Arginine vasopressin enhances periaqueductal gray synthesis and secretion of enkephalin and endorphin in the rat

Abstract

Previous study has proven that arginine vasopressin (AVP) enhances periaqueductal gray (PAG) secreting enkephalin and endorphin in vivo in the rat. Present work investigated that AVP effect on PAG secretion and synthesis of enkephalin and endorphin in vitro. Radioimmunoassy results showed that AVP increased leucine-enkephalin (L-Ek), methionine-enkephalin (M-Ek), β-endorphin (β-Ep) rather than dynorphin A 1–13 (DynA 1–13) concentrations in PAG slice culture liquid, and V 2 receptor antagonist: d(CH 2) 5[D-Ile 2, Ile 4, Ala 9-NH 2]AVP decreased L-Ek, M-Ek and β-Ep, not DynA 1–13 concentrations in PAG slice culture liquid in a dose-dependent manner, but V 1 receptor antagonist: d(CH 2) 5Tyr(Me)AVP did not change these peptide concentrations in PAG slice culture liquid. RT-PCR data displayed that AVP enhanced proenkephalin and proopiomelanocortin (Pro-β-Ep) rather than prodynorphin mRNA expressions in culture PAG tissues, and V 2 receptor antagonist weakened proenkephalin and proopiomelanocortin (Pro-β-Ep), not prodynorphin mRNA expressions in culture PAG tissues, but V 1 receptor antagonist did not influence these mRNA expressions in culture PAG tissues. The data suggest that AVP enhances PAG synthesizing and secreting enkephalin and endorphin rather than dynorphin through V 2 receptors.