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.

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.

Pharmacological Properties and Functional Role of a TRP-Related Ion Channel in Lobster Olfactory Receptor Neurons

2005 ◽  
Vol 93 (3) ◽  
pp. 1372-1380 ◽  
Author(s):  
Yuriy V. Bobkov ◽  
Barry W. Ache
Keyword(s):  
Olfactory Receptor ◽  
Transient Receptor Potential ◽  
Trp Channels ◽  
Receptor Potential ◽  
Ruthenium Red ◽  
Olfactory Receptor Neurons ◽  
Channel Blockers ◽  
Gated Channel ◽  
Receptor Neurons ◽  
Transient Receptor

Odors activate lobster olfactory receptor neurons (ORNs) through phosphoinositide signaling that appears to target a Na+-gated nonselective cation channel. The Na+-gated channel is a potential member of the growing family of transient receptor potential (TRP) channels. Here, we test the effect of potential antagonists on the channel in cell-free patches from cultured lobster ORNs. We show that the channel is antagonized by H+ and the TRP channel blockers 2-aminoethoxydiphenyl borate, SKF96365 , ruthenium red, Al3+, Gd3+, and La3+. We then use this enhanced antagonist profile together with the agonists Na+ and Ca2+ to implicate the channel in signal amplification in the cells.

Inhibitory and excitatory responses of olfactory receptor neurons of xenopus laevis tadpoles to stimulation with amino acids

1999 ◽  
Vol 202 (8) ◽  
pp. 997-1003 ◽  
Author(s):  
C. Vogler ◽  
D. Schild
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Xenopus Laevis ◽  
Olfactory Receptor ◽  
Olfactory Receptor Neurons ◽  
Patch Clamp Technique ◽  
Olfactory Neurons ◽  
Receptor Neurons ◽  
Patch Configuration ◽  
Excitatory Responses

Recordings were made from olfactory receptor neurons of Xenopus laevis tadpoles using the patch-clamp technique to investigate the responses of these cells to odorants. Four amino acids (glutamate, methionine, arginine and alanine) both individually and as a mixture were used as stimuli. Of the 156 olfactory neurons tested, 43 showed a response to at least one of the stimuli. Of the cells tested, 19 % responded to glutamate, 16 % to methionine, 12 % to arginine and 10 % to alanine. Each amino acid was able to induce both excitatory and inhibitory responses, although these occurred in different cells. Each amino acid produced approximately equal numbers of inhibitory and excitatory responses. Inhibitory responses could best be observed in the perforated-patch configuration using gramicidin as an ionophore and a recording configuration that is a current-clamp for fast signals and a voltage-clamp for slow signals. The diversity of the odorant responses, in particular the existence of excitatory and inhibitory responses, is not consistent with a single transduction pathway in olfactory neurons of Xenopus laevis tadpoles.

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.

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