Effects of light on identified Helix pomatia neurons

Abstract

1. 1. The effects of photostimulation were investigated in four identified neurons in Helix pomatia subesophageal ganglia. Three of the tested photosensitive cells reacted to illumination with a depolarization and increment of frequency of spontaneously generated action potentials. One identified cell in the right parietal ganglion reacted to light with hyperpolarization. 2. 2. Analysing the dynamics of action potential frequency changes during 1 or 2 min illuminations as well as during the subsequent dark periods it was found that shortly after the onset of light the action potential frequency reached a maximum and it remained significantly higher till the light was switched off. 3. 3. Hyperpolarization of the membrane enhanced the amplitude of light evoked depolarization in all three tested depolarizing neurons. A linear change of amplitude of light evoked depolarization was observed for the range of light intensities used here. An increment of neurons reactivity to light in the course of adaptation to darkness was observed and analysed.