Frog Olfactory Mucosa Research Articles

Odorant-induced kinetics of Ca2+, NADH, and oxidized flavoproteins in frog olfactory mucosa

A study was made of the odorant-induced changes in the fluorescence of the Ca2+-chlortetracycline-membrane complex, NADH, and oxidized flavoproteins in the frog olfactory epithelium. Cineole and vanillin induce faster changes than camphor and pentanol. The different kinetics of NADH and membrane calcium evoked by these odorants are attributed to the heterogeneity of the molecular mechanisms involved in olfactory signal transduction. By contrast, ammonia and β-mercaptoethanol permeate the olfactory cells and without second messengers inhibit the mitochondrial respiratory chain and suppress the motility of olfactory cilia.

A chemical modification approach to the olfactory code: Vapor phase labeling using photoaffinity odorants.

A photoaffinity labeling technique was used to study the receptors involved in the discrimination of odorants. Aromatic azides, 1-azidonaphthalene (AzN) and 1-azido-4-nitronaphthalene (AsNN), were found to be pleasant-smelling compounds and produced good responses, giving standard EOG's (electro-olfactogram) of the kind observed for normal odorants. Following irradiation of the frog olfactory mucosa with light during constant stimulation with one of the azides vapor, there was a specific partial inhibition of the receptors for that odorant. The extent of reduction in amplitude of the EOG responses to AzN and AzNN varied between 40 to 60% of the original amplitude.

Ion transport across the frog olfactory mucosa: the action of cyclic nucleotides on the basal and odorant-stimulated states

The action of cyclic nucleotides on the short-circuit current across the isolated bullfrog olfactory mucosa was studied both in the absence and presence of odorants. 8-Bromo-cAMP applied to the ciliated side of the mucosa caused a concentration-dependent, reversible increase in the basal short-circuit current, but not when it was applied to the submocosal side. The current had a sigmoidal concentration dependence described by the Hill equation. The magnitude of the odorant-evoked current was enhanced after bathing the ciliated side with cAMP analogs or modulators of intracellular cAMP. GTPγS added to the ciliated side increased the odorant-evoked current, while GDPβS caused a decrease. Current transients induced by stimulating the ciliated side with either pulses of odorant or 8-bromo-cAMP were partially suppressed by amiloride, but only when amiloride and stimulant were presented simultaneously. Pulses of 8-bromo-cAMP and odorant presented simultaneously resulted in currents that added nonlinearly. In the absence of odorant, 8-bromo-cGMP caused a concentration-dependent decrease in net inward current that was reversed by 8-bromo-cAMP. Odorant-evoked currents were also reduced by 8-bromo-cGMP, and these could not be reversed by 8-bromo-cAMP. The results indicate that one type of olfactory transduction process involves the activation by cAMP of an inward current through an amiloride-sensitive apical ion channel and that this mechanism is mediated by a stimulatory G-protein.

The activity of olfactory receptor cells is affected by acetylcholine and substance P

The effects of acetylcholine (ACh) and substance P (SP) on the unit activity of receptor cells recorded from the superfused frog olfactory mucosa were studied. Single neurones were excited or, more rarely, depressed by the application of chemicals. Cholinergic antagonists were used to investigate the involvement of nicotinic and muscarinic receptors in the recorded responses. The ACh-evoked firing was antagonized by d-tubocurarine ( d-TC), atropine (ATR) and SP. Responses to SP appeared to be d-TC resistant, but activation by the peptide was moderately antagonized by ATR. The results suggest that ACh and SP could affect the functioning of the olfactory receptor cells.

Ion transport across the frog olfactory mucosa: the basal and odorant-stimulated states

The Ussing method was adapted to study the basal electrolyte transfer as well as the events that occur upon odorant stimulation in frog olfactory mucosa. The unstimulated short-circuit current was due mainly to a furosemide-sensitive ion transport system on the apical side of the olfactory mucosa. This current was not amiloride sensitive. The current-voltage relationship of the unstimulated state was linear. That of the odorant-evoked current was non-linear and amiloride-sensitive. Ouabain caused collapse of both the unstimulated and odorant-stimulated short-circuit. In this case, voltage-clamping the tissue to non-zero values restored the odorant-evoked current with polarity depending on that of the clamping voltage. This suggested that the direction of the current is determined by that of the sodium electrochemical potential difference. Our results indicate that the unstimulated short-circuit current occurs through an apical sodium cotransport system, while the odorant-evoked current is due to odorant-activated, passive sodium channels that are amiloride sensitive.

