Acute stress induced modifications of calcium signaling in learned helpless rats

Previous reports have demonstrated reduced elevations of free intracellular calcium concentration in blood cells of depressed patients after Various s timuli. Therefore, a disturbance of intracellular calcium (Ca2+) homeostasi s has been postulated to be involved in the pathophysiology of mood disorde rs. It was the aim of the present study to investigate whether Ca2+ signali ng was affected in spleen T-lymphocytes of Fats submitted to a learned help lessness paradigm, an animal model of depression with a high level of const ruct, face and predictive validity. In addition, we tested for effects of a cute stress on the Ca2+ signaling in helpless rats, as compared to non-stre ssed rats. It was found that mitogen-induced Ca2+ signaling only tended to be reduced in helpless rats. However, when helpless rats were submitted to acute immobilization stress, Ca2+ signaling appeared to be significantly bl unted, whereas the same stresser did not affect Ca2+ signaling in the non-h elpless control rats. These acute stress-induced differences in Ca2+ signal ing were not paralleled by a differential increase in plasma corticosterone . It is hypothesized that blunted Ca2+ signaling, as assessed in spleen T-l ymphocytes of helpless rats, may be a correlate of the increased vulnerabil ity of helpless rats to acute stressors.