Hypothermia protects somatostatinergic neurons in rat dentate hilus from zinc accumulation and cell death after cerebral ischemia.

We have previously shown that somatostatin (SS) immunoreactive (-i) neurons, located in the rat dentate hilus, are vulnerable to cerebral ischemia (Johansen et al., 1987). Within 40 h after ischemia, the cells show clear signs of cell death. At the same time, we observed that dying cells, located in the projection field of the mossy fibers (dentate hilus and CA3 mossy fiber layer), accumulate free zinc. We now demonstrate that the hilar cells, accumulating zinc after ischemia, are SS-i cells. Since it is known that hypothermia can ameliorate ischemic brain damage, we furthermore studied whether hypothermia (29 degrees C) protects the vulnerable SS-i neurons in hilus from zinc accumulation and ischemic cell death. We found that hypothermia both prevented ischemia-induced neuronal zinc accumulation and cell death. We speculate that hilar SS-i cells are highly vulnerable to ischemia, and develop rapid ischemic cell death, because they accumulate zinc shortly after ischemia.