Fluorescent Voltage Imaging Technique for the Measurement of Molluscan Neural Activities

Yuuta Hamasaki,Minoru Saito,Shogo Nakada,Tomoya Shimokawa,Makoto Hosoi

doi:10.4236/ojbiphy.2013.31a007

Abstract

The electrophysiological methods using microelectrodes are not appropriate for the simultaneous measurement of neural activities of many neurons. To overcome the difficulty, the fluorescent imaging technique using voltage sensitive dyes can be a powerful technique. The voltage sensitive dyes, however, generally exhibit a relatively small change in their fluorescence intensities, resulting in a low S/N ratio. Additionally, they often exhibit photobleaching and phototoxity. We have therefore improved the fluorescent voltage imaging technique by using a LED as the light source and an electron multiplying (EM)-CCD camera as the fluorescence detector. In this study, we applied our imaging system for the measurement of two kind of molluscan neural activities; one of which is involved in the olfactory processing of the land slug Limax valentianus and the other is involved in the feeding rhythm of the pond snail Lymnaea stagnalis. The system enabled us to measure the neural activities for a long time with a high speed and a high S/N ratio, and the obtained results showed some new physiological findings.

Highlights

The conventional electrophysiological methods have been well used for the measurement of neural activities of vertebrates and invertebrates
We applied our imaging system for the measurement of two kind of molluscan neural activities; one of which is involved in the olfactory processing of the land slug Limax valentianus and the other is involved in the feeding rhythm of the pond snail Lymnaea stagnalis
To realize a high S/N ratio, the light source must show a high intensity because the fluorescence intensity is proportional to the excitation intensity

Summary

Introduction

The conventional electrophysiological methods have been well used for the measurement of neural activities of vertebrates and invertebrates. The direct measurement of activities of a single neuron is possible by the conventional methods using microelectrodes. The fluorescent imaging technique using voltage sensitive dyes or calcium sensitive dyes can be a powerful technique. By using the voltage imaging, the measurement of neural activities was reported in vertebrates [2] and invertebrates [3,4,5]. The voltage sensitive dyes, generally exhibit a relatively small change in the fluorescence intensities, resulting in a low S/N ratio. The calcium sensitive dyes exhibit a larger change in the fluorescence intensities than the voltage sensitive dyes. Their fluorescence changes can be detected and enable us to indirectly measure the neural activities since the intracellular calcium concentration can be often increased with the neural activities [6,7]

Methods

Results

Conclusion