Chem. Senses 27: 817-824,
2002
© Oxford University Press 2002
A Long-term Culture System for Olfactory Explants with Intrinsically Fluorescent Cell Populations
Institute of Physiology, University Hohenheim, Garbenstrasse 30, D-70593 Stuttgart, Germany
Correspondence to be sent to: Jörg Strotmann, Institute of Physiology, University Hohenheim, Garbenstrasse 30, D-70593 Stuttgart, Germany. e-mail: strotman{at}uni-hohenheim.de
 |
Abstract |
|---|
 Top Abstract IntroductionMaterials and methodsResultsDiscussionReferences |
|---|
As a prerequisite for exploring the mechanisms which lead to the formation and maintenance of the precise wiring patterns in the olfactory system, organotypic cultures of olfactory tissue from transgenic mice expressing green fluorescent protein (GFP) under control of the olfactory marker protein promotor have been established. Tissue specimen from embryonic stage 14 were explanted and kept in culture for >1 week. Within the explants, numerous GFP-fluorescent olfactory sensory neurons assembled in an epithelial-like manner during this period. Under optimized culture conditions, strongly GFP-positive axons extended from these explants, fasciculated and formed bundles. When co-cultured with explants from the olfactory bulb, distinct axon populations were attracted by the target tissue; the fluorescent axon bundles invaded the bulbular explants and formed conglomerates at distinct spots. Explants from transgenic mice expressing GFP under control of a given olfactory receptor gene (mOR37A) also comprised labeled neurons that extended intensely fluorescent axonal processes, which all seemed to grow in a common fascicle. The results demonstrate that GFP-labeled olfactory sensory neurons differentiate in the established organotypic cultures, which thus appear to be a useful tool to monitor and to manipulate the processes underlying the axonal wiring between the olfactory epithelium and bulb.
|
Introduction |
|---|
|
TopAbstractIntroductionMaterials and methodsResultsDiscussionReferences |
|---|
The precise spatial organization of the olfactory system is an essential prerequisite for the concept that olfactory coding may involve the transformation of an odorant's molecular features into a spatial map of neuronal activity (Friedrich and Korsching, 1997
,
1998;
Rubin and Katz, 1999;
Meister and Bonhoeffer, 2001).
In particular, the convergent projection of olfactory sensory neurons to the
olfactory bulb (Jastreboff et
al., 1984; Pedersen
et al., 1986), where the axons of several thousand cells
terminate in a small neuropil, the glomerulus, seems to be essential;
2000 of these glomeruli are densely packed beneath the bulbar surface
(Royet et al., 1988;
Meisami and Sendera, 1993).
Recent studies employing gene targeting approaches and generation of
transgenic mouse lines have greatly improved our insight into the principles
underlying the convergent wiring of the olfactory system. Analysis of the
intrinsically labeled cells revealed that all of the 10 000-20 000 neurons
expressing the same receptor subtype typically converge onto two glomeruli,
located at the medial and lateral side of bulb, respectively
(Mombaerts et al.,
1996; Wang et al., 1988); however, there are exceptions
(Strotmann et al.,
2000; Pyrski et al.,
2001). The cellular mechanisms and molecular elements underlying
the formation and maintenance of these precise wiring patterns remain largely
unknown. In fact, appropriate experiments for identifying directional cues
which navigate the outgrowing axons to their defined destination as well as
attractant and repellent compounds which ultimately allow the axons to contact
the appropriate target cells may require suitable in vitro culture
systems, reminiscent of the previous contribution of retinal explant cultures
in the attempts to unravel the molecular network involved in establishing the
retinotectal projection (Baier and
Bonhoeffer, 1990; Müller
et al., 1990; Hoff
et al., 1999). The unique possibility to optically
identify neurons with a distinct molecular identity combined with the
accessibility of an organotypic culture system may enable the monitoring and
experimental manipulation of some of the fundamental steps involved in wiring
the olfactory system, including axonal outgrowth, fasciculation and guidance,
as well as target finding in the olfactory bulb. |
Materials and methods |
|---|
|
TopAbstractIntroductionMaterials and methodsResultsDiscussionReferences |
|---|
Animals
OMP-GFP mice (Potter et al.,
2001) were kindly provided by Prof. Peter Mombaerts; in these
mice, green fluorescent protein (GFP) is expressed from the locus encoding the
olfactory marker protein (OMP). In mOR37A-ITGFP mice
(Strotmann et al.,
2000) only cells which express the olfactory receptor gene
mOR37 also express GFP. Embryos were obtained from timely mated mice;
the time of vaginal plug formation was counted E0.
