海马结构
海马体
神经科学
树突棘
突触
神经油
激素
糖皮质激素
慢性应激
神经元
大脑大小
内分泌学
内科学
生物
心理学
医学
中枢神经系统
磁共振成像
放射科
作者
Despina Α. Tata,Brenda J. Anderson
标识
DOI:10.1016/j.physbeh.2009.09.008
摘要
Glucocorticoids (GCs) are hormones secreted by the adrenal glands as an endocrine response to stress. Although the main purpose of GCs is to restore homeostasis when acutely elevated, animal studies indicate that chronic exposure to these hormones can cause damage to the hippocampus. This is indicated by reductions in hippocampal volume, and changes in neuronal morphology (i.e., decreases in dendritic length and number of dendritic branch points) and ultrastructure (e.g., smaller synapse number). Smaller hippocampal volume has been also reported in humans diagnosed with major depressive disorder or Cushing's disorder, conditions in which GCs are endogenously and chronically elevated. Although a number of studies considered neuron loss as the major factor contributing to the volume reduction, recent findings indicated that this is not the case. Instead, alterations in dendritic, synaptic and glial processes have been reported. The focus of this paper is to review the GC effects on the cell number, dendritic morphology and synapses in an effort to better understand how these changes may contribute to reductions in hippocampal volume. Taken together, the data from animal models suggest that hippocampal volumetric reductions represent volume loss in the neuropil, which, in turn, under-represent much larger losses of dendrites and synapses.
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