A non-invasive rat model of perinatal mild hypoxic brain damage

We aim to introduce a non-invasive perinatal mild hypoxic brain lesion in rats. Nineteen Wistar Han® (RccHan®: WIST) rats, (9 females and 10 males) were randomly divided into hypoxic and control group on postnatal day 1 (P1) when hypoxia was induced in a hypobaric chamber (Atm350mmHg, pO273mmHg, temperature ≈ 25°C) during 2 hours, while controls were kept in normal housing conditions. Behavioral tests were performed at P30 and P70 using the open field, hole board, social choice, and T-maze tests. Samples of brain tissue from adult animals (P105) were used for histochemical examination of the cytoarchitectonics (Nissl staining), interneurons (parvalbumin immunohistochemistry) and perineuronal nets (Wisteria floribunda agglutinin, histochemistry). After short-term perinatal rat brain injury, there were no disturbances in the brain macro-morphology or any other pathoanatomical consequence of the treatment. Also, treated animals had intact exploratory, anxiety-like and social behavior. Still, distinct changes in morphology, number, and distribution of the parvalbumin-immunoreactive neurons and perineuronal nets in different brain regions were observed. Moreover, treated animals displayed significantly impaired learning. In conclusion, the proposed rat model of non-invasive hypoxic brain lesion has indicated consistent disturbances in brain connectivity related to cognitive processes, mimicking perinatal mild post-hypoxia condition in humans. Further characterization and evaluation of the model, on molecular, cytological, and connectivity levels is needed. The study was co-financed by the European Union through the European Regional Development Fund, Operational Programme Competitiveness, and Cohesion, grant agreement No. KK.01.1.1.01.0007, CoRE – Neuro, University of Zagreb Support BM054 and Croatian Science Foundation.