"it showed that the antinociception of ghrelin was correlated with the GHS-R1alpha and d-opioid receptors. Finally the antinociception induced by deltorphin II wasn't blocked by the co-injection (i.c.v.) of [D-Lys(3)]-GHRP-6 indicating that the GHS-R1a isn't on the backward position of delta opioid receptor."xsd:string