Ontogeny of the dopamine innervation in the nucleus accumbens of gerbils.

The postnatal maturation of immunohistochemically stained dopamine (DA) fibres was quantitatively examined in the core and shell subareas of the nucleus accumbens (NAC) of gerbils. Animals of different ages, ranging from juvenile [postnatal day (PD) 14, 30] to adolescent (PD70), adult (PD90, PD180, PD360) and ageing (PD540, PD720) were analysed. The timescale of the maturation of the accumbal DA innervation was regionally different, probably due to the different origin of DA fibres in the mesencephalon. Both the accumbal core, with DA afferents arising from the lateral ventral tegmental area (VTA) and the substantia nigra pars compacta, as well as the accumbal shell, with DA afferents arising from the medial VTA, show moderate DA fibre densities at PD14. The core displayed a significant decrease of the DA fibre density up to PD30 and a subsequent significant increase between PD70 and 90, whereas the shell solely showed an augmentation of the DA innervation between PD70 and 90. Our data suggest that the different maturation of the DA innervation in core and shell might reflect differences in the development of motor and limbic functions, mediated by the nigrostriate and the mesolimbic system, respectively.