Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Olfactory Pathways”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 145 records · Page 8Linked to original sources
PubMedDate not supplied

Herpes simplex encephalitis. Immunohistological demonstration of spread of virus via olfactory pathways in mice.

Six-week-old Balb/c mice were inoculated intranasally with a suspension of HSV1 virus and the distribution of viral antigen in the brain 3-7 days later was surveyed using the immunoperoxidase technique. Virus was first detectable in the brain 4 days later at 2 distinct sites: the trigeminal root entry zone in the brain stem and the olfactory bulbs. On succeeding days virus spread from the trigeminal focus to many other brain stem nuclei and, in some mice, to the thalamus and the cerebellum. From the olfactory bulbs, in a proportion of mice, virus spread to anterior olfactory nucleus, lateral olfactory tract, septal nuclei, temporal lobe, hippocampus and cingulate cortex. Infection of olfactory bulbs was found to occur following intracorneal as well as intranasal inoculation of virus. The relevance of this model to human herpes simplex encephalitis is discussed.

Animals↗
PubMed1986

An accessory olfactory pathway in Lepidoptera: the labial pit organ and its central projections in Manduca sexta and certain other sphinx moths and silk moths.

In the hawkmoth, Manduca sexta, the third segment of each labial palp contains a pit, which houses a densely packed array of sensilla. We have named this structure the labial pit organ (LPO). The sensilla within the pit are typical of olfactory receptors, characterized by a grooved surface, wall pores, and pore tubules. Axons arising from receptor cells that innervate these sensilla project bilaterally to a single glomerulus in each antennal lobe. We have compared this central projection with that in three other species of Manduca (M. quinquemaculata, M. dilucida, and M. lanuginosa) and in the silkmoths Antheraea polyphemus and Bombyx mori. A bilateral projection to a single glomerulus in each antennal lobe is present in all cases. We suggest that the LPO serves as an accessory olfactory organ in adult Lepidoptera.

Animals↗
PubMed1988

Axonal transport of Borna disease virus along olfactory pathways in spontaneously and experimentally infected rats.

In this study it has been shown that infection of mother rats by Borna disease virus (BDV) from infected newborns led to a fatal disease. This differed both in clinical symptoms and in histological alterations from the form of the disease which occurred after intracerebral (i.c.) infection. Both parameters were, however, similar to those seen after experimental intranasal (i.n.) infection of adult rats. Detailed immunohistological studies showed clearly that after experimental i.n. infection, the infecting virus migrates intraaxonally from the neuroreceptors in the olfactory epithelium into the brain. It is therefore suggested that i.n. transmission is an important route of natural BDV infection.

Animals↗
PubMed2005

Expression of the neuronal calcium sensor protein NCS-1 in the developing mouse olfactory pathway.

Neuron specific calcium sensor 1 (NCS-1) is widely expressed in the developing and adult nervous system. Like calmodulin, NCS-1 is a member of a family of calcium binding proteins that contain EF-hand motifs, which bind calcium and induce conformational changes in the protein. Their binding varies with calcium concentration, allowing them to act as true calcium sensors rather than just calcium binding proteins. This family of proteins has been implicated in important synaptic events including neurotransmitter release and synapse formation. We examined the expression of NCS-1 in the developing and mature olfactory system to determine whether this molecule may be playing a role in establishing and/or maintaining olfactory circuitry. During development, expression of NCS-1 in the olfactory epithelium was localized in the dendritic knobs and axons of olfactory sensory neurons. Axonal expression was down-regulated after synapse formation. In the developing olfactory bulb, NCS-1 was expressed in the processes of mitral/tufted and granule cells. However, in the adult olfactory bulb, strongest expression was found in a subset of periglomerular cells (PGCs). This subset of PGCs did not express other known markers of PGCs including tyrosine hydroxylase, glutamic acid decarboxylase, calbindin, or calretinin, and only partially overlapped with the subpopulation of PGCs that express parvalbumin. Together, these data suggest multiple and overlapping roles of NCS-1 in the developing and mature olfactory system.

Animals↗
PubMed1994

Some noradrenergic neurons of locus ceruleus-olfactory pathways contain neuropeptide-Y.

We report a specific tracing technique for studying projections of noradrenergic neurons that contain other transmitters. Autoradiography after retrograde axonal transport of tritiated-noradrenaline ([3H]NA) was combined with immunocytochemical detection of endogenous NA or neuropeptide Y (NPY). The specificity of [3H]NA retrograde labeling was dependent on the concentration of [3H]NA injected at the terminal region. At 2 x 10(-3) M, the specificity of [3H]NA retrograde labeling was confirmed by immunodetection of endogenous NA in radiolabeled cell bodies of the locus ceruleus. Combination of autoradiography of [3H]NA retrograde labeling with immunodetection of NPY demonstrated that a some scattered locus ceruleus noradrenergic neurons (about 26%) projecting to the olfactory bulb do contain NPY.

