Regulation of seasonal reproductive activity in the stallion, ram and hamster

Gerlach, Tanja M.; Aurich, Jörg

doi:10.1016/s0378-4320(99)00093-7

Cited by 110 publications

(81 citation statements)

References 106 publications

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“…For males, gonadal activity, hormone surges, and sexual behavior are timed accordingly. For instance, in various species such as lesser galagos (Galago moholi) [2], roe deer (Capreolus capreolus) [3], domestic stallions [4], and domestic rams [5], sexual behaviors vary in parallel with changes in testicular volume or serum testosterone concentration. Seasonal reproduction has also been described in aquatic mammals, including sea lions (Eumetopias jubatus) [6], manatees (Trichechus manatus manatus) [7], and seals (Phoca vitulian) [8].…”

Section: Introductionmentioning

confidence: 99%

Variation in sexual behaviors in a group of captive male Yangtze finless porpoises (Neophocaena phocaenoides asiaeorientalis): motivated by physiological changes?

Hao

et al. 2010

Theriogenology

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Section: Introductionmentioning

confidence: 99%

Variation in sexual behaviors in a group of captive male Yangtze finless porpoises (Neophocaena phocaenoides asiaeorientalis): motivated by physiological changes?

Hao

et al. 2010

Theriogenology

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“…Horse is a seasonal breeder and its reproductive efficiency varies throughout the year. In the northern hemisphere mares enter anestrus and stallions semen quality sharply declines during late fall and early winter (16,30). Information on photoperiod and the physiological reproductive season in Arabian horse is very limited.…”

Section: Discussionmentioning

confidence: 99%

“…In that study, mean concentrations of testosterone in stallions ranged from 0.7 ng/ml in December to 4.1 ng/ml in August. As a long day breeder, horse reduces reproductive capacity during the decreased photoperiod of the winter months, whereas, short day breeders, such as the sheep, are positively affected during the same period (16). In addition, Tamarkin et al (37) reported that melatonin attenuated gonadal function and decreased gonadotropin concentrations in both sexes of hamster, which is a long day breeder.…”

Section: Discussionmentioning

confidence: 99%

“…In northern hemisphere, animals are exposed to more melatonin during the night, and that during the longer periods of darkness in winter. Conversely, melatonin levels decrease during long days in summer (16,17). The localization of melatonin receptors in the hypothalamus and pituitary indicates a possible interaction of melatonin in regulation of reproduction in horse (35).…”

Section: Introductionmentioning

confidence: 91%

“…The pineal gland is able to receive photo information and measure day length and regulate the secretion of melatonin accordingly (3,19). Melatonin is a key player in controlling reproduction, sleep-wake cycles and other phenomena showing circadian or circanual rhythm (5,16,24). In northern hemisphere, animals are exposed to more melatonin during the night, and that during the longer periods of darkness in winter.…”

Section: Introductionmentioning

confidence: 99%

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Seasonal variations in serum concentrations of melatonin, testosterone, and progesterone in Arabian horse

