Effects of ambient temperature on photo-induced prolactin secretion in three subspecies of white-crowned sparrow, Zonotrichia leucophrys

We tested the effects of naturally relevant ambient temperatures (4, 20, an d 30 degrees C) on photoinduced prolactin (PRL) secretion in three subspeci es of white-crowned sparrow Zonotrichia leucophrys. In all three subspecies , transfer from short to long days triggered an increase in plasma PRL typi cal of an avian seasonal breeder. In z. l. gambelii, which breeds at high l atitudes, temperature does not affect the rate of photoinduced gonadal matu ration or luteinizing hormone (LH) secretion. In this subspecies, we found that changes in plasma PRL concentrations were similar in all temperature t reatments. In Z. l. pugetensis, which breeds in the Pacific Northwest, high temperatures accelerate gonadal development in females but not males and d oes not affect LH secretion. In this subspecies, we found that like gonadal growth, photoinduced changes in PRL secretion in z. l. pugetensis vary wit h ambient temperature in females but not males, In Z. l. oriantha, which br eeds in alpine regions of the West, both males and females respond to tempe rature cues by modulating gonadal growth but not LH secretion. We found in Z. l. oriantha that ambient temperature affects PRL secretion in both sexes . These results suggest that PRL may be involved in the transduction of amb ient temperature cues used to time reproductive development and the termina tion of seasonal breeding. Alternatively, temperature-mediated differences in plasma PRL may be a result rather than a cause of differences in gonadal development, since sex steroids affect PRL secretion in some species. (C) 1999 Academic Press.