Showing papers on "Olfaction published in 1987"

A cyclic nucleotide-gated conductance in olfactory receptor cilia

Abstract: Olfactory transduction is thought to be initiated by the binding of odorants to specific receptor proteins in the cilia of olfactory receptor cells (reviewed in refs 1–3). The mechanism by which odorant binding could initiate membrane depolarization is unknown, but the recent discovery of an odorant-stimulated adenylate cyclase in purified olfactory cilia4,5 suggests that cyclic AMP may serve as an intracellular messenger for olfactory transduction. If so, then there might be a conductance in the ciliary plasma membrane which is controlled by cAMP. Here we report that excised patches of ciliary plasma membrane, obtained from dissociated receptor cells, contain a conductance which is gated directly by cAMP. This conductance resembles the cyclic GMP-gated conductance that mediates phototransduction in rod and cone outer segments6,7, but differs in that it is activated by both cAMP and cGMP. Our data provide a mechanistic basis by which an odorant-stimulated increase in cyclic nucleotide concentration could lead to an increase in membrane conductance and therefore, to membrane depolarization. These data suggest a remarkable similarity between the mechanisms of olfactory and visual transduction and indicate considerable conservation of sensory transduction mechanisms.

Olfactory recognition: differential impairments in early and late Huntington's and Alzheimer's diseases.

Abstract: Forty-two patients with senile dementia of the Alzheimer type (SDAT), 38 patients with Huntington's disease (HD) and matched normal controls were administered tests of olfactory, verbal, and visual recognition after being screened for normal olfactory discrimination. Early-affected Huntington's patients (EHD) with minimal chorea or cognitive deficit displayed marked deficits in olfactory recognition despite normal verbal and visual performance, even after correction for task difficulty, suggesting involvement of olfactory brain regions early in the disease process. In the early Alzheimer's group (EAD), marked deficits were seen on all recognition modalities indicating more global impairment. Both overall (early plus late) patient groups were impaired relative to controls on all recognition tasks, with the olfactory paradigm being most affected.

Contribution of single unit analysis in insects to an understanding of olfactory function

Abstract: The olfactory pathway of the American cockroach is described from antennal receptor input to protocerebral output neurons. Based upon new and reviewed electrophysiological, neuroanatomical and fine structural data, connections and projections of individually identified receptor cells and central neurons are demonstrated. On the basis of investigation of input-output functions of such units modes of neural coding of naturally occurring complex odor stimuli and their constituents are proposed for the first two stages of the pathway. The role of protocerebral neurons is discussed at a functional-neuroanatomical level. A few data are added of descending neurons of moths.

Single-unit analysis of postnatal olfactory learning: modified olfactory bulb output response patterns to learned attractive odors.

Abstract: Neonatal rats learn to approach odors associated with stimulation normally provided by their mother. The present report describes changes in olfactory bulb single-unit activity following olfactory learning in young rats. Rat pups were exposed from postnatal day 1 to 18 to either (1) peppermint-scented air while receiving tactile stimulation (Pepp- Stroked), (2) peppermint-scented air with no tactile stimulation (Pepp- Only), (3) clean air and tactile stimulation (Stroked-Only), or (4) clean air and no tactile stimulation (Naive). On day 19, single-unit activity was recorded from mitral/tufted cells in urethane- anesthetized, freely breathing pups in response to either peppermint or a novel orange odor. Mitral/tufted cell response patterns to peppermint were significantly altered in Pepp-Stroked animals compared to control pups. Peppermint exposure alone, not associated with tactile stimulation (Pepp-Only), did not affect subsequent single-cell response patterns to that odor. In addition, the modification of response patterns was specific to peppermint and was not associated with a change in respiration rate. Furthermore, Pepp-Stroked pups had a relative behavioral preference for peppermint on day 19 compared to control pups. These results demonstrate that postnatal olfactory learning selectively modifies the subsequent response patterns of olfactory bulb output cells to the attractive odor. Furthermore, these results indicate that the initial coding of an odorxy's attractive value occurs within the olfactory bulb.

Old-age deficits in the sense of smell as gauged by thresholds, magnitude matching, and odor identification.

