Arginine-vasopressin fragment 4–9 stimulates the acetylcholine release in hippocampus of freely-moving rats

Abstract

We examined the effects of arginine-vasopressin (AVP) C-terminal fragment 4–9, which facilitates learning and memory, on the extracellular acetylcholine (ACh) release in hippocampus of freely-moving rats using the microdialysis technique. Following administration of AVP 4–9, p-Glu-Asn-Cys[Cys]-Pro-Arg-Gly-NH 2, through the dialysis probe into the hippocampus, ACh levels in dialysates from the hippocampus increased markedly in dose and time dependent manner at 2–2.5 and 2.5–3 hr. AVP 1–9, the parent 3eptide, has a similar enhancing effect on ACh release as AVP 4–9. Stimulated ACh released by AVP4–9 was significantly inhibited by V 1-selective receptor antagonist ([1-(β- mercapto-β,β-cyclopentamethylenepropionic acid), 2-(O-methyl)-tyrosine]AVP), but not by V 2-selective antagonist ([1-(β-mercapto-β,β-cyclopentamethylenepropionic acid), 2-D-Ile, 4-Ile]AVP). From these observations, it is demonstrated that AVP 4–9 stimulates the ACh release in rat hippocampus via mediating V 1-like vasopressin receptors.