title: Co-expression of alpha7 and beta2 nicotinic acetylcholine receptor subunit mRNAs within rat brain cholinergic neurons.
abstract: Nicotine enhances cognitive and attentional processes through stimulation of the basal forebrain cholinergic system. Although muscarinic cholinergic autoreceptors have been well characterized, pharmacological characterization of nicotinic autoreceptors has proven more difficult. The present study used double-labeling in situ hybridization to determine expression of nicotinic acetylcholine receptor (nAChR) subunit mRNAs within basal forebrain cholinergic neurons in order to gain information about possible nAChR autoreceptor properties. Cholinergic cells of the mesopontine tegmentum and striatal interneurons were also examined, as were septohippocampal GABAergic neurons that interact with cholinergic neurons to regulate hippocampal activity. alpha7 and beta2 nAChR mRNAs were found to be co-expressed in almost all cholinergic cells and in the majority of GABAergic neurons examined. alpha4 nAChR mRNA expression was restricted to cholinergic cells of the nucleus basalis magnocellularis, and to non-cholinergic cells of the medial septum and mesopontine tegmentum. These data suggest possible regional differences in the pharmacological properties of nicotinic autoreceptors on cholinergic cells. Whereas most cholinergic cells express rapidly desensitizing alpha7 homomers or alpha7beta2 heteromers, cortical projection neurons may also express a pharmacologically distinct alpha4beta2 nAChR subtype. There may also be differential nAChR regulation of cholinergic and non-cholinergic cells within the mesopontine tegmentum that are implicated in acquisition of nicotine self-administration.
authors.affiliation: Department of Biology, University of Utah, Salt Lake City, UT 84112, USA.
authors.forename: L
authors.initials: L
authors.lastname: Azam
authors.forename: U
authors.initials: U
authors.lastname: Winzer-Serhan
authors.forename: F M
authors.initials: FM
authors.lastname: Leslie
mesh_terms: D000109:Acetylcholine / Q000378:metabolism*; D000818:Animals; D020532:Basal Nucleus of Meynert / Q000166:cytology / Q000378:metabolism; D001921:Brain / Q000166:cytology / Q000378:metabolism*; D002799:Cholinergic Fibers / Q000378:metabolism* / Q000648:ultrastructure; D005786:Gene Expression Regulation / Q000235:genetics; D008297:Male; D017072:Neostriatum / Q000166:cytology / Q000378:metabolism; D009474:Neurons / Q000166:cytology / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011978:Receptors, Nicotinic / Q000235:genetics*; D013681:Tegmentum Mesencephali / Q000166:cytology / Q000378:metabolism; D064569:alpha7 Nicotinic Acetylcholine Receptor; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
chemical_list: D000109:Acetylcholine; D012333:RNA, Messenger; D011978:Receptors, Nicotinic; D064569:alpha7 Nicotinic Acetylcholine Receptor; D005680:gamma-Aminobutyric Acid; C579165:Chrna7 protein, rat; C403531:nicotinic receptor alpha4beta2