Abstract: Twenty elderly subjects (70-90 years old) and 20 young control subjects (18-24 years old) underwent three kinds of olfactory testing: absolute thresholds to three odorants (d-limonene, iso-amyl butyrate, benzaldehyde), magnitude matching of these odorants to salt tastes, and odor identification of 30 common substances. For all three odorants elderly subjects' mean threshold significantly exceeded that of the young by about ninefold for d-limonene, about threefold for benzaldehyde, and about twofold for iso-amyl butyrate. These threshold differences predict approximate concentration differences necessary to arouse the same estimated odor strength above the threshold for the elderly and the young. Young subjects also scored better than the elderly in odor identification, even when subjects were given four alternatives from which to select the correct label. Unimpaired olfactory functioning is uncommon in the elderly; correlational tests show that as a group the young have better olfactory ability and show more interindividual uniformity.

Isolation of an olfactory cDNA: similarity to retinol-binding protein suggests a role in olfaction.

Abstract: Molecular cloning techniques were used to isolate and characterize a protein possibly involved in the signal transducing system in olfactory tissue of the frog Rana pipiens. A complementary DNA library was constructed with messenger RNA obtained from frog olfactory neuroepithelium. A 700-base pair complementary DNA clone encoding a protein with a molecular weight of 20,300 was identified by differential hybridization analysis with polyadenylated RNA from olfactory epithelium and nonsensory respiratory epithelium. The messenger RNA corresponding to this clone was abundant in the cells of Bowman's glands in olfactory tissue but not in respiratory epithelium nor in several other tissues. The predicted sequence of this protein is homologous to members of a family of proteins that bind and transport small molecules in serum, suggesting that this protein may also bind and transport odorants in the mucus secreted by Bowman's glands.

Extreme olfactory sensitivity of mature and gonadally-regressed goldfish to a potent steroidal pheromone, 17α,20β-dihydroxy-4-pregnen-3-one

Abstract: 1. Electrical responses (electro-olfactogram; EOG) were obtained from the olfactory epithelium of goldfish exposed to a variety of sex steroids thought to function as pheromones, severall-amino acids, and a bile acid. Responses of male and female goldfish with both mature and regressed gonads were compared. 2. 17α,20β-dihydroxy-4-pregnen-3-one (17,20P) and progesterone were potent odorants. 17,20P had a detection threshold of 10−13M and at a concentration of 10−8M evoked an EOG response two to three times that of 10−5Ml-serine. Progesterone was less stimulatory than 17,20P. This finding corroborates recent endocrinological and behavioral studies (Stacey and Sorensen 1986; Dulka et al. 1987) which indicate that 17,20P is a potent pheromone in mature male goldfish. 3. Preliminary cross-adaptation experiments suggest that 17,20P is detected by receptor site(s) differing from those which detect bile acids andl-amino acids. 4. The goldfish olfactory epithelium did not respond to etiocholanolone glucuronide, 17β-estradiol glucuronide, testosterone glucuronide and 17β-estradiol, which have also been hypothesized to function as pheromones in fish. 5. The olfactory thresholds of goldfish tol-amino acids and taurocholic acid were similar to other species of fish: approximately 10−13M forl-serine and 10−9M forl-cysteine and taurocholic acid. 6. The olfactory sensitivities of mature male, mature female and gonadally-regressed fish were similar to all compounds tested suggesting that differences in olfactory receptor function are not responsible for the fact that only mature males exhibit behavioral and endocrine responses to pheromonal 17,20P.

Odor preference and social behavior in meadow voles, Microtus pennsylvanicus: seasonal differences

Abstract: Olfactory cues play a major role in inter- and intra-sexual agonistic behavior for Microtus pennsylvanicus. We show that seasonal changes in odor preference and behavioral interactions coincide wit...

