Chronic cerebral hypoperfusion (CCH) is associated with cognitive decline in aging, Alzheimer's disease and vascular dementia. Neural oscillations and their interactions support brain communication and involve in cognitive function. Although arginine vasopressin (AVP) has been linked to spatial learning and memory, the effects of AVP on CCH in terms of the hippocampal neural network is unknown. Here we investigated the dynamics of neural oscillations in the hippocampus in a rat model of permanent bilateral carotid arteries occlusion (two-vessel occlusion, 2VO) under urethane-anesthesia. Hypertonic saline (5.3%) was injected intraperitoneally to induce the endogenous AVP, and SR49059 was used as V1a receptor (an AVP receptor) antagonist. The results showed that AVP partly changed CA3 Schaffer collateral (CA3-SC) power distribution in the rat model of 2VO via V1a receptor, increased theta synchrony between CA3-SC and CA1 areas, enhanced CA3-SC theta-middle gamma phase-phase coupling, and improved spatial learning and memory performance. Biochemical fractionation further confirmed the recovery effect on N-methyl-D-aspartate receptor subunit 2B (NR2B) and postsynaptic density protein 95 (PSD-95) surface expressions after hypertonic saline injection, suggesting a possible molecular mechanism in the hippocampus. The findings shed light on a functional role of endogenous AVP from a neural network perspective that AVP improves theta synchronization and accurate coordination of theta-gamma coupling probably through upregulating NR2B and PSD-95 expressions, and further promotes neural communication in the hippocampus to some extent. As a result, the impairment of spatial learning and memory induced by CCH is significantly alleviated.
Keywords: Arginine vasopressin (AVP); Chronic cerebral hypoperfusion (CCH); Cross-frequency coupling; Synchronization; Two-vessel occlusion (2VO).
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