Reduced cell proliferation in the dentate gyrus is not correlated with the development of learned helplessness.
BACKGROUND
A plethora of indirect findings suggests that mood disorders may be caused by or result in structural changes in the brain, namely decreased hippocampal cell proliferation.


METHODS
To test for these hypotheses, we used a rat model of depression, learned helplessness. Moderate unpredictable and inescapable foot shocks induced learned helplessness only in a portion of the rats. Rats that showed helpless behavior were compared to those behaving normally after inescapable shock. Proliferating cells in the dentate gyrus were labeled with BrdU (bromodeoxyuridine).


RESULTS
Helpless behavior appeared before the decrease of dentate gyrus cell proliferation was maximal. Cell proliferation was decreased to the same extent in animals that developed helplessness as those that were not helpless. Furthermore, immobilization stress, which reduced the rate of cell proliferation, did not induce learned helplessness.


CONCLUSIONS
These results are in line with reports that the rate of dentate gyrus cell proliferation is acutely down-regulated by stress, but the development of helpless behavior does not correlate with this process. Further studies will have to clarify if during learned helpless behavior neurogenesis is impaired by altered differentiation or survival of cells.
Vollmayr
Barbara
B
Central Institute of Mental Health, Mannheim, Germany.
Simonis
Claudia
C
Weber
Silja
S
Gass
Peter
P
Henn
Fritz
F
D000704:Analysis of Variance; D000818:Animals; D001522:Behavior, Animal; D001973:Bromodeoxyuridine / Q000493:pharmacokinetics; D002452:Cell Count; D002455:Cell Division; D018891:Dentate Gyrus / Q000378:metabolism / Q000473:pathology* / Q000528:radiation effects; D004597:Electroshock / Q000379:methods; D006380:Helplessness, Learned; D007103:Immobilization; D007150:Immunohistochemistry; D008297:Male; D011838:Radiation-Sensitizing Agents / Q000493:pharmacokinetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors
D011838:Radiation-Sensitizing Agents; D001973:Bromodeoxyuridine