Sexual dimorphism of arg-vasotocin gene expressing neurons in the telencephalon and dorsal diencephalon of the domestic fowl. An immunocytochemical and in situ hybridization study.

A strong sex dimorphism in the distribution of immunoreactive arginine-vasotocin (AVT) and AVT mRNA was observed in telencephalic and dorsal diencephalic areas of the domestic fowl using immunocytochemistry and in situ hybridization. Two subgroups of immunoreactive parvocellular perikarya surrounded by dense plexus of immunoreactive fibres were found within the bed nucleus of the stria terminalis and the dorsal part of the diencephalic paraventricular region of males. No signs of immunoreactivity were observed within corresponding regions of the female brain. Instead, in females a few scattered weakly stained perikarya were observed rostrally to the level of the anterior commissure, juxtapositioned to the nucleus accumbens and the floor of the lateral ventricle. The distribution of AVT mRNA containing cell profiles fully confirmed the immunocytochemical findings. Osmotic stress induced by water deprivation for 48 h had no influence on the number of immunoreactive or AVT mRNA containing parvocellular cell bodies. However, it resulted in an increase of immunoreactive cell area in the bed nucleus of the stria terminalis and dorsal diencephalon of 5. 9 and 11.7%, respectively. We suggest that the sexually dimorphic vasotocinergic circuit may be involved in the co-ordination of behavioural and autonomic functions in response to environmental stress.