The distribution of substance P and neuropeptide Y in four songbird species: a comparison of food-storing and non-storing birds

The distributions of the neuropeptides substance P (SP) and neuropeptide Y (NPY) were investigated in four songbird species that differ in their food- storing behavior. The food-storing black-capped chickadee (Parus atricapill us) was compared to the non-storing blue tit (Parus caeruleus) and great ti t (Parus major) within the avian family Paridae. as well as to the non-stor ing dark-eyed junco (Junco hyemalis). All four species showed a similar dis tribution of SP throughout the brain with the exception of two areas, the h ippocampal complex (including hippocampus (Hp) and parahippocampus (APH)) a nd the Wulst (including the hyperstriatum accessorium (HA)). SP-like immuno reactivity was found in cells of the Hp in juncos, but not in the three par id species. Two areas within the APH and HA SP-like immunoreactivity in all four species. The more medial of these (designated SPm) is a distinctive f ield of fibers and terminals found throughout the APH and extending into th e HA. A positive relationship between SPm and Hp volume was found for all f our species with the chickadee having a significantly larger SPm area relat ive to telencephalon than the other species. The distribution of SP in this region may be related to differences in food-storing behavior. In contrast to substance R NPY distribution throughout the brain was similar in all fo ur species. Further, NPY-immunoreactive cells were found in the Hp of all f our species and no species differences in the number of NPY cells was obser ved. (C) 2001 Elsevier Science B.V. All rights reserved.