HOME HELP CONTACT US SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Dawson, A. Articles by Goldsmith, A. R. Search for Related Content PubMed Articles by Dawson, A. Articles by Goldsmith, A. R.

Previous studies have shown that an increase in prolactin secretion coincides with the beginning of the photorefractory phase in starlings (Sturnus vulgaris). To determine how closely this increase is associated with the onset of refractoriness, we kept starlings on photoperiods which would induce refractoriness at different rates. Four groups of males and females were transferred from 8 h light: 16 h darkness (8L : 16D) to either 18L : 6D, 13L : 11D, 11L : 13D or 8L : 16D. Weekly blood samples were assayed for LH, FSH and prolactin and the males were frequently laparotomized to determine testis volume.

In males, both 18L and 13L induced marked increases in plasma gonadotrophin levels and rapid gonadal maturation. A photoperiod of 18L induced an earlier onset of refractoriness (2–4 weeks) than 13L (6 weeks). In both cases prolactin levels began to increase immediately before the onset of refractoriness. Males on 11L showed a slight increase in gonadotrophin levels and slow gonadal maturation. There was no increase in prolactin levels and these birds did not become refractory. Hormonal data from the females were similar to those from males. These results confirm that increased prolactin secretion is associated, in some way, with the onset of photorefractoriness in this species, although whether it is a cause or consequence of photorefractoriness, or simply of gonadal regression, remains unclear.

This article has been cited by other articles:

				J. A. Proudman and T. D. Siopes Potential Role of Thyroid Hormones and Prolactin in the Programming of Photorefractoriness in Turkey Hens Poult. Sci., August 1, 2006; 85(8): 1457 - 1461. [Abstract] [Full Text] [PDF]

				K. W. Sockman, T. D. Williams, A. Dawson, and G. F. Ball Prior Experience with Photostimulation Enhances Photo-Induced Reproductive Development in Female European Starlings: A Possible Basis for the Age-Related Increase in Avian Reproductive Performance Biol Reprod, September 1, 2004; 71(3): 979 - 986. [Abstract] [Full Text] [PDF]

				K. A. Young, G. F. Ball, and R. J. Nelson Photoperiod-Induced Testicular Apoptosis in European Starlings (Sturnus vulgaris) Biol Reprod, February 1, 2001; 64(2): 706 - 713. [Abstract] [Full Text]

				A. Dawson and P. J. Sharp The Role of Prolactin in the Development of Reproductive Photorefractoriness and Postnuptial Molt in the European Starling (Sturnus vulgaris) Endocrinology, February 1, 1998; 139(2): 485 - 490. [Abstract] [Full Text] [PDF]

				A. Dawson Plasma-Luteinizing Hormone and Prolactin during Circannual Rhythms of Gonadal Maturation and Molt in Male and Female European Starlings J Biol Rhythms, August 1, 1997; 12(4): 371 - 377. [Abstract] [PDF]

				A. Dawson and F.J. McNaughton Circannual Rhythms in Starlings: Response of Castrated Birds to 12-Hr Days Depends on Photoperiodic History J Biol Rhythms, July 1, 1993; 8(2): 141 - 150. [Abstract] [PDF]

				T. Meijer Photoperiodic Control of Reproduction and Molt in the Kestrel, Falco tinnunculus J Biol Rhythms, September 1, 1989; 4(3): 351 - 364. [Abstract] [PDF]