Permanent, 3-stage, 4-vessel occlusion as a model of chronic and progressive brain hypoperfusion in rats: a neurohistological and behavioral analysis.

Permanent, 3-stage, 4-vessel occlusion (4-VO) was evaluated as a practicable model of progressive, cerebral hypoperfusion in rats, resulting in quantifiable, reproducible, neuronal damage within a time interval shorter than that described in the 2-VO model. The effect of permanent and graded 4-VO on cognition was also evaluated using the newly developed, aversive radial maze. The vertebral arteries (VA) plus the common carotid arteries (CCA) or internal carotid arteries (ICA) were progressively and permanently occluded, following different experimental sequences (CCA--> VA; VA-->CCA-->CCA or VA-->ICA-->ICA) with inter-stage intervals ranging from 1 to 4 weeks. Only two of four groups subjected to 2-stage 4-VO (CCA-->VA) showed modest reduction in the number of normal-appearing CA1 pyramidal cells, despite the significant treatment effect (p < 0.001-0.01 versus sham). A high rate of mortality (63.8%) was associated with 2-stage 4-VO. More pronounced and consistent neuronal damage occurred 8 weeks after 3-stage 4-VO, following the sequence VA --> CCA --> CCA (p < 0.001). One month after this schedule, profound, persistent cognitive impairment was demonstrated in the aversive radial maze (p < 0.01-0.0001). This behavioral effect was not manifested when the ICA, rather than the CCA, were occluded, despite the presence of significant, although less severe, hippocampal lesioning. The mortality rate was significantly reduced when 3-stage 4-VO was used (p < 0.0001). These consistent, histological and behavioral effects, combined with a low mortality rate, suggest that permanent, 3-stage 4-VO may represent a reliable animal model of chronic, progressive, cerebral hypoperfusion.