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Diurnal and photoperiodic changes in thyrotrophin‐stimulating hormone β expression and associated regulation of deiodinase enzymes ( DIO 2, DIO 3 ) in the female juvenile chicken hypothalamus
Author(s) -
Dunn I. C.,
Wilson P. W.,
Shi Y.,
Burt D. W.,
Loudon A. S. I.,
Sharp P. J.
Publication year - 2017
Publication title -
journal of neuroendocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.062
H-Index - 116
eISSN - 1365-2826
pISSN - 0953-8194
DOI - 10.1111/jne.12554
Subject(s) - medicine , endocrinology , pars tuberalis , dio2 , photoperiodism , deiodinase , photostimulation , biology , prolactin , hypothalamus , hormone , circadian rhythm , triiodothyronine , pituitary gland , biochemistry
Increased thyrotrophin‐stimulating hormone β ( TSH β) expression in the pars tuberalis is assumed to be an early step in the neuroendocrine mechanism transducing photoperiodic information. The present study aimed to determine the relationship between long‐photoperiod ( LP ) and diurnal TSH β gene expression in the juvenile chicken by comparing LP ‐photostimulated birds with groups kept on a short photoperiod ( SP ) for 1 or 12 days. TSH β expression increased by 3‐ and 23‐fold after 1 and 12 days of LP ‐photostimulation both during the day and at night. Under both SP and LP conditions, TSH β expression was between 3‐ and 14‐fold higher at night than in the day, suggesting that TSH β expression cycles in a diurnal pattern irrespective of photoperiod. The ratio of DIO 2/3 was decreased on LP s, consequent to changes in DIO 3 expression, although there was no evidence of any diurnal effect on DIO 2 or DIO 3 expression. Plasma prolactin concentrations revealed both an effect of LP s and time‐of‐day. Thus, TSH β expression changes in a dynamic fashion both diurnally and in response to photoperiod.