Hyperpolarization response of an identified neuron of Planobarius corneus mollusks to several cholinomimetic substances]

Two kinds of responses to cholinomimetics were found on the identified neuron (P-2) of Planorbarius corneus pedal ganglion using microelectrode technique. Nicotinomimetics caused depolization whereas some muscarinomimetics caused hyperpolarization of the neuron membrane. Acetylcholine usually depolarized the neuron membrane but after the blockade of nicotinic receptors with tubocurarine one can reveal a hyperpolarizing action of acetylcholine. These findings suggest that two kinds of receptors exist on the P-2 neuron membrane and these receptors differ both in pharmacological characteristics and in ionic permeability changes they control.