Quantitative Histochemical Study of Perineural Nets in the Retrosplenial Cortex of Albino Rats

Abstract

Reticular or net‐like perineuronal coatings enriched with proteoglycans (PGs) and/or glycoproteins (GPs) were demonstrated to ensheathe cell surfaces of certain neuronal circuits in the central nervous system of mammals, reptiles and fishes. In this investigation the coated or ensheathed neurons in the retrosplenial cortex (RSC) of adult albino rats were quantified using a computerised analysing system. They were distributed throughout the II–IV cortical layers and comprised about 24.25% of total neurons. The perineuronal coatings were expressed with a cationic iron colloid (CIC), CIC/Bodian staining and with certain plant lectins from Vicia villosa agglutinin ‘VVA’, Wisteria floribunda agglutinin ‘WFA’ and Glycine max agglutinin ‘SBA’. The mean number of coated neurons per unit area (UA, 60.15 μm2), as labelled by CIC or CIC/Bodian, VVA, WFA and SBA staining was 4.01 ± 0.42, 4.43 ± 0.37, 6.45 ± 0.87, 5.70 ± 0.73 and 3.91 ± 0.53, respectively. In addition, labelling indicated by the aforementioned stains were 10.55%, 11.55%, 16.97%, 15.00% and 10.23%. Notably, the labelled retrosplenial neurons underwent a non‐significant increase with progression of animal age at the first post‐natal year. However, they declined thereafter toward senility. Qualitatively, there were three types of coated neuronal circuits at the RSC of rats: PGs‐, GPs‐ and PGs/GPs‐ coated cells, which comprised 9%, 64% and 27%, respectively. This data indicated that the GPs‐ and GPs/PGs‐ coated neurons in the RSC of albino rats were more prevalent than the PGs‐ coated ones.