PT  - JOURNAL ARTICLE
AU  - Naitoh, Yutaka
AU  - Eckert, Roger
TI  - Ionic Mechanisms Controlling Behavioral Responses of Paramecium to Mechanical Stimulation
AID  - 10.1126/science.164.3882.963
DP  - 1969 May 23
TA  - Science
PG  - 963--965
VI  - 164
IP  - 3882
4099  - http://science.sciencemag.org/content/164/3882/963.short
4100  - http://science.sciencemag.org/content/164/3882/963.full
SO  - Science1969 May 23; 164
AB  - A mechanical stimulus applied to the anterior part of Paramecium causes a transient increase in membrane permeability to calcium. This permits a calcium current to flow into the cell, causing the membrane potential to approach the equilibrium level for calcium. The transient depolarization which results elicits a reversal in the direction of ciliary beat. When the organisms are free-swimming this is seen as the reversed locomotion of Jennings' "avoiding reaction." In contrast, a mechanical stimulus applied to the posterior part results in increased permeability to potassium ions, and hence an outward potassium current. The hyperpolarization which results causes an increase in the frequency of ciliary beat in the normal direction. In free-swimming specimens this is seen as an increase in the velocity of forward locomotion.