Tail artery response to sound in the unanesthetized rat.

Arterial pulsations have been recorded indirectly from the surface of the rat's tail. Slight heating of restrained unanesthetized rats produces vasodilatation and large amplitude pulsations that are influenced by sensory stimuli, in this case, sound. The surface-recorded pulse volume was found to be proportional to pulse pressure, indicating vasoconstriction as the cause of the decline of the pulse amplitude. A one-second noise burst elicited vasoconstriction, the duration of which was proportional to sound level and occurred as low as at hearing threshold. Under the specified conditions, reproducibility was good with no significant habituation both within session, and between sessions with a one week interval. The warming of the rats was found to be critical for the sound-elicited reactions; responses were obtained only within a narrow, individual temperature-range. The possibilities of using tail vasoconstriction for evaluation of hearing was pointed out, as well as for studies of noise effects on peripheral circulation.