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Brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT3) are homologs of the well-known neurotrophic factor nerve growth factor. The three members of this family display distinct patterns of target specificity. To examine the distribution in brain of messenger RNA for these molecules, in situ hybridization was performed. Cells hybridizing intensely to antisense BDNF probe were located throughout the major targets of the rat basal forebrain cholinergic system, that is, the hippocampus, amygdala, and neocortex. Strongly hybridizing cells were also observed in structures associated with the olfactory system. The distribution of NT3 mRNA in forebrain was much more limited. Within the hippocampus, labeled cells were restricted to CA2, the most medial portion of CA1, and the dentate gyrus. In human hippocampus, cells expressing BDNF mRNA are distributed in a fashion similar to that observed in the rat. These findings point to both basal forebrain cholinergic cells and olfactory pathways as potential central targets for BDNF.

In the course of the development of the ovarian follicle and differentiation of granulosa cells into corpus luteum (CL), extensive changes in the microvasculature of these structures take place. This suggests the local release of angiogenic factors. In the present work we examined whether a newly described secreted vascular endothelial growth factor (VEGF) is expressed in normal rat ovary by in situ hybridization. Our results demonstrate the expression of VEGF in the CL but not in mural granulosa cells, suggesting a temporal relation between VEGF expression and growth of capillary vessels. The hybridization pattern in the CL was consistent with localization of VEGF message to luteal cells. Expression of VEGF was detected also in cumulus oophorus cells. These findings suggest that VEGF is involved in the process of CL angiogenesis.

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