contact were not found; both the soma and processes of all bipolar cells were responsive to focally applied GABA. Furthermore, all bipolar cells tested responded to glycine.In conclusion, we have established the presence of GABAA receptors on rat retinal bipolar cells. Our data suggest further that these cells lack GABAB receptors. Finally, our observation that bipolar cells in the rat retina are relatively homogeneous in terms of their sensitivity to GABA and glycine lead us to postulate that the functional significance of the presence of receptors and their distribution on a neuron may be dictated more by the topography of the presynaptic inputs than by its inherent chemosensitivity.

Localized IP3-Evoked Ca2+ Release Activates a K+ Current in Primary Vagal Sensory Neurons

2004 ◽  
Vol 91 (5) ◽  
pp. 2344-2352 ◽  
Author(s):  
Robert E. Hoesch ◽  
Daniel Weinreich ◽  
Joseph P. Y. Kao
Keyword(s):  
Sensory Neurons ◽  
Reversal Potential ◽  
Nodose Ganglion ◽  
Ion Concentration ◽  
Equilibrium Potential ◽  
Nodose Ganglion Neurons ◽  
Patch Pipette ◽  
Intracellular Ca ◽  
K Current ◽  
Ganglion Neurons

Electrophysiological and microfluorimetric techniques were used to determine whether intracellular photorelease of caged IP3, and the consequent release of Ca2+, could trigger a Ca2+-activated K+ current ( IIP3). Photorelease of caged IP3 evoked an IIP3 that averaged 2.36 ± 0.35 (SE) pA/pF in 24 of 28 rabbit primary vagal sensory neurons (nodose ganglion neurons, NGNs) voltage-clamped at –50 mV. IIP3 was abolished by intracellular BAPTA (2 mM), a Ca2+ chelator. Changing the K+ equilibrium potential by increasing extracellular K+ ion concentration caused a predicted Nernstian shift in the reversal potential of IIP3. These results indicated that IIP3 was a Ca2+-dependent K+ current. IIP3 was unaffected by three common antagonists of Ca2+-activated K+ currents: bath-applied iberiotoxin (50 nM) or apamin (100 nM), and intracellular 8-Br-cAMP (100 μM) included in the patch pipette. We have previously demonstrated that both IP3-evoked Ca2+ release and Ca2+-induced Ca2+ release (CICR) are co-expressed in NGNs and that CICR can trigger a Ca2+-activated K+ current. In the present study, using caffeine, a CICR agonist, to selectively attenuate intracellular Ca2+ stores, we showed that IP3-evoked Ca2+ release occurs independently of CICR, but interestingly, that a component of IIP3 requires CICR. These data suggest that IP3-evoked Ca2+ release activates a K+ current that is pharmacologically distinct from other Ca2+-activated K+ currents in NGNs. We describe several models that explain our results based on Ca2+ signaling microdomains in NGNs.

Local superfusion modifies the inward rectifying potassium conductance of isolated retinal horizontal cells

1988 ◽  
Vol 60 (4) ◽  
pp. 1322-1332 ◽  
Author(s):  
I. Perlman ◽  
A. G. Knapp ◽  
J. E. Dowling
Keyword(s):  
White Perch ◽  
Reversal Potential ◽  
Ringer Solution ◽  
Inward Rectifier ◽  
Horizontal Cells ◽  
Equilibrium Potential ◽  
Steady State Current ◽  
Conductance Increase ◽  
Local Superfusion ◽  
Drug Free

