Jn. Armstrong et al., LEARNING AND MEMORY AFTER ADRENALECTOMY-INDUCED HIPPOCAMPAL DENTATE GRANULE CELL DEGENERATION IN THE RAT, Hippocampus, 3(3), 1993, pp. 359-371
Adrenalectomy (ADX) of normal adult rats causes selective hippocampal
dentate granule cell degeneration that is prevented by corticosterone.
The ability to destroy this one hippocampal cell type noninvasively m
ade it possible to address the role of the dentate granule cells in le
arning and memory. Four months after ADX, 31 of 45 rats failed to show
obvious granule cell loss and displayed behavior in the Morris water
maze that was similar to 16 sham-operated control rats and 16 ADX rats
maintained on corticosterone throughout the study. Conversely, 14 of
the 45 ADX rats experienced a loss of granule cells that varied from m
inimal to extensive. Although there were no obvious differences betwee
n groups in motoric and motivational characteristics or search strateg
ies. ADX rats with moderate to extensive granule cell loss acquired pl
ace learning slightly slower than controls or ADX rats with minimal or
no obvious cell loss. Furthermore, the ADX rats with moderate to exte
nsive cell loss were temporarily impaired following alteration of eith
er intramaze or extramaze cues compared to controls. In contrast, the
rats with granule cell loss remembered an old place and learned a new
place as quickly as controls. These results suggest that a normal comp
lement of dentate granule cells may not be necessary for the acquisiti
on or retention of spatial information in the Morris water maze.