Functional Electron Microscopy of the Hypothalamic Median Eminence

Kobayashi, Hideshi; Matsui, Toshiyasu; Ishii, Susumu

doi:10.1016/s0074-7696(08)60039-x

Cited by 194 publications

(50 citation statements)

References 176 publications

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“…The origin of the CSF vasopressin is considered to be hypothalamic vasopressin-containing neurones (Brownfield & Kozlowski, 1977;Buijs, Swaab, Dogterom & Van Leeuwen, 1978;Robinson & Zimmerman, 1973). Subependymal localization of vasopressin-or neurophysin-containing fibres or endings (Brownfield & Kozlowski, 1977;Buijs et al 1978;Robinson & Zimmerman, 1973) may indicate transport of vasopressin into the cerebral ventricles through the ependyma (Kobayashi, Matsui & Ishii, 1970;Rodriguez, 1976), or into the CSF-filled perivascular spaces, presumably those around veins (Rennels, Gregory, Blaumanis, Fujimoto & Grady, 1985), by bulk flow of interstitial fluid (Cserr, Cooper & Milhorat, 1977). Vasopressin so secreted into the ventricles and into the perivascular spaces may then circulate through the ventricles and subarachnoid spaces to gain access to the pial arteries and further to the penetrating arteries through the perivascular spaces (Rennels et al 1985).…”

Section: Discussionmentioning

confidence: 99%

Contractile effects of perivascularly applied vasopressin on the pial artery of the cat brain.

Nakai

1987

The Journal of Physiology

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SUMMARY1. The effects of perivascularly applied vasopressin on the diameter of pial arteries (control 298 + 14 S.E. ,m) of the brain were examined after chronic implantation of a cranial window in fifteen anaesthetized cats.2. Application of vasopressin resulted in a dose-dependent contraction. The threshold concentration for contraction was 3 x 10-10 M, the half-maximal effective concentration (ED50) (16±+02) x 10-9 M, and the maximum reduction in artery diameter 37 + 2 /.3. The contraction was powerfully inhibited by perivascular application of a 10-M solution of the vasopressin antagonist, [1-(,8-mercapto-,8,,8-cyclopenta-methylenepropionic acid),2-(O-methyl)tyrosine]arginine vasopressin. 4. Perivascular application ofnoradrenaline induced a dose-dependent contraction of the pial artery. The ED50 was (8-9 + 2 5) x 10-7 M, and the maximum reduction in artery diameter was 33 + 2 %.5. Such noradrenaline-induced contraction was not modified at all in the presence of a subthreshold dose (2 x 10-10 M) of vasopressin (P > 0 05, for the over-all difference in size of the contraction, ED50 and maximum contraction).6. In another experimental setting it was also found that neither the subthreshold nor a suprathreshold (10-9 M) dose of vasopressin modified the contraction induced by 10-6 M-noradrenaline (P > 0 05, compared to the contraction in the absence of vasopressin).7. Thus a powerful and sensitive contractile response of the pial arteries to perivascularly applied vasopressin was demonstrated. However, the modifying effect of vasopressin on the contraction induced by perivascularly applied noradrenaline was minimal.

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Section: Discussionmentioning

confidence: 99%

Contractile effects of perivascularly applied vasopressin on the pial artery of the cat brain.

Nakai

1987

The Journal of Physiology

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“…Furthermore, it has recently been demonstrated that those small granules separated by an ultracentrifuge from the horse median eminence show high LRF activity (Kobayashi and Ishii, 1969;Kobayashi et al, 1970;Ishii, 1970). Therefore, it is likely that in our experiments implanted DA acted on the axon endings containing LRF in the posterior median eminence, resulting in suppression of LRF release.…”

Section: Discussionmentioning

confidence: 67%

“…It has been suggested from morphological experiments that the small granules with diameters of about 1200 A in the axon endings of the median eminence might be carriers of gonadotropin releasing factors (T. Kobayashi et al, 1963;Harris and Campbell, 1966;Zambrano and de Robertis, 1968 a, b;Zambrano, 1969;Kobayashi and Matsui, 1969 ;Kobayashi, et al, 1970). Furthermore, it has recently been demonstrated that those small granules separated by an ultracentrifuge from the horse median eminence show high LRF activity (Kobayashi and Ishii, 1969;Kobayashi et al, 1970;Ishii, 1970).…”

