Proceedings of The Physiological Society

University of Central Lancashire (2002) J Physiol 543P, S243


Effects of aromatase inhibition on courtship behaviour, and central progesterone and androgen receptor expression in the ring dove (Streptopelia risoria)

M.D.C. Belle, R.W. Lea and P.J. Sharp*

University of Central Lancashire, Department of Biological Sciences, Preston PR1 2HE and *The Roslin Institute, Roslin, Midlothian EH25 9PS, UK

This study investigates the association between courtship behaviour, steroid receptor expression and aromatase P450 enzyme (P450AROM) activity in the brain of the ring dove (Streptopelia risoria). Sexually experienced ring doves (4 males and 4 females) were injected intramuscularly with the aromatase inhibitor fadrozole (0.2 ml of 1 mg ml-1) and paired with saline-injected controls in a cage containing a nest bowl and nesting material. Fadrozole/saline vehicle was administered for 3 days at 12 h intervals. Saline-injected control males displayed significantly (90 %) more aggressive and nest-orientated behaviours compared with fadrozole-treated males. Similarly, saline-injected control females displayed nest-oriented behaviours and were sitting on the nest by day 2, whereas fadrozole-injected females showed none of these behaviours. Following terminal anaesthesia on day 4 by intramuscular injection of pentobarbital (60 mg ml-1), birds were perfuse-fixed with Zamboni's fixative and the brains removed for immunocytochemistry for androgen receptor (AR), progesterone receptor (PR) and P450AROM. All data were subjected to an analysis of variance. In saline-treated birds of both sexes, nuclear AR-ir and PR-ir were observed in the nucleus preopticus, pars suprachiasmatica (POA), nucleus preopticus paraventricularis magnocellularis (PPM), nucleus preopticus medialis (POM) and nucleus preopticus medialis, pars medianis (POMm). In contrast, fadrozole treatment in both sexes resulted in the complete absence of detectable nuclear AR-ir expression, together with a significant decline in the expression of PR-ir in the POM (males 122.33 vs. 25.2, P < 0.001; females 120.89 vs. 29, P < 0.001, S.E.M.) and POMm (males 47.08 vs. 8.36, P < 0.001; females 46.33 vs. 18.9, P < 0.001, S.E.M.). A sex difference in PR-ir expression was observed in the POA (males 138.81; females 84.73, S.E.M., P < 0.001) and PPM (males 76.8; females 106.5, S.E.M., P < 0.001) of fadrozole-treated birds. In controls, AR-ir and PR-ir were co-localised in individual cells. The percentage of PR-ir cells in males containing AR-ir ranged between 46.99 ± 4.33 (POA) and 84.5 ± 2.23 (POM). The percentage of PR-ir cells in females containing AR-ir ranged between 68.42 ± 4.79 (POA) and 86.98 ± 1.93 (POM). A high density of AROM-ir cells was observed in the POM and POMm of saline-injected males, which was found to co-express PR-ir (99 %).

These results suggest that courtship behaviour may be dependent on the expression of aromatisable steroid-induced PR-ir in all preoptic regions other than the POA, and on aromatisable steroid-induced AR-ir in all preoptic regions.

All procedures accord with current UK legislation.

Where applicable, experiments conform with Society ethical requirements