Chronic restraint stress for 6 h/21 days causes hippocampal CA3 apical dendritic retraction,
which parallels spatial memory impairments in male rats. Recent research suggests
that chronic immobilization stress for 2 h/10 days induces CA3 dendritic retraction
[Vyas, A., Mitra, R., Shankaranarayana Rao, B.S., Chattarji, S., 2002. Chronic stress
induces contrasting patterns of dendritic remodeling in hippocampal and amygdaloid
neurons. J. Neurosci. 22, 6810-6818.] and questions whether CA3 dendritic retraction
and spatial memory deficits can be produced sooner than found following 6 h/21 days
of restraint stress. Therefore, this study investigated the effects of four different
durations of chronic restraint stress (varied by hours/day and total number of days)
and the subsequent effects on hippocampal CA3 morphology and spatial memory in the
same male Sprague-Dawley rats. The results showed that only rats exposed to the 6
h/21 days restraint paradigm exhibited CA3 apical dendritic retraction, consistent
spatial memory deficits, and decreased body weight gain compared to experimental counterparts
and controls. While chronically stressing a rat with wire mesh restraint has a physical
component, it acts primarily as a psychological stressor, and these findings support
the interpretation that chronic psychological stress produces hippocampal-dependent
cognitive deficits that are consistent with hippocampal structural changes. Differences
in stress effects observed across different studies may be due to rat strain, type
of stressor, and housing conditions; however, the current findings support the use
of chronic restraint stress, with wire mesh, for 6 h/21 days as a reliable and efficient
method to produce psychological stress and to cause CA3 dendritic retraction and spatial
memory deficits in male Sprague-Dawley rats.