title: Galanin immunoreactivity within the primate basal forebrain: evolutionary change between monkeys and apes.
abstract: Galanin immunoreactivity (GAL-ir) is differentially expressed within the basal forebrain of monkeys and humans. Most monkey magnocellular basal forebrain neurons colocalize GAL-ir. In contrast, virtually no human magnocellular basal forebrain neurons express GAL-ir. Rather, an extrinsic galaninergic fiber plexus innervates these neurons in humans. The present study examined the expression of GAL-ir within the basal forebrain of apes to establish the phylogenetic level at which this transformation occurs. The staining patterns of GAL-ir within the basal forebrain of both lesser (gibbons) and great (chimpanzee and gorilla) apes were compared to that previously observed within monkeys and humans. All apes displayed a pattern of basal forebrain GAL-ir indistinguishable from humans. GAL-ir was not expressed within ape basal forebrain magnocellular neurons as seen in monkeys. Rather like humans, a dense collection of GAL-ir fibers was seen in close apposition to magnocellular perikarya. In addition, a few GAL-ir parvicellular neurons were scattered within the ape basal forebrain. These data indicate that the evolutionary change in the expression of GAL-ir within the primate basal forebrain occurs at the branch point of monkeys and apes.
authors.affiliation: Department of Neurological Sciences, Rush Presbyterian St. Luke's Medical Center, Chicago, Illinois 60612.
authors.forename: W C
authors.initials: WC
authors.lastname: Benzing
authors.forename: J H
authors.initials: JH
authors.lastname: Kordower
authors.forename: E J
authors.initials: EJ
authors.lastname: Mufson
mesh_terms: D000818:Animals; D005075:Biological Evolution; D005260:Female; D019004:Galanin; D006071:Gorilla gorilla / Q000378:metabolism*; D006801:Humans; D006922:Hylobates / Q000378:metabolism*; D007150:Immunohistochemistry; D008297:Male; D009479:Neuropeptides / Q000032:analysis*; D002679:Pan troglodytes / Q000378:metabolism*; D010455:Peptides / Q000032:analysis*; D016548:Prosencephalon / Q000737:chemistry*
chemical_list: D009479:Neuropeptides; D010455:Peptides; D019004:Galanin