| CHRONIC IMMOBILIZATION STRESS ALTERS MEASURES OF EMOTIONALITY
IN THE RAT |
| G.E.Wood1*; E.H.Norris2;
J.Gal1; E.M.Waters1; C.J.Wang1; B.S.McEwen1
|
| 1. Lab of Neuroendocrinology, 2. Lab of Neurobiology &
Genetics, Rockefeller Univ, New York, NY, USA |
|
Chronic immobilization stress (2 h/ day for 10 days)
alters dendritic length and branch point number on neurons in the
rat hippocampus and amygdala. Chronic restraint stress (6 h/day for
21 days) also alters neurons in these limbic brain regions, and potentiates
several measures of emotionality in rats. Chronic restraint stress
potentiates fear conditioning (Conrad et al., 1999), as well as the
incidence of aggressive conflicts after stress exposure (Wood, et
al. 2003). Thus, we tested if chronic immobilization stress would
similarly alter measures of emotionality after 10 days of immobilization
stress. Here we report that chronic immobilization stress significantly
potentiates contextual (P < 0.05), but not cued (P = 0.125) fear
conditioning in stressed rats compared to unstressed controls. In
addition, the chronic stress treatment significantly increased the
incidence of aggressive conflicts between familiar cagemates. Thus,
chronic immobilization stress significantly potentiates several measures
of emotionality. Aggressive behavior was recorded after release from
restrainers on day 1 (acute stress) and day 10 (chronic stress) among
stress rats, as well as unstressed control rats on the same days.
There is a significant increase in aggressive responses observed after
10 days of stress (P < 0.05), relative to unstressed controls.
The baseline, contextual, and cued aspects of fear conditioning were
measured over several days following the cessation of stress. A lasting
effect on emotionality was expected, as this stressor induces long
lasting changes in the amygdala. These data suggest that chronic immobilization
stress potentiates some of the same measures of emotionality as chronic
restraint stress, despite the substantial difference in time exposed
to the stressor (i.e., 10 versus 21 days). Furthermore, we consider
the relationship between behavioral strategies observed among stressed
and unstressed rats, and the reported effects on emotionality.
Support Contributed By: MH58911 (GEW), MH 41256 (BSM)
|
 |
|
|
|
