PERINATAL HYPOXIC INJURY MODULATES NEURONAL AND EXTRACELLULAR MATRIX ORGANIZATION IN THE ADULT MIDCINGULATE CORTEX IN RATS

This study examines the effects of short-term perinatal hypoxia in rats on the morphology, distribution, and number of NeuN-positive neurons (NeuN⁺), parvalbumin-positive neurons (PV⁺), perineuronal net (PNN) – PV colocalization, and total PNNs in the cortical layers of mature midcingulate cortex (MCC). Forty-eight Wistar Han (RccHan: WIST) rat pups (P1) were randomly assigned to hypoxic or control groups, with sexes equally distributed. Animals were exposed for 2h in a heated chamber to hypoxia (pO_₂ 9.73kPa; p^ATM 46.66kPa) or normoxia (pO_₂ 21.20kPa; p^ATM 101.33kPa). At 3.5 months of age, brain sections were triple-immunofluorescence-stained and analysed for WFA-positive PNNs and colocalization with NeuN⁺ and PV⁺ neurons in the MCC (bregma −1.56 to −1.92mm according to the Paxinos and Watson atlas). PNNs displayed a more reticular and condensed morphology in layers II, III, Va, and Vb, and were significantly more numerous following hypoxia. PV⁺ neurons were also significantly increased in the hypoxic group, especially in layer I. PNNs surrounded PV⁺ neurons throughout the MCC. However, following hypoxia, more numerous PNNs were observed that did not associate with PV⁺, but instead surrounded NeuN⁺ neurons in layers II, III, Va, and Vb. These findings indicate that perinatal hypoxia induces permanent, structural, cortical-layer-specific neuronal and ECM reorganization in MCC as a plasticity response to a moderate lesion.
(Acknowledgements: Croatian Science Foundation: HRZZ-IP-2024-05-4135 and DOK-NPOO-2023-10-7312; PK.1.1.10.0009.)