Linkage of hippocampal proteins to spatial memory formation and strain-dependence in Apodemus sylvaticus, C57BL/6J and PWD/PhJ mice.

Strain-dependence of performance in the Morris water maze (MWM) has been reported but information on underlying differences at the protein level as well as linkage of hippocampal proteins to memory is limited. No data are available on differences in hippocampal protein levels between (within-strain) "good" and "bad" performers in the MWM. Hippocampi of wild-caught mouse strain Apodemus sylvaticus (AS), laboratory inbred mouse strain C57BL/6J and wild-derived inbred mouse strain PWD/PhJ, that were tested in the MWM, were taken and postsynaptic density protein 95, neuronal marker protein NeuN, dendritic spine protein drebrin, synapsins 1a and 1b and synaptosomal protein syntaxin of the SNARE complex were determined by immunoblotting. These mouse strains with known different performance in the MWM showed different hippocampal protein patterns and by the use of yoked controls proteins could be identified as linked to memory formation. When mice, classified as good or bad performers by the median of time spent in the target quadrant on day 12 of the MWM, experiments, NeuN was discriminating good from bad performers in AS at the stringent statistical level of P<0.0001, an effect not seen in the corresponding yoked controls. Strain-dependence of performance in the MWM was reflected by different hippocampal protein levels. Most hippocampal proteins given above were linked to memory formation in the MWM. The finding that the neuronal protein NeuN is able to discriminate between good and bad performers in the MWM may be of major interest and may open a new area in the search for protein markers of spatial memory performance.