Cell culture conditions
Cultures were grown in glass-bottomed dishes which were coated with 10
µg/ml laminin (Invitrogen, Karlsruhe, Germany) in Hank's balanced salt
solution (HBBS; Invitrogen) for 3 h at 37°C and 5% CO2. The
dishes were subsequently washed with HBSS and Neurobasal-Asupp
medium (Brewer et al.,
1993; Brewer,
1995): Neurobasal-A (Invitrogen) supplemented with 0.8 mM
L-glutamine (Invitrogen), 0.4% methylcellulose (Sigma, Taufkirchen, Germany),
10 mM HEPES, pH 7.5, 5 µg/ml Gentamycin (Invitrogen) and 0.02 x
B27-supplement (Invitrogen).
Tissue preparation
Pregnant mice were killed by cervical dislocation; embryos were decapitated and the heads stored in ice-cold HBSS. Dissection of the olfactory epithelium from the nasal septum and the turbinates was performed under a stereo-microscope in L-15 medium (Invitrogen). The cellular layer containing olfactory sensory neurons (OSNs) was removed from the underlying lamina propria using a lancet. Olfactory bulbs were removed from the bony capsule after cutting the olfactory nerves. The bulbs were cut into small pieces in a black microscope-tray filled with Neurobasal-Asupp.
About 20-30 explants were transferred to the center of a culture dish, where four metal blocks formed a small basin of 10 mm x 10 mm x 2 mm, filled with 200 µl of Neurobasal-Asupp. The metal blocks were subsequently pulled apart to generate a thin film of medium covering the explants and pressing them down to the bottom.
Explants were cultured at 37°C, 5% CO2 and 95% humidity. Four to six hours after dissection, 1 ml of sterile H2O was added to the outer rim of the culture dish to avoid evaporation of the medium. After the explants had attached to the culture dish (4 h), 200-500 µl of Neurobasal-Asupp was added to the cultures; half of the medium was replaced every other day.
Microscopy and photography
Cultures were observed using an inverted microscope (Olympus IX70; Olympus, Hamburg, Germany) with fluorescence optics. Images were taken using a digital camera (Micromax 5 MHz, Princeton Scientific Instruments, Inc., Monmouth Junction, NJ).
|
Results |
|---|
|
TopAbstractIntroductionMaterials and methodsResultsDiscussionReferences |
|---|
The nasal epithelium of OMP-GFP mice (Potter et al., 2001
)
appeared to be most suitable for establishing an organotypic culture system of
the olfactory epithelium to monitor OSNs under controlled and manipulable
conditions in vitro. In these mice, GFP is expressed from the locus
encoding the OMP, which is expressed at high levels and selectively in mature
OSNs (Margolis, 1972). Since
the onset of OMP expression occurs around embryonic stage 14 (E14)
(Monti-Graziadei et al.,
1980), the olfactory epithelia (OEs) from mice of this stage were
dissected and small pieces were cultured under conditions as described in
Materials and methods. After 2 days in vitro, intensely green
fluorescent cells were visible within the OE explants
(Figure 1a,b); they seemed to
be arranged randomly. The majority of the cells showed the typical morphology
of OSNs, with a dendrite extending from one pole of the cell body ending in a
small swelling, the dendritic knob (Figure
1a), and a thin axonal process extending from the opposite pole of
the soma (Figure 1b).
|
After 6 days in culture, fluorescent OSNs within the OE explants were arranged in a characteristic parallel, epithelial-like manner (Figure 1c); this is quite reminiscent of their arrangement in situ, where OSNs form a pseudo-stratified epithelium with their dendrites in a palisade-like parallel orientation. In small explants, the dendrites of GFP-positive cells formed a spherical arrangement with a central cavity (Figure 1d). The center of the cavity was not fluorescent and thus most likely represented a liquid-filled space.
