Upregulation of polysialylated neural cell adhesion molecule in the dorsal hippocampus after contextual fear conditioning is involved in long-term memory formation.

M. A. Lopez-Fernandez, M.-F. Montaron, E. Varea, G. Rougon, C. Venero, D. N. Abrous, C. Sandi
Journal of Neuroscience. 2007-04-25; 27(17): 4552-4561
DOI: 10.1523/jneurosci.0396-07.2007

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1. J Neurosci. 2007 Apr 25;27(17):4552-61.

Upregulation of polysialylated neural cell adhesion molecule in the dorsal
hippocampus after contextual fear conditioning is involved in long-term memory
formation.

Lopez-Fernandez MA(1), Montaron MF, Varea E, Rougon G, Venero C, Abrous DN, Sandi
C.

Author information:
(1)Brain Mind Institute, Swiss Federal Institute of Technology, CH-1015 Lausanne,
Switzerland.

The role of the hippocampus in pavlovian fear conditioning is controversial.
Although lesion and pharmacological inactivation studies have suggested a key
role for the dorsal hippocampus in contextual fear conditioning, the involvement
of the ventral part is still uncertain. Likewise, the debate is open with regard
to the putative implication of each hippocampal subdivision in fear conditioning
to a discrete conditioned stimulus. We explored the potential existence of
dissociations occurring in the dorsal versus ventral hippocampus at the cellular
level while dealing with either contextual or cued fear conditioning and focused
in a molecular “signature” linked to structural plasticity, the polysialylated
form of the neural cell adhesion molecule (PSA-NCAM). We found an upregulation of
PSA-NCAM expression in the dorsal (but not ventral) dentate gyrus at 24 h after
contextual (but not tone) fear conditioning. Specific removal of PSA through
microinfusion of the enzyme endoneuraminidase-N in the dorsal (but not ventral)
hippocampus reduced freezing responses to the conditioned context. Therefore, we
present evidence for a specific role of PSA-NCAM in the dorsal hippocampus in the
plasticity processes occurring during consolidation of the context representation
after “standard” contextual fear conditioning. Interestingly, we also found that
exposing animals just to the context induced an activation of PSA-NCAM in both
dorsal and ventral dentate gyrus. Altogether, these findings highlighting the
distinctive occurrence of these neuroplastic processes in the dorsal hippocampus
during the standard contextual fear-conditioning task enlighten the ongoing
debate about the involvement of these hippocampal subdivisions in pavlovian fear
conditioning.

DOI: 10.1523/JNEUROSCI.0396-07.2007
PMID: 17460068 [Indexed for MEDLINE]

Auteurs Bordeaux Neurocampus