The Expression of Connexins during Growth and Development of Skeletal Elements in the Dog

The brain extracellular matrix (ECM) has attracted growing interest due to its highly regulated spatiotemporal expression during development and maturation of central nervous system. The present study deals with the post-natal appearance and transformation into adult distribution patterns of the ECM components related to proteoglycans (PGs) and glycoproteins (GPs) in the retrosplenial cortex (RSC) of albino rats at birth (P0), 1 week (P1), P2, P3, P4, P5, P6, P7 and P8. The differentiating PGs and GPs components of the ECM were shown to make their appearance as early as 1–2 weeks post-natally. At this developmental stage, these components of the ECM appeared in association with some neurons and glia cells or diffusely localized at the neutrophill. Interestingly, Golgi complexes of labelled neurons were usually stained with lectin VVA or WFA, and this labelling dramatically disappeared on reaching P4. During P2–3, the pericoated neuronal cells underwent a progressive increment in number, and presented an inside-out pattern of migration and differentiation (toward the V-II cortical layers). On reaching P4, most of the coated neurons appeared distributed into the cortical layer IV and II. At a later stage (P5–8), the overall density and intensity of labelled neurons progressively increased and apparently reached the adult stage of development. They also displayed the usual differential labelling characteristics, after using the cationic iron colloid/lectin staining, for the first time at this juncture. The present findings indicated that the perineuronal ECM components are significantly correlated with age and suggest a possible developmental or biological significance including promotion of migration, as well as functional maturation of the retrosplenial neurons.