Response of Aplysia statocyst receptor cells to physiologic stimulation.
1. The electrical responses of Aplysia statocyst receptor cells were investigated using intracellular micro-electrodes. These ciliated mechanoreceptor cells were stimulated by downward tilting about a horizontal axis. 2. Tilting so that the receptor cell was excited produced a depolarizing receptor potential which, if large enough, could generate action potentials. 3. Large fluctuations in membrane potential were evident during depolarizing receptor potentials and were reduced or sometimes absent when a cell was tilted upward. Power-density spectra of the noise voltage revealed that most of the energy added by downward tilt is contained in frequency components below 3 Hz. 4. Removing synaptic input to the receptor cells by cutting the statocyst nerve or adding excess Mg2+ to the bath did not abolish the increase in fluctuations caused by downward, excitatory tilts. 5. The depolarizing receptor potential was often associated with a decrease in membrane resistance as measured with constant current pulses using a bridge circuit. 6. Replacing most of the Na+ in the bath with either Tris or Mg2+ abolished both potential and resistance changes caused by downward tilt. These results indicate that an increased permeability to Na+ underlies the receptor potential.
D000818:Animals; D004553:Electric Conductivity; D066298:In Vitro Techniques; D008274:Magnesium / Q000494:pharmacology; D008465:Mechanoreceptors / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects; D008974:Mollusca / Q000502:physiology*; D010812:Physical Stimulation; D012964:Sodium / Q000494:pharmacology; D014325:Tromethamine / Q000494:pharmacology
D014325:Tromethamine; D012964:Sodium; D008274:Magnesium