Inheritance of olfactory response to sex pheromone components in Ostrinia nubilalis

Abstract: Fig. 3. Distribution of electrosensory organs in two sections of skin excised after 42 days (A) and 112 days (B, cluster of Fig. 2 B) following nerve deflection. Dimensions of the histologically examined sections of skin in mm the photographed area (Fig. 2A). It is unclear why a maximum of 90 out of an expected 350 organs were induced in the observed area and why the proportion of the three organ types in the newly induced population is different from the original innervated population (note only one mormyromast in Fig. 3 A). The spatial distribution of the newly induced organs of different types within a cluster appears random (Fig. 3). This indicates that every region in the observed sensory skin area is equally capable of differentiation into the receptor type which is coded by the organ-controlling substance specific to the regenerated nerve fiber. In Fig. 3 A, accumulation of ampullary and tuberous organs is found in the upper and lower half of the cluster, respectively. There is a tendency for tuberous organs to accumulate in the upper right and lower left of the skin section of Fig. 3 B. A reasonable explanation for this phenomenon may be that the afferent fibers belonging to one organ type are grouped within the nerve trunk.

Mothers' recognition of their newborns by olfactory cues

Abstract: We report that 90% of women tested in the present study identified their newborns by olfactory cues after only 10 min-1 hr exposure to their infants. All of the women tested recognized their babies' odor after exposure periods greater than 1 hr. The robust results are due in part to the implementation of an initial screening phase in which individuals with obvious olfactory deficits were excluded from the sample. These results suggest that odor cues from newborns are even more salient to their mothers than have been thought heretofore.

New routes to early memories.

Abstract: Stimulation of one side of the olfactory system during training with odor-milk pairings in neonatal rats results in their ability to recall an odor memory by using the trained but not the untrained side of the brain. In 12-day-old rats, olfactory learning can be recalled by stimulation of either the trained or untrained side. The development of bilateral recall reflects the maturation of olfactory commissural pathways that provide access to the olfactory memory stored on the contralateral side. Furthermore, the commissural pathways need not be present at the time of memory formation but can establish new and specific access to already existing olfactory memories.

Characterization of Olfactory Dysfunction

Abstract: • Management of dysosmic patients frequently is hampered by an incomplete description of their chief complaint and sometimes inadequate qualitative analysis of their symptoms. Qualitative analysis of olfactory dysfunction by an Odorant Confusion Matrix helps to characterize more fully sense of smell in the dysosmic patient. It is well grounded in psychophysical theory, thereby permitting physiological inferences about specific neural dysfunctions. The quantitative measure derived from the matrix correlates well with another quantitative measure of olfactory ability, the Smell Identification Test, and provides the opportunity for valid comparisons among and within patients. Examination of illustrative case reports demonstrates that the qualitative features of the Odorant Confusion Matrix offer additional insights to support etiologic diagnoses of disturbances in sense of smell. ( Arch Otolaryngol Head Neck Surg 1987;113:163-168)

Molecular cloning and sequencing of a cDNA for olfactory marker protein.

Abstract: cDNA clones corresponding to mRNA for rat olfactory marker protein (OMP) were isolated from a cDNA library. The library was constructed from olfactory mucosa poly(A)+ RNA enriched for OMP mRNA and cloned into a pBR322-derived plasmid, pMG5. OMP cDNA clones were detected by using a 17-base oligonucleotide probe that contained all 16 possible sequences coding for a known partial amino acid sequence of rat OMP. The identity of these clones was confirmed by hybrid-selected translation and nucleotide sequencing. The sequence of one clone was determined and contained the complete OMP coding region of 486 nucleotides followed by 1630 nucleotides of the 3' untranslated region. The 3' untranslated region included the polyadenylylation signal 16 nucleotides upstream of the poly(A) tail. No other ATG-initiated open reading frame larger than 20 codons was present in register. RNA blot analysis of olfactory mucosa poly(A)+ RNA using this clone as a probe indicated that the level of OMP mRNA, but not its size, declined significantly within a few days following olfactory bulbectomy. OMP mRNA was not detected in 14 nonolfactory rat tissues. Surprisingly, a small amount of OMP mRNA was observed in olfactory bulb. The presence of OMP mRNA in olfactory bulb was confirmed by in vitro translation and immunoprecipitation. These results suggest either that a previously undescribed population of neurons in the olfactory bulb synthesize OMP or that OMP mRNA is transported to the bulb by axonal transport.

