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.

Odor-induced currents in Xenopus olfactory receptor cells measured with perforated-patch recording

1995 ◽  
Vol 74 (1) ◽  
pp. 479-483 ◽  
Author(s):  
A. B. Zhainazarov ◽  
B. W. Ache
Keyword(s):  
Olfactory Receptor ◽  
Reversal Potential ◽  
Olfactory Receptor Neurons ◽  
Whole Cell ◽  
Time To Peak ◽  
Olfactory Receptor Cells ◽  
Whole Cell Recording ◽  
Cell Recording ◽  
Receptor Neurons ◽  
Induced Currents

1. Odor-evoked currents were recorded in Xenopus laevis olfactory receptor neurons (ORNs) by the use of conventional, as well as nystatin and gramicidin-perforated, whole cell recording. The odor-evoked current ran down quickly in conventional, but not in perforated, whole cell recording. All three types of recording gave similar values for the amplitude, latency, time-to-peak, recovery time, and reversal potential of the odor-evoked current. 2. A secondary Cl current comprised a significant part of the odor-evoked current (55-65%). ECl measured by gramicidin perforation, which does not alter [Cl-]i, was -2.3 +/- 5.0 (SE) mV, indicating that these neurons maintain a high [Cl-]i and that the secondary Cl current plays an excitatory role in olfactory transduction.

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.

scholarly journals Muscarinic activation of ionic currents measured by a new whole-cell recording method.

1988 ◽  
Vol 92 (2) ◽  
pp. 145-159 ◽  
Author(s):  
R Horn ◽  
A Marty
Keyword(s):  
Membrane Conductance ◽  
Ionic Currents ◽  
Response Curves ◽  
Whole Cell ◽  
Whole Cell Recording ◽  
Muscarinic Response ◽  
Cell Recording ◽  
K Current ◽  
A Cell ◽  
K Currents

A new method is described as an alternative to whole-cell recording in order to prevent "wash-out" of the muscarinic response to acetylcholine (ACh) in rat lacrimal gland cells. The membrane of a cell-attached patch is permeabilized by nystatin in the patch pipette, thus providing electrical continuity between the pipette and the cytoplasm of the cell without the loss or alteration of cytoplasmic compounds necessary for the maintenance of the response to ACh. With normal whole-cell recording in these cells, the response to ACh, seen as the activation of Ca-activated K and Cl currents, lasts for approximately 5 min. With the nystatin method, the response is not diminished after 1 h. Nystatin, applied extracellularly, is shown to cause a rapid and reversible increase of membrane conductance to cations. In the absence of wash-out, we were able to obtain dose-response curves for the effect of ACh on Ca-activated K currents. An increase of [ACh] caused an increase in the K current, with apparent saturation at concentrations above approximately 1 microM ACh. The delay between ACh application and the activation of K current was inversely related to [ACh] and reached a minimum value of 0.7-1.0 s at high [ACh].

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.

Whole-cell recording of anoxic effects on hippocampal neurons in slices

1993 ◽  
Vol 69 (1) ◽  
pp. 118-127 ◽  
Author(s):  
L. Zhang ◽  
K. Krnjevic
Keyword(s):  
Hippocampal Neurons ◽  
Input Resistance ◽  
Sprague Dawley ◽  
Whole Cell ◽  
Potassium Gluconate ◽  
Whole Cell Recording ◽  
Sprague Dawley Rats ◽  
Pyramidal Layer ◽  
Cell Recording ◽  
A Minor