After 9 days in culture, the OE explants contained numerous GFP-fluorescent cells displaying a morphology typical for OSNs (data not shown). These results thus demonstrate that, under the optimized culture conditions, explants from an embryonic OE maintained and probably generated mature olfactory neurons, which formed a characteristic epithelial-like assembly.
Since the established culture conditions allowed the survival and epithelial arrangement of olfactory sensory neurons in vitro, we next asked whether these neurons may form axons and whether these processes may contain sufficient GFP to visualize fluorescent fibers. Figure 2a shows a representative OE explant after 4 days in culture. In this overview, fluorescent somata of OSNs are visible in the explant (Figure 2b), they direct their dendrites towards the center of this structure; in addition, several intensely green fluorescent fiber bundles are extending from the OE explant, projecting in different directions. At certain distances (100-150 µm) from the explant, these bundles defasciculated into smaller bundles and finally into what appear to be individual fibers. At the points of defasciculation, groups of axons initially growing in the same direction now change their trajectory. High magnification of their distal termini (Figure 2c) revealed typical filopodia-like structures reminiscent of growth cones, suggesting that these processes are indeed axons of OSNs. Thus, the results demonstrate that even in the most distal compartment of the cells the level of GFP was high enough to visualize and monitor the growth cones of olfactory axons in vitro.
|
Since the organotypic culture conditions allowed the OSNs to maintain their morphological as well as their growth characteristics, we next analyzed whether the direction of axonal outgrowth may be influenced by explants from the olfactory bulb. To this end, OE explants were co-cultured with explants from developing bulbs (E14) which were placed a suitable distance from the OE explants. Typical results of such a co-culture experiment are shown in Figure 3a,b. After 4 days of co-culturing, fluorescent fiber bundles extended radially from the OE explants, growing in all directions. Fiber bundles which grew in directions without bulb tissue seemed unaffected; in contrast, fiber bundles which grew in the direction of bulb explants apparently entered the target tissue. Certain fibers seemed to be redirected toward the bulb explant (arrows in Figure 3a,b). In most cases, bundles initially passing the bulb explant tangentially, defasciculated at a distinct position, where some axons changed their direction and now grew towards the bulb, whereas other axons continued to grow along the original route (Figure 3b). These results demonstrate that, under these in vitro conditions, outgrowing axons seem to be attracted by bulb tissue. This targeting process seemed to be selective; only a subpopulation of axons appeared to enter the bulb explant, while most of the visible axons grew along the surface of the bulb (Figure 3c) but did not invade the tissue.
|
Since the convergence of olfactory axons to two or more glomeruli may
represent one of the fundamental pre-requisites for olfactory coding, we next
examined whether OSNs converge in vitro to distinct spots in their
target tissue. It was found that in co-culture preparations, after 6 days,
GFP-fluorescent axons extended from the epithelium and entered the bulb tissue
(Figure 3d). Many axons
apparently condensed into a particular spot
(Figure 3e), whereas the
remaining bulb tissue seemed to receive only a few ingrowing axons. Similar
structures were observed in a variety of bulb explants; the size of such
axonal conglomerates was in the range of 50 µm.
