BRAIN GANGLIOSIDES AND MEMORY FORMATION

It is generally accepted that the process of molecular facilitation of neuronal circuits by means of stabilization of synaptic contacts repr esents the structural basis for memory formation. At the distinct zone of synaptic contact the following basic events occur: alterations of the electrical held strength at the outer surface of synaptic membrane s, conformational changes of membrane-bound functional proteins (ion c hannels, ion pumps, receptors) and activation of second messenger casc ade. Finally a trophic feed-back between synaptic terminals and their cell bodies through retro- and anterograde neuronal transport exists, which guarantees a stabilization of the newly formed synaptic connecti on. As a controlled Ca2+-exchange between the extracellular space (mM Ca2+-concentration) and the synaptoplasm (mu M Ca2+) is essential for all these events, the present reseach concentrates on Ca2+-mediated pr imary messenger systems at the outer leaflet of synaptic membranes and on Ca2+-mediated modulatory mechanisms. These enable an always effici ent electroresponsiveness although the environmental temperature might have changed. In this regard gangliosides being amphiphilic sialic ac id containing glycosphingolipids, which are highly accumulated in comp lex composition in synaptic membranes play an important role. Accordin g to specific physico-chemical properties, they are assumed to fulfill the task of neuromodulators in connection with calcium, and thus cont ribute to the transmission and storage of information. The outcome of a series of experiments derived from neurology, ecophysiology, behavio ral sciences, electron microscopy, biochemistry and physical chemistry give strong circumstantial evidence for this concept.