2 TYPES OF REORGANIZATION IN MULTIFUNCTIONAL NEURAL NETWORKS OF HELIX-POMATIA L

The visceral functions of the snail Helix pomatia L. were shown to be regulated by overlapping and variable neural networks consisting of mu ltifunctional neurons distributed in various parts of the CNS. The res ults showed that: 1. reorganization of the neural networks is accompan ied by alterations in the firing mode of the neurons; 2. most identifi ed neurons change their firing pattern from a tonic to a phasic type d epending on the combination of signal molecules present or on the acti vation of their synaptic inputs; 3. the appearance of a slow membrane oscillation or burst firing was shown to make the neurons insensitive to input activation originating from visceral organs; 4. inputs from v arious visceral organs converge on a large number of neurons in the te mporarily formed neural networks. In the vicinity of the multifunction al neurons a whole group of neurons can store various forms of transit ory patterns; 5. both voltage (I-K and I-Ca) and ligand (Ach and GABA) activated currents can be targets of signal molecules in altering the firing mode of the neurons. This will result in the reconfiguration o f circuits; 6. because of to the large number of neurons involved in t he regulation of visceral organs, the overlapping and reorganizing cir cuit can be interpreted more efficiently as a distributed network also including elements of dedicated regulatory circuits.