Brain Natriuretic Peptide (BNP) injections in adult "healthy" or infarcted mice led to increased number of non-myocyte cells (NMCs) expressing the nuclear transcription factor Nkx2.5. The aim of this study was to identify the nature of the cells able to respond to BNP as well as the signaling pathway involved. BNP treatment of neonatal mouse NMCs stimulated Sca-1 ⁺ cell proliferation. The Sca-1 ⁺ cells were characterized as being a mixed cell population involving fibroblasts and multipotent precursor cells. Thus, BNP treatment led also to increased number of Sca-1 ⁺ cells expressing Nkx2.5, in Sca-1 ⁺ cell cultures in vitro and in vivo, in the hearts of neonatal and adult infarcted mice. Whereas BNP induced Sca-1 ⁺ cell proliferation via NPR-B receptor and protein kinase G activation, CNP stimulated Sca-1 ⁺ cell proliferation via NPR-B and a PKG-independent mechanism. We highlighted here a new role for the natriuretic peptide receptor B which was identified as a target able to modulate the proliferation of the Sca-1 ⁺ cells. The involvement of NPR-B signaling in heart regeneration has, however, to be further investigated.