[Monosynaptic pathway responsible for generation of burst activity in neuron PPa1 of Helix pomatia]

The connections between an interneuron in the visceral ganglion initiating the pacemaker activity in RPa1 neuron and RPa1 neuron itself have been analyzed in snail. The interneuron stimulation led to initiation of the bursting activity in the RPa1 neuron. Replacement of extracellular Ca2+ by Mg2+ ions, as well as addition of CdCl2 to the external solution reversibly inhibited the effect of the interneuronal stimulation on the RPa1 neuron. An increase of extracellular Ca2+ ions concentration to 70 mM did not prevent the effect. Intracellular Cs+ and TEA injection in the interneuron increasing the action potential duration in the interneuron increased also the effectiveness of connection between the neurons. It is concluded that the connection between the neurons under investigation is monosynaptic and peptidergic.