Abstract
The cellular and spatial distribution of the presumptive retrograde transmitter nitric oxide, detected by NADPH-diaphorase histochemistry and of immunocytochemically labeled monoaminergic fiber systems was compared in regions of the medial prefrontal cortex of the precocious rodent Octodon degus. The staining patterns at two postnatal stages (PO and P14) were compared to those found in adult animals (P90). At birth, NADPH-diaphorase positive neurons were found in all cortical layers of the anterior cingulate, infralimbic and prelimbic cortex. During postnatal development the number of diaphorase-positive cells gradually decreased in layers II-VI and remained unchanged in layer I of these cortical regions. All NADPH-diaphorase positive neurons appeared to be spineless and pyramidal cells never contained NADPH-diaphorase. No colocalization of NADPH-diaphorase with either serotonin or TH was detectable. However, at all developmental stages the somata and proximal dendritic shafts of some of the NADPH-diaphorase containing bi-or multipolar neurons in layers V-VI were contacted by serotonin-and tyrosine hydroxylase-immunoreactive fibers. In a subpopulation of GABAergic interneurons in the deeper layers (V-VI) NADPH-diaphorase activity was colocalized with calbindin-D 28 k immunoreactivity.The abundance of nitridergic systems in regions of the medial prefrontal cortex already at birth together with their close spatial relationship with monoaminergic afferent systems as well as local GABAergic units may indicate a yet to determine role of these transmitter systems in early learning.
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