The LH-RH system of the male European starling: photoperiod induces changes to a possible multifunctional peptide system.
In many birds reproduction is triggered by long daylengths but, paradoxically, continued exposure to long days leads to photorefractoriness and a complete shut down of the reproductive system. As these effects are thought to be mediated through the secretion of LH-RH, immunocytochemical techniques were used to investigate changes in the LH-RH system when European starlings were exposed to different photoperiods. Starlings exposed to 11L:13D and with mature testes show strong immunostaining both of LH-RH perikarya and fibers. Photosensitive short-day (8L:16D) starlings with undeveloped testes show an almost identical distribution of strongly immunoreactive perikarya but with less dense fibre staining. However, long-day (18L:6D) photorefractory starlings with fully regressed testes, show a profound reduction in LH-RH immunostaining. Perikarya have the same distribution but show a much reduced intensity of staining and fibers had almost entirely disappeared from all regions of the brain. Preliminary observations on the ultrastructure of immunocytochemically identified LH-RH neurones are also reported.
Foster
R G
RG
Department of Zoology, University of Bristol, United Kingdom.
Plowman
G
G
Goldsmith
A R
AR
Follett
B K
BK
Parry
D M
DM
D000818:Animals; D001717:Birds; D002940:Circadian Rhythm; D007987:Gonadotropin-Releasing Hormone / Q000502:physiology*; D007150:Immunohistochemistry; D008297:Male; D009474:Neurons / Q000648:ultrastructure; D009479:Neuropeptides / Q000502:physiology*; D010786:Photoreceptor Cells / Q000502:physiology; D012032:Refractory Period, Electrophysiological
D009479:Neuropeptides; D007987:Gonadotropin-Releasing Hormone