Section: Discussionmentioning

confidence: 99%

“…Using electron microscopy, several investigators have identified small granules having diameters of about 1000 A in the external layer of the tetrapod median eminence (for reviews see Kobayashi and Matsui, 1969;Kobayashi et al, 1970). Kobayashi (1964) these granules are probably carriers of monoamines.…”

mentioning

confidence: 99%

“…Javon. February 1971 Kobayashi and Ishii, 1969;Kobayashi and Matsui, 1969;Kobayashi, 1970;Kobayashi et al, 1970 cannula was lowered into the brain so that the tip was placed in the desired position. After the cannula was lowered, it was fixed securely to the skull with dental resin and two anchoring screws.…”

mentioning

confidence: 99%

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Effects of Dopamine Implanted in the Median Eminence on the Estrous Cycle of the Rat

Uemura¹,

Kobayashi²

1971

Endocrinol Japon

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SynopsisA mixture (DA-C) of dopamine hydrochloride and cholesterol in a ratio of 2 to 1 or 5 to 1 by weight was implanted into different hypothalamic regions of the rat and allowed to persist for more than two weeks. The estrous cycles and ovarian histology were examined to determine effects of the treatment. When the tip of the cannula containing DA-C (2 to 1) hit the posterior median eminence (ME) and a small part of the arcuate nucleus (AN), the rats showed prolonged estrus. The ovaries of these rats showed big follicles and no corpora lutea. When the tip of the cannula of DA-C (5 to 1) hit the posterior ME and a small part of the AN, the rats showed prolonged diestrus. The follicles and corpora lutea were small in the ovaries of these rats. Under our experimental conditions, DA seems to inhibit LH and FSH release at the level of the ME. When the tips of the cannulae containing DA-C were placed in AN, n. ventromedialis, n. premamillaris ventralis, n. premamillaris dorsalis, n. dorsomedialis pars ventralis or adenohypophysis, the rats showed cycles with or without minor irregularities.

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Tanycytes and pituicytes: Morphological and functional aspects of neuroglial interaction

Wittkowski

1998

Microsc. Res. Tech.

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The hypothalamo‐hypophyseal system is supplied with two types of specialized glial cells that interact in neuroendocrine functional dynamics: the tanycytes and the pituicytes. Tanycytes are the dominating glial cells within the median eminence. Similar to radial glia, they extend from the floor of the third ventricle to the neurohemal surface of the median eminence. Pituicytes, as specialized astrocytes, are the main glial cells of the neural lobe. They are in intimate contact with the perivascular space of the sinusoidal vessels. Morphological similarities between the two cell types focus on their interaction with terminal branches of hypothalamic neurons in both regions of the neurohypophysis, the median eminence and the neural lobe. Release of hypothalamic hormones is apparently influenced by pituicytes and tanycytes. For instance, both types of cells are capable of closing or opening the access to the vessels. Thereby, in contrast to the “blood–brain‐barrier” function of astrocytes, pituicytes and tanycytes display “brain–blood‐barrier” functions. Pituicytes are characterized by the expression of specific membrane‐bound receptors for opioids, vasopressin, and β‐adrenoceptors, indicating that they receive input by numerous neuroactive substances. Integration of these incoming signals may result in a regulation of neurosecretion, especially by morphological changes and by modulation of extracellular ion concentrations. Comparable modulatory mechanisms of tanycytes have not yet been elucidated in a convincing manner. Besides possible regulatory functions, tanycytes are considered to possess guiding functions for hypothalamic axons and to be involved in transport mechanisms between ventricle and blood vessels of the portal system. Microsc. Res. Tech. 41:29–42, 1998 © 1998 Wiley‐Liss, Inc.

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Functional Electron Microscopy of the Hypothalamic Median Eminence

Cited by 194 publications

References 176 publications

Contractile effects of perivascularly applied vasopressin on the pial artery of the cat brain.

Contractile effects of perivascularly applied vasopressin on the pial artery of the cat brain.

Effects of Dopamine Implanted in the Median Eminence on the Estrous Cycle of the Rat

Tanycytes and pituicytes: Morphological and functional aspects of neuroglial interaction

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