Sub/Supraependymal Axonal Net in the Brains of Sharks and Probable Targets in Parasynaptic Relationship

MacDonnell, Malcolm F.

doi:10.1159/000116506

Cited by 3 publications

(3 citation statements)

References 17 publications

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“…However, further experiments are needed to test this supposition because the VIP-immunoreactive neurons of the nucleus accumbens remained unlabeled in 11 reptilian species (Hirunagi et al, 1993) by antibodies against bovine rodopsin and chicken cone opsin (see section on deep encephalic photoreceptors). As emphasized in previous studies on pinealocytes and CSFcontacting neurons, negative immunocytochemical results with antisera presently available do not exclude the presence of a certain opsin and thus the photoreceptive capacity of a cell type under study (Vigh-Teichmann and Vigh, 1983, 1989.…”

Section: Csf-contacting Neurons In the Lateral Telencephalonmentioning

confidence: 89%

“…The fine structure of intraventricular neurons was first described in the infundibulum of the hedgehog (Fig. 25); subsequently, supraependymal neurons, intraventricular synapses, and axons were found in the third ventricle from fish to mammals (Hirunagi et al, 1989a,b;Jonsson et al, 1972;Leonhardt, 1980;MacDonnell, 1989;Mestres, 1981;Mestres and Rascher, 1981;Mestres et al, 1985;Vigh-Teichmann et al, 1970b, 1980a.…”

Section: Intraventricular Axons and Perikaryamentioning

confidence: 98%

“…In light and scanning electron microscopic examinations, a midline ridge formation was described on the ventricular surface of the mesencephalic optic tectum (MacDonnell, 1983(MacDonnell, , 1989, which contains large CSF-contacting perikarya in cartilaginous fish (sharks, Holocephali). Using high performance liquid chromatography, monoamines were detected in this area (Howard et al, 1989).…”

Section: Csf-contacting Neurons Of the Mesencephalon And Diencephalonmentioning

confidence: 99%

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Actual problems of the cerebrospinal fluid-contacting neurons

Vígh

Vigh-Teichmann

1998

Microsc. Res. Tech.

133

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Cerebrospinal fluid (CSF)‐contacting neurons form a part of the circumventricular organs of the central nervous system. Represented by different cytologic types and located in different regions, they constitute a CSF‐contacting neuronal system, the most central periventricular ring of neurons in the brain organized concentrically according to our concept. Because the central nervous system of deuterostomian echinoderm starfishes and the prochordate lancelet is composed mainly of CSF‐contacting‐like neurons, we hypothesize that this cell type represents ancient cells, or protoneurons, in the vertebrate brain. Neurons may contact the ventricular CSF via their dendrites, axons, or perikarya. Most of the CSF‐contacting nerve cells send their dendritic processes into the ventricular cavity, where they form ciliated terminals. These ciliated endings resemble those of known sensory cells. By means of axons, the CSF‐contacting neurons also may contact the external CSF space, where the axons form terminals of neurohormonal type similar to those known in the neurohemal areas. The most simple CSF‐contacting neurons of vertebrates are present in the terminal filum, spinal cord, and oblongate medulla. The dendritic pole of these medullospinal CSF‐contacting neurons terminates with an enlargement bearing many stereocilia in the central canal. These cells are also supplied with a 9 × 2 + 2 kinocilium that may contact Reissner's fiber, the condensed secretory material of the subcommissural organ. The Reissner's fiber floating freely in the CSF leaves the central canal at the caudal open end of the terminal filum in lower vertebrates, and open communication is thus established between internal CSF and the surrounding tissue spaces. Resembling mechanoreceptors cytologically, the spinal CSF‐contacting neurons send their axons to the outer surface of the spinal cord to form neurosecretory‐type terminals. They also send collaterals to local neurons and to higher spinal segments. In the hypothalamic part of the diencephalon, neurons of two circumventricular organs, the paraventricular organ and the vascular sac, of the magnocellular neurosecretory nuclei and several parvocellular nuclei, form CSF‐contacting dendritic terminals. A CSF‐contacting neuronal area also was found in the telencephalon. The CSF‐contacting dendrites of all these areas bear solitary 9 × 2 + 0 cilia and resemble chemoreceptors and developing photoreceptors cytologically. In electrophysiological experiments, the neurons of the paraventricular organ are highly sensitive to the composition of the ventricular CSF. The axons of the CSF‐contacting neurons of the paraventricular organ and hypothalamic nuclei terminate in hypothalamic synaptic zones, and those of magno‐ and parvocellular neurosecretory nuclei also form neurohormonal terminals in the median eminence and neurohypophysis. The axons of the CSF‐contacting neurons of the vascular sac run in the nervus and tractus sacci vasculosi to the nucleus (ganglion) sacci vasculosi. Some hypothalamic CSF‐contacti...

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Section: Csf-contacting Neurons In the Lateral Telencephalonmentioning

confidence: 89%