1. In 400-microns-thick slices from young adult Sprague-Dawley rats, CA1 pyramidal layer neurons were studied by the whole-cell recording technique. The patch pipettes were filled most often with (in mM) 140 potassium gluconate, 2 MgCl2, and 0.2 guanosine triphosphate (GTP): in many cases, 2 mM ATP and/or 1.1 mM EGTA and 0.1 mM Ca were added. The slices were kept at 30–32 degrees C. 2. Cells recorded with ATP-containing electrodes had a much higher input resistance (RN, 101 +/- 5.6 M omega, mean +/- SE) and somewhat less negative resting potentials (Vm; -59.8 +/- 1.1 mV) than cells recorded with ATP-free electrodes (71 +/- 2.7 M omega and -63.1 +/- 0.8 mV). The presence or absence of ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) or the substitution of KCl for potassium gluconate did not significantly affect Vm or RN. 3. Overall changes in Vm and RN elicited by anoxia (95% N2-5% CO2 for 3–6 min) were much less pronounced than those seen previously with intracellular electrodes: instead of a hyperpolarization and a approximately 50% fall in RN, there was only a minor depolarization (by 2.4 +/- 0.7 mV) and a small reduction in RN (by 12 +/- 2.4%). During voltage clamp, at holding potentials approximately -35 mV, anoxia evoked only very small outward currents, especially when we recorded with ATP-containing electrodes. 4. The remaining anoxic changes in RN (but not Vm) were very significantly smaller (P < 0.001) when recorded with ATP-containing electrodes (-6 +/- 1.4%) than with ATP-free electrodes (-19 +/- 2.7%). The presence of internal EGTA (1.1-11 mM) was associated with significantly smaller (P < 0.05) anoxic changes in RN: -9.7 +/- 2.0% versus -17 +/- 3.1% in its absence. EGTA also reduced slow afterhyperpolarizations by 80%, though even 11 mM EGTA did not abolish them. However, EGTA had no significant effect on anoxic changes in Vm and did not suppress voltage sags observed during applications of hyperpolarizing current pulses. 5. Judging by these observations, it appears that 1) the much greater anoxic changes in Vm and RN recorded with intracellular electrodes are probably mediated by a diffusible cytosolic agent and 2) during whole-cell recording, both resting RN and the anoxic fall in RN are more strongly determined by cytosolic [ATP] than [Ca]. How ATP affects RN and anoxic changes in RN remains to be established.

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.

Mechanisms of Afterhyperpolarization in Lobster Olfactory Receptor Neurons

1998 ◽  
Vol 80 (3) ◽  
pp. 1268-1276 ◽  
Author(s):  
Frank S. Corotto ◽  
William C. Michel
Keyword(s):  
Voltage Clamp ◽  
Olfactory Receptor ◽  
Reversal Potential ◽  
Input Resistance ◽  
Olfactory Receptor Neurons ◽  
Resting Potential ◽  
Equilibrium Potential ◽  
Pipette Solution ◽  
Cation Current ◽  
Receptor Neurons

Corotto, Frank S. and William C. Michel. Mechanisms of afterhyperpolarization in lobster olfactory receptor neurons. J. Neurophysiol. 80: 1268–1276, 1998. In lobster olfactory receptor neurons (ORNs), depolarizing responses to odorants and current injection are accompanied by the development of an afterhyperpolarization (AHP) that likely contributes to spike-frequency adaptation and that persists for several seconds after termination of the response. A portion of the AHP can be blocked by extracellular application of 5 mM CsCl. At this concentration, CsCl specifically blocks the hyperpolarization-activated cation current ( I h) in lobster ORNs. This current is likely to be active at rest, where it provides a constant, depolarizing influence. Further depolarization deactivates I h, thus allowing the cell to be briefly hyperpolarized when that depolarizing influence is removed, thus generating an AHP. Reactivation of I h would terminate the AHP. The component of the AHP that could not be blocked by Cs+ (the Cs+-insensitive AHP) was accompanied by decreased input resistance, suggesting that this component is generated by increased conductance to an ion with an equilibrium potential more negative than the resting potential. The Cs+-insensitive AHP in current clamp and the underlying current in voltage clamp displayed a reversal potential of approximately –75 mV. Both E K and E Cl are predicted to be in this range. Similar results were obtained with the use of a high Cl– pipette solution, although that shifted E Cl from –72 mV to –13 mV. However, when E K was shifted to more positive or negative values, the reversal potential also shifted accordingly. A role for the Ca2+-mediated K+ current in generating the Cs+-independent AHP was explored by testing cells in current and voltage clamp while blocking I K(Ca) with Cs+/Co2+-saline. In some cells, the Cs+-independent AHP and its underlying current could be completely and reversibly blocked by Cs+/Co2+ saline, whereas in other cells some fraction of it remained. This indicates that the Cs+-independent AHP results from two K+ currents, one that requires an influx of extracellular Ca2+ and one that does not. Collectively, these findings indicate that AHPs result from three phenomena that occur when lobster ORNs are depolarized: 1) inactivation of the hyperpolarization-activated cation current, 2) activation of a Ca2+-mediated K+ current, and 3) activation of a K+ current that does not require influx of extracellular Ca2+. Roles of these processes in modulating the output of lobster ORNs are discussed.

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