Histochemical and morphometric studies of perfneuronal nets in the retrosplenial cortex of albino rat

ABSTRACT

Reticular or net-like perineuronal coatings, termed perineuronal nets [PNs], enriched with proteoglycans [PGs] and/or glycoproteins [GPs] were demonstrated to ensheath cell surfaces of certain neuronal circuits in the central nervous system of mammals, reptiles and fishes. In this investigation, three types of coated neuronal circuits were histochernically demonstrated in the adult rat retrosplenial cortex [RSC]; PGs-, GPs- and PGs/GPs- coated neuronal types. The PGs coated neurons were histochemically detected with a cationic iron colloid [CIC] staining or CIC/Bodian enhancement procedure. The GPs coated ones were detected with certain plant lectins from Vicia villosa agglutinin VVA Wisteria florihunda agglutinin WFA or Glycine max agglutinin SBA for N-acetylgalactosamine-binding. The netassociated neurons were mostly distributed throughout the cortical layers II-V Their mean number per UA [60.15 micro M[2] was ranged from 9.87 +/- 0.43-10.50+2.61 in 8-month old rat and forming about 24-26% of total neuronal population. Statistical Analysis revealed that the mean numbers of PGs, GPs and PGs/GPs coated cells were 0.84 +/- 0.07, 6.33 +/- 0.34 and 2.70 +/- 0.22, respectively. Their percentages represented about 9%, 64% and 27% of total coated neurons in RSC, respectively. Notably, the labeled retrosplenial neurons underwent a non-significant increase in number with progression of age during the first post natal year; however, they declined thereafter toward senility. This data indicated that the extracellular matrix of net- associated retrosplenial neurons in adult albino rat was enriched with GPs and/or PGs molecules and this neurochemical heterogeneity might have diverse biological and functional properties of the neurons in RSC