How a number of biological effects of the peptide neuroprotector HLDF-6-amide work are still unknown and require further study. It was found that HLDF-6-amide dose-dependent (1–100 μM) stimulates the proliferation of Tetrahymena pyriformis infusoria, and the MK801 glutamate NMDA receptor antagonist partially blocks this effect. The introduction of a peptide (12.5–100 μM) reduces the cytotoxic and cytostatic effect of doxorubicin (25 μM) on infusoria. Radio-ligand analysis revealed the presence of specific binding sites of [3H] Ac-HLDF-6-amide on the cell membranes of the rat brain cortex, which indicates the receptor mechanism of action of the peptide. Thus, it was shown for the first time that HLDF-6-amide stimulates proliferation and has cytoprotective properties, which may underlie its wound-healing, nootropic and neuroprotective effects. The participation of the glutamate system, in particular ionotropic NMDA receptors, in these effects was established.