Cochlear blood flow autoregulation in Wistar-Kyoto rats

Area of Science:

• Otoacoustic emissions and inner ear physiology
• Vascular physiology and autoregulation
• Renal and cardiovascular pharmacology

Background:

• Cochlear blood flow (CoBF) is crucial for inner ear function.
• Autoregulation mechanisms in the cochlea are not fully understood.
• The role of angiotensin II (AII) in cochlear hemodynamics requires further investigation.

Purpose of the Study:

• To investigate the autoregulation of cochlear blood flow (CoBF) in Wistar-Kyoto rats (WKY).
• To determine the specific role of angiotensin II (AII) in modulating CoBF.
• To explore the involvement of vascular angiotensin receptors in CoBF regulation.

Main Methods:

• Intra-arterial infusion of vasoactive agents (angiotensin II, phenylephrine) in WKY rats.
• Laser Doppler flowmetry to measure cochlear blood flow (CoBF).
• Direct infusion of AII into the anterior inferior cerebellar artery (AICA) and administration of angiotensin receptor antagonist (sarthran).

Main Results:

• Systemic infusion of AII and phenylephrine initially increased CoBF, followed by a return to baseline despite elevated blood pressure, indicating autoregulation.
• Direct AICA infusion of AII significantly reduced CoBF without altering systemic blood pressure.
• Sarthran pretreatment attenuated AII-induced reductions in CoBF, implicating angiotensin receptors.

Conclusions:

• Cochlear blood flow (CoBF) in Wistar-Kyoto rats exhibits autoregulation.
• Angiotensin II (AII) directly causes vasoconstriction in cochlear vasculature.
• Vascular angiotensin receptors play a role in the autoregulation of CoBF.