Trigeminal substance P-like immunoreactive fibres in the frog olfactory mucosa

Trigeminal substance P-like immunoreactive fibres in the frog olfactory mucosa

Ultrastructural and Electrophysiological Changes in the Olfactory Epithelium following Exposure to Organic Solvents

The present study describes some effects on frog olfactory mucosa following acute exposure to styrene and toluene, two organic solvents. The olfactory summed receptor potential (EOG) was recorded in order to monitor the functional effect. The olfactory epithelium was examined with transmission electron microscopy, using both thin section and freeze-fracture technique. The ultrastructural changes in the olfactory epithelium following exposure to the solvents were mainly of two types: (1) an increased secretion from the sustentacular cells, (2) membrane fusion of the cilia, sometimes with a loosening of the ciliary membrane. The tight junctional complex between the receptor and sustentacular cells at the epithelial surface remained intact. The EOG amplitude generally showed some degree of reduction following exposure, with a gradual recovery towards pre-exposure values.

Evidence for electrogenic active ion transport across the frog olfactory mucosa in vitro

Evidence for electrogenic active ion transport across the frog olfactory mucosa <i>in vitro</i>

Investigations of the discriminative properties of the frog's olfactory mucosa using a photoactivable odorant

The photoactivable compound phenylazide interacts reversibly with the frog's olfactory epithelium when delivered as an olfactory stimulus. Its application together with UV irradiation resulted in a differential reduction of the responses (electro-olfactogram) to several odorants. It was found that this chemical modification of the sensory membrane affected the responses in relative ratios which could be predicted from a classification of the odorants based upon independent studies of receptor cell odor sensitivity. The responses to chemicals representative of the ‘aromatic group’ were clearly more reduced than those to compounds of the ‘camphoraceous group’. It is suggested that the olfactory discrimination mechanisms can be approached by the use of this method.

Modification of transduction mechanisms in the frog's olfactory mucosa using a thiol reagent as olfactory stimulus

The effects of the thiol-specific reagent N-ethylmaleimide (NEM) used in the vapour phase have been tested on the olfactory epithelium of the frog when recording the electro-olfactogram (EOG) and spike activity from single receptor cells. The reagent was delivered alone or mixed with the odorant isoamyl acetate. At low concentration the reagent induced slow potentials resembling simple EOGs. At higher concentrations (20% of the saturated vapour) three negative and one positive slow components were observed in the response. A complex relationship was found between the amplitude of the slow potential and the concentration of the reagent. Repeated stimulations at high concentration caused the suppression of the negative voltage transients and the development of the positive component. NEM vapour elicited spike discharges in some of the recorded units, with the responses resembling those evoked by usual odorants. After long-lasting stimulations (30 sec) with NEM, the receptors failed to respond to both reagent and odorant. This suppression of response could be partly prevented by exposing the olfactory epithelium to the odorant vapour before and during the exposure to the reagent (protection). The results indicate that NEM acts on the olfactory epithelium in several ways, including an odorant-like action on olfactory receptor sites. An effect on the supporting cells is also suggested. Hypotheses for explaining the protection mechanism are considered.

A chemical-modification approach to the olfactory code. Studies with a thiol-specific reagent