Çiğdem;ÜNER¹

2009

Ankara Üniversitesi Veteriner Fakültesi Dergisi

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Summary:The objective of this study was to characterize seasonal variations in serum concentrations of melatonin, testosterone, and progesterone in Arabian horses under natural photoperiodic conditions. Peripheral blood samples were collected during breeding and non-breeding seasons from mares and stallions. Serum concentrations of melatonin, testosterone, and progesterone were determined by radioimmunoassay. Serum concentrations of melatonin were greater in the non-breeding season (42.41±1.59 and 37.68±1.55 pg/ml) when compared to breeding season (23.52±1.24 and 17.22±2.10 pg/ml) in both mares and stallions, respectively. Melatonin concentrations were low but not different between the luteal and follicular phases during breeding season in cyclic mares. Mares had greater concentrations of melatonin than stallions in both breeding and non-breeding season. Mean concentrations of testosterone were greater during breeding season (6.58±0.50 ng/ml) than non-breeding season (3.64±0.48 ng/ml) in stallions. There was a negative correlation (r=-0.658, p<0.01) with melatonin and testosterone levels in both season in stallions. A negative correlation (r=-0.829, p<0.05) in luteal phase and a positive correlation (r=0.847, p<0.05) in non-breeding season were found between melatonin and progesterone concentrations in mares. We conclude that changes in day length act as a regulator and photoperiod can be used to modify the seasonal reproduction in Arabian horse.Key words: Arabian horse, melatonin, photoperiod, progesterone, testosterone. Arap atlarında serum melatonin, testosteron ve progesteron seviyelerinin mevsimsel değişimleriÖzet: Bu çalışmanın amacı, doğal fotoperiyodik koşullarda Arap atlarının serum melatonin, testosteron ve progesteron seviyelerinin mevsimsel değişimlerini belirlemektir. Kısrak ve aygırlardan üreme döneminde ve üremenin olmadığı dönemde toplanan kan örneklerinden, radioimmunoassay yöntemi ile serum melatonin, testosteron ve progesteron seviyeleri belirlenmiştir. Sırasıyla hem kısrak hem de aygırlarda melatonin seviyeleri üremenin olmadığı dönemde (42.41±1.59 ve 37.68±1.55 pg/ml) üreme dönemine göre (23.52±1.24 ve 17.22±2.10 pg/ml) daha yüksek bulunmuştur. Üreme döneminde östrus siklusu gösteren kısraklarda melatonin seviyelerinin düşük fakat luteal ve foliküler dönemler arasında fark yoktu. Kısraklar hem üreme döneminde hem de üremenin olmadığı dönemde aygırlara göre daha yüksek melatonin seviyelerine sahipti. Aygırlarda üreme dönemindeki (6.58±0.50 ng/ml) testosteron seviyeleri üremenin olmadığı dönemden (3.64±0.48 ng/ml) daha yüksekti. Aygırlarda her iki dönemde melatonin ile testosteron seviyeleri arasında negatif bir ilişki vardı (r=-0.658, p<0.01). Kısrakların melatonin ve progesteron seviyeleri arasında ise luteal dönemde negatif (r=-0.829, p<0.05), üremenin olmadığı dönemde de pozitif bir ilişki (r=0.847, p<0.05) bulundu Bu çalışma ile Arap atlarında, gün uzunluğundaki değişikliklerin mevsimsel üremede bir düzenleyici olarak görev aldığı ve fotoperiyodun bu düzenlemede değiştirici etkisi olduğu ...

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Immunohistochemical and Morphometric Study of Pituitary Pars Distalis Thyrotrophs of Male Viscacha (Lagostomus maximus maximus): Seasonal Variations and Effect of Melatonin and Castration

Filippa¹,

Mohamed²

2008

The Anatomical Record

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The physiology and behavior of viscacha vary along the year according to the modifications of environmental signals such as the photoperiod length, temperature, rainfall pattern, food composition, and social interactions. The pituitary pars distalis thyrotrophs (TSH cells) of male viscacha were immunohistochemically identified, and the morphometric parameters: percentage of immunopositive area (% IA), cell percentage in pars distalis (% PDC), number of cells per reference area (no. cells/RA), and major cellular and nuclear diameters were analyzed. Three different groups of adult male viscachas were used: (1) captured in their natural habitat during the year, (2) melatonin-administered, and (3) castrated. The thyrotrophs were localized in the ventromedial sector, mainly in the pars distalis cephalic extreme. They were oval or pyramidal in shape, and their immunostaining intensity was heterogeneous. The % IA, % PDC, and no. cells/RA exhibited a significant decrease in June-July (winter, gonadal regression period) in relation to February-March (summer-early autumn, reproductive period), and they were recovered in August-September (later winter-early spring, gonadal recovery period). No morphometric variations of TSH cells were observed in melatonin-treated animals, whereas a decrease of the % IA, % PDC, and no. cells/RA was observed in castrated animals in relation to the intact animals. Our results show TSH cell morphometric variations during the year in agreement with the animal's different physiological conditions during the reproductive cycle, and probably in response to the environmental signals changes. Melatonin does not have a direct effect on the TSH cells. However, castration modifies some thyrotroph morphometric parameters, reinforcing the hypothesis that androgens affect the cells activity.

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Regulation of seasonal reproductive activity in the stallion, ram and hamster

Cited by 110 publications

References 106 publications

Variation in sexual behaviors in a group of captive male Yangtze finless porpoises (Neophocaena phocaenoides asiaeorientalis): motivated by physiological changes?

Variation in sexual behaviors in a group of captive male Yangtze finless porpoises (Neophocaena phocaenoides asiaeorientalis): motivated by physiological changes?

Seasonal variations in serum concentrations of melatonin, testosterone, and progesterone in Arabian horse

Immunohistochemical and Morphometric Study of Pituitary Pars Distalis Thyrotrophs of Male Viscacha (Lagostomus maximus maximus): Seasonal Variations and Effect of Melatonin and Castration

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