scholarly journals Patch-clamp studies of isolated mouse olfactory receptor neurons.

1987 ◽  
Vol 90 (1) ◽  
pp. 95-125 ◽  
Author(s):  
R A Maue ◽  
V E Dionne
Keyword(s):  
Patch Clamp ◽  
Olfactory Receptor ◽  
Membrane Conductance ◽  
Olfactory Receptor Neurons ◽  
Membrane Properties ◽  
K Channel ◽  
Patch Clamp Technique ◽  
Adult Mice ◽  
Intracellular Ca ◽  
Receptor Neurons

Olfactory receptor neurons isolated from embryonic, neonatal, and adult mice were studied using the patch-clamp technique. Several distinct types of ion channels were characterized in patches of membrane from the neuronal soma and the dendritic knob of receptor neurons, including a 130-pS Ca++-activated K+ channel with voltage-dependent kinetics, an 80-pS Ca++-activated K+ channel with voltage-insensitive kinetics, a 25-pS K+ channel with properties similar to inward rectifiers, and a 40-pS K+ channel that was activated and then inactivated by rapid depolarization. Evidence of large-conductance (greater than 200 pS) Cl- channels, which were Ca++ insensitive and increasingly active at depolarizing membrane potentials, and voltage-activated Ca++ channels (16 pS) was also obtained. From K+ channel activity recorded from cell-attached patches, the intracellular [Ca++] was inferred to be below 0.1 microM, and the membrane potential was inferred to be approximately -50 mV. The receptor neurons had high input resistances, and action potentials could be elicited by picoampere amounts of depolarizing current. The receptor neurons responded to applied odorant molecules and to forskolin with increases in membrane conductance. These results provide a description of the membrane properties of olfactory receptor neurons and a basis for understanding their electrical activity and response to odorants.

scholarly journals Chemosensory responses in isolated olfactory receptor neurons from Necturus maculosus.

1992 ◽  
Vol 99 (3) ◽  
pp. 415-433 ◽  
Author(s):  
V E Dionne
Keyword(s):  
Olfactory Receptor ◽  
Membrane Conductance ◽  
Input Resistance ◽  
Primary Response ◽  
Olfactory Receptor Neurons ◽  
Whole Cell ◽  
Whole Cell Recording ◽  
Necturus Maculosus ◽  
Cell Recording ◽  
Receptor Neurons

Olfactory receptor neurons were isolated without enzymes from the mudpuppy, Necturus maculosus, and tested for chemosensitivity. The cells responded to odorants with changes in firing frequency and alterations in excitability that were detected with tight-seal patch electrodes using on-cell and whole-cell recording conditions. Chemosensitive cells exhibited two primary response characteristics: excitation and inhibition. Both types of primary response were observed in different cells stimulated by mixtures of amino acids as well as by the single compound L-alanine, suggesting that there may be more than one transduction pathway for some odorants. Using the normal whole-cell recording method, the chemosensitivity of competent cells washed out rapidly; a resistive whole-cell method was used to record odorant responses under current-clamp conditions. In response to chemical stimulation, excitability appeared to be modulated in several different ways in different cells: odorants induced hyperpolarizing or depolarizing receptor potentials, elicited or inhibited transient, rhythmic generator potentials, and altered excitability without changing the membrane potential or input resistance. These effects suggest that olfactory transduction is mediated through at least three different pathways with effects on four or more components of the membrane conductance. Polychotomous pathways such as these may be important for odor discrimination and for sharpening the "odor image" generated in the olfactory epithelium.

scholarly journals Maxi K+ channels and their relationship to the apical membrane conductance in Necturus gallbladder epithelium.

1990 ◽  
Vol 95 (5) ◽  
pp. 791-818 ◽  
Author(s):  
Y Segal ◽  
L Reuss
Keyword(s):  
Patch Clamp ◽  
Apical Membrane ◽  
Membrane Conductance ◽  
Membrane Depolarization ◽  
Membrane Voltage ◽  
K Channel ◽  
Gallbladder Epithelium ◽  
Patch Clamp Technique ◽  
K Channels ◽  
Necturus Gallbladder

