β-Lactotensin, a neurotensin agonist peptide derived from bovine β-lactoglobulin, enhances memory consolidation in mice

β-Lactotensin (His-Ile-Arg-Leu) is an ileum-contracting tetrapeptide isolated from bovine β-lactoglobulin. We previously reported that a neurotensin agonist β-lactotensin shows antinociceptive effect through neurotensin NT2 receptor. We found that centrally or orally administered β-lactotensin at a dose of 60 nmol/mouse or 300-500 mg/kg, respectively, increased memory consolidation in the step-through-type inhibitory avoidance test in mice. The memory-enhancing activity of β-lactotensin was inhibited by the dopamine D2 receptor antagonist raclopride but not the D1 receptor antagonist SCH23390. Taken together, β-lactotensin might improve memory consolidation through activating the dopamine D2 receptor.