Cr. Neal et al., Expression of orphanin FQ and the opioid receptor-like (ORL1) receptor in the developing human and rat brain, J CHEM NEUR, 22(4), 2001, pp. 219-249
The orphanin peptide system, although structurally similar to the endogenou
s opioid family of peptides and receptors, has been established as a distin
ct neurochemical entity. The distribution of the opioid receptor-like (ORL1
) receptor and its endogenous ligand orphanin FQ (OFQ) in the central nervo
us system of the adult rat has been recently reported, and although diffuse
ly disseminated throughout the brain, this neuropeptide system is particula
rly expressed within stress and pain circuitry. Little is known concerning
the normal expression of the orphanin system during gestation, nor how opia
te or stress exposure may influence its development. Using in situ hybridiz
ation techniques, the present study was undertaken to determine the normal
pattern of expression of ORL1 mRNA in the human and rat brain at various de
velopmental stages. Rat embryos, postnatal rat brains and postmortem human
brains were collected. frozen and cut into 15 [im coronal sections. In situ
hybridization was performed using riboprobes generated from cDNA containin
g representative human and rat ORL1 and OFQ sequences. Both ORL1 and OFQ mR
NA is detected as early as E12 in the cortical plate, basal forebrain, brai
nstem and spinal cord. Expression for both ORL1 and OFQ is strongest during
the early postnatal period, remaining strong in the spinal cord, brainstem
. ventral forebrain, and neocortex into the adult. Human ORL1 and OFQ expre
ssion is observed at 16 weeks gestation, remaining relatively unchanged up
to 36 weeks. The influence of early orphanin expression on maturation of st
ress and pain circuitry in the developing brain remains unknown. (C) 2001 E
lsevier Science B.V. All rights reserved.