Laser Doppler imaging of changes in cerebral blood flow during acute carotid occlusion

Objective: To determine by laser Doppler imaging (LDI) the spatial and temp oral characteristics of the changes in cerebral blood flow (CBF) in respons e to electrical forepaw stimulation in rats before and during acute unilate ral carotid occlusion, Background Data: Single laser Doppler (LD) probes pr ovide a minimally invasive approach for measuring CBF changes due to functi onal stimulation. Using an electrical forepaw stimulation model in rats, we have previously demonstrated a prolongation in the temporal dynamics of th e CBF response during acute mechanical carotid occlusion, However, the spat ial resolution of this model system was limited by the diameter of the sing le LD probe. Recently, we have successfully used LDI, which uses an optical ly driven low power laser beam to measure CBF changes in two dimensions, to investigate the spatial and temporal changes in CBF due to forepaw stimula tion. Methods: LDI was used to measure the spatial and temporal characteris tics of the changes in CBF response in alpha-chloralose anesthetized rats ( n = 5) both before and during acute unilateral occlusion of the common caro tid contralateral to the forepaw stimulated. Results: Acute mechanical occl usion of the common carotid contralateral to the forepaw stimulated did not affect the area of activation due to functional stimulation. However, the amplitude of the CBF response was significantly reduced compared to prior t o occlusion, Further, acute occlusion led to a significant prolongation of temporal dynamics of the CBF response. These observations are in agreement with previous results we have obtained using a single LD probe, Conclusions : Our results suggest a promising role for the application of LDI to study the spatial and temporal characteristics of CBF changes in animal models an d may allow a diagnostic technique for testing patients with carotid occlus ion.