An identified neuron (L Ped-2) of the Planorbarius corneus left pedal ganglion was isolated after the treatment of the ganglionic ring with pronase. The LPed-2 retains after the isolation the main features characteristic of this neuron in the ganglion. Nicotinomimetics (nicotine, suberyldicholine) produced depolarization whereas muscarinomimetics (F-2268, arecoline, methylfurmethide, acetyl-beta-methylcholine) hyperpolarized the cell membrane. Acetylcholine (ACh) in small concentrations (less than 1.10(-6) M) caused depolarization followed by hyperpolarization; greater concentrations depolarized the cell membrane. In the presence of tubocurarine ACh produced pure hyperpolarization. The conclusion was drawn that two kinds of cholinoreceptors exist on the membrane of LPed-2 neuron which differ both in pharmacological properties and in the sign of the response they mediate. The isolated neuron is much more sensitive to cholinomimetics than the same neuron in the ganglion.