To analyze a more definite OSN subpopulation, explants from the transgenic
mouse line mOR37A-GFP (Strotmann et
al., 2000) were employed. In this mouse line olfactory
neurons expressing the receptor subtype OR37A also express GFP. Since the
onset of receptor expression for this receptor type occurs early in
development (Conzelmann et al.,
2001), OE explants from E14 embryos were dissected from those
regions of the epithelium where OR37-expressing neurons are located. After 2
days in culture, GFP-fluorescent cells were detectable in the explants
(Figure 4a), usually located
within slightly different focal planes; as expected, this contrasts to the
large number of OMP-GFP positive cells. All fluorescent cells exhibited the
typical morphology of OSNs (Figure
4a); somata, dendrites and even the initial segments of cilia were
visible due to their intense fluorescence.
|
Since the fluorescent axons from the large OMP-GFP-labeled neuron population appeared to extend from the explants in distinct fiber bundles (see Figure 3a), it is of particular interest whether the axons of a defined neuron subpopulation sharing the same receptor subtype may grow out in a common fascicle or in distinct bundles. The examination of four independent cultures of epithelial explants containing mOR37A-GFP-expressing neurons revealed in all cases only a single fluorescent fiber bundle extending from the explant (Figure 4b). At distinct distances from the explant, a defasciculation of the bundle was observed; individual fibers deviated from the main fascicle. These results suggest that axons of a receptor-specific neuron population initially grow together in one fiber bundle. It is currently unknown whether axons of subpopulations expressing other receptor types are also part of these bundles.
|
Discussion |
|---|
|
TopAbstractIntroductionMaterials and methodsResultsDiscussionReferences |
|---|
In the present study conditions were designed and optimized to allow for the first time the culture of nasal explants with GFP-labeled OSNs for more than 1 week in vitro. Due to their fluorescence, the cells could be visualized and monitored for a considerable period of time. It was found that, under adequate in vitro conditions, the olfactory neurons established organotypical features, and the differentiation processes mimicked those observed during development in vivo. OMP-expressing, and thus mature, OSNs have been maintained for >9 days in vitro, a period significantly longer than in cultures reported previously (Calof and Chikaraishi, 1989
;
Chuah et al., 1991;
Mahantappa and Schwarting, 1993; Gong
et al., 1996;
Cunningham et al.,
1999; McEntire and Pixley,
2000); this emphasizes that the culture conditions seem to be
suitable for OSNs in vitro. The observation that, even after >1
week in vitro, numerous GFP-positive cells were detectable within the
OE explants even in the absence of their target tissue strongly suggests that
these cells were newly generated from basal cells in the explant. It has
previously been reported that basal cells can differentiate into mature OSNs
even without the bulb (Carr et
al., 1998); however, for survival, they depend on trophical
support from bulb tissue (Schwob et
al., 1992). Thus, the presence of GFP-positive cells showing
the characteristic morphological features of mature OSNs in long-term cultures
of OE explants indicates that these cells went through the full program of
differentiation in vitro.
In this study, for the first time, conditions have been established which
allowed us to monitor the expression of an OR gene in vitro, an
important prerequisite for manipulating transcription control mechanisms. The
results emphasize that `turn on' of receptor gene expression is an intrinsic
feature of the epithelium, and thus are supportive of previous studies
demonstrating that receptor expression is not initiated by the target tissue
(Strotmann et al.,
1995; Sullivan et
al., 1995).
The culture conditions allowed an extensive outgrowth of multiple OSN
processes from the explants, which, due to their intense green fluorescence,
could be visualized even in the most distal regions, the growth cones. The GFP
fluorescence of axonal processes from OSNs expressing a distinct OR gene even
allowed us to assess a distinct subpopulation of processes which in
vivo share a common destination. These preparations now offer the
possibility to employ time-lapse techniques and monitor the outgrow and
pathfinding of axonal processes; in addition, it may be possible to
experimentally interfere with the process by employing appropriate agents.