1. Horizontal cells were enzymatically and mechanically dissociated from the white perch (Roccus americana) retina and voltage clamped using patch electrodes. Steady-state current-voltage (I-V) relationships of solitary horizontal cells were determined by changing the membrane potential in a rampwise fashion. 2. The I-V curve of cells bathed in normal Ringer solution exhibited a large conductance increase at negative membrane potentials. This conductance activated near the K+ equilibrium potential, had no clear reversal potential, was enhanced by raising the extracellular concentration of K+, and was suppressed by external Cs+. These properties identify the conductance as the inward (anomalous) rectifier. 3. Continuous superfusion of the cells' local environment with drug-free Ringer reduced the magnitude of the inward rectifier current and shifted its activation point to more negative potentials. This effect developed over approximately 30 s, lasted as long as superfusion continued and was reversible upon cessation of superfusion. 4. Pressure ejection of drug-free Ringer solution onto cells bathed in the identical solution also reduced the magnitude of the inward rectifier current, although the effects were more rapid and more transient than those exerted by superfusion. Pressure ejection had little effect when cells were simultaneously superfused with Ringer, suggesting a common mode of action on the inward rectifier. 5. In the absence of superfusion, pressure ejection of Ringer containing 200 microM L-glutamate had a biphasic effect on membrane conductance. At potentials above -60 mV, glutamate caused a conductance increase with a reversal potential near +10 mV. At potentials below -60 mV, glutamate caused a conductance decrease whose reversal potential could not reliably be determined. The latter effect was similar to the suppression of the inward rectifier by application of Ringer alone, suggesting that it may represent an artifact of pressure ejection rather than a direct effect of glutamate. 6. In support of this interpretation, we found that pressure ejection of glutamate in the presence of external Cs+ (which blocks the inward rectifier) or during local superfusion with Ringer (which prevents attenuation of the inward rectifier by pressure ejection) did not cause a conductance decrease at negative potentials. Under these conditions, glutamate caused primarily a conductance increase with a reversal potential near +10 mV.(ABSTRACT TRUNCATED AT 400 WORDS)

A voltage-gated chloride conductance in rat cultured astrocytes

1986 ◽  
Vol 228 (1252) ◽  
pp. 267-288 ◽  
Keyword(s):  
Time Course ◽  
Reversal Potential ◽  
Outward Current ◽  
Chloride Ions ◽  
Chloride Conductance ◽  
Equilibrium Potential ◽  
Free Calcium ◽  
Patch Clamp Technique ◽  
Bathing Medium ◽  
Cultured Astrocytes

Large voltage-dependent outward currents are recorded with the wholecell patch-clamp technique from rat cultured astrocytes under conditions where an outward movement of potassium ions is excluded (either by blockage of the potassium channels pharmacologically or by replacement of the internal potassium by the impermeant large organic cation N -methyl-( + )-glucamine). The current, which is activated at potentials more positive than —40 to —50 mV, is normally carried by an inward movement of chloride ions. Its reversal potential is the same as the chloride equilibrium potential. With depolarization to +60 mV (for 225 ms) little or no inactivation of the current occurs: with depolarizations to +90 to +110 mV a time-dependent decay is seen. The current, which is often not marked immediately after formation of the whole-cell clamp, generally increases over a period of a few minutes to a maximum (after which it usually declines), as if some as yet unknown intracellular factor keeping the channels closed were being washed away from the membrane. The time course of this phenomenon is not affected by changing of the internal free calcium concentration (from 10 -8 to 10 -6 m) or by an intracellular mixture of cyclic AMP (1 mm), ATP (4 mm) and Mg + (2 mm). The conductance is slightly increased when the chloride of the bathing medium is replaced by bromide; is much reduced on replacement by methylsulphate, sulphate, isethionate, or acetate; and is virtually abolished on replacement by the large anion gluconate. The outward current is inhibited by the disulphonate stilbenes DIDS and SITS; this blocking action was initially partly reversible, although never completely so. It is suggested that the chloride conductance plays a role in the spatial buffering of potassium by astrocytes.

Reversal potential of GABA-induced currents in rod bipolar cells of the rat retina

1991 ◽  
Vol 6 (4) ◽  
pp. 399-401 ◽  
Author(s):  
Masayuki Yamashita ◽  
Heinz Wässle
Keyword(s):  
Cell Membrane ◽  
Reversal Potential ◽  
Bipolar Cells ◽  
Cell Interior ◽  
Rat Retina ◽  
Adult Rat ◽  
Patch Pipette ◽  
Patch Clamp Electrode ◽  
Induced Currents ◽  
Rod Bipolar Cells

AbstractGABA-induced whole-cell currents were measured in rod bipolar cells dissociated from the adult rat retina. The patch-clamp electrode contained nystatin, which made the cell membrane electrically permeable without rupture, thus retarding the rate of diffusion of Cl– ions from the patch pipette to the cell interior. The reversal potential of the GABA-induced currents was around –70 mV at an extracellular Cl-–concentration of 149 mM. We conclude that GABA generates hyperpolarizing responses in rod bipolar cells of the rat retina.

