Pineal Gland Of Golden Hamsters Research Articles

Effect of different photoperiods on the diurnal rhythm of 5-methoxytryptamine in the pineal gland of golden hamsters (Mesocricetus auratus)

This study tested the photo-dependency of the rhythmic synthesis of 5-methoxytryptamine (5-MT) in the pineal gland of golden hamsters. After pargyline administration, pineal 5-methoxytryptamine and melatonin were measured by HPLC in male golden hamsters kept under short and long photoperiod. In both photoperiodic regimes, a clear 5-MT rhythm was observed which fitted a sinusoidal function with high values occurring during the daytime and low values occurring during the night-time. The duration of the low night-time levels was clearly proportional to the length of the dark phase. A marked rhythm of melatonin synthesis was also seen with low daytime levels and high night-time values. An inverse relationship between 5-MT and melatonin levels was observed. Thus, after pargyline administration, the rhythms of 5-MT and melatonin in the pineal gland of golden hamsters are photoperiod-dependent and show a reciprocal relationship.

Low ambient temperature does not affect the pineal concentrations of either 5‐methoxytryptamine or melatonin in golden hamsters kept under short photoperiod

This work investigates the rhythmic synthesis of pineal 5-methoxytryptamine and related indoles in golden hamsters as a function of ambient temperature. 5-methoxytryptamine, 5-methoxytryptophol, 5-methoxyindole acetic acid, and melatonin were measured by high pressure liquid chromatography (HPLC) in the pineal gland of golden hamsters after inhibition of monoamine oxidase. In our experimental conditions, the pineal 5-methoxyindole concentrations of hamsters kept at 5 degrees C were similar to those observed at 20 degrees C. These results suggest that low temperature, which is known to accelerate the short photoperiod-induced gonadal regression, acts at a level different to that of the pineal gland or affects another compound in the pineal gland.

Immunohistochemical studies of tyrosine hydroxylase-positive, dopamine-b-hydroxylase-negative neuron-like cells in the pineal gland of golden hamsters

Immunohistochemical studies of tyrosine hydroxylase-positive, dopamine-b-hydroxylase-negative neuron-like cells in the pineal gland of golden hamsters

Effects of constant light and darkness on the intrapineal neurons of golden hamsters, stained for tyrosine hydroxylase A morphometric analysis

Tyrosine hydroxylase (TH)-positive neurons (TH neurons) were found in the pineal gland of golden hamsters. To examine possible relations between TH neurons and environmental light, we kept male animals under constant light (LL) and darkness (DD) for a week, and morphometrically compared the number, size, and immunoreactivity of TH neurons with those of control animals kept under 12L/12D (LD), using an image processor, Nexus 6400. In LL animals, the number of TH neurons/mm2 of pineal tissue and each cell area were decreased, and immunoreactivity to TH was less than in LD animals. In DD animals, the number of TH neurons and each cell area were increased, and immunoreactivity decreased slightly. These data suggested that environmental light affected the TH neurons, and the amount of TH in the neurons would be decreased by LL, but increased by DD.

An Electron Microscopic Immunocytochemical Study on the Tyrosine Hydroxylase‐Positive, Dopamine Beta‐Hydroxylase‐Negative Cells in the Pineal Gland of Golden Hamsters

Abstract We have examined the ultrastructure of tyrosine hydroxylase-positive, dopamine beta-hydroxylase-negative neuron-like cells in the pineal gland of golden hamsters by electron microscopic immunocytochemistry using antiserum to tyrosine hydroxylase. The tyrosine hydroxylase-positive cells were scattered throughout the parenchyma of the pineal gland. Their cell bodies were oval or spindle-shaped (maximum diameter 15 to 20 mum) with one or two short cell processes and a large round nucleus. They contained mitochondria, short rough-surfaced endoplasmic reticulum, Golgi apparatus, and granulated vesicles (50 to 100 nm). The cell membrane was in close contact with the pinealocyte cell body, pinealocyte processes and tyrosine hydroxylase-negative or -positive nerve terminals.

Ontogeny of tyrosine hydroxylase-positive but dopamine β-hydroxylase-negative neuron-like cells in the pineal gland of golden hamsters

The ontogeny of tyrosine hydroxylase (TH)-positive but dopamine β-hydroxylase (DBH)-negative neuron-like cells in the pineal gland of golden hamsters was investigated by double immunostaining. These cells first appeared on the 6th postnatal day and thereafter increased in number. On the other hand, TH- and DBH-positive nerve fibers, probably originating from the superior cervical ganglion, were already present in the pineal gland at birth.

