title: Decreased α4β2 nicotinic receptor number in the absence of mRNA changes suggests post-transcriptional regulation in the spontaneously hypertensive rat model of ADHD.
abstract: The spontaneously hypertensive rat (SHR) is widely used as a model of attention-deficit/hyperactivity disorder (ADHD). Deficits in central nicotinic receptors (nAChRs) have been previously observed in SHRs, which is interesting since epidemiological studies have identified an association between smoking and ADHD symptoms in humans. Here, we examine whether nAChR deficits in SHRs compared with Wistar Kyoto rat (WKY) controls are nAChR subtype-specific and whether these deficits correlate with changes at the level of mRNA transcription in specific brain regions. Levels of binding sites (B(max) ) and dissociation constants (K(d)) for nAChRs were determined from saturation curves of high-affinity [³H]epibatidine- and [³H] Methyllycaconitine (MLA) binding to membranes from cortex, striatum, hippocampus and cerebellum. In additional brain regions, nAChRs were examined by autoradiography with [¹²⁵I]A-85380 and [¹²⁵I]α-bungarotoxin. Levels of mRNA encoding nAChR subunits were measured using quantitative real-time PCR (qPCR). We showed that the number of α4β2 nAChR binding sites is lower globally in the SHR brain compared with WKY in the absence of significant differences in mRNA levels, with the exception of lower α4 mRNA in cerebellum of SHR compared with WKY. Furthermore, nAChR deficits were subtype- specific because no strain difference was found in α7 nAChR binding or α7 mRNA levels. Our results suggest that the lower α4β2 nAChR number in SHR compared with WKY may be a consequence of dysfunctional post-transcriptional regulation of nAChRs.
authors.affiliation: Department of Biochemistry, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway.
authors.forename: Mattis B
authors.initials: MB
authors.lastname: Wigestrand
authors.forename: Yann S
authors.initials: YS
authors.lastname: Mineur
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Heath
authors.forename: Frode
authors.initials: F
authors.lastname: Fonnum
authors.forename: Marina R
authors.initials: MR
authors.lastname: Picciotto
authors.forename: Sven Ivar
authors.initials: SI
authors.lastname: Walaas
mesh_terms: D000157:Aconitine / Q000031:analogs & derivatives / Q000378:metabolism; D000818:Animals; D001289:Attention Deficit Disorder with Hyperactivity / Q000235:genetics* / Q000523:psychology*; D001384:Azetidines / Q000378:metabolism; D001923:Brain Chemistry / Q000235:genetics / Q000502:physiology; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000378:metabolism; D002038:Bungarotoxins / Q000378:metabolism; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D008566:Membranes / Q000187:drug effects / Q000378:metabolism; D018722:Nicotinic Agonists / Q000378:metabolism; D018733:Nicotinic Antagonists / Q000378:metabolism; D011499:Protein Processing, Post-Translational / Q000235:genetics / Q000502:physiology; D011725:Pyridines / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics*; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D011978:Receptors, Nicotinic / Q000096:biosynthesis / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013816:Thermodynamics
chemical_list: C104288:A 85380; D001384:Azetidines; D019086:Bridged Bicyclo Compounds, Heterocyclic; D002038:Bungarotoxins; D018722:Nicotinic Agonists; D018733:Nicotinic Antagonists; D011725:Pyridines; D012333:RNA, Messenger; D011978:Receptors, Nicotinic; C403531:nicotinic receptor alpha4beta2; C054634:methyllycaconitine; C082748:epibatidine; D000157:Aconitine