title: Estrous cycle influences on sexual diergism of HPA axis responses to cholinergic stimulation in rats.
abstract: Central cholinergic systems differentially modulate hypothalamic-pituitary-adrenal (HPA) axis activity in female and male animals (sexual diergism). We previously reported that male rats had significantly greater HPA axis responses to stimulation by physostigmine (PHYSO), an acetylcholinesterase (AChE) inhibitor, compared to females. Females in defined estrous cycle stages, however, were not studied because of sample size limitations. We, therefore, determined HPA axis responses to stimulation by PHYSO in females during all estrous cycle stages (n = 78), and in male rats (n = 75). Plasma arginine vasopressin (AVP), adrenocorticotropic hormone (ACTH), and corticosterone (CORT) were measured. Estrous cycle stage was determined by light microscopy of vaginal smears. Proestrous and estrous females had higher ACTH and CORT responses compared to metestrous and diestrous females. Males had higher ACTH and AVP responses compared to females in all cycle stages. CORT responses followed the ACTH responses, except that females started from a higher baseline in all estrous stages, compared to males. These results suggest that cholinergic regulation of the HPA axis differs among females across stages of the estrous cycle, as well as between males and females. These effects are likely due to differences in circulating sex steroids and their actions within the brain.
authors.affiliation: Center for Neurosciences Research, Allegheny-Singer Research Institute, Allegheny General Hospital, Pittsburgh, PA 15212, USA. mrhodes@wpahs.org
authors.forename: Michael E
authors.initials: ME
authors.lastname: Rhodes
authors.forename: Elena M
authors.initials: EM
authors.lastname: Balestreire
authors.forename: R Kenneth
authors.initials: RK
authors.lastname: Czambel
authors.forename: Robert T
authors.initials: RT
authors.lastname: Rubin
mesh_terms: D000324:Adrenocorticotropic Hormone / Q000097:blood; D000818:Animals; D001127:Arginine Vasopressin / Q000097:blood; D002800:Cholinesterase Inhibitors / Q000494:pharmacology*; D003345:Corticosterone / Q000097:blood; D030762:Estrous Cycle / Q000187:drug effects / Q000502:physiology*; D005260:Female; D007030:Hypothalamo-Hypophyseal System / Q000187:drug effects / Q000502:physiology*; D008297:Male; D010830:Physostigmine / Q000494:pharmacology*; D010913:Pituitary-Adrenal System / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012737:Sex Factors; D014626:Vaginal Smears
chemical_list: D002800:Cholinesterase Inhibitors; D001127:Arginine Vasopressin; D000324:Adrenocorticotropic Hormone; D010830:Physostigmine; D003345:Corticosterone