Stereological Evidence of Non-Selective Hippocampal Neurodegeneration, Growth Factors Depletion, and Behavioral Deficit Following Short-Term Bilateral Adrenalectomy in Wistar Rats 

Abstract

In the current study we investigated the impact of short-term adrenalectomy on hippocampal neurons of Wistar rats. In addition, the underlying mechanism(s) of degeneration in these neurons was investigated by measuring the levels of insulin-like growth factor-1 and β-nerve growth factor. Moreover, we investigated the cognitive behavior in these rats. The stereological counting in the hippocampus revealed a significant neuronal death in the dentate gyrus and CA3, but not in the CA2 and CA1, area 7 and 14 days post adrenalectomy. The ultrastructural examinations revealed degenerated and degenerating neurons only in the dentate as well as CA4, and CA3 areas over the course of 3, 7 and 14 days. The levels of IGF-1 were significantly decreased in the hippocampus of ADX rats 12 h post adrenalectomy and lasted over the course of two weeks. However, β-NGF was significantly reduced in ADX rats only at 14 days postoperatively. Using passive avoidance test we found a cognitive deficit in the ADX compared to the sham operated rats over time. In conclusion, both granule and pyramidal cells were degenerated in the hippocampus following short-term adrenalectomy. The early depletion of IGF-1 might play a role in the hippocampal neuronal degeneration. Consequently, the loss of the hippocampal neurons after adrenalectomy leads to cognitive deficits.