title: Infralimbic cortex controls the activity of the hypothalamus-pituitary-adrenal axis and the formation of aversive memory: Effects of environmental enrichment.
abstract: The aim of the present study was to investigate the effects of the stimulation and inhibition of the ventral part of the medial prefrontal cortex (infralimbic cortex) on basal and stress-induced plasma levels of corticosterone and on the acquisition of aversive memory in animals maintained in control and environmental enrichment (EE) conditions. Intracortical microinjections of the GABAA antagonist picrotoxin and agonist muscimol were performed in male Wistar rats to stimulate and inhibit, respectively, the activity of the infralimbic cortex. Injections were performed 60 min before foot shock stress and training in the inhibitory avoidance task. Picrotoxin injections into the infralimbic cortex increased basal plasma levels of corticosterone. These increases were higher in EE rats which suggest that EE enhances the control exerted by infralimbic cortex over the hypothalamus-pituitary-adrenal (HPA) axis and corticosterone release. Muscimol injections into the infralimbic cortex reduced the stress-induced plasma levels of corticosterone and the retention latency 24h after training in the inhibitory avoidance performance in control and EE animals, respectively. These results further suggest that the infralimbic cortex is required for the activation of the HPA axis during stress and for the acquisition of contextual aversive memories.
authors.affiliation: Department of Physiology, Faculty of Medicine, Universidad Complutense, 28040 Madrid, Spain. Electronic address: g.ronzoni@pdi.ucm.es.
authors.forename: Giacomo
authors.initials: G
authors.lastname: Ronzoni
authors.affiliation: Department of Physiology, Faculty of Medicine, Universidad Complutense, 28040 Madrid, Spain.
authors.forename: Maria
authors.initials: M
authors.lastname: Antón
authors.affiliation: Department of Physiology, Faculty of Medicine, Universidad Complutense, 28040 Madrid, Spain.
authors.forename: Francisco
authors.initials: F
authors.lastname: Mora
authors.affiliation: Department of Physiology, Faculty of Medicine, Universidad Complutense, 28040 Madrid, Spain.
authors.forename: Gregorio
authors.initials: G
authors.lastname: Segovia
authors.affiliation: Department of Physiology, Faculty of Medicine, Universidad Complutense, 28040 Madrid, Spain; HESRM, School of Applied Sciences, University of Mississippi, Oxford, MS 38677, USA.
authors.forename: Alberto
authors.initials: A
authors.lastname: Del Arco
mesh_terms: D000818:Animals; D001362:Avoidance Learning / Q000502:physiology*; D002540:Cerebral Cortex / Q000503:physiopathology*; D003345:Corticosterone / Q000097:blood; D004195:Disease Models, Animal; D004644:Emotions / Q000502:physiology; D004777:Environment; D006799:Housing, Animal; D007030:Hypothalamo-Hypophyseal System / Q000503:physiopathology*; D008297:Male; D008568:Memory / Q000502:physiology*; D009043:Motor Activity / Q000502:physiology; D009118:Muscimol; D010852:Picrotoxin; D010913:Pituitary-Adrenal System / Q000503:physiopathology*; D017208:Rats, Wistar; D013315:Stress, Psychological / Q000503:physiopathology* / Q000628:therapy
chemical_list: D003345:Corticosterone; D009118:Muscimol; D010852:Picrotoxin
keywords: Corticosterone; Emotional memory; Muscimol; Picrotoxin; Prefrontal cortex; Stress