Local neurovascular coupling in the amygdala is responsible for context-dependent emotional adjustment

Abstract

Proper brain function depends on intact neurovascular coupling (NVC). Through NVC, local cerebral blood flow (CBF) is rapidly increased in activated cerebral regions to meet the corresponding demands of neural activities. NVC has been believed to support advanced cerebral functions such as complex emotional homeostasis. However, few studies provide causal link evidence with specific molecular and cellular identities. Here, using RNAscope, cell-type specific conditional knockout (cKO) perturbation in BL6/C57 mice, laser speckle contrast imaging, and mouse behavior assays, we demonstrated that the N-methyl-D-aspartic acid (NMDA) receptor noncore subunit NR2D is only expressed in cerebral arteriole smooth muscle cells (aSMCs) but not in peripheral aSMCs. Both aSMC-NR2D cKO and aSMC-NR2D+NMDA receptor subunit 1 (NR1) double cKO mice displayed a severe decline in functional hyperemia induced by whisker stimulation. In addition, the NR2D pathway was independent of previously demonstrated COX-2-PGE2-dependent mechanism and high-fat diet (HFD)-induced impairments in NVC. Caldesmon is a potential downstream protein in the NR2D pathway for NVC regulation. Notably, we demonstrated that NVC deficits caused abnormalities in complex emotional behaviors, such as anxiety-like behaviors (exhibiting increased defecation and urine), reduced curiosity and decreased fear instinct (displaying less fear of aggressive CD1 mice). Furthermore, fear-response gene c-FOS expression in the amygdala neurons was attenuated in aSMC-NR2D knockout mice after response to acute stresses. In contrast, its expression level remained unchanged in the non-fear-related cerebral regions such as the piriform cortex and hippocampus. These findings demonstrated that inadequate functional hyperemia impaired cerebral complex emotional functions and suggested a co-existence of anxiety and fearlessness in single individuals.