Pigeon homing: Different effects of olfactory deprivation in different countries

Abstract: This study compares the orientation of untreated pigeons and pigeons subjected to olfactory deprivation at two lofts near Pisa, Italy, at a loft at Ithaca, New York, USA, and at a loft at Frankfurt a.M., FRG. The experimental birds were rendered anosmic by nasal plugs until Gingicain, a local anaesthetic, was applied shortly before release. The Italian and American control pigeons appeared to orient towards home equally well, while the control pigeons in Germany frequently preferred directions that deviated significantly from the home direction. The effect of olfactory deprivation was small in the USA and in Germany; it was significantly larger in Italy, indicating that Italian pigeons depend on olfactory information to a much greater extent. These findings suggest that there are important regional differences in the strategies and cues pigeons use to navigate. The varied roles of olfactory information, and the reasons for these differences are discussed.

Differentiation of roles of chemosensory organs in food discrimination among host and non-host plants by larvae of the tobacco hornworm, Manduca sexta

Abstract: . The contributions of olfactory and gustatory organs in food plant discrimination were examined in larvae of Manduca sexta (Johan.) (Lepidoptera, Sphingidae). Larvae, from which various chemosensory organs had been removed surgically, were tested for feeding preferences for a host, tomato (Lycopersicon esculentum); a weakly acceptable non-host, rape (Brassica napus); and an unacceptable non-host canna (Canna generalis), using a two-choice disc bioassay. Removal of all known chemosensory organs resulted in failure to show discriminatory behaviour in a strictly chemosensory bioassay, indicating that all external chemosensory organs have been accounted for. The involvement of non-chemosensory organs results in residual discrimination for leaves by individuals with total chemosensory ablations. Larvae possessing either olfactory or gustatory organs still exhibit normal preferences for tomato over rape. Gustatory (but not olfactory) organs are required for larvae to show normal preferences for tomato over canna; in fact, olfactory organs do not appear to participate in this decision. To examine which if any of the plant species is being selected in two-choice tests, larvae were given a choice between each leaf species and a ‘neutral’ substance (wet filter paper). Both olfactory and gustatory organs are required for normal preferences for tomato, but either alone will suffice for rape. Only gustation is needed to select canna, and participation of either the epipharyngeal sensilla or a single medial sensillum styloconicum is sufficient to elicit complete rejection behaviour. We conclude that, in larvae of M. sexta, the complement of chemosensory organs needed for food plant discrimination varies with the plant species sampled. Evidence is presented exposing a potential artefact of ablation experiments; extirpation of one sensory organ may affect the functioning of others nearby, even though they may appear normal by visual inspection.

Olfactory mechanisms in the control of maternal aggression, appetite, and fearfulness: effects of lesions to olfactory receptors, mediodorsal thalamic nucleus, and insular prefrontal cortex.

Abstract: During lactation the female rat is hyperphagic, aggressive toward adult conspecifics, and less fearful than usual. In the first experiment the importance of olfactory receptors was investigated by surgically removing the olfactory epithelium of the nasal cavity. Mother rats subjected to this treatment consumed significantly less food and weighed less than sham-operated females. Moreover, experimental subjects displayed a dramatic decrease in maternal aggression. Fear behavior (sound-elicited freezing), on the other hand, was not affected by the lesions. The mediodorsal thalamic nucleus and the prefrontal insular cortex form part of the central olfactory system. The second experiment assessed the involvement of this olfactory-related thalamocortical system and the behavioral profile of mother rats. It was found that whereas the thalamic and cortical lesions left food intake and fear behavior unaffected, they significantly decreased the frequency with which the mother would attack an intruder male placed into her home cage. The sense of smell appears, according to the present experiments, to play a crucial role in maternal aggression.

An investigation of the role of dopamine in the antennal lobes of the honeybee, Apis mellifera

Abstract: The effects of dopamine applied to the antennal lobes of the honeybee are investigated using the proboscis conditioning paradigm (Kuwabara 1957). The percentage of bees responding to a conditioned olfactory stimulus after a single conditioning trial is reduced significantly by the application of dopamine (10−6M) to the antennal lobes of the bee brain. Reduction in response levels is significantly smaller in bees conditioned to the olfactory stimulus in multiple conditioning trials prior to treatment with dopamine. The effects of dopamine on the percentage of bees responding to a conditioned olfactory stimulus are blocked by the butyrophenone, haloperidol (10−5M). The possible role of dopaminergic interneurones in the antennal lobes of the bee brain is discussed.