A subset of nociceptin/orphanin FQ receptor-expressing neurons in the anterior hypothalamic area, as revealed in mice with lacZ reporter gene.

Nociceptin/orphanin FQ (N/OFQ) is an endogenous peptide agonist for the opioid receptor homolog, N/OFQ receptor, and serves for the central control of autonomic functions. Morphological details including the cell types that may account for such N/OFQ functions, however, remain unclear. By using X-gal histochemistry for the detection of receptor-expressing cells at both light and electron microscopic levels, we examined the hypothalamus from the receptor-deficient mice bearing a lacZ insertional mutation in the N/OFQ receptor gene. The N/OFQ receptor reflected by lacZ expression was seen at high levels in the anterior hypothalamic area. With electron microscopy, lacZ expression was observed in a subset of neurons showing large cell size and indented nucleus.