Fear memory for cue and context: Opposite and time-dependent effects of a physiological dose of corticosterone in male BALB/c and C57BL/6J mice

Publication Type:

Journal Article

Source:

Brain Res, Volume 1466, p.112–118 (2012)

ISBN:

1872-6240 (Electronic)00

DOI Name (links to online publication)

10.1016/j.brainres.2012.05.016

Abstract:

Highly emotional, stress reactive BALB/c mice secrete more corticosterone in response to fear conditioning than the low stress reactive C57BL/6J mice. Fear memory to cue and context differs between the strains. We injected corticosterone at physiological concentrations (250mug/kg i.p.) 30min before fear conditioning. Fear memory was tested 48 and 72h later. Although corticosterone had little effect on acquisition, it differentially affected fear memories in strain dependent manner: while BALB/c mice decreased freezing during cue and context episodes, C57BL/6J mice showed an overall increase in freezing. BALB/c mice showed extinction over days while no such extinction was seen in C57BL/6J mice. Evaluation of these data in the perspective of previous studies using the same fear conditioning paradigm with corticosterone injections 5min before or immediately after acquisition, revealed the impact of corticosterone during conditioning on the strength of fear memories. In C57BL/6J mice the overall increase in fear memories was higher if corticosterone was injected 30min pre acquisition than if injected 5min pre. In contrast, BALB/c mice showed reduced fear memories when injected 30min pre compared to that seen 5min pre acquisition. Both strains showed decreased fear memories compared to vehicle if corticosterone was administered immediately after acquisition. We conclude that the timing of physiologically relevant, stress levels increase in corticosterone is essential for the processing of aversive events and the formation of fear memories. However, the quality of the effect depends on the genetic background. These findings contribute to the understanding of the etiology of stress-related disorders.

18/01/2013