Nitric Oxide Activates Leak K+ Currents in the Presumed Cholinergic Neuron of Basal Forebrain

2007 ◽  
Vol 98 (6) ◽  
pp. 3397-3410 ◽  
Author(s):  
Youngnam Kang ◽  
Yoshie Dempo ◽  
Atsuko Ohashi ◽  
Mitsuru Saito ◽  
Hiroki Toyoda ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Basal Forebrain ◽  
Reversal Potential ◽  
Soluble Guanylyl Cyclase ◽  
Outward Current ◽  
Pump Current ◽  
Atp Depletion ◽  
Equilibrium Potential ◽  
No Donor ◽  
Bath Application

Learning and memory are critically dependent on basal forebrain cholinergic (BFC) neuron excitability, which is modulated profoundly by leak K+ channels. Many neuromodulators closing leak K+ channels have been reported, whereas their endogenous opener remained unknown. We here demonstrate that nitric oxide (NO) can be the endogenous opener of leak K+ channels in the presumed BFC neurons. Bath application of 1 mM S-nitroso- N-acetylpenicillamine (SNAP), an NO donor, induced a long-lasting hyperpolarization, which was often interrupted by a transient depolarization. Soluble guanylyl cyclase inhibitors prevented SNAP from inducing hyperpolarization but allowed SNAP to cause depolarization, whereas bath application of 0.2 mM 8-bromoguanosine-3′,5′-cyclomonophosphate (8-Br-cGMP) induced a similar long-lasting hyperpolarization alone. These observations indicate that the SNAP-induced hyperpolarization and depolarization are mediated by the cGMP-dependent and -independent processes, respectively. When examined with the ramp command pulse applied at –70 mV under the voltage-clamp condition, 8-Br-cGMP application induced the outward current that reversed at K+ equilibrium potential ( EK) and displayed Goldman-Hodgkin-Katz rectification, indicating the involvement of voltage-independent K+ current. By contrast, SNAP application in the presumed BFC neurons either dialyzed with the GTP-free internal solution or in the presence of 10 μM Rp-8-bromo-β-phenyl-1,N2-ethenoguanosine 3′,5′-cyclic monophosphorothioate sodium salt, a protein kinase G (PKG) inhibitor, induced the inward current that reversed at potentials much more negative than EK and close to the reversal potential of Na+-K+ pump current. These observations strongly suggest that NO activates leak K+ channels through cGMP-PKG-dependent pathway to markedly decrease the excitability in BFC neurons, while NO simultaneously causes depolarization by the inhibition of Na+-K+ pump through ATP depletion.

Reciprocal inhibition of voltage-gated potassium currents (IK(V)) by activation of cannabinoid CB1and dopamine D1receptors in ON bipolar cells of goldfish retina

2005 ◽  
Vol 22 (1) ◽  
pp. 55-63 ◽  
Author(s):  
SHIH-FANG FAN ◽  
STEPHEN YAZULLA
Keyword(s):  
G Protein ◽  
Receptor Agonist ◽  
Lucifer Yellow ◽  
Reciprocal Inhibition ◽  
Receptor Activation ◽  
Light Signal ◽  
Bipolar Cells ◽  
Protein G ◽  
Calcium Dependent ◽  
Voltage Dependent

