DEVELOPMENT OF METABOLIC RESPONSE IN MALE QUAIL BRAIN DURING SEXUAL-MATURATION

Seasonal reproductive activities of Japanese quail Coturnix japonica a re induced most obviously by stimulatory effects of long-day photoperi od. This study addressed the metabolic response, as measured by 2-deox yglucose (2-DG), in brain of male quail during sexual maturation. At 7 weeks of age, reproductively quiescent quail exposed to a short photo period of 6L:18D, received 2-DG on day 0 and +3, +6, +9, +12, +15 and +18 days after onset of 16L:8D. Brains were processed for autoradiogra phy; serum testosterone was measured to indicate reproductive response to photoperiod. Circulating testosterone remained low until day 9, th en rose sharply, reaching maximum levels at day 18. Heavily labeled nu clei were identified in some discrete neural pathways: both tectofugal and thalamofugal visual pathways, ascending auditory pathway, efferen t vocalization pathway, and limbic structures. Metabolic activity of t he terminal nucleus (ectostriatum) of the tectofugal pathway increased significantly by day 18, but in the terminal nuclei (the Wulst) of th e thalamofugal visual pathway activity did not change significantly. E nergy metabolism of some nuclei of the auditory pathway rose significa ntly by day 3, although in the vocal pathway it did not show augmentat ion until days 15-18. The metabolic activity of limbic structures also increased. These results suggest that, in Japanese quail, sensory nuc lei and some of their integrative areas become sensitive to environmen tal cues in response to long-day photoperiod. It is possible that the external environmental cues that affect the reproductive activities of quail act through sensory systems.