Animals↗
PubMed1990

Hormonal control of neuropeptide gene expression in sexually dimorphic olfactory pathways.

An abundance of experimental literature has established that gonadal steroid hormones are responsible for the sexual differentiation of neural circuitry, mediating a variety of reproductive behaviors and physiological mechanisms. These same hormones regulate the expression of reproductive function in the adult and may influence the responsiveness of the brain to specific olfactory cues. The recent demonstration that the expression of the neuropeptide cholecystokinin is activationally regulated by estrogen at the mRNA level, within a sexually dimorphic population of neurons in the medial amygdala, suggests a possible cellular mechanism for the hormonal modulation of olfactory information relayed along the vomeronasal pathway to the hypothalamus.

Animals↗
PubMed2000

Ultrastructural characterizations of olfactory pathway neurons in layer II of the entorhinal cortex in monkey.

The somatic size, shape, dendritic and axonal morphology, and synaptology of representative neurons in layer II of the primate entorhinal cortex (EC) were analyzed. Layer II "islands" contained large spinous multipolar cells with triangular somata and local circuit axons in addition to multipolar neurons with large, radially arrayed, aspinous, primary processes and thick tapering axons. Small pyramidal neurons with a single, spinous, apical primary segment that bifurcated a short distance from the somata were also found in layer II. Subsequent spinous segments of these neurons with long terminal segments exhibited a paucity of branching in addition to having thick axons tapering into subjacent layers. The importance of providing these additional axonal, dendritic, and synaptic characterizations lies in the contextual role these neurons play in the connectional patterns of the EC with regard to olfaction, olfactory memory, and pathological variations.

Animals↗
PubMedDate not supplied

Olfactory pathway evoked potentials in response to hypothalamic stimulation.

Ipsilateral and contralateral stimulation of lateral, ventromedial and posterior hypothalamic nuclei produced evoked responses in the olfactory bulb and in the prepyriform cortex. No differences in the latencies were found by stimulation of each nucleus in the homo and contralateral olfactory structures. The high amplitude of the fast component (N1) was obtained with stimuli applied to the ventral zones and the slow components (N2, N3) were obtained with more dorsal stimulation. An ipsilateral pathway is indicated at the supramammillary and posterior commissure level, since severing these structures abolishes the evoked responses. A bilateral projection is proposed for the olfactory bulb.

Animals↗
PubMed2002

Adenovirus-mediated WGA gene delivery for transsynaptic labeling of mouse olfactory pathways.

Detailed knowledge of neuronal connectivity patterns is indispensable for studies of various aspects of brain functions. We previously established a genetic strategy for visualization of multisynaptic neural pathways by expressing wheat germ agglutinin (WGA) transgene under the control of neuron type-specific promoter elements in transgenic mice and Drosophila. In this paper, we have developed a WGA-expressing recombinant adenoviral vector system and applied it for analysis of the olfactory system. When the WGA-expressing adenovirus was infused into a mouse nostril, various types of cells throughout the olfactory epithelium were infected and expressed WGA protein robustly. WGA transgene products in the olfactory sensory neurons were anterogradely transported along their axons to the olfactory bulb and transsynaptically transferred in glomeruli to dendrites of the second-order neurons, mitral and tufted cells. WGA protein was further conveyed via the lateral olfactory tract to the olfactory cortical areas including the anterior olfactory nucleus, olfactory tubercle, piriform cortex and lateral entorhinal cortex. In addition, transsynaptic retrograde labeling was observed in cholinergic neurons in the horizontal limb of diagonal band, serotonergic neurons in the median raphe nucleus, and noradrenergic neurons in the locus coeruleus, all of which project centrifugal fibers to the olfactory bulb. Thus, the WGA-expressing adenovirus is a useful and powerful tool for tracing neural pathways and could be used in animals that are not amenable to the transgenic technology.

Adenoviridae↗
PubMed2005

The olfactory pathway for individual recognition in the American lobster Homarus americanus.

Individual recognition in the lobster Homarus americanus (Milne-Edwards), is based on detection of urine pheromones via chemoreceptors of the lateral antennular flagellum. The specific sensory pathway mediating this recognition is not known. Most of the chemoreceptor cells of this flagellum are found in the unimodal aesthetasc sensilla and project specifically to the glomeruli of the olfactory lobe in the brain. Additional chemoreceptor cells are located among mechanoreceptor cells in bimodal sensilla, including the guard hairs; they do not project to the olfactory lobe. This neuroanatomy suggested that aesthetascs were essential to all complex chemosensory tasks until it was shown that spiny lobsters Panulirus argus can still perform complex food odor discrimination and localization tasks without aesthetascs. Here, we demonstrate that the aesthetascs of H. americanus contain the chemoreceptors necessary for individual recognition of familiar opponents. In contrast to intact and guard hair-shaved animals, lobsters with aesthetascs removed did not recognize previous opponents as shown by second encounters statistically similar in length and aggression to first-encounter fights. Non-aesthetasc chemosensory pathways were incapable of rescuing opponent recognition. Subsequent lesion of all remaining chemoreceptor cells (by immersion in distilled water) abolished recognition and renewed fighting.

