Melanocortins produce neuroprotection against
ischemic stroke with subsequent long-lasting functional recovery, through
melanocortin MC(4) receptor activation. Here we investigated whether the long-lasting beneficial effect of
melanocortins in
stroke conditions is associated with a stimulation of neurogenesis. Gerbils were subjected to transient global
cerebral ischemia by occluding both common carotid arteries for 10 min; then, they were prepared for
5-bromo-2'-deoxyuridine (
BrdU) labeling of proliferating cells.
Delayed treatment (up to 9 h after the ischemic injury) for 11 days with the
melanocortin analog [Nle(4),D-Phe(7)]α-
melanocyte-stimulating hormone (NDP-α-
MSH) improved learning and memory throughout the 50-day observation period. Immunohistochemical examination of the hippocampus on day 50 showed, in the dentate gyrus, an elevated number of
BrdU immunoreactive cells colocalized with NeuN (used as
indicator of mature neurons) and Zif268 (used as
indicator of functionally integrated neurons). Retrospective analysis during the early stage of neural stem/progenitor cell development (days 3 and 4 after
stroke) showed, in NDP-α-
MSH-treated gerbils, a high degree of daily cell proliferation and revealed that NDP-α-
MSH favorably affects Wnt-3A signaling pathways and doublecortin expression. Pharmacologic blockade of MC(4) receptors prevented all effects of NDP-α-
MSH. These data indicate that treatment of
cerebral ischemia with MC(4) receptor agonists induces, with a broad window of therapeutic opportunity, long-lasting functional recovery associated with a large number of mature and likely functional newborn neurons in brain injured areas. Our findings reveal previously undescribed effects of
melanocortins which might have major clinical implications.