Protein Synthesis in Presynaptic Endings of Squid Brain: Regulation by Ca2+ Ions

It is generally accepted that long-term synaptic plasticity induced by electrophysiological or behavioral stimulation requires the modulation of gene expression, eventually leading to modification of the set of synaptic proteins (Montarolo et al., 1986; Otani et al., 1989). These changes are believed to occur in presynaptic and postsynaptic sites (dendrites) of the neuron. The ability of dendrites to synthesize proteins, is largely accepted (Rao & Steward, 1991). On the other hand, the concept of protein synthesis in presynaptic terminals is still controversial. This possibility was considered in the past (Austin et al., 1967; Morgan & Austin, 1968; Gordon & Deanin, 1968; Bridgers et al., 1971; Cotman & Taylor, 1971), but failed to achieve acceptance as the protein synthetic activity of synaptosomal fractions could be attributed to contaminating fragments of glial cells or dendrites, rather than to nerve endings.