title: Luteinizing hormone-releasing hormone gene expression differs in young and middle-aged females on the day of a steroid-induced LH surge.
abstract: LHRH mRNA levels were examined in young and middle-aged female rats at 4 times (10:00 h, 14:00 h, 18:00 h and 20:00 h) on the day of a steroid-induced LH surge by in situ hybridization with a digoxigenin-labeled riboprobe. Young, but not middle-aged females, exhibited dynamic temporal changes in the number of LHRH mRNA positive neurons detected in the organum vasculosum of the lamina terminalis-preoptic area (OVLT-POA) continuum. Specifically, fewer LHRH mRNA positive neurons were detected at 18:00 h compared with the number detected at 14:00 h and 20:00 h (P < 0.01) in the OVLT-POA of young females. All LHRH mRNA positive neurons present in 4 anatomically matched sections through the rostral POA of young and middle-aged animals were digitized for detailed computer-assisted analysis of the hybridization reaction product. The mean hybridization area (P < 0.00025) and integrated optical density per cell (P < 0.006) were reduced in middle-aged compared to young females consistent with a relative age-related decline in LHRH mRNA levels. Moreover, an age-related reduction in cellular and/or regional hybridization area was noted at each of the time points examined (P < 0.05-P < 0.001). These data confirm earlier reports of dynamic changes in LHRH mRNA levels on the day of an LH surge. Furthermore, they support a role for age-related alterations in LHRH gene expression in the disruption of regular estrous cyclicity in middle-aged females.
authors.affiliation: Department of Anatomy and Cellular Biology, Tufts University Schools of Medicine, Boston, MA 02111, USA. brubin@opal.tufts.edu
authors.forename: B S
authors.initials: BS
authors.lastname: Rubin
authors.forename: C E
authors.initials: CE
authors.lastname: Lee
authors.forename: M
authors.initials: M
authors.lastname: Ohtomo
authors.forename: J C
authors.initials: JC
authors.lastname: King
mesh_terms: D000375:Aging / Q000502:physiology*; D000818:Animals; D002452:Cell Count; D004076:Digoxigenin; D004971:Estrus / Q000502:physiology; D005260:Female; D018507:Gene Expression Regulation, Developmental / Q000502:physiology; D007987:Gonadotropin-Releasing Hormone / Q000235:genetics*; D007031:Hypothalamus / Q000166:cytology / Q000502:physiology; D007091:Image Processing, Computer-Assisted; D017403:In Situ Hybridization; D007986:Luteinizing Hormone / Q000097:blood*; D009474:Neurons / Q000737:chemistry / Q000166:cytology; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors
chemical_list: D012333:RNA, Messenger; D007987:Gonadotropin-Releasing Hormone; D007986:Luteinizing Hormone; D004076:Digoxigenin