Physiological role of a novel neuropeptide, apelin, and its receptor in the rat brain

J Neurochem. 2001 May;77(4):1085-96. doi: 10.1046/j.1471-4159.2001.00320.x.


Apelin, a peptide recently isolated from bovine stomach tissue extracts, has been identified as the endogenous ligand of the human orphan APJ receptor. We established a stable Chinese hamster ovary (CHO) cell line expressing a gene encoding the rat apelin receptor fused to the enhanced green fluorescent protein, to investigate internalization and the pharmacological profile of the apelin receptor. Stimulation of this receptor by the apelin fragments K17F (Lys1-Phe-Arg-Arg-Gln-Arg-Pro-Arg-Leu-Ser-His-Lys-Gly-Pro-Met-Pro-Phe17) and pE13F (pGlu5-Arg-Pro-Arg-Leu-Ser-His-Lys-Gly-Pro-Met-Pro-Phe17) resulted in a dose-dependent inhibition of forskolin-induced cAMP production and promoted its internalization. In contrast, the apelin fragments R10F (Arg8-Leu-Ser-His-Lys-Gly-Pro-Met-Pro-Phe17) and G5F (Gly13-Pro-Met-Pro-Phe17) were inactive. The physiological role of apelin and its receptor was then investigated by showing for the first time in rodent brain: (i) detection of apelin neurons in the supraoptic and paraventricular nuclei by immunohistochemistry with a specific polyclonal anti-apelin K17F antibody; (ii) detection of apelin receptor mRNA in supraoptic vasopressinergic neurons by in situ hybridization and immunohistochemistry; and (iii) a decrease in vasopressin release following intracerebroventricular injection of K17F, or pE13F, but not R10F. Thus, apelin locally synthesized in the supraoptic nucleus could exert a direct inhibitory action on vasopressinergic neuron activity via the apelin receptors synthesized in these cells. Furthermore, central injection of pE13F significantly decreased water intake in dehydrated normotensive rats but did not affect blood pressure. Together, these results suggest that neuronal apelin plays an important role in the central control of body fluid homeostasis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adipokines
  • Amino Acid Sequence
  • Animals
  • Apelin
  • Apelin Receptors
  • Blood Pressure / drug effects
  • Brain / physiology*
  • CHO Cells
  • Carrier Proteins / chemistry
  • Carrier Proteins / pharmacology
  • Carrier Proteins / physiology*
  • Cerebral Ventricles / drug effects
  • Cerebral Ventricles / physiology
  • Colforsin / pharmacology
  • Cricetinae
  • Cyclic AMP / metabolism
  • Drinking Behavior / drug effects
  • In Situ Hybridization
  • Injections, Intravenous
  • Injections, Intraventricular
  • Intercellular Signaling Peptides and Proteins
  • Male
  • Mice
  • Molecular Sequence Data
  • Neurons / physiology
  • Peptide Fragments / administration & dosage
  • Peptide Fragments / pharmacology
  • RNA, Messenger / analysis
  • Rats
  • Rats, Inbred WKY
  • Receptors, Dopamine D2 / drug effects
  • Receptors, Dopamine D2 / genetics
  • Receptors, Dopamine D2 / physiology*
  • Receptors, G-Protein-Coupled*
  • Transfection
  • Vasopressins / blood
  • Water Deprivation


  • APLNR protein, human
  • Adipokines
  • Apelin
  • Apelin Receptors
  • Apln protein, mouse
  • Apln protein, rat
  • Aplnr protein, mouse
  • Aplnr protein, rat
  • Carrier Proteins
  • Intercellular Signaling Peptides and Proteins
  • Peptide Fragments
  • RNA, Messenger
  • Receptors, Dopamine D2
  • Receptors, G-Protein-Coupled
  • Vasopressins
  • Colforsin
  • Cyclic AMP