Diurnal variations of urinary 6‐sulphatoxymelatonin in male intact or ganglionectomized mink

Maurel, Daniel; Mas, N.; Roch, G; Boissin, J.; Arendt, Joséphine

doi:10.1111/j.1600-079x.1992.tb00065.x

Cited by 9 publications

(6 citation statements)

References 29 publications

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“…The nature of the conjugation products of melatonin was reported over 40 yr ago in rats to be 6-sulphatoxymelatonin and 6-glucuronylmelatonin (20), and this was subsequently confirmed in humans (9,22,23,37). With the development of a RIA for 6-sulphatoxymelatonin (1), it has been possible to monitor the excretion of 6-sulphatoxymelatonin into the urine of humans (10), rats (17), Djungarian hamsters (21), minks (26), and pigs (19). In all cases, the excretion rate of 6-sulphatoxymelatonin is rhythmic and can be used as an index of pineal gland rhythmicity (10).…”

Section: Discussionmentioning

confidence: 99%

Melatonin in mice: rhythms, response to light, adrenergic stimulation, and metabolism

Kennaway

Voultsios

Varcoe

et al. 2002

American Journal of Physiology-Regulatory, Integrative and Comp

108

111

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There has been relatively little research conducted on pineal melatonin production in laboratory mice, in part, due to the lack of appropriate assays. We studied the pineal and plasma rhythm, response to light, adrenergic stimulation, and metabolism of melatonin in CBA mice. With the use of a sensitive and specific melatonin RIA, melatonin was detected in the pineal glands at all times of the day >21 fmol/gland in CBA mice but not in C57Bl mice. Both plasma and pineal melatonin levels peaked 2 h before dawn in a 12:12-h light-dark photoperiod (162 ± 31 pM and 1,804 ± 514 fmol/gland, respectively). A brief light pulse (200 lx/15 min), 2 h before lights on, suppressed both plasma and pineal melatonin to near basal levels within 30 min. Exposure to light pulses 4 h after lights off or 2 h before lights on resulted in delays and advances, respectively, in the early morning decline of plasma and pineal melatonin on the next cycle. Administration of the β-adrenergic agonist isoproterenol (20 mg/kg) 2 and 4 h after lights on in the morning resulted in a fivefold increase in plasma and pineal melatonin 2.5 to 3 h after the first injection. In the mouse, unlike the rat, melatonin was shown to be metabolized almost exclusively to 6-glucuronylmelatonin rather than 6-sulphatoxymelatonin. These studies have shown that the appropriate methodological tools are now available for studying melatonin rhythms in mice.

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Section: Discussionmentioning

confidence: 99%

Melatonin in mice: rhythms, response to light, adrenergic stimulation, and metabolism

Kennaway

Voultsios

Varcoe

et al. 2002

American Journal of Physiology-Regulatory, Integrative and Comp

108

111

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“…In ganglionectomized mink, we have previously demonstrated that the plasma melatonin rhythm, as evaluated by urinary 6-sulphatoxymelatonin excretion, was abolished following pineal deafferentation (Maurel et al, 1992b), which results in a loss of the transmission of photoperiodic information. In this study, melatonin implants were used to overcome the effects of removing the superior cervical ganglion, and successfully restored the activity of the hypothalamo-pituitarygonadal axis.…”

Section: Discussionmentioning

confidence: 99%

“…Furthermore, when deafferentation of the pineal by superior cervical ganglionectomy is performed during sexual quiescence (daylength longer than 10 h), it prevents autumnal recrudescence of testicular activity and blocks the seasonal reactivation of the immunoreactive hypothalamic GnRH system (Maurel et al, 1992a). The latter could be caused by the abolition of the diurnal rhythm of melatonin, observed by Maurel et al (1992b) after pineal deafferentation. Interestingly, in ganglionectomized sexually inactive mink, subcutaneous implants of melatonin produced a resumption of testicular activity after 2 months (Maurel et al, 1992a).…”

Section: Introductionmentioning

confidence: 99%

Effects of Superior Cervical Ganglionectomy and Melatonin Replacement on Intra-hypothalamic LHRH Content and Pulsatile Luteinizing Hormone Release in the Mink

