Differences of CA3 bursting in DBA/1 and DBA/2 inbred mouse strains with divergent shuttle box performance.

The CA3 bursting activity was compared in slices from two genetically closely related inbred mouse strains with divergent shuttle box performance (low level performing DBA/1 and high performing DBA/2 strains) and a control, behaviorally untested inbred strain, NMRI. Spontaneous population bursts of hippocampal CA3 pyramidal cells (measured extracellularly as field potentials) occurred more frequently in slices of the DBA/2 strain (in 62.5% of the slices in DBA/2 mice) than in the DBA/1 strain (in 33.3% of the slices in DBA/1 mice) and the control NMRI strain (in 33.3% of the slices), whereas the ratio of bursting and nonbursting cells was not different. The resting membrane potential of spontaneously bursting and nonbursting cells was hyperpolarized and the frequency of spontaneous cell bursts were higher in DBA/2 mice compared with both other strains. Slices from the high performing DBA/2 strain had significantly lower thresholds for population bursts evoked by mossy fiber (but not perforant path) stimulation. Electrophysiological properties and bursting patterns of CA3 pyramidal cells are shown to correlate with learning behavior in three different mouse strains. This result is in keeping with an important role of CA3 bursting in memory trace formation.