Diurnal changes in melatonin binding sites of hamster and rat brains. Correlation with neuroendocrine responsiveness to melatonin

Vacas, María I.; Cardinali, Daniel P.

doi:10.1016/0304-3940(79)96123-8

Cited by 92 publications

(37 citation statements)

References 9 publications

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“…Moreover, the specific binding of MLT was significantly higher for SCN cells prepared at 1:00 PM than that prepared at 1:00 AM. This result supports findings of other studies in which the number of MLT binding sites in the rat SCN showed a significant 24-h rhythm with higher levels in the light phase (Vacas and Cardinali, 1979;Gauer et al, 1993;Tenn and Niles, 1993). In addition, not only the exposure to MLT but also the photoperiod plays an important role in regulating MLT receptor(s) density in SCN cells (Masson-Pevet et al, 2000).…”

Section: Discussionsupporting

confidence: 91%

Chronopharmacology of Melatonin in Mice to Maximize the Antitumor Effect and Minimize the Rhythm Disturbance Effect

Akagı

Ushinohama

Ikesue

et al. 2003

J Pharmacol Exp Ther

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The influence of dosing time on the antitumor effect and the rhythm disturbance effect of melatonin (MLT) was investigated in ICR male mice under a light/dark (12:12) cycle. In tumorbearing mice, the antitumor effect of MLT (1 mg/kg intraperitoneal) was most effective in the dark phase; and the rhythm disturbance effect of MLT on the locomotor activity was more serious in the light phase than in the dark phase. The antitumor effect and the rhythm disturbance effect of MLT increased when the specific binding of MLT receptor in target tissues, tumor or suprachiasmatic nucleus, increased and they decreased when the level decreased. Furthermore, because luzindole, an MT 1 and MT 2 blocker, caused the antitumor effect or rhythm disturbance effect of MLT to decrease, it is suggested that the time-dependent change of the pharmacological effects of MLT were influenced by that of MLT receptor(s) function. On the other hand, there was no significant dosing time-dependent change of MLT concentration in tumor or brain after injection. Thus, the pharmacokinetic factor does not seem to contribute to the dosing time-dependent effect of MLT. These results suggest that by choosing the most suitable dosing time for MLT, the efficacy of the drug can be increased, and the toxicity of the drug can be decreased in certain experimental and clinical situations.

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Section: Discussionsupporting

confidence: 91%

Chronopharmacology of Melatonin in Mice to Maximize the Antitumor Effect and Minimize the Rhythm Disturbance Effect

Akagı

Ushinohama

Ikesue

et al. 2003

J Pharmacol Exp Ther

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“…Melatonin by itself was able to augment j6CI-influx in PMBH 900xg pellets, probably because of an interaction with endogenous GABA. Therefore, a correlation exists between the increase in the number of melatonin binding sites (14)(15)(16) and the biologic activity of the hormone in the late evening. It is difficult to make comparisons between the in vivo activity of melatonin on GAD activity and the in vitro modifica-tion of PMBH C1-uptake reported here, because there is no information on the levels of melatonin reaching the hypothalamus a t the doses employed.…”

Section: Discussionmentioning

confidence: 99%

“…In a study on melatonin effect on 2-deoxyglucose uptake by rat suprachiasmatic nuclei, a single melatonin injection at late evening, but not at the 2nd h of the dark phase of daily photoperiod, inhibited the uptake (17), and more recently, the same authors described maximal effects of melatonin on 2-deoxyglucose uptake at late evening, and secondarily just before dawn (18). Although the neurochemical mechanisms through which melatonin acts remain largely undefined, recent data suggest that GABAergic neurotransmission could be a target for melatonin in rat brain (1 [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23]. By pursuing these studies, we now report the in vivo effect of melatonin on brain glutamic acid decarboxylase (GAD) activity and the in vitro effect of melatonin on 36Cl-uptake by hypothalamic 900 x g pellets at two different times in the diurnal cycle in rats, i.e.…”

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confidence: 99%

“…In hamsters (3,(10)(11)(12) and rats (13) a late afternoon-early evening period of sensitivity, and a brief period of sensitivity just preceding the time of lights on, were found. In the late evening an increase in brain membrane melatonin binding has been reported in rats (14)(15)(16) and hamsters (14). In a study on melatonin effect on 2-deoxyglucose uptake by rat suprachiasmatic nuclei, a single melatonin injection at late evening, but not at the 2nd h of the dark phase of daily photoperiod, inhibited the uptake (17), and more recently, the same authors described maximal effects of melatonin on 2-deoxyglucose uptake at late evening, and secondarily just before dawn (18).…”

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confidence: 99%

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Time‐Dependent Effect of Melatonin on Glutamic Acid Decarboxylase Activity and ³⁶CI⁻ Influx in Rat Hypothalamus

