TY - JOUR
T1 - Responses of the endolymphatic sac to perilymphatic injections and withdrawals
T2 - Evidence for the presence of a one-way valve
AU - Salt, Alec N.
AU - Rask-Andersen, Helge
N1 - Funding Information:
We thank Dr. Robert Kimura, for loaning us the slides of one guinea pig inner ear specimen. We also appreciate the technical assistance of John DeMott in the collection of electrophysiological data, of Ingvor Forsberg for processing one of the histological specimens, and of Ruth Gill for photographing specimens and preparing illustrations. This work was supported by research grant RO1 DC01368 to Alec Salt from the National Institute on Deafness and Other Communication Disorders (NIDCD), National Institutes of Health and by grants to Helge Rask-Andersen from the Swedish Research Council (VR Proj. No. 3908) and Stiftelsen Tysta Skolan.
PY - 2004/5
Y1 - 2004/5
N2 - Although the endolymphatic sac (ES) is thought to be a primary site for endolymph volume regulation, we have limited knowledge of how it responds to volume and pressure changes. In a prior publication, we demonstrated changes of K+, Na+ and endolymphatic sac potential (ESP) resulting from volume injections into, and withdrawals from, scala media of the cochlea. In the present study, we compared the influence of injections into and withdrawals from scala tympani of the cochlea on the endolymphatic sac. It is assumed that similar pressure changes are induced in endolymph and perilymph of both the cochlear and vestibular compartments of the ear. Pressure changes induced by the perilymphatic injections and withdrawals did not induce similar K+ changes in the ES. The majority of perilymph withdrawals caused K+ and ESP reductions in the sac, but few injections caused any measurable changes in the sac. Pressure measurements from the ES demonstrated that transmission of labyrinthine pressures to the lumen was directionally sensitive, with negative pressure transmitted more effectively than positive. In other experiments, application of infrasonic stimulation to the ear canal resulted in K+ increase in the ES. These physiological measurements suggest that the endolymphatic duct may be closed by sustained positive pressure in the vestibule but open during pressure fluctuations. Study of the anatomy where the endolymphatic duct enters the vestibule suggests that the membranous sinus of the endolymphatic duct could act as a mechanical valve, limiting the flow of endolymph from the saccule to the endolymphatic sac when pressure is applied. This structure could therefore play an important role in endolymph volume regulation.
AB - Although the endolymphatic sac (ES) is thought to be a primary site for endolymph volume regulation, we have limited knowledge of how it responds to volume and pressure changes. In a prior publication, we demonstrated changes of K+, Na+ and endolymphatic sac potential (ESP) resulting from volume injections into, and withdrawals from, scala media of the cochlea. In the present study, we compared the influence of injections into and withdrawals from scala tympani of the cochlea on the endolymphatic sac. It is assumed that similar pressure changes are induced in endolymph and perilymph of both the cochlear and vestibular compartments of the ear. Pressure changes induced by the perilymphatic injections and withdrawals did not induce similar K+ changes in the ES. The majority of perilymph withdrawals caused K+ and ESP reductions in the sac, but few injections caused any measurable changes in the sac. Pressure measurements from the ES demonstrated that transmission of labyrinthine pressures to the lumen was directionally sensitive, with negative pressure transmitted more effectively than positive. In other experiments, application of infrasonic stimulation to the ear canal resulted in K+ increase in the ES. These physiological measurements suggest that the endolymphatic duct may be closed by sustained positive pressure in the vestibule but open during pressure fluctuations. Study of the anatomy where the endolymphatic duct enters the vestibule suggests that the membranous sinus of the endolymphatic duct could act as a mechanical valve, limiting the flow of endolymph from the saccule to the endolymphatic sac when pressure is applied. This structure could therefore play an important role in endolymph volume regulation.
KW - CSF, Cerebrospinal fluid
KW - ES, Endolymphatic sac
KW - ESP, Endolymphatic sac potential
KW - Endolymphatic hydrops
KW - Endolymphatic sinus
KW - Meniere's disease
KW - Saccule
UR - http://www.scopus.com/inward/record.url?scp=1942421779&partnerID=8YFLogxK
U2 - 10.1016/j.heares.2003.12.018
DO - 10.1016/j.heares.2003.12.018
M3 - Article
C2 - 15109708
AN - SCOPUS:1942421779
VL - 191
SP - 90
EP - 100
JO - Hearing Research
JF - Hearing Research
SN - 0378-5955
IS - 1-2
ER -