These manipulatory approaches (inhibitory antibodies, antisense oligos, RNA
interference) may eventually lead to the identification of attractant and/or
repellent cues for outgrowing olfactory axons. Diffusible factors secreted
from the bulb which may attract OSN axons have been proposed in the past
(Ressler et al.,
1994; Vassar et al.,
1994); however, experimental evidence is still elusive. In
addition, the identification of putative guidance molecules in the olfactory
tissue (Key and Akeson, 1990;
Puche and Key, 1996; Kafiz and
Greer, 1997, 1998; Yoshihara et
al., 1997; Tisay and Key,
1999; Schwarting et
al., 2000; St John et
al., 2000) has so far not been supplemented by functional
evidence demonstrating their direct involvement in axon outgrowth and
pathfinding. The observation that distinct axons appear to be attracted to and
grow towards the bulb tissue (see Figure
3) seems to support the view. Using GFP-fluorescent OSNs, it has
been possible for the first time to demonstrate that axons are capable of
converging onto distinct positions within the bulb in vitro. The axon
bundles tended to defasciculate at distinct distances from the OE explants,
mimicking the re-sorting of olfactory axons which occurs when they reach the
outer nerve layer of the bulb (Key and
Akeson, 1993; St John and Key,
2001) [for a recent review see
(St John and Key, 2002)].
In sum, the results demonstrate that GFP-labeled OSNs in organotypic cultures appear to be a useful tool for monitoring and manipulating the processes underlying the axonal wiring between the olfactory epithelium and bulb.
|
Acknowledgments |
|---|
This work was supported by the Deutsche Forschungsgemeinschaft Leibniz Program and SFB 495.
|
References |
|---|
|
TopAbstractIntroductionMaterials and methodsResultsDiscussionReferences |
|---|
Baier, H. and Bonhoeffer F. (1990) Axon guidance by gradients of a target-derived component.Science , 255,472 -475.
Brewer, G.J. (1995) Serum-free B27/neurobasal medium supports differentiated growth of neurons from the striatum, substantia nigra, septum, cerebral cortex, cerebellum, and dentate gyrus. J. Neurosci. Res., 42,674 -683.[Web of Science][Medline]
Brewer, G.J., Torricelli, J.R., Evege, E.K. and Price, P.J. (1993) Optimized survival of hippocampal neurons in B27-supplemented neurobasal TM, a new serum-free medium combination.J. Neurosci. Res. , 35,567 -576.[Web of Science][Medline]
Calof, A.L. and Chikaraishi, D.M. (1989) Analysis of neurogenesis in a mammalian neuroepithelium: proliferation and differentiation of an olfactory neuron precursor in vitro.Neuron , 3,115 -127.[Web of Science][Medline]
Carr, M.V., Walters, E., Margolis; F.L. and Farbman, A.I. (1998) An enhanced olfactory marker protein immunoreactivity in individual olfactory receptor neurons following olfactory bulbectomy may be related to increased neurogenesis. J. Neurobiol., 34,377 -390.[Web of Science][Medline]
Chuah, M.I., David, S. and Blaschuk, O. (1991) Differentiation and survival of rat olfactory epithelial neurons in dissociated cell culture. Devl Brain Res., 60,123 -132.[Medline]
Conzelmann, S., Malun, D., Breer, H., and Strotmann, J. (2001) Brain targeting and glomerulus formation of two olfactory neuron populations expressing related receptor types.Eur. J. Neurosci. , 14,1623 -1632.[Web of Science][Medline]
Cunningham, A.M., Manis, P.B., Reed, R.R. and Ronnett, G.V. (1999) Olfactory receptor neurons exist as distinct subclasses of immature and mature cells in primary culture.Neuroscience , 93,1301 -1312.[Web of Science][Medline]
Friedrich, R.W. and Korsching, S.I. (1997) Combinatorial and chemotopic odorant coding in the zebrafish olfactory bulb visualized by optical imaging.Neuron , 18,737 -752.[Web of Science][Medline]
Friedrich, R.W. and Korsching, S.I.
(1998) Chemotopic, combinatorial, and noncombinatorial
odorant representations in the olfactory bulb revealed using a
voltage-sensitive axon tracer. J. Neurosci.,18
, 9977-9988.
