Light detection by Vertebrate Ancient Opsin in the bird brain

Birds use the annual change in day length to time seasonal rhythms in reproduction. Photoreceptors located in the hypothalamus have long been known to detect light and stimulate reproductive development. An opsin photopigment with a λmax of approximately 492nm underlies the action spectrum for the avian reproductive photoperiodic response. Multiple opsin photoreceptors have emerged as potential candidates, but only vertebrate opsin meets the criteria for light detection in the avian hypothalamus. This presentation will cover the signal transduction pathways of light detection by photoreceptors and criteria for light detection in the bird brain. Then recent evidence from studies employing targeted functional manipulation of proposed photoreceptors such as vertebrate ancient opsin and neuropsin will be covered. A series of models are described to illustrate how vertebrate ancient opsin cells provide direct, and indirect regulation of gonadotropin-releasing hormone synthesis and secretion into the hypophyseal portal system. Overall, the presentation will propose that light detection in the avian hypothalamus is predominantly driven by vertebrate ancient opsin.