The neurobiology of central dopamine and progesterone in the reproductive cycle of the ring dove (Streptopelia risoria)

Abstract

The ring dove (Streptopelia risoria) is a usefUl animal model for the identification of neural and hormonal determinants of reproductive behaviours. Studies were undertaken to investigate the role of dopamine and progesterone in the expression of sexually differentiated patterns of behaviours during the breeding cycle, and provide the first mapping of tyrosine hydroxylase immunoreactive (Til-ir) structures in the ring dove brain.
Quantitative analysis revealed increased TFJ-ir cells, in male and female brooding doves, in the nuclei periventricularis magnocellularis, dorsomedialis anterior thalami, pretectalis medialis; and in the nucleus dorsomedialis posterior thalami in female brooding birds.
This confirms that increases in dopamine activity during the brooding period are exhibited in regions integrating neuroendocrine and sensory information to mediate the expression of parental defence behaviours.
Immunofluorescence studies revealed no co-localisation of progesterone receptor (PR-fr) in TM-fr cells, but demonstrated the presence of TH-fr terminals in axosomatic contact with PR-fr-containing cells in the preoptic region, which may enable dopamine activation of the progesterone receptor, via the Dl receptor.
A collaborative study with the University of Hiroshima, demonstrated increased progesterone concentrations in the diencephalon of male brooding doves compared with non-breeding male doves. Measurement of 3[3-HSD enzymatic activity confirmed the synthesis of progesterone in the ring dove diencephalon. This may be sexually differentiated and mediated by proliferating glial cells, under the influence of VIP and prolactin.
Primary glial cell culture techniques established the presence of PR-fr in cultured ring dove brain cells. These studies suggest that nest defence behaviour in male and female ring doves may be mediated by differentially elevated levels of centrally acting progesterone, arising as a consequence of increasing dopante activity in the preoptic area. The possibility of progesterone inhibition of y-aminobutyric acid (GABA) activity, to disliThibit dopamine neuronal activity during incubation and brooding, and enable the expression of defensive behaviours is discussed.