title: Social isolation increases the response of peripheral benzodiazepine receptors in the rat.
abstract: Social isolation of rats for 30 days immediately after weaning reduces the cerebrocortical and plasma concentrations of progesterone, 3alpha-hydroxy-5alpha-pregnan-20-one (3alpha,5alpha-TH PROG), and 3alpha,5alpha-tetrahydrodeoxycorticosterone (3alpha,5alpha-TH DOC). The percentage increases in the brain and plasma concentrations of these neuroactive steroids apparent 30 min after intraperitoneal injection of the peripheral benzodiazepine receptor (PBR) ligand CB 34 (25 mg/kg) have now been shown to be markedly greater in isolated rats than in group-housed controls. The CB 34-induced increase in the abundance of 3alpha,5alpha-TH PROG was more pronounced in the brain than in the plasma of isolated rats. Analysis of [3H]PK 11195 binding to membranes prepared from the cerebral cortex, adrenals, or testis revealed no significant difference in either the maximal number of binding sites for this PBR ligand or its dissociation constant between isolated and group-housed animals. Social isolation also induced a small but significant decrease in the plasma concentration of adrenocorticotropic hormone. Moreover, CB 34 increased the plasma concentration of this hormone to a greater extent in isolated rats than in group-housed animals. The persistent decrease in the concentrations of neuroactive steroids induced by social isolation might thus be due to an adaptive decrease in the activity either of the hypothalamic-pituitary-adrenal axis or of PBRs during the prolonged stress, reflecting a defense mechanism to limit glucocorticoid production. The larger increase in neuroactive steroid concentrations induced by CB 34 and the enhanced pituitary response to this compound in isolated rats indicate that this mild stressor increases the response of PBRs.
authors.affiliation: Department of Experiemental Biology, Center for Excellence for Neurobiology of Dependence, University of Cagliari, Italy. mserra@unica.it
authors.forename: Mariangela
authors.initials: M
authors.lastname: Serra
authors.forename: M Giuseppina
authors.initials: MG
authors.lastname: Pisu
authors.forename: Ivan
authors.initials: I
authors.lastname: Floris
authors.forename: Silvia
authors.initials: S
authors.lastname: Floris
authors.forename: Emanuela
authors.initials: E
authors.lastname: Cannas
authors.forename: Alessandra
authors.initials: A
authors.lastname: Mossa
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Trapani
authors.forename: Andrea
authors.initials: A
authors.lastname: Latrofa
authors.forename: Robert H
authors.initials: RH
authors.lastname: Purdy
authors.forename: Giovanni
authors.initials: G
authors.lastname: Biggio
mesh_terms: D000324:Adrenocorticotropic Hormone / Q000097:blood; D000818:Animals; D007093:Imidazoles / Q000378:metabolism / Q000494:pharmacology; D008297:Male; D011374:Progesterone / Q000378:metabolism; D011485:Protein Binding / Q000502:physiology; D011725:Pyridines / Q000378:metabolism / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011963:Receptors, GABA-A / Q000378:metabolism*; D012934:Social Isolation
chemical_list: C120709:CB 34; D007093:Imidazoles; D011725:Pyridines; D011963:Receptors, GABA-A; D011374:Progesterone; D000324:Adrenocorticotropic Hormone