Figure 6.

An orchestrated set of paracrine interactions mediates adult HVC neurogenesis. This schematic highlights the role of HVC MMP2 during testosterone-induced neuronal recruitment by the adult HVC. Together with the gonadal steroid-mediated induction of both VEGF and its receptor VEGFR2/flk1, which leads in turn to angiogenesis and BDNF production by the activated microvascular bed, the androgen-triggered vascular production of MMP2 appears to comprise a critical gate-keeping step, that establishes the permissiveness of the adult brain parenchyma to accept new neuronal immigrants (adapted in part from Louissaint et al., 2002).