Contribution of the anterior inferior cerebellar artery to cochlear blood flow in guinea pig: A model-based analysis

This study was performed to determine the contribution of the anterior inferior cerebellar artery (AICA) to cochlear blood flow (CBF) in guinea pig. The AICA and the basilar-vertebral arterial complex in twelve animals was exposed through the basal portion of the skull. The cochlea was ventrally approached and the CBF of the apical area monitored with laser Doppler flowmetry. A specially designed microclamp was held in a micromanipulator and used to obstruct the AICA. When the AICA was clamped, CBF decreased to approximately 60% of baseline (BL) (not to 'biological zero'), followed by a gradual increase. When the clamp was released, CBF quickly increased to more than 160% BL and then slowly declined to baseline. To quantify the contribution of AICA to CBF, we formulated an electrical analog model of the cochlear vessel system. With this model, AICA contribution to CBF and the relationship among blood pressure, blood flow, and vascular resistance or vascular conductance in the cochlea can be explored. Results in the present study indicate that the AICA contributes only about 45% of CBF to the cochlea; 55% of CBF must come from other supplying vessels. Contrary to previous reports, CBF response to AICA clamping did not exhibit a stable or constant decrease but showed time-dependent dynamic changes. In addition, the cochlear vascular system showed a marked autoregulatory response, instead of a passive response, to the perfusion pressure change. AICA clamping is, therefore, not a suitable model for investigation of ischemia effects in the guinea pig cochlea, but it is a useful approach to study autoregulation and the myogenic mechanism of the cochlear vascular system.