Exploration of Cochlear Potentials in Guinea Pig with a Microelectrode

Abstract

The ac ("microphonic") cochlear potential and the positive dc "endolymphatic" potential have been recorded simultaneously as the exploring electrode was introduced into scala media or as other parameters were varied. Negative intracellular dc potentials were demonstrated in the cells of the organ of Corti. The zone of positive endolymphatic potential is bounded by the reticular lamina, not by the basilar membrane. The cochlear microphonic reverses phase as the exploring electrode penetrates the reticular lamina. A dc polarizing current with the positive pole in scala media (and negative in scala tympani) increases the cochlear microphonic just as it does when the positive pole is located in the scala vestibuli. These facts indicate that the source of the ac (microphonic) potential seems clearly to be at the hair-bearing end of the hair cells and that the source of the dc endolymphatic potential is probably here also, while Reissner's membrane is not the source of either the ac or the dc potential. No steady dc current flow outside scala media was found such as would be expected if stria vascularis were the dc source and if the hair cells modulated a dc current flow through them. The dc endolymphatic potential may be increased by as much as 10 percent if and while the basilar membrane is displaced toward scala vestibuli and may be decreased to 50 percent or less when and while it is displaced toward scala tympani. Isotonic solutions rich in potassium depressed the ac potential and nerve responses when introduced into scala tympani but not when in scala vestibuli only. The dc potential, however, was not altered by high potassium concentration in scala tympani.

Purinergic Modulation of Cochlear Partition Resistance and Its Effect on the Endocochlear Potential in the Guinea Pig

“…The small increase in EP is similar to the findings of Kakigi and Takeda (1998) who injected up to 2 ll of artificial endolymph into scala media in guinea pigs. The increase in EP and CoPR may be due to a volume-induced downward shift of the basilar membrane (Tasaki et al 1954), possibly affecting the silent current. This small EP increase shows that the effect of increasing endolymphatic volume, at least in the range used in this study, had limited effect on the scala media compartment and its surrounding tissues.…”

Deafness inClaudin 11-Null Mice Reveals the Critical Contribution of Basal Cell Tight Junctions to Stria Vascularis Function

“…Early experiments in the cochlea demonstrate a strong voltage potential at the surface of the stria vascularis (Tasaki et al, 1952;von Bekesy, 1952). Subsequent electrophysiological studies indicate that a compartment within this lateral wall epithelium exhibits an electrochemical potential with respect to surrounding tissue and a low K ϩ concentration compared with those of an intracellular milieu and endolymph.…”

Saccular potentials of the vocal plainfin midshipman fish, Porichthys notatus

“…Furikawa and Ishii (1967) also documented a similar observation for the goldfish saccule in which the saccular potentials were evoked greatest at twice the frequency of the sound stimulus. In contrast to the double frequency effect of the evoked potentials from the lateral line and saccule, the evoked potentials of the semicircular canals (de Vries and Bleeker 1949) and the cochlea (Tasaki et al 1954) are known to be evoked greatest at the same frequency of the stimulus. These differences in the evoked potential responses among the different receptor organs can be accounted for by the differences in the spatial orientation of hair cells within the receptor organs (Flock 1965;Flock andWersall 1962,1963;Lowenstein and Sand 1940;Wersall and Flock 1965;Hama 1969).…”

“…This double frequency effect of the evoked potentials was first reported for the lateral line organ of the ruff (Acerina cernua) where the two groups of opposite oriented hair cells produce two evoked potentials during every stimulus cycle (Jielof et al 1952;Flock 1965;Wersall and Flock 1965). In contrast to auditory end organs, the mammalian cochlea and the crista ampullaris have hair cells that are oriented in the same direction and hence have potentials that are evoked at the same auditory stimulus frequency (de Vries and Bleeker 1949;Tasaki et al 1954). …”