Using the patch-clamp technique, we have identified large-conductance (maxi) K+ channels in the apical membrane of Necturus gallbladder epithelium, and in dissociated gallbladder epithelial cells. These channels are more than tenfold selective for K+ over Na+, and exhibit unitary conductance of approximately 200 pS in symmetric 100 mM KCl. They are activated by elevation of internal Ca2+ levels and membrane depolarization. The properties of these channels could account for the previously observed voltage and Ca2+ sensitivities of the macroscopic apical membrane conductance (Ga). Ga was determined as a function of apical membrane voltage, using intracellular microelectrode techniques. Its value was 180 microS/cm2 at the control membrane voltage of -68 mV, and increased steeply with membrane depolarization, reaching 650 microS/cm2 at -25 mV. We have related maxi K+ channel properties and Ga quantitatively, relying on the premise that at any apical membrane voltage Ga comprises a leakage conductance and a conductance due to maxi K+ channels. Comparison between Ga and maxi K+ channels reveals that the latter are present at a surface density of 0.09/microns 2, are open approximately 15% of the time under control conditions, and account for 17% of control Ga. Depolarizing the apical membrane voltage leads to a steep increase in channel steady-state open probability. When correlated with patch-clamp studies examining the Ca2+ and voltage dependencies of single maxi K+ channels, results from intracellular microelectrode experiments indicate that maxi K+ channel activity in situ is higher than predicted from the measured apical membrane voltage and estimated bulk cytosolic Ca2+ activity. Mechanisms that could account for this finding are proposed.

Patch-Clamp Measurements on Mammalian Olfactory Receptor Neurons

1994 ◽  
pp. 168-172
Author(s):  
Peter H. Barry ◽  
Joseph W. Lynch ◽  
Sundran Rajendra
Keyword(s):  
Patch Clamp ◽  
Olfactory Receptor ◽  
Olfactory Receptor Neurons ◽  
Receptor Neurons

Transduction diversity in olfaction.

1994 ◽  
Vol 194 (1) ◽  
pp. 1-21 ◽  
Author(s):  
V E Dionne ◽  
A E Dubin
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Olfactory Receptor ◽  
Membrane Conductance ◽  
Chemical Signals ◽  
Odor Discrimination ◽  
Olfactory Receptor Neurons ◽  
Electrophysiological Recordings ◽  
The Central Nervous System ◽  
Receptor Neurons

Odors are powerful stimuli that can focus the attention, elicit behaviors (or misbehaviors) and even resurrect forgotten memories. These actions are directed by the central nervous system, but they depend upon the initial transduction of chemical signals by olfactory receptor neurons. Electrophysiological recordings suggest that the responses of olfactory receptor neurons to odors are more diverse than was initially believed, being mediated by effects on several different conductances. Both excitatory and inhibitory responses are produced by these effects and some, if not all, odors can affect more than one component of the membrane conductance. The extent of this diversity is reviewed here, and its impact on our understanding of odor discrimination is discussed.

scholarly journals Standing calcium gradients in olfactory receptor neurons can be abolished by amiloride or ruthenium red.

1993 ◽  
Vol 102 (5) ◽  
pp. 817-831 ◽  
Author(s):  
F W Lischka ◽  
D Schild
Keyword(s):  
Spatial Distribution ◽  
Intracellular Calcium ◽  
Olfactory Receptor ◽  
Ruthenium Red ◽  
Olfactory Receptor Neurons ◽  
Patch Clamp Technique ◽  
Pipette Solution ◽  
Fura 2 ◽  
Receptor Neurons ◽  
In Cells

Digital imaging and the patch clamp technique were used to investigate the intracellular calcium concentration in olfactory receptor neurons using the Ca2+ indicator dyes fura-2 and fura-2/AM. The spatial distribution of Cai2+ as well as its modification by the drugs Amiloride and Ruthenium Red were studied. Resting calcium concentrations in cells loaded with fura-2/AM were between 10 and 200 nM. In cells that were loaded with the pentapotassium salt of fura-2 through the patch pipette, calcium concentrations were in the same range if ATP was added to the pipette solution. Otherwise, Ca2+ reached concentrations of approximately 500 nM. Most of the observed cells showed a standing gradient of calcium, the calcium concentrations in the distal dendritic end of the cell being higher than in the soma. In some cells, the gradient was markedly reduced or abolished by adding either Amiloride or Ruthenium Red to the bath solution. In a few cells, neither drug had any effect upon the gradient. It is suggested that the inhomogenous spatial distribution of intracellular calcium in olfactory cells of Xenopus laevis is brought about by an influx of calcium ions through two different calcium permeable conductances in the peripheral compartments of the cells. The fact that only either Ruthenium Red or Amiloride abolished the standing calcium gradient further suggested that the two conductances blocked were presumably not coexpressed in the same cells.

