A gadolinium and pH-sensitive hyperpolarization-activated cation current in acutely isolated single neurones from Fasciola hepatica

• Published in: Parasitology 2002-11, Vol.125 (5), p.423-430
• Main Authors: KIM, H. S., KAM, K. Y., RYU, P. D., HONG, S. J., JEON, J. S., JEON, B. H., KIM, K. J., PARK, J. B.
• Format: Article
• Language: English
• Subjects: Animals; Biochemistry. Physiology. Immunology. Molecular biology; Biological and medical sciences; Cations - metabolism; Cesium - pharmacology; Cyclic Nucleotide-Gated Cation Channels; Electric Conductivity; Fasciola hepatica; Fasciola hepatica - cytology; Fundamental and applied biological sciences. Psychology; Gadolinium; Gadolinium - pharmacology; Hydrogen-Ion Concentration; Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; I h current; Inactivation; Invertebrates; Ion Channel Gating - drug effects; Ion Channels - metabolism; Membrane Potentials - drug effects; Nemathelminthia. Plathelmintha; neurone; Neurons - drug effects; Neurons - metabolism; Original Article; Patch-Clamp Techniques; Physiology. Development; Potassium Channels; Reverse Transcriptase Polymerase Chain Reaction
• ISSN: 0031-1820; 1469-8161
• DOI: 10.1017/S0031182002002299

Fasciola hepatica, a parasitic flatworm belonging to the Class Trematoda, is one of the first metazoan groups to possess a centralized nervous system. However, the electrophysiological properties of neurones in F. hepatica are largely unknown. In the present study, we acutely isolated viable neurones from F. hepatica and characterized their electrophysiological properties. A hyperpolarization-activated cation current was recorded in the cells using the whole-cell patch-clamp. The current was found to be activated slowly at membrane potentials negative to 0 mV and did not display any time-dependent inactivation. This current was reduced by 1 mM Gd3+ to the level of the leak current, while 3 mM of Cs+ had no effect. However, the current was inhibited by extracellular acidosis in the pH range 7.0–7.8, and the membrane potentials of these cells were depolarized by extracellular alkalosis in the pH range of 5.8 to 8.2. Gd3+ (1 mM), which inhibited the pH-sensitive hyperpolarization-activated cation current, also hyperpolarized the cells. In summary, we isolated single neurones from F. hepatica, and these were found to express a pH-sensitive hyperpolarization-activated cation current. This current may participate in the membrane depolarization of F. hepatica neurones during alkaline challenge.