Rosenstein¹,

Estévez²,

Cardinali³

1989

J Neuroendocrinology

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The objective of the first series of experiments was to assess whether melatonin treatment modifies the activity of the y-aminobutyric acid synthesizing enzyme, glutamic acid decarboxylase, in the preoptic-medial basal hypothalamic area, cerebral cortex and cerebellar cortex of rats receiving 25 to 300 pg of melatonin in the early morning and late evening in the diurnal cycle. A significant increase of apparent V , , , and K , of the enzyme was found in the hypothalamus of rats killed at the 12th h of the light phase (i.e. the time when lights were turned off) and receiving 25 to 300 pglkg of melatonin 3 h earlier. In the early morning, only a 300 pglkg dose of melatonin (injected in the 1st h of the light phase) was effective to increase V , , , and K , of hypothalamic glutamic acid decarboxylase 3 h later. In cerebral and cerebellar cortices, increases in V , , , and K , of enzyme activity were apparent only in the evening and with the highest melatonin dose employed (300 pglkg). In a second series of experiments the activity of melatonin to modify in vitro3%-influx by 900 x g pellets of rat preoptic-medial basal hypothalamic area was studied at the 4th and 12th h of the light phase of daily photoperiod. Melatonin increased 36CI-influx at a minimum concentration of 100 nM (in the morning) or 10 nM (in the evening). The effect of melatonin on 36CI-influx was prevented by co-incubation with 100 pM picrotoxin. Addition of 10 to 100 pM of yaminobutyric acid to the resuspended 900 x g pellets brought about a dose-dependent increase of 36CI-influx. Preincubation with melatonin at threshold doses of 1 pM (in the morning) or 0.1 pM (in the evening) significantly augmented y-aminobutyric acid effect on 36CI-uptake. These results indicate that melatonin facilitates pre-and postsynaptic activities of y-aminobutyric acid neurons, particularly in the hypothalamus, through an effect that displays a diurnal sensitivity compatible with the documented activity of the hormone on a number of physiological functions.The pineal gland functions as a neuroendocrine transducer converting information about daylength into the nocturnal release of its hormone melatonin (1-3). In reptiles and birds the pineal gland is a major pacemaker for biologic rhythms, whereas in mammals this function is mediated principally by the hypothalamic suprachiasmatic nucleus (4-6). Melatonin acts on the suprachiasmatic nucleus to modulate mammalian circadian rhythmicity, as shown by the entrainment of locomotor activity in rats treated with the pineal hormone, an effect which is blocked by suprachiasmatic nuclei ablation (7-9). The time of administration of melatonin is critical for melatonin action. In hamsters (3, 10-12) and rats (13) a late afternoon-early evening period of sensitivity, and a brief period of sensitivity just preceding the time of lights on, were found. In the late evening an increase in brain membrane melatonin binding has been reported in rats (14-16) and hamsters (14). In a study on melatonin effect on 2-deoxyglucose uptake by...

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“…The to tal number of binding sites (Bmax) in the mem brane preparations from mid-light samples was 32% higher than that from mid-dark chickens. No significant variation in the bind ing affinity (IQ) was recorded ( A diurnal variation in both high and/or low affinity 2-[125I]iodomelatonin binding sites has been reported for the chicken, quail, rat and hamster brain as well as in other tissues [24][25][26][27][28][29][30]. In membrane preparations of the chicken (Gallus domesticus) brain [30], the binding density (Bmax) of 2-[125I]iodomelatonin binding sites exhibited a diurnal variation with the lowest level at late dark period and highest level at late light period, but without changes in binding affinity (IQ).…”

Section: Circadian Studiesmentioning

confidence: 99%

Melatonin Receptors in the Spinal Cord

1997

Neurosignals

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Diurnal changes in melatonin binding sites of hamster and rat brains. Correlation with neuroendocrine responsiveness to melatonin

Cited by 92 publications

References 9 publications

Chronopharmacology of Melatonin in Mice to Maximize the Antitumor Effect and Minimize the Rhythm Disturbance Effect

Chronopharmacology of Melatonin in Mice to Maximize the Antitumor Effect and Minimize the Rhythm Disturbance Effect

Time‐Dependent Effect of Melatonin on Glutamic Acid Decarboxylase Activity and ³⁶CI⁻ Influx in Rat Hypothalamus

Melatonin Receptors in the Spinal Cord

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Diurnal changes in melatonin binding sites of hamster and rat brains. Correlation with neuroendocrine responsiveness to melatonin

Cited by 92 publications

References 9 publications

Chronopharmacology of Melatonin in Mice to Maximize the Antitumor Effect and Minimize the Rhythm Disturbance Effect

Chronopharmacology of Melatonin in Mice to Maximize the Antitumor Effect and Minimize the Rhythm Disturbance Effect

Time‐Dependent Effect of Melatonin on Glutamic Acid Decarboxylase Activity and 36CI− Influx in Rat Hypothalamus

Melatonin Receptors in the Spinal Cord

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Time‐Dependent Effect of Melatonin on Glutamic Acid Decarboxylase Activity and ³⁶CI⁻ Influx in Rat Hypothalamus