Immunohistochemical studies on tyrosine hydroxylase(TH)-positive, dopamine β-hydroxylase(DBH)-negative neuron-like cells in the pineal gland of golden hamsters

Immunohistochemical studies on tyrosine hydroxylase(TH)-positive, dopamine β-hydroxylase(DBH)-negative neuron-like cells in the pineal gland of golden hamsters

Immunohistochemical demonstration of tyrosine hydroxylase (TH)-positive but dopamine β-hydroxylase (DBH)-negative neuron-like cells in the pineal gland of golden hamsters

Double immunostaining for tyrosine hydroxylase (TH) and dopamine β-hydroxylase (DBH) in the pineal gland revealed many TH-positive but DBH-negative, neuron-like cells in golden hamsters, but not in rats and gerbils. They were scattered in the meshwork of TH- and DBH-positive nerve fibers throughout the parenchyma. Their cell bodies were oval or spindle-shaped (maximum diameter: 15–20 μm). They had sometimes one or two short cell processes. Bilateral superior cervical ganglionectomy diminished strikingly the number of TH- and DBH-positive nerve fibers, but did not affect the number of TH-positive cells.

Day–night rhythm of 5-methoxytryptamine biosynthesis in the pineal gland of the golden hamster (Mesocricetus auratus)

5-Methoxytryptamine is a potent agonist of presynaptic 5-hydroxytryptamine autoreceptors modulating serotonin release in the central nervous system. This methoxyindole can be synthesized in the pineal gland, but its presence in vivo is still controversial, probably because of rapid catabolism by monoamine oxidase. An improved high-pressure liquid chromatography method, with coulometric detection, has been developed for the simultaneous measurement of melatonin, 5-methoxytryptamine, 5-methoxytryptophol and 5-methoxyindolacetic acid. We have demonstrated a day-night rhythmicity in the amount of 5-methoxytryptamine in the pineal gland of golden hamsters (Mesocricetus auratus) maintained under a long photoperiod (14 h light: 10 h darkness) and pretreated with the monoamine oxidase inhibitor pargyline. Levels of 5-methoxytryptamine were highest at 16.30 h and lowest at 00.30 h. The rhythm for 5-methoxytryptamine appears to be the same as for serotonin (opposite in phase to that of melatonin). The identification of 5-methoxytryptamine has been confirmed by analysis with gas chromatography-mass spectrometry.

Electrophysiological characterization of the pineal gland of golden hamsters.

In one of the most-widely used species in pineal gland research, the strongly photoperiodic golden hamster, Mesocricetus auratus, no electrophysiological data on pinealocytes are currently available. To fill this gap, in the present study 185 spontaneously active pinealocytes from male golden hamsters were recorded extracellularly, both during day- and night-time (light: dark cycle 12: 12, lights on at 07.00 h). As in other species, pinealocytes exhibited action potentials of 1-2 ms duration. An irregular firing pattern was observed in 95% of the pinealocytes, the remainder fired more regularly or showed a phasic discharge pattern. The firing frequencies ranged from 0.2 to 25 Hz and showed clear time-dependent differences. From 07.00 h to 22.00 h the mean firing frequencies were identical, i.e. in the range of 2 Hz; between 22.00 h and 01.00 h mean discharge rate increased to 5 Hz and exhibited a peak of 7 Hz between 01.00 h and 04.00 h, followed by a decrease to 4 Hz between 04.00 h and 07.00 h. Electrical stimulation of the superior cervical ganglion during day-time resulted in an augmentation of firing frequency in some pinealocytes and a decrease in others; during night-time, inhibitory responses only were observed. Photic stimulation, or electrical stimulation of either the optic chiasm or the habenular nuclei mostly decreased the firing rate of pinealocytes. Compared to other mammalian species, the electrophysiological properties of golden hamster pinealocytes appear to be basically similar.

Ultrastructural changes of the pineal gland of golden hamsters after the artificial winter season in a climatic chamber

Ultrastructural changes of the pineal gland of golden hamsters after the artificial winter season in a climatic chamber