Maurel¹,

Jallageas²,

Mas³

et al. 1997

Biological Rhythm Research

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Long-term effects of subcutaneous melatonin implants on intrahypothalamic LHRH content and on pulsatile luteinizing hormone release have been investigated in ganglionectomized male mink. Animals were submitted to bilateral removal of the superior cervical ganglion in mid-April. A preliminary study revealed that plasma LH concentrations remain at a basal level throughout the year following ganglionectomy. In a second experiment, one month after ganglionectomy and transfer from the natural photoperiod environment to short daylengths (LD 4:20), melatonin pellets were subcutaneously implanted to overcome deafferentation of the pineal. Progressive effects of treatment were studied 7 days, 15 days, and one, two and three months after insertion of the melatonin implants. The intra-hypothalamic LHRH content in ganglionectomized mink was at a basal level similar to that observed during seasonally sexual quiescence, or after exposure to inhibitory long days (LD 20:4). A significant and transient elevation in LHRH content was observed already after fifteen days, and also one month after insertion of melatonin implants. This resulted in mean values similar to those observed during the breeding season, or after exposure to stimulatory short days (LD 4:20). A decrease in hypothalamic LHRH content started after two months. No pattern of pulsatile LH secretion was recorded in ganglionectomized untreated mink. A significant increase in all parameters of pulsatile LH secretion was observed fifteen days after the elevation of LHRH content induced by melatonin treatment, and maximum values were reached after two months. Pituitary activity tended to decrease after three months, characterized in particular by a significant decrease in the mean frequency of LH pulses. In addition, the increase in pulsatile characteristics of LH release occurred two months before the peripheral renewal of testicular activity. Apparently, the reproductive endocrine function in ganglionectomized mink treated with melatonin implants is restored more rapidly at the hypothalamic level than at the pituitary or testicular levels.

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“…As previously suggested, the change in the pattern of melatonin secretion as a result of SCN destruction or SCGx is responsible for the lack of response of the gonadotropin releasing hormone (GnRH) axis to photoperiodic stimulation. Indeed, in SCGx mink, constant low melatonin levels are recorded (Maurel et al., 1992b).…”

Section: Discussionmentioning

confidence: 99%

“…We checked the efficacy of the melatonin implants by determining urinary 6‐sulphatoxymelatonin (AMT6s) concentration for animals with implants, using a commercial RIA kit (Stockgrand Ltd, Guildford, UK). Urine collection, and the protocol and validation for RIA have been described in detail elsewhere for this species (Maurel et al., 1992b).…”

Section: Methodsmentioning

confidence: 99%

Testicular activity is restored by melatonin replacement after suprachiasmatic nucleus lesion or superior cervical ganglionectomy in mink

Maurel

Saad

Roch

et al. 2002

Journal of Pineal Research

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Subcutaneous melatonin implants were inserted in mink subjected to natural (autumn) or experimental gonadostimulatory short-days (4L:20D), after lesion of the suprachiasmatic nucleus (SCNx) or after superior cervical ganglionectomy (SCGx). Gonad stimulation was assessed by measuring testicular volume and plasma testosterone level. In SCNx and SCGx animals, all measurements were indicative of sexual quiescence. In contrast, both SCNx and SCGx animals with melatonin, maintained in natural or experimental gonadostimulating short-days, showed an increase in testicular activity 2 months after melatonin implantation. Thus, melatonin (and pineal activity) is a prerequisite for the photoperiodic stimulation of reproductive activity, and the SCN is not necessarily the target site for melatonin action on the renewal of reproduction in the mink.

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Diurnal variations of urinary 6‐sulphatoxymelatonin in male intact or ganglionectomized mink

Cited by 9 publications

References 29 publications

Melatonin in mice: rhythms, response to light, adrenergic stimulation, and metabolism

Melatonin in mice: rhythms, response to light, adrenergic stimulation, and metabolism

Effects of Superior Cervical Ganglionectomy and Melatonin Replacement on Intra-hypothalamic LHRH Content and Pulsatile Luteinizing Hormone Release in the Mink

Testicular activity is restored by melatonin replacement after suprachiasmatic nucleus lesion or superior cervical ganglionectomy in mink

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