ИСТИНА

A different role of hippocampal subfields in processing of spatial information is extensively discussed. There are scant findings which demonstrate of different characteristics of the CA1, CA3 and dental gyrus (DG) along the rostrocaudal axis. Extensive study is necessary to assess of this subfield functional specialization. Previously we found that the exploration of an illuminated open field after familiarization in darkness (dark-light shift) as compared with control group (dark-dark condition) specifically affected c-Fos expression in the whole CA1 and rostral part of CA3 but not in DG in mice (Kuptsov et al., 2010 FENS, 2011 IBRO). In the present work we studied the effects of changing familiar environment from illuminated to dark condition. Two groups of C57BL/6 mice were familiarizied in the light open field (3 days, 2 trials per day). On the 4th day (6 trials) one group was tested under dark (infrared illuminated) condition, control group was tested in light. C-Fos expression was measured in all subfields at 8 levels along the rostrocaudal axis. Light-dark shift increased locomotion in the arena and decreased number of stops. C-Fos activity was increased only in intermediate part of DG as compared to control. Thus the effect of light-dark shift was less than dark-light shift and CA1 and CA3 subfields were not affected in this case. The fundamental difference in hippocampal activation pattern after light-dark and dark-light shift suggested that pattern of neural activity in subfields depended on the type of initial and novel environmental information which determined of different mapping and remapping processes. Supported by RFBR 10-04-00891