Figure 1.

St-KKYL-NH₂ protects against β-amyloid neurotoxicity. Experiments were conducted as described (16) and repeated seven independent times (each time in duplicate or triplicate). In short, cerebral cortical cultures from newborn rats (mixed neuron and glia preparations) were incubated with increasing concentrations of the test substance in the presence of 25 μM β-amyloid peptide (see Materials and Methods). After a 5-day incubation period, cells were stained with antibodies against neuron-specific enolase, and surviving neurons were counted (60 fields for each 35-mm plate). Untreated sister culture counts (100%) were: 130, 131, 164, 172, 225, 253, and 319. For SNV treatment, experiments were repeated five times (each time in duplicate or triplicate), and control counts were 131, 164, 197, 253, and 319. The apparent increase in the EC₅₀ for SNV observed here in comparison to previous results (16) may be due to the decreased number of total neurons in the current experiments. As for the control peptide, St-KKYL-OH, the experiment was performed in triplicate, and the control counts were 149, 169, and 174.