The effects of thiol-specific reagents on the amplitude of the electro-olfactogram (E.O.G.) responses elicited from frog olfactory mucosa by pulses of odorant vapours was studied. The impermeant thiol-specific reagent mersalyl [(3-{[2-(carboxymethoxy)-benzoyl]amino}-2-methoxypropyl)hydroxymercury monosodium salt] brings about a rapid decrease in the E.O.G. signal obtained with the odorant pentyl acetate. The extent of the decrease is proportional to the concentration of the mersalyl applied and the effect of the reagent is partially but incompletely reversed by treatment of the labelled mucosa with dithiothreitol. The sites labelled by mersalyl can be protected by pretreating the mucosa with a dilute solution of the odorant pentyl acetate and leaving the solution in contact with the tissue after the addition of mersalyl. When the protecting odorant is washed out of the tissue, the original E.O.G. amplitude is regained. Pentyl acetate applied to the mucosa protected the E.O.G. response to vapour pulses of the following odorants from the effects of mersalyl: n-butyric acid, n-butyl acetate, phenylacetaldehyde and cineole (1,3,3-trimethyl-2-oxabicyclo[2.2.2]octane). The pentyl acetate applied to the mucosa failed to protect the E.O.G. response to vapour pulses of the following odorants from the effects of mersalyl: butan-1-ol, benzyl acetate, nitrobenzene, beta-ionone and linalyl acetate. The significance of the differential protection effects for the odour-quality-coding mechanism in the olfactory primary neurons is discussed. It is suggested that the olfactory code at this level of the olfactory system may be elucidated by chemical-modification methods.

Odorant removal from the frog olfactory mucosa

Odorant removal from the frog olfactory mucosa

Olfactory receptor response characteristics: A factor analysis

The responses to odor stimulation of 22 single olfactory units in the frog olfactory mucosa were recorded with metal filled micropipettes. Seven purified odorants matched in concentration and a pure air stimulus were administered. The change in firing frequency for each unit to each chemical was evaluated to determine: (1) whether the response patterns developed across all units are different from chemical to chemical and, (2) whether individual units can be grouped in terms of their similarity of their responses to all odorants. The results of a Bartlett Sphericity test suggest that each odorant produces an independent pattern of responses across units. To answer the second question, a factor analysis was employed. It examined the responses of each unit to all chemicals and yielded 7 out of a possible 22 independent factors, suggesting that there are 7 ways by which the units studied look at the odorant stimuli and an air control employed in this study. These analyses were evaluated and discussed in terms of previously published data suggesting receptor site specificity.

Electrogenic sources of slow voltage transients recorded from frog olfactory epithelium.

Electrogenic sources of slow voltage transients recorded from frog olfactory epithelium.T V GetchellT V GetchellPublished Online:01 Nov 1974https://doi.org/10.1152/jn.1974.37.6.1115MoreSectionsPDF (3 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInEmailWeChat Back to Top Next Download PDF FiguresReferencesRelatedInformationCited ByOdorant Concentration Dependence in Electroolfactograms Recorded From the Human Olfactory EpitheliumHadas Lapid, Han-Seok Seo, Benno Schuster, Elad Schneidman, Yehudah Roth, David Harel, Noam Sobel*, and Thomas Hummel*1 October 2009 | Journal of Neurophysiology, Vol. 102, No. 4Modulation of Spontaneous and Odorant-Evoked Activity of Rat Olfactory Sensory Neurons by Two Anorectic Peptides, Insulin and LeptinAgnès Savigner, Patricia Duchamp-Viret, Xavier Grosmaitre, Michel Chaput, Samuel Garcia, Minghong Ma, and Brigitte Palouzier-Paulignan1 June 2009 | Journal of Neurophysiology, Vol. 101, No. 6Behavioural and electrophysiological responses by reproductive female Neogobius melanostomus to odours released by conspecific malesJournal of Fish Biology, Vol. 65, No. 4Impacts of carbamate pesticides on olfactory neurophysiology and cholinesterase activity in coho salmon (Oncorhynchus kisutch)Aquatic Toxicology, Vol. 69, No. 2Evidence for peripheral plasticity in human odour response10 December 2003 | The Journal of Physiology, Vol. 554, No. 1Chemosterilization of male sea lampreys ( Petromyzon marinus ) does not affect sex pheromone releaseCanadian Journal of Fisheries and Aquatic Sciences, Vol. 60, No. 1Spatially Organized Response Zones in Rat Olfactory EpitheliumJohn W. Scott, Donna E. Shannon, Jeff Charpentier, Lisa M. Davis, and Craig Kaplan1 April 1997 | Journal of Neurophysiology, Vol. 77, No. 4Spatial projections to the olfactory bulb of functionally distinct and randomly distributed primary neurons in salmonid fishesNeuroscience Research, Vol. 26, No. 1Synaptic organization, local neuronal circuitry, and functional segregation of the teleost olfactory bulbProgress in Neurobiology, Vol. 34, No. 2Ion transport across the frog olfactory mucosa: the basal and odorant-stimulated statesBiochimica et Biophysica Acta (BBA) - Biomembranes, Vol. 902, No. 1Masera's organ responds to odorantsBrain Research, Vol. 366, No. 1-2The characteristics of the electro-olfactogram (EOG): Its loss and recovery following olfactory nerve section in rainbow trout (Salmo gairdneri)Brain Research, Vol. 330, No. 1Topographic coding of odorant quality is maintained at different concentrations in the salamander olfactory epitheliumBrain Research, Vol. 297, No. 2Intracellular recording from salamander olfactory receptor cellsBrain Research, Vol. 268, No. 2Olfactory receptors respond to blood-borne odorantsBrain Research, Vol. 265, No. 2Comparison of olfactory receptor (EOG) and bulbar (EEG) responses to amino acids in the catfish,Ictalurus punctatusBrain Research, Vol. 249, No. 1Analysis of intracellular recordings from salamander olfactory epitheliumBrain Research, Vol. 123, No. 2 More from this issue > Volume 37Issue 6November 1974Pages 1115-30 https://doi.org/10.1152/jn.1974.37.6.1115PubMed4548085History Published online 1 November 1974 Published in print 1 November 1974 Metrics

