Immunohistochemical Localization of the Mu Opioid Receptors

Using antibodies generated to the C-terminal 63 amino acids of the cloned rat mu receptor, the present study examines the distribution of the mu receptorlike immunoreactivity (li) in perfused rat brain sections. Generally, the localization of the mu receptor-li compares well with previous receptor binding studies, with staining observed in such regions as the caudateputamen, nucleus accumbens, hippocampus, amygdala, thalamus, superior and inferior colliculi, interpeduncular nucleus, parabrachial nucleus, locus coeruleus, raphe nuclei, nucleus tractus solitarius, and the dorsal horn of the spinal cord. This distribution is consistent with the broad number of functions associated with mu receptors, including inhibition of sensory transmission and the regulation of neuroendocrine and neurotransmitter release.