The effect of photoperiod on central steroid receptor expression and plasma hormone concentration in the ring dove (Streptopelia Risoria)

Abstract

The hormonal control of the ring dove (Streptopelia risoria) breeding cycle is well established and influenced by photoperiod. This present study was designed to investigate the influence of photoperiod upon plasma prolactin and luteinizing hormone (LH) concentrations, together with the expression of androgen receptor immunoreactivity (ARir) and progesterone receptor immunoreactivity (PR-ir) within the brain and anterior pituitary gland of both male and female ring doves. Quantitative analysis revealed that there was no significant variation (P>0.05) in plasma prolactin concentrations of short day and long day (non breeding) doves of either sex. Plasma LH concentrations were significantly reduced (P<0.05) in both male and female SD doves when compared to non breeding doves.
Little or no AR-ir expression was detected in short day doves of either sex within any of the four hypothalamic regions tested (POA, PPM, PLH and TU). In contrast, doves maintained on long days had detectable levels of AR-ir in all these areas. PR-ir was present in both long day and short day birds in all areas, although the number of PR-ir cells in long day birds was significantly greater (Pc0.05) than in short day birds in the four hypothalamic regions known to express the receptor (POA, PPM, PLH & TU). In the anterior pituitary gland a sex difference was apparent. Both sexes on short days expressed
no detectable AR-ir. However, short day females expressed significantly higher PR-ir (P<0.05) compared to short day males, although this was significantly reduced (Pc0.05) compared to long day birds.
No significant variation in AR-ir or PR-ir expression was detected between long term (6 weeks) and short term (2 weeks) short day birds of either sex in any of the hypothalamic regions tested or within the anterior pituitary gland. There was significantly higher PR-ir expression in adult female SD doves (Pc0.01) compared to juvenile female SD doves.
The results of this study are consistent with an inhibitory photoperiodic response acting upon the anterior pituitary gland and the four hypothalamic brain regions involved in the ring dove breeding cycle.