Background

Currently, chronic brain hypoperfusion (CBH) is considered as a preclinical condition of mild cognitive impairment, which is thought to precede dementia (Ruitenberg et al., 2005; Gorelick et al., 2011). However, how CBH produces dementia is largely unknown.

The method of permanent occlusion of bilateral common carotid arteries (2VO) in rat was first established in the 1970s (Eklof and Siesjo, 1972). Since 2VO in rats provokes CBH without motor dysfunction, it is considered as a suitable animal model to elicit CBH status (Tanaka et al., 1996). After the 2VO procedures, three phases are theoretically determined by the degree of cerebral blood flow (CBF) and metabolic changes of rats (Farkas et al., 2007). After initiation of 2VO procedures, the first phase of acute ischemia lasts for about 2-3 days (Ohta et al., 1997; Otori et al., 2003; Tomimoto et al., 2003). During this period, the CBF drops dramatically and remains at a significantly low level in the following 4 weeks with reduced glucose utilization (Otori et al., 2003), sudden depletion of ATP and phosphocreatine (Plaschke, 2005). The second phase lasts for 8 to 12 weeks and corresponds well with the CBH in aging and dementia, and a slight reduction of the CBF with restored ATP as well as remaining low level of phosphocreatine. However, in the final phase, the CBF recovers to the baseline and the metabolic changes gradually cease after 6 months of 2VO (Ohta et al., 1997; Otori et al., 2003).

We also noted that numerous studies using 2VO rat model also reveal lots of pathological characteristics, including impaired learning and memory evaluated by both Morris water maze or eight-arm radial maze, where the 2VO rats display longer escape latencies to find hiding platform in Morris water maze (Liu et al., 2005) and commit more errors to enter a never-baited arm than the rats from sham group in the eight-arm radial maze (Sopala and Danysz, 2001); the neuronal cell death in hippocampus (Farkas et al., 2004); reduced dendritic arborizations (Chen et al., 2017); astrocytic reactions (Panickar and Norenberg, 2005) and microglial activation (Abraham and Lazar, 2000), etc. All these phenomena provide the sounded evidence that 2VO rat model is a valuable animal model to study the molecular mechanism of CBH associated diseases. In this protocol, we describe the detailed procedures of how to successfully establish a rodent model of CBH by permanently ligating the bilateral common carotid arteries of rat. And this protocol was based on and modified from the previously published paper: Kumaran et al., 2008.