Quantification of Daily Melatonin Synthesis in the Hamster Pineal Gland*

Rollag, Mark D.; Panke, Elizabeth S.; Trakulrungsi, Wantanee; Trakulrungsi, Chatchai; Reíter, Russel J.

doi:10.1210/endo-106-1-231

Cited by 119 publications

(51 citation statements)

References 21 publications

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“…is important to bear in mind that, for technical reasons, it was not possible to determine serum melatonin concentrations, and so it can only be assumed, but not proven, that the pattern of the signal cxperienced by the animal reflected the infusion profile. Given that melatonin is cleared rapidly from the circulation, changes in the infusion rate might be expected to be translated rapidly into changes in circulating levels (25)(26)(27). Moreover, the amounts of melatonin infused were close to the nocturnal physiological secretion rates estimated for pineal intact animals (26), and so it is unlikely that metabolic clearance pathways would be overwhelmed by supraphysiological amounts of hormone.…”

Section: Discussionmentioning

confidence: 90%

“…Given that melatonin is cleared rapidly from the circulation, changes in the infusion rate might be expected to be translated rapidly into changes in circulating levels (25)(26)(27). Moreover, the amounts of melatonin infused were close to the nocturnal physiological secretion rates estimated for pineal intact animals (26), and so it is unlikely that metabolic clearance pathways would be overwhelmed by supraphysiological amounts of hormone. Such an assumption is, therefore, probably valid, and it can be concluded that the brain does not respond solely to the presence of a peak of melatonin secretion which extends for 10 h. Nor does it respond to a peak of this duration which rises by a certain amplitude above baseline levels.…”

Section: Discussionmentioning

confidence: 90%

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Occlusion of the Melatonin‐Free Interval Blocks the Short Day Gonadal Response of the Male Syrian Hamster to Programmed Melatonin Infusions of Necessary Duration and Amplitude

Maywood

Lindsay

Karp

et al. 1991

J Neuroendocrinology

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Photoperiodic control of the neuroendocrine axis is mediated by changes in the duration of the nocturnal melatonin signal. This study tested the hypothesis that reading of the signal depends upon the presence of a period free of melatonin between successive signals. Adult male Syrian hamsters were pinealectomized and received chronic subcutaneous infusions of melatonin or saline for 6 weeks. Animals which received saline had large testes. Those which received a single daily infusion which lasted for 10 h (50 ng/h) followed by 14 h without infusion underwent gonadal atrophy. Other animals received a compound melatonin signal in which the melatonin-free interval was occluded by a continuous infusion (25 nglh). Superimposed upon this was a 10 h phasic increase in infusion rate such that the maximum rate of infusion was equivalent to that observed in controls (25 ng/h increase, 50 nglh peak rate), or the increase in rate over the baseline was the same as in controls (50 nglh increase, 75 nglh peak rate). In neither group did the animals undergo gonadal regression. Analysis of iodomelatonin binding sites by in vitro autoradiography failed to reveal any systematic difference between animals which did and did not respond to melatonin and so the absence of a response could not be attributed to loss of receptors. These data demonstrate that the photoperiodic system cannot identify the melatonin signal solely upon the features of nocturnal peak height or amplitude of the peak over baseline. They are consistent with the hypothesis that the melatonin-free interval plays a significant role in photoperiodic time measurement.

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Section: Discussionmentioning

confidence: 90%

Section: Discussionmentioning

confidence: 90%

Occlusion of the Melatonin‐Free Interval Blocks the Short Day Gonadal Response of the Male Syrian Hamster to Programmed Melatonin Infusions of Necessary Duration and Amplitude

Maywood

Lindsay

Karp

et al. 1991

J Neuroendocrinology

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“…Typically, under light: dark cycles o f 14:10 h the first 4-6 h o f darkness is not fol lowed by a significant increase in pineal melatonin produc tion [13,20]. However, between 02.00 and 06.00 h there is a sharp rise in pineal melatonin content with the peak usually occurring at 04.00-05.00 h. It appears then, that the night time rise in melatonin in the hamster pineal gland could be controlled by the sensitivity o f the membrane receptors to the neurotransmitter N E .…”

Section: Discussionmentioning

confidence: 99%

Norepinephrine or Isoproterenol Stimulation of Pineal N-Acetyltransferase Activity and Melatonin Content in the Syrian Hamster Is Restricted to the Second Half of the Daily Dark Phase

et al. 1987

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Seven experiments were performed to investigate the sensitivity of the hamster pineal gland to exogenously administered norepinephrine (NE). In these studies NE (1 mg/kg) administration was preceded (10 min earlier) by the injection of the catecholamine uptake inhibitor desmethylimipramine (DM I; 5 mg/kg). When DMIand NE were given at night, the hamsters were exposed to light to depress pineal N-acetyltransferase activity and melatonin values to low levels; the drugs were then given 20 (DMI) and 30 (NE) min later, and the subsequent changes in pineal N-acetyltransferase and melatonin were monitored. The combination of DMI and NE administration anytime during the normal light period or during the first 4 h of the normal dark period failed to stimulate either pineal N-acetyltransferase activity or melatonin levels. Conversely, DMI followed by NE (injected either intraperitoneally or subcutaneously) in the second half of the dark phase typically stimulated pineal melatonin production. Likewise, the NE agonist isoproterenol promoted pineal melatonin production only in the latter half of the dark phase. If hamsters were exposed to continual light at night or if they were superior cervical ganglionectomized, a procedure which sympathetically denervates the pineal gland, the stimulatory effect of NE on melatonin production was significantly suppressed. Thus, the hamster pineal gland is sensitive to NE only during the latter half of the normal dark period and both darkness and an intact sympathetic innervation to the pineal gland are required for the gland to develop maximal sensitivity to the catecholamine. Also, the hamster pineal seems not to exhibit a supersensitivity response to NE following a period of reduced exposure to the catecholamine. The normal nocturnal rise in melatonin production in the hamster pineal gland seems to be determined by two parameters: an increased production and secretion of NE by sympathetic nerve endings in the pineal at night and (2) an increased sensitivity of the β-receptors on the pinealocyte membranes to NE during the late dark phase.

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“…In the Syrian hamster, the nocturnal increase in MEL synthesis occurs late in the dark phase (Rollag et al, 1980;Miguez et al, 1995a). Daytime MEL values are approximately 0.2 ng/gland and increase up to 2 ng/gland at ZT 21 in LP (Miguez et al, 1995a).…”

Section: Daily Regulation Of Melatonin Synthesis a Daily Regulation mentioning

confidence: 99%

Generation of the Melatonin Endocrine Message in Mammals: A Review of the Complex Regulation of Melatonin Synthesis by Norepinephrine, Peptides, and Other Pineal Transmitters

2003

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Quantification of Daily Melatonin Synthesis in the Hamster Pineal Gland*

Cited by 119 publications

References 21 publications

Occlusion of the Melatonin‐Free Interval Blocks the Short Day Gonadal Response of the Male Syrian Hamster to Programmed Melatonin Infusions of Necessary Duration and Amplitude

Occlusion of the Melatonin‐Free Interval Blocks the Short Day Gonadal Response of the Male Syrian Hamster to Programmed Melatonin Infusions of Necessary Duration and Amplitude

Norepinephrine or Isoproterenol Stimulation of Pineal N-Acetyltransferase Activity and Melatonin Content in the Syrian Hamster Is Restricted to the Second Half of the Daily Dark Phase

Generation of the Melatonin Endocrine Message in Mammals: A Review of the Complex Regulation of Melatonin Synthesis by Norepinephrine, Peptides, and Other Pineal Transmitters

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