title: Alpha 7 nicotinic receptor subunit is present on serotonin neurons projecting to hippocampus and septum.
abstract: The serotonergic transmitter system regulates hippocampal activity through its raphe projection to hippocampus and medial septum/diagonal band of Broca complex (MS/DBB), and most likely also indirectly through its interaction with the cholinergic neurotransmitter system. Nicotine, e.g., enhances hippocampal serotonin release probably through presynaptic nicotinic receptors. We investigated the possible presence of the alpha 7-nicotinic subunit on serotonergic neurons projecting to hippocampus and MS/DBB. By retrograde neuronal tracing, hippocampal serotonergic neurons were identified and with double fluorescence immunostaining and Alexa-488 bound alpha-bungarotoxin the presence of active alpha 7 receptor on their soma was determined. Most of the retrogradely labeled serotonin neurons contained the alpha 7 subunit. A low degree of colocalization between alpha-bungarotoxin and serotonin-positive neurons suggest that the alpha 7 subunit may be transported anterogradely to the serotonergic axonal terminals.
authors.affiliation: Neurobiology Research Unit, Copenhagen University Hospital, 2100 Copenhagen, Denmark. saznar@nru.dk
authors.forename: Susana
authors.initials: S
authors.lastname: Aznar
authors.forename: Viktorija
authors.initials: V
authors.lastname: Kostova
authors.forename: Søren H
authors.initials: SH
authors.lastname: Christiansen
authors.forename: Gitte M
authors.initials: GM
authors.lastname: Knudsen
mesh_terms: D000818:Animals; D001370:Axonal Transport / Q000502:physiology; D001667:Binding, Competitive / Q000502:physiology; D002038:Bungarotoxins / Q000378:metabolism; D020667:Diagonal Band of Broca / Q000166:cytology / Q000378:metabolism; D004525:Efferent Pathways / Q000166:cytology / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D006624:Hippocampus / Q000166:cytology / Q000378:metabolism*; D006834:Hydrazines; D008863:Microspheres; D009474:Neurons / Q000166:cytology / Q000378:metabolism*; D017729:Presynaptic Terminals / Q000378:metabolism / Q000648:ultrastructure; D021122:Protein Subunits / Q000378:metabolism; D011903:Raphe Nuclei / Q000166:cytology / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011978:Receptors, Nicotinic / Q000378:metabolism*; D020665:Septum of Brain / Q000166:cytology / Q000378:metabolism*; D012701:Serotonin / Q000378:metabolism*; D013266:Stilbamidines; D009435:Synaptic Transmission / Q000502:physiology; D064569:alpha7 Nicotinic Acetylcholine Receptor
chemical_list: C049774:2-hydroxy-4,4'-diamidinostilbene, methanesulfonate salt; C417561:Alexa 488 hydrazide; D002038:Bungarotoxins; C579165:Chrna7 protein, rat; D006834:Hydrazines; D021122:Protein Subunits; D011978:Receptors, Nicotinic; D013266:Stilbamidines; D064569:alpha7 Nicotinic Acetylcholine Receptor; D012701:Serotonin