Mono- and polysynaptic connections between identified neurons in the system of the passive avoidance reflex of the snail.

The structure of the synaptic connections between identified sensory and giant command neurons of the parietal ganglia of the snail is examined. It is shown that the excitatory postsynaptic potential arising in the giant neuron in response to the generation of a single action potential in the presynaptic neuron consists of several monosynaptic components and may include polysynaptic components. It is hypothesized that monosynaptic components of the elementary excitatory postsynaptic potential that differ in the duration of the latent period and the dynamics of habituation may be associated with the activation of synaptic buttons on axon terminals of varying length.

[The mono- and polysynaptic connections between identified neurons in the system of the passive defensive reflex in the edible snail].

A structure of synaptic connections between the identified sensory and giant command neurons of Helix lucorum was studied. It was found that EPSPs arising in the giant neuron as responses to single action potentials generation in sensory neuron consist of several monosynaptic and several polysynaptic components having different magnitude, latencies, and plasticity. The latencies of monosynaptic components are determined by different presynaptic terminals' lengths.

Monosynaptic connection: identifiable synapses in the CNS of the edible snail.

The microanatomy of the pre- and postsynaptic neurons and the structure of the monosynaptic connection LPa7-LPa3 are described on the basis of planar reconstruction of sections of preparations of the CNS of the edible snail with neurons marked by heavy metal salts. Some physiological features of the presynaptic neuron and the monosynaptic connection were studied. The criteria for the identification of the LPa7 neuron according to its position in the ganglion, to the physiological reaction of LPa3, and to its microanatomy were determined.

[The monosynaptic connection: identified synapses in the CNS of the edible snail].

By electrophysiological and microanatomical methods of analysis of snail CNS small neurones it was shown that a number of neurones form a monosynaptic connection (MSC) with the gigantic polyfunctional neurone LPa3. By using cobalt and nickel staining, the structure of MSC cells LPa7--LPa3 was studied. Six identified synapses in two LPa3 processes zones were found.