Electrophysiological properties of neurones in the right parietal ganglia of Helix aspersa

Abstract

It becomes so important to understand the ionic mechanisms and intrinsic electrical properties of neurones. In this study, suboesophageal ganglia of Helix aspersa was just submerged in the organ bath with ringer solution and intracellular recordings were made from the right parietal ganglia neurones by using current clamp technique in vitro. Action potentials (APs) were recorded from four cells having same electrophysiological properties and placed in the medial part of right parietal ganglia. The duration and amplitude were 5.1 ± 1.8 ms and 80-100 mV respectively. All action potentials overshooted and had a small hyperpolarization after AP (undershoot). Resting membrane potential of these cells was -52.8 ± 7.5 mV. The current-voltage (I-V) relationship was linear and the cell fired regularly with a frequency of 1.5 Hz. The APs of second type of neurones, placed in the lateral part of right parietal ganglia had different biophysical properties with two frequencies. In the first term, the frequency was 3.5 Hz and the resting membrane potential was -38 mV. The AP amplitude was 40 mV. In the second term, the frequency was less than 0.5 Hz. The cell was hyperpolarized up to -65 mV and the amplitude of AP was increased up to 80-100 mV. The AP firing was regular in the first term and it became irregular in the second term. This may account for the evidence that the cell receive either excitatory or inhibitory signals spontaneously. The I-V relationship could not be determined due to the unsteady state in these cells.