Search results for "pineal gland"
showing 10 items of 143 documents
An intrinsic neuronal-like network in the rat pineal gland
1999
Recent studies have shown that in rat pineal glands kept in vitro action potential-producing cell clusters are demonstrable. To test whether the clusters interact, multiple-unit recordings were carried out simultaneously from different clusters, with or without electrical stimulation. Clusters with rhythmic burst activity exhibit highly synchronized firing and electrical stimulation of one cluster elicits an immediate response in another one, apparently involving synapses but not gap junctions. It is hypothesized that the interacting clusters form a network. As the firing is affected by norepinephrine, acetylcholine and Ca2+, the network may monitor the interstitial concentrations of these …
Day/night changes of pineal gland volume and pinealocyte nuclear size assessed over 10 consecutive days
1984
Previous studies aimed at elucidating day/night changes of pineal gland size and pinealocyte nuclear volume have yielded contradictory results. The aim of the present investigation was to examine the above parameters over a period of 10 successive days, at 6-hour intervals under a lighting regimen of LD 12:12 (7 a.m. to 7 p.m.). It was found that changes in pineal gland volume could not be correlated with the light/dark phases; instead, a rhythm with a two-day period was encountered. Pinealocyte nuclear volume, by contrast, showed clear circadian changes, exhibiting troughs during photophase and peaks during scotophase. In this experimental series, the karyometric results conformed to the m…
Influence of melatonin and serotonin on the number of rat pineal ?synaptic? ribbons and spherules in vitro
1985
Previous studies have shown that the "synaptic" ribbons (SR) and spherules (SS) of the mammalian pineal gland may respond differently under physiological and various experimental conditions. The aim of the present study was to gain insight into the mechanisms that may be responsible for the numerical changes of these organelles during a 24-h cycle. As the possibility exists that the structures are influenced by substances synthesized within the pinealocyte, rat pineal glands were cultured with and without added melatonin or serotonin, using an experimental protocol such that the addition of melatonin and serotonin mimicks the circadian changes of the respective substances within the pineal.…
p-Chlorophenylalanine treatment depresses the number of synaptic ribbon profiles in the rat pineal gland, but does not abolish their day-night rhythm
1995
It is largely unknown as to how the day/night rhythm of pineal synaptic ribbon number is regulated. Transcriptional events related to the nocturnal formation of new synaptic ribbons occur early in the morning, when pineal serotonin levels begin to increase. The present study was carried out in order to elucidate as to how altered serotonin levels affect the day/night changes in the number of synaptic ribbon profiles. To this end, male Sprague-Dawley rats received a single dose of p-chlorophenylalanine (pCPA, 300 mg/kg body weight, 72 hours before sacrifice), which depresses tryptophan hydroxylase activity and hence pineal serotonin levels. Control animals received saline injections. Experim…
Alterations in the spontaneous activity of cells in the guinea pig pineal gland and visual system produced by pineal indoles
1982
The indoles serotonin (SER), melatonin (MEL), 5-methoxytryptophol (5-MTL) and 5-hydroxytryptophol (5-HTL) were administered during daytime microelectrophoretically to 240 cells in the pineal gland of the guniea-pig. The action of SER and 5-HTL was predominantly depressant on the electrical activity, MEL and 5-MTL caused an excitation in most of the units. Although MEL and 5-MTL caused fairly similar reactions on average, they appear to act on different cells. The effects of microelectrophoretically applied MEL and 5-MTL on the spontaneous or evoked activity in the visual system (retinal ganglion cells, optic tract, lateral lateral geniculate body, superior colliculus) of the guinea-pig were…
Electrophysiological investigations on the central innervation of the rat and guinea-pig pineal gland
1984
The possible influence of central nervous structures on the electrical activity of single pineal cells was investigated in rat and guinea-pig. In the rat electrical stimulation of the hippocampal formation elicited both single cell responses with different latencies and mostly long-term excitations in single pineal cells, while stimulation of the habenular nuclei caused clear orthodromical responses with different latencies, alterations in the rate of spontaneous electrical activity and evoked discharges of "silent" units. In the guinea-pig electrical stimulation of the paraventricular nucleus influenced predominantly cells in the deeper layers of the posterior part of the pineal gland. Ele…
Ultrastructural observations on the central innervation of the guinea-pig pineal gland.
1981
In the present study the central innervation of the guinea-pig pineal gland was investigated. The habenulae and the pineal stalk contain myelinated and non-myelinated nerve fibres with few dense-cored and electron-lucent vesicles. Some myelinated fibres leave the main nerve fibre bundles, lose their myelin-sheaths and terminate in the pineal gland. Although direct proof is lacking, the non-myelinated fibres appear to end near the site where the bulk of the myelinated fibres are located. Here a neuropil area exists where synapses between non-myelinated fibre elements are abundant. Neurosecretory fibres were also seen. The results support the concept of functional interrelationships between h…
Occurrence and regional distribution of calcareous concretions in the rat pineal gland.
1978
Serial sections of 90 Sprague-Dawley rat brains with the pineal in situ were scanned to determine the occurrence and regional distribution of calcareous concretions within the pineal gland and its surrounding leptomeningeal tissue. In 90% of the cases examined concretions were found in varying number and appearance, predominantly lying in the dorsal region of the pineal gland and in the distal portion of the pineal stalk. Discussing the hypothesis advanced by Lukaszyk and Reiter (1975) that the origin of pineal concretions may be related to a neurosecretory process involving a pineal carrier protein, called neuroepiphysin, it is thought that, in view of the intra- and extra-pineal occurrenc…
Pineal ?synaptic? ribbons and spherules during the estrous cycle in rats
1983
In previous studies pineal "synaptic" ribbons have been shown to undergo striking numerical changes under various physiological and experimental conditions and to be regulated by beta-adrenergic mechanisms. The aim of the present investigation was to study the numbers of pineal "synaptic" ribbons and spherules in Wistar rats throughout the estrous cycle and to compare them with those in males. There were no statistically significant differences in the numbers of ribbons and spherules between males and females and in the females at the different stages of the estrous cycle, indicating that the structures in question, in vivo, do not appear to be regulated by naturally occurring changes of se…
Substance P- and calcitonin gene-related peptide-like immunoreactive neurons in the rat trigeminal ganglion — with special reference to meningeal and…
1992
Summary The distribution of perikarya showing substance P- ( SP ) or calcitonin gene-related peptide-like inununoreactivity ( CGRP-LI ) in the rat trigeminal ganglion ( TG ) were investigated by means of immunohistochemical methods. Approximately 50% of the perikarya contain CGRP while SP-Ll was observed in 1/3 of the cells. IR fibres were seen to leave the ganglion via the ophtalmic, maxillary, and mandibular nerves. The combination of peptide histochemistry and retrograde labelling of cells in the ganglion following injection of a fluorescent tracer into the pineal gland reveals that few SP- or CGRP-LI trigeminal neurons innervate the pineal gland. In contrast, the vast majority of perika…