title: Organization of the cholinergic systems in the brain of two lungfishes, Protopterus dolloi and Neoceratodus forsteri.
abstract: Lungfishes (dipnoans) are currently considered the closest living relatives of tetrapods. The organization of the cholinergic systems in the brain has been carefully analyzed in most vertebrate groups, and major shared characteristics have been described, although traits particular to each vertebrate class have also been found. In the present study, we provide the first detailed information on the distribution of cholinergic cell bodies and fibers in the central nervous system in two representative species of lungfishes, the African lungfish (Protopterus dolloi) and the Australian lungfish (Neoceratodus forsteri), as revealed by immunohistochemistry against the enzyme choline acetyltransferase (ChAT). Distinct groups of ChAT immunoreactive (ChAT-ir) cells were observed in the basal telencephalon, habenula, isthmic nucleus, laterodorsal tegmental nucleus, cranial nerve motor nuclei, and the motor column of the spinal cord, and these groups seem to be highly conserved among vertebrates. In lungfishes, the presence of a cholinergic cell group in the thalamus and the absence of ChAT-ir cells in the tectum are variable traits, unique to this group and appearing several times during evolution. Other characters were observed exclusively in Neoceratodus, such as the presence of cholinergic cells in the suprachiasmatic nucleus, the pretectal region and the superior raphe nucleus. Cholinergic fibers were found in the medial pallium, basal telencephalon, thalamus and prethalamus, optic tectum and interpeduncular nucleus. Comparison of these results with those from other classes of vertebrates, including a segmental analysis to correlate cell populations, reveals that the cholinergic systems in lungfishes largely resemble those of amphibians and other tetrapods.
authors.affiliation: Department of Cell Biology, Faculty of Biology, University Complutense, 28040, Madrid, Spain.
authors.forename: Jesús M
authors.initials: JM
authors.lastname: López
authors.forename: Laura
authors.initials: L
authors.lastname: Domínguez
authors.forename: Ruth
authors.initials: R
authors.lastname: Morona
authors.forename: R Glenn
authors.initials: RG
authors.lastname: Northcutt
authors.forename: Agustín
authors.initials: A
authors.lastname: González
mesh_terms: D000818:Animals; D001921:Brain / Q000033:anatomy & histology* / Q000378:metabolism*; D064026:Calbindins; D002795:Choline O-Acetyltransferase / Q000378:metabolism; D005260:Female; D005399:Fishes / Q000033:anatomy & histology* / Q000378:metabolism*; D008297:Male; D011950:Receptors, Cholinergic / Q000378:metabolism*; D064030:S100 Calcium Binding Protein G / Q000378:metabolism; D013493:Suprachiasmatic Nucleus / Q000033:anatomy & histology / Q000378:metabolism; D003336:Tectum Mesencephali / Q000033:anatomy & histology / Q000378:metabolism; D013687:Telencephalon / Q000033:anatomy & histology / Q000378:metabolism; D013788:Thalamus / Q000033:anatomy & histology / Q000378:metabolism; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism
chemical_list: D064026:Calbindins; D011950:Receptors, Cholinergic; D064030:S100 Calcium Binding Protein G; D014446:Tyrosine 3-Monooxygenase; D002795:Choline O-Acetyltransferase