Cyclic AMP Cascade Mediates the Inhibitory Odor Response of Isolated Toad Olfactory Receptor Neurons

2005 ◽  
Vol 94 (3) ◽  
pp. 1781-1788 ◽  
Author(s):  
Rodolfo Madrid ◽  
Ricardo Delgado ◽  
Juan Bacigalupo
Keyword(s):  
Cyclic Amp ◽  
Olfactory Receptor ◽  
Membrane Conductance ◽  
Receptor Potential ◽  
Olfactory Receptor Neurons ◽  
Direct Role ◽  
Olfactory Neurons ◽  
Pharmacological Agents ◽  
Receptor Neurons ◽  
20 Nm

Odor stimulation may excite or inhibit olfactory receptor neurons (ORNs). It is well established that the excitatory response involves a cyclic AMP (cAMP) transduction mechanism that activates a nonselective cationic cyclic nucleotide-gated (CNG) conductance, accompanied by the activation of a Ca2+-dependent Cl− conductance, both causing a depolarizing receptor potential. In contrast, odor inhibition is attributed to a hyperpolarizing receptor potential. It has been proposed that a Ca2+-dependent K+ (KCa) conductance plays a key role in odor inhibition, both in toad and rat isolated olfactory neurons. The mechanism underlying odor inhibition has remained elusive. We assessed its study using various pharmacological agents and caged compounds for cAMP, Ca2+, and inositol 1,4,5-triphosphate (InsP3) on isolated toad ORNs. The odor-triggered KCa current was reduced on exposing the cell either to the CNG channel blocker LY83583 (20 μM) or to the adenylyl cyclase inhibitor SQ22536 (100 μM). Photorelease of caged Ca2+ activated a Cl− current sensitive to niflumic acid (10 μM) and a K+ current blockable by charybdotoxin (20 nM) and iberiotoxin (20 nM). In contrast, photoreleased Ca2+ had no effect on cells missing their cilia, indicating that these conductances are confined to the cilia. Photorelease of cAMP induced a charybdotoxin-sensitive K+ current in intact ORNs. Photorelease of InsP3 did not increase the membrane conductance of olfactory neurons, arguing against a direct role of InsP3 in chemotransduction. We conclude that a cAMP cascade mediates the activation of the ciliary Ca2+-dependent K+ current and that the Ca2+ ions that activate the inhibitory current enter the cilia through CNG channels.

scholarly journals Modulation of Cl-, K+, and nonselective cation conductances by taurine in olfactory receptor neurons of the mudpuppy Necturus maculosus.

1993 ◽  
Vol 101 (4) ◽  
pp. 469-485 ◽  
Author(s):  
A E Dubin ◽  
V E Dionne
Keyword(s):  
Olfactory Receptor ◽  
Membrane Conductance ◽  
Olfactory Receptor Neurons ◽  
Whole Cell ◽  
Necturus Maculosus ◽  
Cation Conductance ◽  
Receptor Neurons ◽  
Excitatory Responses ◽  
Cl Conductance

Odors are transduced by processes that modulate the membrane conductance of olfactory receptor neurons. Olfactory neurons from the aquatic salamander, Necturus maculosus, were acutely isolated without enzymes and studied with a resistive whole-cell method to minimize loss of soluble intracellular constituents. 55 of 224 neurons responded to the test compound taurine at concentrations between 10 nM and 100 microM. Four different conductance changes were elicited by taurine: an increased Cl- conductance (33%), an increased nonselective cation conductance (15%), a decreased Cl- conductance (15%), and a decreased K+ conductance (15%); in addition, responses too small to be characterized were elicited in some neurons. In most cases, taurine appeared to modulate only a single conductance in any particular cell. Modulation of each conductance was dose dependent, and each response ran down quickly in the normal whole-cell mode, presumably due to washout of a diffusible component in the transduction pathway. Modulation of taurine-sensitive conductances caused either inhibitory or excitatory responses. A similar diversity of responses in vivo would produce a complex pattern of electrical activity that could encode the identity and characteristics of an odor.

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