Distribution of nociceptin/orphanin FQ in adult human brain.

Nociceptin/orphanin FQ (N/OFQ), the endogenous agonist for the opioid receptor-like receptor 1 (ORL1), shows significant similarities to dynorphin A in structure and distribution in rat central nervous system. The distribution of N/OFQ in human brain has not been studied. We measured the concentrations of N/OFQ in 47 microdissected areas of the central nervous system of adult human brain using radioimmunoassay (RIA). Significant heterogeneity was found in the levels of N/OFQ concentration in the various analyzed regions. The highest concentrations were measured in the dorsal central gray matter (periaqueductal gray), the locus coeruleus, the ventromedial nucleus of hypothalamus, the septum and the dorsal horn of the spinal cord. High concentrations were also detected in other hypothamamic nuclei, the inferior colliculus, the ventral central gray matter, the pontine tegmentum, the amygdala, the reticular formation and the spinal trigeminal nucleus. Considerable similarity with the distribution of N/OFQ in rat CNS was observed. The widespread distribution in CNS predicts multifaceted functions for N/OFQ.