title: Alcohol-preferring rats show decreased corticotropin-releasing hormone-2 receptor expression and differences in HPA activation compared to alcohol-nonpreferring rats.
abstract: BACKGROUND
  Corticotropin-releasing hormone (CRH) and urocortins (UCNs) bind to corticotropin-releasing hormone type 2 receptor (CRF2 receptor ), a Gs protein-coupled receptor that plays an important role in modulation of anxiety and stress responses. The Crhr2 gene maps to a quantitative trait locus (QTL) for alcohol preference on chromosome 4 previously identified in inbred alcohol-preferring (iP) and-nonpreferring (iNP) F2 rats.
  
  
  METHODS
  Real-time polymerase chain reaction was utilized to screen for differences in Crhr2 mRNA expression in the central nervous system (CNS) of male iP and iNP rats. DNA sequence analysis was then performed to screen for polymorphism in Crhr2 in order to identify genetic variation, and luciferase reporter assays were then applied to test their functional significance. Next, binding assays were used to determine whether this polymorphism affected CRF2 receptor binding affinity as well as CRF2 receptor density in the CNS. Finally, social interaction and corticosterone levels were measured in the P and NP rats before and after 30-minute restraint stress.
  
  
  RESULTS
  Crhr2 mRNA expression studies found lower levels of Crhr2 mRNA in iP rats compared to iNP rats. In addition, DNA sequencing identified polymorphisms in the promoter region, coding region, and 3'-untranslated region between the iP and iNP rats. A 7 bp insertion in the Crhr2 promoter of iP rats altered expression in vitro as measured by reporter assays, and we found that CRF2 receptor density was lower in the amygdala of iP as compared to iNP rats. Male P rats displayed decreased social interaction and significantly higher corticosterone levels directly following 30-minute restraint when compared to male NP rats.
  
  
  CONCLUSIONS
  This study identified Crhr2 as a candidate gene of interest underlying the chromosome 4 QTL for alcohol consumption that was previously identified in the P and NP model. Crhr2 promoter polymorphism is associated with reduced mRNA expression in certain brain regions, particularly the amygdala, and lowered the density of CRF2 receptor in the amygdala of iP compared to iNP rats. Together, these differences between the animals may contribute to the drinking disparity as well as the anxiety differences of the P and NP rats.
authors.affiliation: Institute of Laboratory Animal Science , Chinese Academy of Medical Sciences (CAMS) & Peking Union Medical College (PUMC), Beijing, China; Department of Pediatrics , Indiana University School of Medicine, Indianapolis, Indiana.
authors.forename: Weidong
authors.initials: W
authors.lastname: Yong
authors.forename: John Paul
authors.initials: JP
authors.lastname: Spence
authors.forename: Robert
authors.initials: R
authors.lastname: Eskay
authors.forename: Stephanie D
authors.initials: SD
authors.lastname: Fitz
authors.forename: Ruslan
authors.initials: R
authors.lastname: Damadzic
authors.forename: Dongbing
authors.initials: D
authors.lastname: Lai
authors.forename: Tatiana
authors.initials: T
authors.lastname: Foroud
authors.forename: Lucinda G
authors.initials: LG
authors.lastname: Carr
authors.forename: Anantha
authors.initials: A
authors.lastname: Shekhar
authors.forename: Julia A
authors.initials: JA
authors.lastname: Chester
authors.forename: Markus
authors.initials: M
authors.lastname: Heilig
authors.forename: Tiebing
authors.initials: T
authors.lastname: Liang
mesh_terms: D000437:Alcoholism / Q000235:genetics* / Q000503:physiopathology; D000818:Animals; D001923:Brain Chemistry / Q000187:drug effects / Q000235:genetics; D003345:Corticosterone / Q000097:blood; D007030:Hypothalamo-Hypophyseal System / Q000503:physiopathology*; D008297:Male; D010913:Pituitary-Adrenal System / Q000503:physiopathology*; D020641:Polymorphism, Single Nucleotide / Q000235:genetics; D040641:Quantitative Trait Loci; D051381:Rats; D011919:Rats, Inbred Strains; D018019:Receptors, Corticotropin-Releasing Hormone / Q000032:analysis / Q000235:genetics* / Q000502:physiology; D013315:Stress, Psychological / Q000503:physiopathology
chemical_list: C101531:CRF receptor type 2; D018019:Receptors, Corticotropin-Releasing Hormone; D003345:Corticosterone
keywords: Alcoholism; Amygdala; Corticotropin-Releasing Hormone Type 2 Receptor; Selective Breeding; Stress