Monosynaptic connections between LPa7-LPa3 and LPa9-LPa3 neurons in the central nervous system of helix pomatia. Electrophysiological characteristics, monosynaptic plasticity, neurotransmission.

Monosynaptic inputs from LPa7 and LPa9 cells onto the LPa3 neuron were investigated in the isolated central neurons system (CNS) of snail Helix by means of simultaneous intracellular recording from pre- and post-synaptic neurons and electrical stimulation of the presynaptic neuron through the recording microelectrode. Each action potential of either presynaptic cell produced excitatory postsynaptic potential (EPSP) in the follower one with an amplitude of 0.6-5 mV. Repetitive suprathreshold stimuli, applied at frequencies higher than 1 per 5 min, induced depression of the monosynaptic response. The cholinergic antagonists, atropine and d-tubocurarine (10(-6)M- 10(-4)M), dose-dependently inhibited monosynaptic EPSP from either presynaptic cell. Cholinergic transmission is suggested between LPa7-LPa3 and LPa9-LPa3 cells.