The hippocampus and prefrontal cortex are differentially involved in serial memory retrieval in non-stress and stress conditions

• Published in: Neurobiology of learning and memory Vol. 91; no. 4; pp. 447 - 455
• Main Authors: Chauveau, Frédéric, Piérard, Christophe, Tronche, Christophe, Coutan, Mathieu, Drouet, Isabelle, Liscia, Pierrette, Béracochéa, Daniel
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Inc 01.05.2009; Elsevier; Elsevier BV
• Subjects: Acute stress; Analysis of Variance; Animals; Behavioral psychophysiology; Biological and medical sciences; Catheterization; Corticosterone; Corticosterone - administration & dosage; Corticosterone - blood; Corticosterone - metabolism; Discrimination Learning - physiology; Electroshock; Fundamental and applied biological sciences. Psychology; Glucocorticoids; Hippocampus; Hippocampus - physiology; Learning; Male; Memory; Memory - physiology; Memory retrieval; Mental Recall - physiology; Mice; Mice, Inbred BALB C; Microinjections; Neurology; Prefrontal cortex; Prefrontal Cortex - physiology; Psychology. Psychoanalysis. Psychiatry; Psychology. Psychophysiology; Rodents; Serial spatial memory; Stress; Stress, Physiological - physiology; Memory retrieval; Acute stress; Glucocorticoids; Corticosterone; Mice; Prefrontal cortex; Hippocampus; Serial spatial memory; Steroid hormone; Acute; Rodentia; Central nervous system; Glucocorticoid; Stress; Encephalon; Vertebrata; Mammalia; Mouse; Animal; Adrenal hormone; Spatial memory
• ISSN: 1074-7427; 1095-9564; 1095-9564
• DOI: 10.1016/j.nlm.2008.12.003

We previously showed that 24 h after learning, mice significantly remembered the first (D1) but not the second (D2) discrimination in a serial spatial task and that an acute stress delivered 5 min before the test phase reversed this memory retrieval pattern. A first experiment evaluated the effects of dorsal hippocampus (HPC) or prefrontal cortex (PFC) lesions, these two brain areas being well-known for their involvement in serial and spatial memory processes. For this purpose, six independent groups of mice were used: non-lesioned (controls), PFC or HPC-lesioned animals, submitted or not to an acute stress (electric footshocks; 0.9 mA). Results show that (i) non-stressed controls as well as PFC-lesioned mice (stressed or not) remembered D1 but not D2; (ii) stressed controls and HPC-lesioned mice (stressed or not) remembered D2 but not D1; (iii) stress significantly increased plasma corticosterone in controls and PFC-lesioned mice, but not in HPC-lesioned mice which already showed a significant plasma corticosterone increase in non-stressed condition. Since data from this first experiment showed that stress inhibited the hippocampal-dependent D1 memory retrieval, a second experiment evaluated the behavioral effect of intrahippocampal corticosterone injection in non-stressed mice. Results show that intrahippocampal corticosterone injection induced a reversal of serial memory retrieval pattern similar to that induced by acute stress. Overall, our study shows that (i) in non-stress condition, the emergence of D1 is HPC-dependent; (ii) in stress condition, the emergence of D2 requires the PFC integrity; moreover, intrahippocampal corticosterone injection mimicked the effects of stress in the CSD task.