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 position in the ganglion of three other neurons which form monosynaptic connections with LPa3 is described. The plasticity of the LPa7-LPa3 connection is demonstrated. The possibility of the realization of plasticity through the cutting off of individual synapses composing the connection is hypothesized. The results of 65 experiments on the identification of LPa7, the physiological characteristics of this cell, and its monosynaptic connection with LPa3, are summarized in this study. One preparation with a monosynaptic connection is reconstructed.