Dexamethasone induces different morphological changes in the dorsal and ventral hippocampus of rats

Dexamethasone (DEX), a synthetic glucocorticoid widely used in neurological illnesses because of its antiinflammatory properties, has many serious side effects, including severe psychiatric symptoms such as psychoses. The hippocampus is divided in the dorsal hippocampus (DH) and ventral hippocampus (VH) with each region having a subfield of CA1 and CA3 pyramidal layers. Great interest has recently emerged showing that the DH and VH are functionally different. In our work we determined whether, and what, changes occurred, after five days of DEX (0.2 mg/kg) treatment, on the dendritic morphology of the CA1 and CA3 pyramidal neurons of the DH and VH of adult Sprague-Dawley rats. The dendritic morphology and characteristics were measured by using the Golgi-Cox procedure followed by a Sholl analysis. DEX decreased the number of dendritic spines of both apical and basolateral dendrites. Interestingly, this decrease was more pronounced in the VH. Only the VH neurons were affected by DEX with a decrease in their total dendritic length (TDL). An interesting point is that the VH neurons are longer that the DH neurons among the groups injected with saline only as the control. The length per branch order was only altered in the apical dendritic tree of the CA1 neurons. These data taken together show that the VH is more susceptible to DEX and its neurons are larger than the DH neurons. These results support previous observations related to differences between the DH and VH and suggest differences in the expression of the glucocorticoid receptors in connectivity and the space to elongate their dendritic arbor.

► Dexamethasone induces morphological changes in pyramidal neurons of hippocampus.
► Dexamethasone effect is different in CA1 and CA3 pyramidal neurons of dorsal hippocampus and CA1 and CA3 pyramidal neurons of ventral hippocampus.
► Total dendritic length of apical and basilar trees of ventral CA3 neurons is bigger than dorsal CA3 neurons in vehicle groups.
► Dexamethasone induces a decrease of dendritic spine density in pyramidal neurons of dorsal and ventral hippocampus.