Seasonal profiles of melatonin in adult rams

Sheikheldin, M. A.; Howland, B. E.; Palmer, W. M.

doi:10.1111/j.1600-079x.1992.tb00027.x

Cited by 14 publications

(5 citation statements)

References 39 publications

(14 reference statements)

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“…This confirms once more that the seasonal changes in the daily pattern of melatonin synthesis are more complicated than a single change in the duration of the night peak of melatonin [9, 11]. It is now clearly established that in many mammals housed in natural environment, the amplitude of the nocturnal peak of melatonin content or AA‐NAT activity varies with seasons [18, 31–35]. Depending on the species, the maximal amplitude of the daily melatonin peak appears in summer and autumn (tammar, ram, horse), in winter and spring (Syrian or Djungarian hamster), in autumn and winter (European hamster), or in spring in Arvicanthis .…”

Section: Discussionmentioning

confidence: 67%

Environmental control and adrenergic regulation of pineal activity in the diurnal tropical rodent, Arvicanthis ansorgei

Garidou-Boof

Sicard²,

Bothorel

et al. 2004

Journal of Pineal Research

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Like nocturnal rodents, the diurnal tropical rodent Arvicanthis ansorgei shows a daily rhythm in pineal melatonin content. Seasonal and photoperiodic variations in the biosynthetic activity of the pineal gland: arylalkylamine-N-acetyltransferase (AA-NAT), hydroxyindole-O-methyltransferase (HIOMT) activities and melatonin content were measured in male and female A. ansorgei captured near Samaya, Mali, and kept either under artificial laboratory photoperiods [light-dark (LD) cycles: LD 14:10, LD 12:12 or LD 10:14 or caught in the field in Mali and killed at four different times of the year (January, April, June and November). Under artificial photoperiod, the duration of the nocturnal peak of AA-NAT activity and melatonin content increased with the duration of the dark period while the amplitude did not significantly change. In the field, annual variations in the amplitude of the nocturnal melatonin peak were observed with a maximum in April (highest temperature, low humidity and no grass availability, only seeds) and a minimum in November (high humidity, maximum green grass availability). The variations in the amplitude of the melatonin peak were not correlated with changes in AA-NAT HIOMT activities, suggesting that seasonal variations in the amplitude of the melatonin peak are not driven by these enzymes. Daytime injections of the beta-adrenergic agonist, isoproterenol, stimulated melatonin synthesis in January, April and June, but not in November. The annual differences in the amplitude of the melatonin peak as well as the seasonal differences in the response to an adrenergic stimulation suggest that environmental factors other than photoperiod, such as temperature, humidity and consequent food availability, could be important in the regulation of the annual variations in the pineal biosynthetic activity in this species.

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Section: Discussionmentioning

confidence: 67%

Environmental control and adrenergic regulation of pineal activity in the diurnal tropical rodent, Arvicanthis ansorgei

Garidou-Boof

Sicard²,

Bothorel

et al. 2004

Journal of Pineal Research

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“…Melatonin is also found in human follicular fluid [29, 30] and other biological fluids including cerebrospinal fluid [31], bile [32] and bone marrow [33]. Furthermore, we have also reported that melatonin concentration in ram seminal plasma is lower in spring (nonbreeding season) than in autumn ( P < 0.05) and winter ( P < 0.01) [27], which reflects the seasonal variations of melatonin in ram blood [28]. Therefore, seasonal variations of the melatonin in seminal plasma might be partly responsible for differences in semen quality and fertility rate observed between seasons [7, 34], and after melatonin treatment [17, 18].…”

Section: Introductionmentioning

confidence: 98%

“…Furthermore, we have recently shown the presence of melatonin in ram seminal plasma [27] and that in this fluid it reaches values higher those that in serum [28]. Melatonin is also found in human follicular fluid [29, 30] and other biological fluids including cerebrospinal fluid [31], bile [32] and bone marrow [33].…”

Section: Introductionmentioning

confidence: 99%

Melatonin prevents capacitation and apoptotic‐like changes of ram spermatozoa and increases fertility rate

