How the Developing Septo-Preoptic Medial Basal Hypothalamus Stimulates the Development of Placode-Derived LHRH Neurons.

Daikoku, Shigeo; Koide, Ikue; Yoshinaka, Yoshiyuki; Oka, Tatsuzo; Natori, Yasuo

doi:10.1679/aohc.58.77

Cited by 13 publications

(5 citation statements)

References 55 publications

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“…Thus, the sharp dorsal turning of ventral axons in the nasal septum is certainly consistent with the presence of a putative dorsoventral gradient of guidance cues in the caudal portion of the septum. That the overlying brain could be responsible for establishing this gradient is also consistent with reports that the ventral telencephalon secretes diffusible factors that stimulate differentiation and growth of LHRH neurons in the olfactory neuroepithelium (Daikoku et al, 1991(Daikoku et al, , 1995Daikoku and Koide, 1994;Rogers et al, 1997).…”

Section: Discussionsupporting

confidence: 88%

Target tissue influences the peripheral trajectory of mouse primary sensory olfactory axons

Storan

Key

2004

J. Neurobiol.

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Primary olfactory neurons situated in the nasal septum project axons within fascicles along a highly stereotypical trajectory en route to the olfactory bulb. The ventral fascicles make a distinct dorsovental turn at the rear of the septum so as to reach the olfactory bulb. In the present study we have used a brain and nasal septum coculture system to examine the role of target tissue on the peripheral trajectory of olfactory sensory axons. In cultures of isolated embryonic nasal septa, olfactory axons form numerous parallel fascicles that project caudally in the submucosa, as they do in vivo. The ventral axon fascicles in the septum, however, often fail to turn, and do not project dorsally towards the roof of the nasal cavity. The presence of olfactory bulb, cortical, or tectal tissue apposed to the caudal end of the septum rescued this phenotype, causing the ventral fascicles to follow a normal in vivo-like trajectory. Ectopic placements of the explants revealed that brain tissue is not tropic for olfactory axons but appears to maintain the peripheral trajectory of growing axons in the nasal septum. Although primary olfactory axons are able to penetrate into olfactory bulb in vitro, they only superficially enter cortical tissue, whereas they do not grow into tectal explants. The ability of axons to differentially grow into different brain regions was shown to be unrelated to the migratory behavior of olfactory ensheathing cells, indicating that olfactory axons are directly responsive to guidance cues in the brain.

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Section: Discussionsupporting

confidence: 88%

Target tissue influences the peripheral trajectory of mouse primary sensory olfactory axons

Storan

Key

2004

J. Neurobiol.

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“…The embryos at E13.5 determined as previously described [14]were kept in ice-cold Gey’s buffer saturated with O 2 , and the heads were cut off in a flat glass dish filled with ice-cold Gey’s buffer. The head was sectioned sagittally into three pieces with ophthalmic scissors to expose the medial walls of the nasal pits (medial nasal placode, NAP) in the middle piece under a dissection microscope.…”

Section: Methodsmentioning

confidence: 99%

Pulsatile Gonadotropin-Releasing Hormone (GnRH) Secretion Is an Inherent Function of GnRH Neurons, as Revealed by the Culture of Medial Olfactory Placode Obtained from Embryonic Rats

Funabashi

Daikoku²,

Shinohara³

et al. 2000

Neuroendocrinology

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To determine whether gonadotropin-releasing hormone (GnRH) neurons in culture without the hypothalamus secrete GnRH in a pulsatile fashion, the nasal placode (NAP) was obtained at day 13.5 of gestation and cultured by a roller tube method. If the GnRH release occurs in a pulsatile fashion, it can be said that the pulse generator of GnRH exists inherently in each cell or community of cells in the culture. The concentration of GnRH in the NAP culture medium collected at 8-min intervals for 160 min after 2- to 4-week cultures showed that GnRH release occurred in a pulsatile fashion with a mean interpulse interval of 29.8 ± 2.3 min (n = 9). When the NAP was cultured with tissues of the forebrain vesicle (n = 3) or the hypothalamus (n = 4), GnRH was also released in a pulsatile fashion with similar intervals (27.3 ± 1.0 min for the NAP+forebrain vesicle culture and 36.0 ± 6.3 min for the NAP+hypothalamus culture) as those in cultures without brain tissues. It is concluded that pulsatile GnRH release is an inherent function of GnRH neurons.

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“…E13.5 embryos, determined as previously reported [20], were kept in 4°C Gey’s buffer saturated with O 2 and their heads were cut off in a flat glass dish filled with 4°C Gey’s buffer. The head was sectioned sagittally into three pieces with ophthalmic scissors to expose the medial wall of the nasal pits (medial nasal placode) in the middle piece under a dissection microscope.…”

Section: Methodsmentioning

confidence: 99%

Role of Gamma-Aminobutyric Acid Neurons in the Release of Gonadotropin-Releasing Hormone in Cultured Rat Embryonic Olfactory Placodes

Funabashi

Daikoku²,

Suyama³

et al. 2002

Neuroendocrinology

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We recently established a primary cell culture system of gonadotropin-releasing hormone (GnRH) neurons originating from olfactory placodes of rat embryos at E13.5 and showed that cultured olfactory placodes released GnRH into the medium in a pulsatile fashion with an interpulse interval of about 30 min. Since the reported presence of γ-aminobutyric acid (GABA) neurons in the culture of rat olfactory placode raises questions as to the role played by these GABA neurons in the GnRH pulse generation, we immunostained GnRH neurons and GABA neurons in this culture system to examine the interrelationship between both types of neurons, and determined the effects of GABA and the GABA_A receptor antagonist, bicuculline, on GnRH release. The immunohistochemical study showed that GnRH neurons received fiber terminals from GABA neurons. GnRH neurons in culture released GnRH into the medium at intervals of 30–40 min, confirming our previous study. Treatment with 20 µM GABA prolonged the interpulse interval and decreased the amplitude of GnRH pulses. Bicuculline administered at 20 µM did not affect either parameter, but 50 µM bicuculline elevated the mean GnRH level, although it did not affect either the interpulse interval or the amplitude of GnRH pulses. In addition, 50 µM bicuculline increased the mean trough levels of GnRH pulses, although 20 µM bicuculline did not. In light of the in vivo studies performed previously, we suggest that the GnRH pulse generator, which probably consists of a small population of GnRH neurons in the culture, does not involve GABA neurons to generate the pulsatile GnRH release, although it may be responsive to the inhibitory transmitter GABA. We also found that there may be another population of GnRH neurons in the culture whose activity is strongly suppressed by the tonic inhibition of GABA neurons. Although it is speculative, these latter GnRH neurons may be responsible for the surge of GnRH release.

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How the Developing Septo-Preoptic Medial Basal Hypothalamus Stimulates the Development of Placode-Derived LHRH Neurons.

Cited by 13 publications

References 55 publications

Target tissue influences the peripheral trajectory of mouse primary sensory olfactory axons

Target tissue influences the peripheral trajectory of mouse primary sensory olfactory axons

Pulsatile Gonadotropin-Releasing Hormone (GnRH) Secretion Is an Inherent Function of GnRH Neurons, as Revealed by the Culture of Medial Olfactory Placode Obtained from Embryonic Rats

Role of Gamma-Aminobutyric Acid Neurons in the Release of Gonadotropin-Releasing Hormone in Cultured Rat Embryonic Olfactory Placodes

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