title: Quantification of extracellular levels of corticosterone in the basolateral amygdaloid complex of freely-moving rats: a dialysis study of circadian variation and stress-induced modulation.
abstract: Corticosterone influences emotion and cognition via actions in a diversity of corticolimbic structures, including the amygdala. Since extracellular levels of corticosterone in brain have rarely been studied, we characterized a specific and sensitive enzymatic immunoassay for microdialysis quantification of corticosterone in the basolateral amygdaloid complex of freely-moving rats. Corticosterone levels showed marked diurnal variation with an evening (dark phase) peak and stable, low levels during the day (light phase). The "anxiogenic agents", FG7142 (20 mg/kg) and yohimbine (10 mg/kg), and an environmental stressor, 15-min forced-swim, induced marked and sustained (1-3 h) increases in dialysis levels of corticosterone in basolateral amygdaloid complex. They likewise increased dialysis levels of dopamine and noradrenaline, but not serotonin and GABA. As compared to basal corticosterone levels of ~200-300 pg/ml, the elevation provoked by forced-swim was ca. 20-fold and this increase was abolished by adrenalectomy. Interestingly, stress-induced rises of corticosterone levels in basolateral amygdaloid complex were abrogated by combined but not separate administration of the corticotrophin releasing factor(1) (CRF(1)) receptor antagonist, CP154,526, and the vasopressin(1b) (V(1b)) receptor antagonist, SSR149,415. Underpinning their specificity, they did not block forced-swim-induced elevations in dopamine and noradrenaline. In conclusion, extracellular levels of corticosterone in the basolateral amygdaloid complex display marked diurnal variation. Further, they are markedly elevated by acute stressors, the effects of which are mediated (in contrast to concomitant elevations in levels of monoamines) by co-joint recruitment of CRF(1) and V(1b) receptors.
authors.affiliation: Psychopharmacology Department, Institut de Recherches Servier, 125 Chemin de Ronde, 78290 Croissy-sur-Seine, France.
authors.forename: Gaëlle
authors.initials: G
authors.lastname: Bouchez
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Millan
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Rivet
authors.forename: Rodolphe
authors.initials: R
authors.lastname: Billiras
authors.forename: Raphaël
authors.initials: R
authors.lastname: Boulanger
authors.forename: Alain
authors.initials: A
authors.lastname: Gobert
mesh_terms: D000679:Amygdala / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D002243:Carbolines / Q000494:pharmacology; D002940:Circadian Rhythm / Q000502:physiology*; D003345:Corticosterone / Q000378:metabolism* / Q000494:pharmacology; D004298:Dopamine / Q000378:metabolism; D017551:Microdialysis; D009638:Norepinephrine / Q000378:metabolism; D051381:Rats; D012701:Serotonin / Q000378:metabolism; D013315:Stress, Psychological / Q000378:metabolism*; D015016:Yohimbine / Q000494:pharmacology; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
chemical_list: D002243:Carbolines; D015016:Yohimbine; D012701:Serotonin; D005680:gamma-Aminobutyric Acid; C035874:FG 7142; D004298:Dopamine; D003345:Corticosterone; D009638:Norepinephrine