Methods
An enzyme mixture was applied locally over the neuronal soma to remove the glial cells and expose the neuronal membrane. Macropatch and single channel recordings were performed in cell attached configuration. The normal astacus saline was used both as pipette solution and bath solution. Two electrode intracellular voltage clamp technique was also used to record membrane current and potential.

Results
(1) Application of the enzyme mixture for an appropriate period gave sufficiently clean neuronal membrane for patch clamping. After enzymatic treatment SA neurons had resting membrane potential of 62.6 ± 1.4 mV and relative action potential amplitude of 66.6 ± 5.0 mV. (2) Macropatch currents from SA neuronal soma showed different magnitude of maximal inward and outward currents, noise levels and inactivation properties, suggesting that the Na+ and K+ channel distribution varied over the SA neuronal soma with current density being higher in lower part of the soma than upper part of the soma. (3) A 13 pS delayed outward rectified K+ channel was identified in SA neuronal soma. It could only be activated by at least 10-20 mV depolarization, and little inactivation was observed within 80 ms-long depolarization. This 13 pS K+ channel plays a considerable role in the repolarization of action potentials. (4) Intracellular recordings revealed that voltage-gated Na+ channels in SA neurons were present both in the soma and the axon, whereas the Na+ channels in RA neurons were dominant in the axon, at least 250 micrometer away from the soma.

Conclusions
This study indicates that several kinds of Na+ and K+ channels are present in SA and RA neurons, which differ in the relative occurrence and spatial distribution between SA and RA neurons, and may contribute to the impulses generation and adaptation behaviours.