Cannabinoid CB1receptor (viaGs) and dopamine D2receptor (viaGi/o) antagonistically modulate goldfish cone membrane currents. As ON bipolar cells have CB1and D1receptors, but not D2receptors, we focused on whether CB1receptor agonist and dopamine interact to modulate voltage-dependent outward membrane K+currentsIK(V)of the ON mixed rod/cone (Mb) bipolar cells. Whole-cell currents were recorded from Mb bipolar cells in goldfish retinal slices. Mb bipolar cells were identified by intracellular filling with Lucifer yellow. The bath solution was calcium-free and contained 1 mM cobalt to block indirect calcium-dependent effects. Dopamine (10 μM) consistently increasedIK(V)by a factor of 1.57 ± 0.12 (S.E.M.,n= 15). A CB receptor agonist, WIN 55212-2 (0.25–1 μM), had no effect, but 4 μM WIN 55212-2 suppressedIK(V)by 60%. IfIK(V)was first increased by 10 μM dopamine, application of WIN 55212-2 (0.25–1 μM) reversibly blocked the effect of dopamine even though these concentrations of WIN 55212-2 had no effect of their own. If WIN 55212-2 was applied first and dopamine (10 μM) was added to the WIN-containing solution, 0.1 μM WIN 55212-2 blocked the effect of dopamine. All effects of WIN 55212-2 were blocked by coapplication of SR 141716A (CB1antagonist) and pretreatment with pertussis toxin (blocker of Gi/o) indicating actionviaCB1receptor activation of G protein Gi/o. Coactivation of CB1and D1receptors on Mb bipolar cells produces reciprocal effects onIK(V). The CB1-evoked suppression ofIK(V)is mediated by G protein Gi/o, whereas the D1-evoked enhancement is mediated by G protein Gs. As dopamine is a retinal “light” signal, these data support our notion that endocannabinoids function as a “dark” signal, interacting with dopamine to set retinal sensitivity.

Neuronal Sodium Leak Channel Is Responsible for the Detection of Sodium in the Rat Median Preoptic Nucleus

2011 ◽  
Vol 105 (2) ◽  
pp. 650-660 ◽  
Author(s):  
Christina Tremblay ◽  
Emmanuelle Berret ◽  
Mélaine Henry ◽  
Benjamin Nehmé ◽  
Louis Nadeau ◽  
...  
Keyword(s):  
Close Contact ◽  
Critical Role ◽  
Reversal Potential ◽  
Outward Current ◽  
The Body ◽  
Equilibrium Potential ◽  
Preoptic Nucleus ◽  
Leak Channel ◽  
Median Preoptic Nucleus ◽  
Electrophysiological Recordings

Sodium (Na+) ions are of primary importance for hydromineral and cardiovascular homeostasis, and the level of Na+ in the body fluid compartments [plasma and cerebrospinal fluid (CSF)] is precisely monitored in the hypothalamus. Glial cells seem to play a critical role in the mechanism of Na+ detection. However, the precise role of neurons in the detection of extracellular Na+ concentration ([Na+]out) remains unclear. Here we demonstrate that neurons of the median preoptic nucleus (MnPO), a structure in close contact with the CSF, are specific Na+ sensors. Electrophysiological recordings were performed on dissociated rat MnPO neurons under isotonic [Na+] (100 mM NaCl) with local application of hypernatriuric (150, 180 mM NaCl) or hyponatriuric (50 mM NaCl) external solution. The hyper- and hyponatriuric conditions triggered an in- and an outward current, respectively. The reversal potential of the current matched the equilibrium potential of Na+, indicating that a change in [Na+]out modified the influx of Na+ in the MnPO neurons. The conductance of the Na+ current was not affected by either the membrane potential or the [Na+]out. Moreover, the channel was highly selective for lithium over guanidinium. Together, these data identified the channel as a Na+ leak channel. A high correlation between the electrophysiological recordings and immunofluorescent labeling for the NaX channel in dissociated MnPO neurons strongly supports this channel as a candidate for the Na+ leak channel responsible for the Na+-sensing ability of rat MnPO neurons. The absence of NaX labeling and of a specific current evoked by a change in [Na+]out in mouse MnPO neurons suggests species specificity in the hypothalamus structures participating in central Na+ detection.

Cholecystokinin-gated currents in neurons of the rat solitary complex in vitro

1993 ◽  
Vol 70 (6) ◽  
pp. 2584-2595 ◽  
Author(s):  
P. Branchereau ◽  
J. Champagnat ◽  
M. Denavit-Saubie
Keyword(s):  
Voltage Clamp ◽  
Potassium Current ◽  
Reversal Potential ◽  
Input Resistance ◽  
Calcium Currents ◽  
Equilibrium Potential ◽  
Potassium Ions ◽  
Nernst Equation ◽  
Membrane Hyperpolarization ◽  
Cckb Receptor