Autoradiographic and ultrastructural observations on the frog's olfactory mucosa.

Autoradiographic techniques have been employed to study the cell turnover in the olfactory mucosa of frog. It has been established that basal cells of the olfactory epithelium divide and differentiate into mature neurons in adult animals. These findings prove that the olfactory neurons are replaced during the adult life. Supporting cells were also found to undergo turnover. The basal cells are indicated as the stem elements of both supporting and sensory cells as they undergo division and maturation processes leading to the replacement of both supporting and sensory cells.

The spatiotemporal analysis of odorants at the level of the olfactory receptor sheet.

Activity in two separate regions of the frog olfactory mucosa was sampled by simultaneously recording the summated neural discharges from the olfactory nerve branches originating from them. The difference in the activity from these two regions in response to a stimulus was measured by: (a) the ratio of the response amplitude recorded from the lateral nerve branch to that recorded from the medial nerve branch (LB/MB ratio), (b) the latency difference (or time interval) between these two responses. Equal concentrations of four different odorants were drawn into the nose by an artificially produced sniff of known dimensions. At each concentration in every animal the four chemicals were ranked in order of the magnitudes of their LB/MB ratios and again in order of their latency differences. Regardless of their concentration, the same chemicals fell into the same ranks in different animals. In addition, for each chemical the magnitudes of the ratios and latency differences showed only minimal changes with concentration. Thus, spatiotemporal patterns of relative response magnitudes and latency differences across the mucosa differentially represented the odorants. Such a spatiotemporal code, together with physicochemical considerations, suggested that the nose separates vapors in a manner similar to a gas chromatograph. This is further supported by the previously observed reversal of the ratio patterns with reversal of air flow direction through the olfactory sac.

EVIDENCE FOR SORPTION AS A MECHANISM OF THE OLFACTORY ANALYSIS OF VAPOURS.

THE physiological basis for olfactory discrimination may involve at least two basic mechanisms which need not be mutually exclusive : (a) the receptors themselves may be more or less selectively sensitive to different groups of chemicals ; (b) the receptor sheet as a whole might separate chemical vapours by adsorption or absorption in a manner analogous to gas chromatography columns. There has been some supporting evidence for the first mechanism1,2, and suggestive evidence for the second has recently been reported3. The evidence suggesting the second mechanism depends, in part, on sampling the activity from different regions of the frog olfactory mucosa by recording the discharges from two olfactory nerve branches (a lateral one and a medial one), which under a dissecting microscope appear to subserve different mucosal regions. That these branches do indeed subserve different mucosal regions is supported by recent electrical stimulation experiments. The antidromically conducted discharges in response to individual stimulation of the lateral and medial nerve branches were recorded by an electrode placed at several points on the epithelium. The discharge tracts for the two branches were quite separate and localized (Fig. 1).