Purification and structural analysis of hippocampal cholinergic neurostimulating peptide.

Hippocampal soluble fraction stimulates acetylcholine (AcCho) synthesis of medial septal nuclei in explant culture system. This stimulating activity was purified from 10-12-day-old rat hippocampus. During purification, the activity was separated into two fractions and a previously unreported peptide was purified from one fraction. The structure of this novel peptide is acetyl-Ala-Ala-Asp-Ile-Ser-Gln-Trp-Ala-Gly-Pro-Leu and we designated it as hippocampal cholinergic neurostimulating peptide (HCNP). Synthesized HCNP and de-acetylated HCNP (free-HCNP) stimulated AcCho synthesis of medial septal nuclei culture, in a dose-dependent manner, but not cultures of corpus striatum or anterior spinal cord. Mean half-maximal concentrations of HCNP and free-HCNP in AcCho synthesis of medial septal nuclei culture were 1.0 +/- 0.3 x 10(-10) M and 1.0 +/- 0.6 x 10(-11) M, respectively. Affinity purified polyclonal antibody to the free-HCNP neutralized the activity of crude hippocampal extract, as well as synthetic HCNP and free-HCNP. These observations suggested that HCNP was present in the hippocampal extract and was involved in development of specific cholinergic neuron in central nervous system.