Neuroprotective Properties of Inhaled Argon-Oxygen Mixture after Photochemically Induced Ischemic Stroke

The aim of this study was to investigate the effects of three 60-minute inhalations of an argon-oxygen gas mixture (Ar 70%/O₂ 30%) on the severity of neurological deficits, brain lesion volume, inflammatory and cellular responses, and cytokine levels in rats after photochemically induced ischemic stroke. Materials and Methods. The experiment was performed in 21 male Wistar rats (250–300 g) randomly assigned to three groups: (1) ischemia + N₂ 70%/O₂ 30% inhalation (ischemia group, N =10); (2) ischemia + Ar 70%/O₂ 30% inhalation (ischemia + iAr group, N =8); and (3) sham-operated animals (sham group, N =3). Neurological status was assessed over 14 days using the limb placement test. On day 14 post-ischemia, animals underwent magnetic resonance imaging (MRI), histological and immunohistochemical analyses, and RT-PCR using RNA extracted from the liquid homogenate of the entire brain to evaluate the relative levels of IL-1β, IL-6, and TNF mRNAs. Results. Significant differences in limb placement test scores were observed between ischemia and ischemia + iAr groups on day 3 (7.3 [5.3; 10.4] vs. 9.9 [10.2; 13.2], P =0.045) and day 7 (8.0 [7.3; 9.2] vs. 10.0 [9.0; 11.5], P =0.027). MRI showed a significantly smaller ischemia volume in the ischemia + iAr group compared to the ischemia group (12.5 [8.5; 17.4] mm³ vs. 21.0 [17.5; 22.68] mm³, P =0.01). Pro-inflammatory cytokine levels were significantly lower following argon-oxygen inhalation: IL-1β — 205 [175.5; 247.5] in the Ischemia + iAr group vs. 328.5 [299; 347.5] in the Ischemia group ( P =0.001); TNF — 110.5 [93.5; 113] vs. 149.5 [126.5; 176.5], respectively ( P =0.001). Conclusion. Repeated 60 min inhalation of argon-oxygen mixture (Ar 70%/O₂ 30%) after photochemically induced ischemic stroke significantly reduces neurological impairment, modulates pro-inflammatory cytokine levels, and affects inflammatory and cellular responses.