Aggression↗
PubMed1977

Denervation in the primary olfactory pathway of mice. IV. Biochemical and morphological evidence for neuronal replacement following nerve section.

Unilateral olfactory nerve section was performed in the mouse. Three biochemical markers of the olfactory chemoreceptor neurons: carnosine, carnosine synthetase activity and the olfactory marker protein, were measured in the olfactory bulb and epithelium. Parallel observations were made by light microscopy as well as at the ultrastructural level. The specific biochemical markers decrease rapidly in both bulb and epithelium and reach a minimum by the end of the first week after surgery. They then slowly return to 80% of control values by one month. Carnosinase activity in epithelium was essentially unaffected. These biochemical observations coincide temporally with the onset of degenerative changes seen morphologically, in both the bulb and epithelium. The degenerative changes persist for up to two weeks in the bulb and for about one week in the epithelium. At this time basal cell division and differentiation begins in the epithelium with subsequent regrowth of olfactory axons into the glomerular layer of the olfactory bulb with ther reappearance of olfactory axon terminals. The temporal coincidence of these biochemical and morphological observations suggests they are manifestations of the same process, and is consistent with the idea that the olfactory chemoreceptor neurons are perhaps unique in being able to be replaced from undifferentiated stem cells.

Animals↗
PubMed1991

Trigeminal and olfactory pathways mediating isolation distress and companion comfort responses in rat pups.

Isolation in a novel test cage elicits ultrasonic vocalization (USV) in 12-13-day-old rat pups, and the presence of an anesthetized littermate companion reduces USV while eliciting body contact. These responses were studied in pups with surgical lesions of trigeminal snout afferents and after olfactory denervation by nasal ZnSO4 perfusion. With lesions of only one system, body contact with the passive companion was reduced by 20%, and interpup orientation was differentially affected by the two types of lesions. However, USV rates were no different from littermate controls in the presence of the companion or when tested alone. Combined lesions of both systems reduced contact time 55% and eliminated any reduction in USV rates by the companion while leaving intact USV and locomotor responses to isolation. These results suggest that different sensory pathways may mediate isolation distress and companion comfort responses.

Animals↗
PubMed1993

Viral infection and dissemination through the olfactory pathway and the limbic system by Theiler's virus.

Theiler's murine encephalomyelitis virus (TMEV) infection of mice can produce a biphasic disease of the central nervous system (CNS). Most susceptible strains of mice survive the acute infection and develop a chronic demyelinating disease. In this report, we analyzed the routes of spread of TMEV within the CNS of nude mice and target sites eventually infected in the CNS. Compared to the immunocompetent mouse, in which an antiviral immune response is mounted but virus persists, the nude mouse develops a severe encephalomyelitis due to the lack of functional T lymphocytes and provides a useful model for the study of viral dissemination. We demonstrated, by immunohistochemistry, the presence of viral antigen in defined regions of the CNS, corresponding to various structures of the limbic system. In addition, we found a different time course for viral spread using two different sites of intracerebral inoculation, ie, via the olfactory bulb or the cortex. Limbic structures were rapidly infected following olfactory bulb infection and then showed a decrease in viral load, presumably due to loss of target neurons. Using either route of infection, the virus was able to disseminate to similar regions. These results indicate that limbic structures and their connections are very important for the spread of TMEV in the brain. In the spinal cord, not only neuronal but hematogenous pathways were suspected to be involved in the dissemination of Theiler's virus.

Animals↗
PubMed2005

Morphological and functional plasticity of olfactory ensheathing cells.

In the primary olfactory pathway, olfactory ensheathing cells (OECs) extend processes to envelop bundles of olfactory axons as they course towards their termination in the olfactory bulb. The expression of growth-promoting adhesion and extracellular matrix molecules by OECs, and their spatially close association with olfactory axons are consistent with OECs being involved in promoting and guiding olfactory axon growth. Because of this, OECs have been employed as a possible tool for inducing axonal regeneration in the injured adult CNS, resulting in significant functional recovery in some animal models and promising outcomes from early clinical applications. However, fundamental aspects of OEC biology remain unclear. This brief review discusses some of the experimental data that have resulted in conflicting views with regard to the identity of OECs. We present here recent findings which support the notion of OECs as a single but malleable phenotype which demonstrate extensive morphological and functional plasticity depending on the environmental stimuli. The review includes a discussion of the normal functional role of OECs in the developing primary olfactory pathway as well as their interaction with regenerating axons and reactive astrocytes in the novel environment of the injured CNS. The use of OECs to induce repair in the injured nervous system reflects the functional plasticity of these cells. Finally, we will explore the possibility that recent microarray data could point to OECs assuming an innate immune function or playing a role in modulating neuroinflammation.

Animals↗