Location and Neuroendocrine Function of Putative Encephalic Photoreceptors

University Of Arkansas, Fayetteville AR

Investigators

Abstract

Lay Abstract Many vertebrates, including various species of birds anticipate seasonal changes each year and an environmental cue utilized to predict the occurrence of seasons is day length or photoperiod. For many years scientists have hypothesized that avian species have photoreceptors and neural systems designed to register day length and this information to determine the opportune time to migrate or to reproduce and raise young successfully. A question that remains unanswered is, where are the photoreceptors utilized for seasonal information located and how do they work? Photoreceptors have been localized in the eyes, pineal gland, and brain. Scientists refer to photoreceptors in the brain as encephalic photoreceptors (EPRs). One of the most robust, seasonal events displayed by several avian species is rapid development of the reproductive system when day length has increased. Therefore it is important to evaluate each set of receptors that could play a role in this phenomenon. A combination of techniques that rapidly stimulate development of the gonads coupled with microsurgical techniques directed to anatomical sites where photoreceptors are known to occur, will be utilized to determine which group of receptors play a role in seasonal growth of the reproductive system, such as development of the gonads. In the present studies a cell culture procedure will be utilized to keep photoreceptors viable for hours, to determine whether cells respond to direct flashes of light with a significant reduction in calcium concentration. These experiments should (1) establish whether or not EPRs are solely responsible for development of the reproductive system in chicks, and (2) positive research experience to both undergraduate and graduate students.. These results provide important information for geneticists responsible for monitoring domestic or wild breeder flocks. Avian geneticists could selectively choose breeder flocks that exhibit increased numbers or responses of EPRs to light to maximize the response of maturing chicks to photoperiodic manipulation thereby increasing reproductive efficiency.