1. Ionic conductances controlled by type A and type B cholecystokinin (CCK) receptors were studied in neurons of the rat nucleus tractus solitarius (NTS) and dorsal motor nucleus of the vagus (DMNV), using intracellular and whole-cell patch clamp recordings in current or voltage clamp configuration during bath application of agonists (CCK8, CCK4, BC 264) and antagonists. 2. CCKA receptor-related inhibition was associated with a membrane hyperpolarization and a decrease in input resistance that developed 2-6 min after the arrival of drug into the extracellular medium. These effects were induced by 5 nM CCK8 but not BC 264 and they were blocked by the CCKA antagonist, L-364,718, but not by the CCKB antagonist, L-365,260. 3. CCKA receptor-related inhibition was generated by a potassium current that reversed at a reversal potential E(rev) of -73 +/- 1 (mean +/- SE) mV with bathing potassium concentration [K+]o = 6 mM and at -88 +/- 1 with [K+]o = 3 mM, in agreement with the Nernst equation for potassium ions. 4. CCKB receptor-related excitation was associated with a membrane depolarization and an increase of the input resistance induced by the following agonists at threshold concentrations: CCK8 (0.2 nM) > or = BC 264 (0.4 nM) > CCK4 (10.9 nM). The increase of input resistance was abolished by L-365,260 and was maintained after blockade of the CCKA current by L-364,718. 5. CCKB receptor-related excitation, in the neurons (30% of cases) in which clear response reversal was observed, appeared to be generated by a decrease of a potassium conductance. Responses showed a reversal potential E(rev) of -68 +/- 4 mV with [K+]o = 6 mM and -89 +/- 1 mV with [K+]o = 3 mM, verifying predictions from the Nernst equation applied to potassium ions. However, in 70% of cases, clear reversal was not observed at membrane potentials negative to the theoretical potassium equilibrium potential EK. 6. In voltage clamp studies, CCK8 induced a 181 +/- 17 pA inward current associated with a 26 +/- 4% decrease in the instantaneous current (I(ins)) generated by hyperpolarizing voltage steps. This effect on I(ins) was demonstrated in the absence of effects on the outward noninactivating potassium current (IM) and on the inward noninactivating cationic current (IQ). 7. CCKB receptor-mediated excitation was not suppressed by cobalt, a blocker of calcium currents, and was not associated with a change of the calcium-dependent potassium current (IK(Ca)).(ABSTRACT TRUNCATED AT 400 WORDS)

Whole cell current analyses of pancreatic acinar AR42J cells. I. Voltage- and Ca(2+)-activated currents

1991 ◽  
Vol 260 (5) ◽  
pp. C934-C948 ◽  
Author(s):  
K. Kusano ◽  
H. Gainer
Keyword(s):  
Reversal Potential ◽  
Outward Current ◽  
Pancreatic Acinar Cells ◽  
Equilibrium Potential ◽  
Channel Blockers ◽  
Whole Cell ◽  
Inward Current ◽  
Tail Current ◽  
Ar42j Cells ◽  
Conductance Increase

Voltage- and Ca(2+)-activated whole cell currents were studied in AR42J cells, a clonal cell line derived from rat pancreatic acinar cells, using a patch electrode voltage-clamp technique. Four kinds of ionic currents were identified by their ionic dependencies, pharmacological properties, and kinetic parameters: 1) an outward current flow due mainly to a voltage-dependent K(+)-conductance increase, 2) an initial transient inward current due to an Na(+)-conductance increase, 3) transient and long-duration inward current due to a Ca(2+)-conductance increase, and 4) a slowly activating inward current that persists over the duration of the depolarizing pulse and deactivates slowly upon repolarization, producing a slow inward tail current. The slow inward tail current was particularly robust and was interpreted as due to a Ca(2+)-activated Cl(-)-conductance increase, since 1) the generation of this current was blocked by removing the extracellular Ca2+, applying Ca(2+)-channel blockers (Cd2+, nifedipine), or by lowering the intracellular Ca2+ concentration [( Ca2+]i) with EGTA; and 2) the reversal potential (Erev) of the slow inward tail current was close to 0 mV in the control condition (152 mM [Cl-]o/154 mM [Cl-]i), and changes of the [Cl-]o/[Cl )i ratio shifted the Erev toward the predicted Cl- equilibrium potential.

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