2 DIFFERENT MOLECULES, NGF AND FREE-HCNP, STIMULATE CHOLINERGIC ACTIVITY IN SEPTAL NUCLEI IN-VITRO IN A DIFFERENT MANNER

Hippocampal cholinergic neurostimulating peptide (HCNP), a novel pepti de purified from 10- to 12-day-old rat hippocampus, specifically enhan ces acetylcholine (AcCho) synthesis in medial septal nuclei in vitro. synthetic de-acetylated HCNP (free-HCNP) elicits more potent enhanceme nt than HCNP. Nerve growth factor (NGF), a neurotrophic substance foun d in the hippocampus, enhances the cholinergic activity of medial sept al nuclei both in vivo and in vitro. The effects of free-HCNP on the d evelopment of various cholinergic phenotypes and the interaction of NG F and free-HCNP on cholinergic neurons in vitro were studied. In media l septal nuclei, free-HCNP enhanced AcCho synthesis and choline acetyl transferase (ChoATase) activity and increased V-max. It did not modula te culture morphology, choline (Cho) uptake, or acetylcholinesterase ( AcChoEase) activity. NGF stimulated AcCho synthesis and both ChoATase and AcChoEase activity in the medial septal nuclei and also enhanced A cCho synthesis in a corpus striatum culture. Compared with the effect of either agent alone, the simultaneous application of 3.8 x 10(-11) M NGF and 3 x 10(-11) M free-HCNP (maximal stimulation) to medial septa l nucleus culture resulted in a more than additive enhancement of AcCh o synthesis, an additive increase in ChoATase activity, and a signific ant increase in Cho uptake. In corpus striatum and spinal cord culture s, there was no cooperative increase in AcCho synthesis with NGF and f ree-HCNP nor any enhancement of AcCho synthesis by free-HCNP. These fi ndings suggest that NGF and free-HCNP play a cooperative role during t he biochemical differentiation of cholinergic neurons in medial septal nuclei.