The hippocampus and prefrontal cortex are differentially involved in serial memory retrieval in non-stress and stress conditions.
We previously showed that 24h 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 5min 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; 0.9mA). 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.
Chauveau
Frédéric
F
Centre de Neurosciences Intégratives et Cognitives (CNIC), Universités de Bordeaux, UMR-CNRS 5228, Bâtiment Biologie Animale, Avenue des facultés, Talence, France.
Piérard
Christophe
C
Tronche
Christophe
C
Coutan
Mathieu
M
Drouet
Isabelle
I
Liscia
Pierrette
P
Béracochéa
Daniel
D
D000704:Analysis of Variance; D000818:Animals; D002404:Catheterization; D003345:Corticosterone / Q000008:administration & dosage / Q000097:blood / Q000378:metabolism; D004193:Discrimination Learning / Q000502:physiology; D004597:Electroshock; D006624:Hippocampus / Q000502:physiology*; D008297:Male; D008568:Memory / Q000502:physiology*; D011939:Mental Recall / Q000502:physiology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008845:Microinjections; D017397:Prefrontal Cortex / Q000502:physiology*; D013312:Stress, Physiological / Q000502:physiology*
D003345:Corticosterone