Casao

Mendoza

Pérez‐Pé

et al. 2009

Journal of Pineal Research

118

116

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We recently demonstrated the presence of melatonin in ram seminal plasma and differences in its concentration in this fluid between the breeding and nonbreeding season. In this study, we investigate the hypothesis that in vitro treatment with melatonin affects ram sperm quality, and that this is reflected in the in vitro fertilization (IVF) results. Semen from nine rams was collected during the nonreproductive season and treated with 1 mum, 10 nm and 100 pm melatonin. Samples were incubated at 39 degrees C and 5% CO2, and motility, viability, capacitation status and phosphatidylserine (PS) translocation were assessed before and after melatonin addition, either 1 or 3 hr of incubation. Fertility rate of the melatonin-treated samples was determined by means of IVF. Although melatonin failed to affect both sperm kinematic parameters and viability, the exposure of ram spermatozoa to melatonin has a direct effect, decreasing capacitation and PS translocation at 1 mum, and increasing short-term capacitation at 100 pm, which caused an increased oocyte fertilization rate following IVF. Furthermore, cleavage rate of oocytes fertilized with 100 pm melatonin-treated spermatozoa was higher than that with 1 mum melatonin and control samples (P < 0.1). These results prove that melatonin has a direct effect on ram spermatozoa in the nonreproductive season, which can be explained, at least in part, by the melatonin capacity as a reactive oxygen species scavenger and antioxidant. These findings might help to select the optimal experimental conditions for IVF and to improve sperm preservation protocols.

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“…Discrepancies concerning melatonin efficiency in the improvement of semen quality in both breeding and non‐breeding bucks could be explained by seasonal and monthly variations in melatonin concentrations. Sheikheldin, Howland, and Palmer () reported that melatonin concentrations during summer and autumn (breeding season) were significantly higher than in winter and spring (non‐breeding season). Accordingly, the application of exogenous melatonin during the breeding season, when endogenous melatonin reaches maximum concentrations, presents an additional effect, resulting in extraordinary improvement of semen quality in relation to the non‐breeding period when endogenous melatonin is at its lowest values.…”

Section: Discussionmentioning

confidence: 99%

Monitoring of libido and semen quality parameters in melatonin‐treated French alpine bucks during the non‐breeding season

Vince

Valpotić

Berta

et al. 2017

Reprod Domestic Animals

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The aim of this study was to investigate the effects of exogenous melatonin on libido and semen quality parameters in bucks during the non-breeding season. Twelve bucks of the French alpine breed from 1.5 to 4 years of age were assigned into melatonin (MG) and control (CG) groups, with 6 bucks in each group. The experimental period was 3 months (March-May), divided into six periods of 15 days each. The bucks in the MG group received four melatonin implants at the end of March. Two semen samples were taken from the bucks by artificial vagina once per week and their libido estimated. Volume and spermatozoa concentration, their mass motility and motility, proportion of live and total abnormal and forms with abnormal head and tail were determined in the obtained ejaculate samples. The total number of spermatozoa and functional spermatozoa fraction in the ejaculate was also calculated. The MG bucks had significantly higher mass motility and motility of spermatozoa in the first half of April, and a higher proportion of live spermatozoa in the first and second half of April (p < .05). Differences in libido intensity were not significant. The results indicated that the application of melatonin significantly improved the qualitative parameters of semen in bucks, as seen in increased mass motility, motility of spermatozoa and proportion of live spermatozoa shortly following melatonin insertion. Therefore, the results of the current study are novel regarding the use of melatonin treatment during the non-breeding season to improve the qualitative parameters of ejaculates in bucks.

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Seasonal profiles of melatonin in adult rams

Cited by 14 publications

References 39 publications

Environmental control and adrenergic regulation of pineal activity in the diurnal tropical rodent, Arvicanthis ansorgei

Environmental control and adrenergic regulation of pineal activity in the diurnal tropical rodent, Arvicanthis ansorgei

Melatonin prevents capacitation and apoptotic‐like changes of ram spermatozoa and increases fertility rate

Monitoring of libido and semen quality parameters in melatonin‐treated French alpine bucks during the non‐breeding season

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