Day:Night variations of melatonin, 5-hydroxyindole acetic acid, serotonin, serotonin N-acetytransferase, tryptophan, norephinephrine and dopamine in the rabbit pineal gland

Brainard, George C.; Matthews, Susan A.; Steger, Richard W.; Reíter, Russel J.; Asch, Ricardo H.

doi:10.1016/0024-3205(84)90361-8

Cited by 21 publications

(13 citation statements)

References 22 publications

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“…the minimum levels) were raised significantly in the dark phase. These are in line with other findings in rabbits concerning day/ night variations in pineal [24] and circulating [16] melatonin. The day/night difference in the mean melatonin level within the confluens sinuum of blinded rabbits revealed in the present study is comparable to that observed in the systemic circulation of rabbits [16].…”

Section: Discussionsupporting

confidence: 81%

Patterns of Pineal Melatonin Secretion in Rabbits: Diurnal Variation of Basal and Pulsatile Release

Chan

Cheung²,

Pang³

1990

Neuroendocrinology

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The level and release pattern of plasma melatonin in the confluens sinuum of 28 sighted and 18 blinded (i.e. acute bilateral orbital enucleation) rabbits anesthetized with pentobarbital were studied. The animals had been adapted to a 12:12 h light-dark regime. Blood samples were collected from the cannulated confluens sinuum and/or the femoral artery at either 2- or 4-min intervals in both the light and dark phases. Plasma melatonin was determined by radioimmunoassay. In all rabbits studied, plasma melatonin in the confluens sinuum exhibited an episodic release pattern, with pulses superimposed on a basal level. At 4-min sampling intervals, the pulsatile release of melatonin in sighted rabbits were 3.8 peaks/h in the light phase; shorter sampling interval (2-min) revealed more frequent pulsatile release of melatonin (5.1 peaks/h). In sighted animals in the light phase, the level of melatonin in the plasma of confluens sinuum was 7–15 times higher than that obtained from the plasma collected at the same time from the peripheral artery where the level of melatonin also exhibited pulsatile pattern. In blinded animals, melatonin levels in terms of mean concentration, mean maximum level and mean minimum (or baseline) level obtained in the dark phase were 12–14 times higher than those obtained in the light phase. These results suggest that the level of melatonin exhibits a diurnal rhythm in the confluens sinuum of rabbits.

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Section: Discussionsupporting

confidence: 81%

Patterns of Pineal Melatonin Secretion in Rabbits: Diurnal Variation of Basal and Pulsatile Release

Chan

Cheung²,

Pang³

1990

Neuroendocrinology

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“…The peak [DA] in the dark phase demonstrated in the adult animals is consistent with the work of others showing peak DA levels during the dark phase in the pineal gland of adult rats [11] and rabbits [12] as well as in the whole brain and in selective brain regions [13][14][15][16] of adult rats and mice. Although our data did not demonstrate statis tically significant daily rhythms in the caudal and rostral pons and the inferior colliculi of adult animals, the tendency was for higher DA levels during the late light phase through the early dark phase as was shown in the medulla and in the superior colliculi of adult animals.…”

Section: Discussionsupporting

confidence: 77%

Ontogeny of Dopamine Daily Rhythms within Rabbit Brainstem Regions

1995

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To examine the development of daily variations in dopamine levels, we measured dopamine concentrations within five distinct brainstem regions in 3- and 21-day-old, and adult rabbits at 09.30, 15.30, 21.30 and 03.30 h. Dopamine was measured by radioenzymatic assay and the dopamine concentration was expressed relative to wet tissue weight. In addition to defining the presence of a daily variation in the dopamine concentration in the whole brainstem, we were interested in identifying brainstem region-specific differences in this daily variation. Our data suggest that daily variations in dopamine concentrations are established by 3 days of life. Analysis of gross brainstem daily variation data suggest a peak in the dopamine concentration during the early light phase (09.30 h) for 3-day-old animals in contrast to a late light phase peak (15.30 h) for 21-day-old animals. Adult animals showed a peak in the early dark phase (21.30 h). These gross daily variations reflect the net sum of distinct region-specific patterns in the dopamine concentration. Analysis by region reflects a region-specific ontogeny in the development of daily variations for dopamine. Dopamine is involved in cardiorespiratory regulation. The observed developmental patterns may relate to the maturation and integration of these physiologic processes.

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“…After the onset of darkness, the rate-limiting enzyme N-acetyltransferase activity increases to values that are 15-to 30-fold greater than those that occur during light periods (22). The melatonin level in the rabbit pineal gland was 25 times greater at night than in the day (23). Therefore, in the present study, the significant increase in plasma melatonin concentration resulting from zaleplon administration was considered to be within the normal range of fluctuation of this physiological level of secretion.…”

Section: Discussionmentioning

confidence: 89%

Effect of Zaleplon, a Non-benzodiazepine Hypnotic, on Melatonin Secretion in Rabbits

Noguchi¹,

Kitazumi²,

Mori³

et al. 2003

J Pharmacol Sci

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Abstract. Melatonin, a major hormone secreted by the pineal gland, is known to play an important role in regulation of the circadian rhythm. (N-[3-(3-cyanopyrazolo[1,5-a]pyrimidin-7-yl)phenyl]-N-ethylacetamide (zaleplon) is a non-benzodiazepine hypnotic that acts via the benzodiazepine site of the GABA A receptor. In the present study, we investigated the effect of zaleplon on melatonin secretion in rabbits using RIA and compared the effect to triazolam and zopiclone. Zaleplon increased a dose-dependent concentration of melatonin in rabbit plasma collected at 30 min after intravenous administration at doses of 1 and 2 mg / kg. The zaleploninduced increase in plasma melatonin level was not blocked by flumazenil, a benzodiazepinereceptor antagonist. In contrast, triazolam and zopiclone failed to affect the plasma melatonin level. We also investigated the effect of zaleplon on intracellular cAMP in rat pinealocytes. Consequently, zaleplon had no effect on the intracellular cAMP levels in rat pinealocytes. These results of the present studies suggest that zaleplon may promote melatonin secretion and the elevation of plasma levels of melatonin may suggest an influence of zaleplon on chronobiology.

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Day:Night variations of melatonin, 5-hydroxyindole acetic acid, serotonin, serotonin N-acetytransferase, tryptophan, norephinephrine and dopamine in the rabbit pineal gland

Cited by 21 publications

References 22 publications

Patterns of Pineal Melatonin Secretion in Rabbits: Diurnal Variation of Basal and Pulsatile Release

Patterns of Pineal Melatonin Secretion in Rabbits: Diurnal Variation of Basal and Pulsatile Release

Ontogeny of Dopamine Daily Rhythms within Rabbit Brainstem Regions

Effect of Zaleplon, a Non-benzodiazepine Hypnotic, on Melatonin Secretion in Rabbits

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