BREEDLOVE, SM IBN 98-10342 The proposed project will study changes in the structure of the nervous system that mediate changes in behavior. These experiments take advantage of a model system in which there is normally occurring plasticity induced by the seasons. In seasonal breeders such as the Siberian hamster (Phodopus sungorus), animals born in the Fall show a much slower pace of development than do animals born in the Spring. Likewise, adult animals will, come autumn, undergo a nearly complete shut down of reproductive systems and then, when Spring returns, the reproductive system becomes functional again. Other researchers have demonstrated that these same phenomena can be reproduced in the laboratory by manipulating a single environmental variable: hours of exposure to light each day. Most animals will show these same changes simply by exposing them to either winter-like short days or summer-like long days, even if ample food, water and warmth are provided. Pilot data indicate that such photoperiodic manipulations also affect the structure and function of spinal motor centers crucial for reproduction in male hamsters. Experiments will investigate how photoperiod affects the structure and function of spinal motoneurons both in adulthood and in development. Understanding how benign, non-invasive environmental manipulations affect neuronal plasticity in these animals could shed light on neuronal plasticity in other circumstances and in other species.
