Photoperiodic Regulation of Neuroendocrine-Gonadal Activity

Turek, Fred W.; Campbell, Constance S.

doi:10.1093/biolreprod/20.1.32

Cited by 224 publications

(82 citation statements)

References 138 publications

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“…It is doubtful therefore that any residual imprinting of photoperiod (Poulton, 1986) would have remained. This seasonal variation in LH concentrations in castrated fallow bucks contrasts with observations on male red deer (Lincoln & Kay, 1979) but is similar to that reported in a variety of other seasonal breeders (Turek & Campbell, 1979), including some breeds of rams (Pelletier & Ortavant, 1975). Both the LH pulse frequency and mean concentrations in the castrated bucks were always higher than in the entire bucks, indicating the negative feedback of testicular hormones on LH secretion in fallow bucks.…”

Section: Discussionsupporting

confidence: 84%

Seasonal pattern of LH and testosterone secretion in adult male fallow deer, Dama dama

Asher¹,

Peterson²,

Bass³

1989

Reproduction

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Section: Discussionsupporting

confidence: 84%

Seasonal pattern of LH and testosterone secretion in adult male fallow deer, Dama dama

Asher¹,

Peterson²,

Bass³

1989

Reproduction

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“…The pineal is innervated by sympathetic nerves arriving by way of the superior cervical ganglia, and any procedure which interrupts this nerve supply disrupts the normal secretory activity of the gland (Moore, 1978 Herbert, 1981). Melatonin is one of the principal products of the pineal which is thought to influence the secretion of the anterior pituitary gland and affect reproduction (Wurtman & Moskowitz, 1977;Turek & Campbell, 1979;Reiter, 1980). In the sheep, there is a marked change in the circulating levels of melatonin from day to night and this daily pattern of secretion under long days is different from that under short days (Rollag et al, 1978;Lincoln & Short, 1980;Arendt et al, 1980;Lincoln, Almeida, Klandorf & Cunningham, 1982).…”

Section: Discussionmentioning

confidence: 99%

Inhibition of reproduction in rams by long daylengths and the acute effect of superior cervical ganglionectomy

Lincoln¹,

Almeida²

1982

Reproduction

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Summary. Six castrated Soay rams were given testosterone implants, and exposed to an artificial lighting regimen of alternating 16-week periods of long days (16L:8D) and short days (8L:16D) for over 1 year. Under these conditions, the blood plasma concentration of testosterone was maintained relatively constant (4\ m=. \ 3\ p=n-\ 6\ m=. \ 4ng/ml), while the levels of LH and prolactin varied in relation to the alterations in the photoperiod; low levels of LH occurred during long days when the rams were hyperprolactinaemic. During the last period of exposure to long days, 4 of the rams were cranially sympathectomized by removing the superior cervical ganglia. The effect of long daylengths on the secretion of LH and prolactin was blocked; prolactin concentrations began to decline after 2 weeks and LH levels increased. Ganglionectomy also influenced the plasma levels of melatonin; after the operation there was no longer a consistent 24-h rhythm in melatonin values and the increase associated with darkness was abolished. This result supports the view that the regulation of melatonin secretion is involved in the photoperiodic control of reproduction in rams.

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“…In many species, a period of sensitivity to a light cycle is followed by a period of insensitivity. The phenomenon of photorefractoriness has been studied in birds and mammals (Turek & Campbell, 1979). Exposure of rams (a short-day breeder) to prolonged periods of stimulatory short days resulted in gonadal redevelopment, but after 16 weeks alternating periods of gonadal involution and reactivation were observed (Almeida & Lincoln, 1984).…”

Section: Lh and Testosteronementioning

confidence: 99%