Chronic 3.5 GHz radiofrequency exposure is associated with behavioral, molecular, and histopathological changes in the rat hippocampus

Purpose: Chronic exposure to mid-band radiofrequency (RF) electromagnetic fields at 3.5 GHz is increasingly relevant to modern wireless environments; however, its effects on hippocampal circuit stability under non-thermal conditions remain unclear. We investigated whether prolonged 3.5-GHz RF exposure is associated with anxiety-like behavior and hippocampal transcript-level changes consistent with excitatory–inhibitory (E/I) imbalance, and whether thymoquinone (TQ) or taurine (TAU) are associated with modulation of these responses. Materials and methods: Adult male Wistar rats (n = 28) were assigned to Sham, RF, RF + TQ (20 mg/kg), or RF + TAU (20 mg/kg) groups (n = 7/group). Animals were exposed to a GSM-like 3.5-GHz RF signal (2 W; 2 h/day; 5 days/week; 10 weeks). Anxiety-like behavior and spatial learning were assessed using the Elevated Plus Maze (EPM) and Morris Water Maze (MWM). Hippocampal gene expression (bdnf, creb1, camk2a, th, tph2, gad1, slc17a7) was quantified by RT–qPCR, and histopathology by H&E staining. Results: Dosimetry indicated whole-body SAR of 0.0383 W/kg and brain gray matter SAR of 0.3411 W/kg. RF exposure was associated with reduced open-arm time in the EPM. Expression of slc17a7 increased in the RF group, suggesting a shift toward excitation. Under RF co-exposure conditions, TQ and TAU were associated with changes in slc17a7 expression and with increases in bdnf, creb1, and camk2a, along with inhibitory and monoaminergic markers. RF-exposed hippocampi showed neuronal degeneration, less pronounced in antioxidant-treated groups. Conclusions: Chronic non-thermal 3.5-GHz RF exposure is associated with anxiety-like behavior and a hippocampal molecular–structural profile consistent with E/I imbalance and tissue stress. TQ and TAU were associated with context-dependent changes under RF co-exposure conditions; however, due to the absence of antioxidant-only control groups, independent effects cannot be determined. These findings suggest that synaptic homeostasis may represent a potential target of prolonged mid-band RF exposure.