Gong, Q., Liu, W.-L., Srodon, M., Foster, T.D. and Shipley, M.T. (1996) Olfactory epithelial organotypic slice cultures: a useful tool for investigating olfactory neural development. Int. J. Devl Neurosci.,14 , 841-852.[Web of Science][Medline]
Hoff, A., Hämmerle, H. and Schlosshauer, B. (1999) Organotypic culture system of chicken retina.Brain Res. Brain Res. Protoc. , 4,237 -248.[Medline]
Jastreboff, P.J., Pedersen, P.E., Greer, C.A., Stewart, W.B.,
Kauer, J.S., Benson, T.E. and Shepherd, G.M. (1984)
Specific olfactory receptor populations projecting to identified glomeruli
in the rat olfactory bulb. Proc. Natl Acad. Sci. USA,81
, 5250-5254.
Kafitz, K.W. and Greer, C.A. (1997) Role of laminin in axonal extension from olfactory receptor cells.J. Neurobiol. , 32,298 -320.[Web of Science][Medline]
Kafitz, K.W. and Greer, C.A. (1998) Differential expression of extracellular matrix and cell adhesion molecules in the olfactory nerve and glomerular layers of adult rats.J. Neurobiol. , 34,271 -282.[Web of Science][Medline]
Key, B. and Akeson, R.A. (1990)
Olfactory neurons express a unique glycosylated form of the neural cell
adhesion molecule (N-CAM). J. Cell Biol.,110
, 1729-1743.
Key, B. and Akeson, R.A. (1993) Distinct subsets of olfactory sensory neurons: possible role in the formation of the mosaic olfactory projection. J. Comp. Neurol., 335,355 -368.[Web of Science][Medline]
Mahanthappa, N.K. and Schwarting, G.A. (1993) Peptide growth factor control of olfactory neurogenesis and neuron survival in vitro: roles of EGF and TGF-bs. Neuron, 10,293 -305.[Web of Science][Medline]
Margolis, F.L. (1972) A brain protein
unique to the olfactory bulb. Proc. Natl Acad. Sci.,69
, 1221-1224.
McEntire, J.K. and Pixley, S.K. (2000)
Olfactory receptor neurons in partially purified epithelial cell cultures:
comparison of techniques for partial purification and identification of
insulin as an important survival factor. Chem. Senses,25
, 93-101.
Meisami, E. and Sendera, T.J. (1993) Morphometry of rat olfactory bulbs stained for cytochrome oxidase reveals that the entire population of glomeruli forms early in the neonatal period. Brain Res. Devl Brain Res.,71 , 253-257.[Medline]
Meister, M. and Bonhoeffer, T. (2001)
Tuning and topography in an odor map on the rat olfactory bulb.J. Neurosci.
, 21,1351
-1360.
Mombaerts, P., Wang, F., Dulac, C., Chao, S.K., Nemes, A., Mendelsohn, M., Edmondson, J. and Axel, R. (1996) Visualizing an olfactory sensory map. Cell,87 , 675-686.[Web of Science][Medline]
Monti-Graziadei, Stanley, R.S. and Graziadei, P.P.C. (1980) The olfactory marker protein in the olfactory system of the mouse during development. Neuroscience,5 , 1239-1252.[Web of Science][Medline]
Müller, B., Stahl, B. and Bonhoeffer, F.
(1990) In vitro experiments on axonal guidance and
growth-cone collapse. J. Exp. Biol.,153
, 29-46.
Pedersen, P.E., Jastreboff, P.J., Stewart, W.B. and Shepherd, G.M. (1986) Mapping of an olfactory receptor population that projects to a specific region in the rat olfactory bulb.J. Comp. Neurol. , 250,93 -108.[Web of Science][Medline]
Potter, S.M., Zheng, C., Koos, D.S., Feinstein, P., Fraser,
S.E. and Mombaerts, P. (2001) Structure and
emergence of specific glomeruli in the mouse. J.
Neurosci., 21,9713
-9723.
Puche, A.C. and Key, B. (1996) N-Acetyl-lactosamine in the rat olfactory system: expression and potential role in neurite growth. J. Comp. Neurol.,364 , 267-278.[Web of Science][Medline]
Pyrski, M., Xu, Z., Walters, E., Gilbert, D.J., Jenkins, N.A.,
Copeland, N.G. and Margolis F.L. (2001) The
OMP-lacZ transgene mimics the unusual expression pattern of OR-Z6,
a new odorant receptor gene on mouse chromosome 6: implication for
locus-dependent gene expression. J. Neurosci.,21
, 4637-4648.
