TESTOSTERONE MODULATION OF PEPTIDERGIC PATHWAYS IN THE SEPTOPREOPTIC REGION OF MALE JAPANESE-QUAIL

Multiple peptidergic innervation occurs in prosencephalic regions of q uail that are characterized by a wide distribution of sex steroid rece ptors or gonadotropin releasing hormone elements, suggesting that neur opeptides could influence circuitries involved in the control of repro ductive activities in birds. In the present study we investigated the existence of a testosterone (T) dependent modulation of peptidergic pa thways in the septo-preoptic region of quail, We quantitatively analyz ed the immunocytochemical distribution of vasotocin (VT), substance P, neuropeptide Y (NPY), and vasoactive intestinal polypeptide (VIP) in intact, castrated, or castrated T-treated male quail. In intact males the distribution of the investigated peptidergic structures was peptid e-specific and region-specific, NPY-or VT-immunoreactive (ir) structur es were detected in both the medial preoptic nucleus (POM) and the sep tum, whereas VIP-ir elements were particularly abundant in the latter region and almost absent in the POM, The reduction of T circulating le vels after castration markedly decreases the VT innervation of the POM and of the lateral septum, The innervation was completely restored by T treatment, On the contrary, castration resulted in an increase of t he VIP innervation of the septum at its most caudal level, Hence, T ex erted an opposite effect upon these two neuropeptide systems inducing a decrease of VIP-ir fibres and an enhancement of VT-ir elements, Our results confirm previous data on T-dependent VT innervation of the sep tal area of the canary and of several mammalian species, Additionally, in quail the VT-ergic innervation of preoptic region is modulated by T. Further studies should clarify whether the T-sensitive VT innervati on of the POM comes from intrinsic or extrinsic pathways.