Possible Involvement of Capsaicin-sensitive Sensory Nerves in the Regulation of Cochlear Blood Flow in the Guinea Pig

Abstract

Capsaicin-induced microcirculatory changes in the cochlea of anaesthetized guinea pigs were examined by laser-Doppler flowmetry. Close intraarterial capsaicin infusion into the anterior inferior cerebral artery at doses of 10–50 pmol/min was followed by dose-dependent vasodilatation. Capsaicin infused in a dose of 150–200 pmol/min or above resulted in vasoconstriction in the region examined. Topical capsaicin administration into the cochlea (50–150 pmol) resulted in very moderate vasodilation with a latency of 1–2min. Perivascular capsaicin application onto the anterior inferior cerebellar artery elicited an elevated blood flow in the cochlea, too. It is concluded that the release of vasoactive substances from capsaicin-sensitive nerve fibres in the inner ear of the guinea pig may play a role in the control of the local microcirculation. These nerves may also be involved in the neurogenic inflammatory processes in the region.

Key Words:

• capsaicin
• laser-Doppler flowmetry
• basilar artery
• anterior inferior cerebellar artery
• microperfusion