Ressler, K.J., Sullivan, S.L. and Buck, L.B. (1994) Information coding in the olfactory system: evidence for a stereotyped and highly organized epitope in the olfactory bulb.Cell , 79,1245 -1255.[Web of Science][Medline]
Royet, J.B., Souchier, C., Jourdan, F. and Ploye, H.J. (1988) Morphometric study of the glomerular population in the mouse olfactory bulb: numerical density and size distribution along the rostrocaudal axis. J. Comp. Neurol., 270,559 -568.[Web of Science][Medline]
Rubin, B.D. and Katz LC. (1999) Optical imaging of odorant representations in the mammalian olfactory bulb. Neuron, 23,499 -511.[Web of Science][Medline]
Schwarting, G.A., Kostek, C., Ahmad, N., Dibble, C., Pays,
L. and Puschel, A.W. (2000) Semaphorin 3A is
required for guidance of olfactory axons in mice. J.
Neurosci., 20,7691
-7697.
Schwob, J.E., Szumowski, K.E. and Stasky, A.A. (1992) Olfactory sensory neurons are trophically dependent on the olfactory bulb for their prolonged survival. J. Neurosci., 12,3896 -3919.[Abstract]
St John J. and Key, B. (2001) Chemically and morphologically identifiable glomeruli in the rat olfactory bulb. J. Comp. Neurol., 436,497 -507.[Web of Science][Medline]
St John J. and Key, B. (2002) Axon
navigation in the mammalian primary olfactory pathway: where to next?Chem. Senses
, 27,245
-260.
St John, J.A., Tisay, K.T., Caras, I.W. and Key B. (2000) Expression of EphA5 during development of the olfactory nerve pathway in rat. J. Comp. Neurol.,416 , 540-550.[Web of Science][Medline]
Strotmann, J., Wanner, I., Helfrich, T. and Breer, H. (1995) Receptor expression in olfactory neurons during rat development: in situ hybridization studies. Eur. J. Neurosci., 7,492 -500.[Web of Science][Medline]
Strotmann, J., Conzelmann, S., Beck, A., Feinstein, P., Breer,
H. and Mombaerts, P. (2000) Local permutations in
the glomerular array of the mouse olfactory bulb. J.
Neurosci., 20,6927
-6938.
Sullivan, S.L., Bohm, S., Ressler, K.J., Horowitz, L.F. and Buck, L.B. (1995) Target-independent pattern specification in the olfactory epithelium. Neuron,15 , 779-89.[Web of Science][Medline]
Tisay, K.T. and Key, B. (1999) The
extracellular matrix modulates olfactory neurite outgrowth on ensheathing
cells. J. Neurosci., 19,9890
-9899.
Vassar, R., Chao, S.K., Sitcheran, R., Nunez, J.M., Vosshall, L.B. and Axel, R. (1994) Topographic organization of sensory projections to the olfactory bulb. Cell,79 , 981-991.[Web of Science][Medline]
Wang, F., Nemes, A., Mendelsohn, M. and Axel, R. (1998) Odorant receptors govern the formation of a precise topographic map. Cell, 93,47 -60.[Web of Science][Medline]
Yoshihara, Y., Kawasaki, M., Tamada, A., Fujita, H., Hayashi,
H., Kagamiyama, H. and Mori, K. (1997) OCAM: a new
member of the neural cell adhesion molecule family related to zone-to-zone
projection of olfactory and vomeronasal axons. J.
Neurosci., 17,5830
-5842.
Accepted August 30, 2002
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  G. Pinato, J. Rievaj, S. Pifferi, M. Dibattista, L. Masten, and A. Menini Electroolfactogram Responses from Organotypic Cultures of the Olfactory Epithelium from Postnatal Mice Chem Senses, April 1, 2008; 33(4): 397 - 404. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||