Distribution of immunoreactive dynorphin A 1–8 in discrete nuclei of the rat brain: Comparison with dynorphin A

Abstract

The distribution of immunoreactive (ir)-dynorphin A 1–8 (Dyn A 1–8) in 78 microdissected rat brain areas as well as in the neurointermediate lobe of pituitary gland was determined using a highly specific radioimmunoassay. The highest concentrations of Dyn A 1–8 in brain were found in substantia nigra (673.8 fmol/mg protein) and lateral preoptic area (565.1 fmol/mg protein). High concentrations of ir-Dyn A 1–8(> 240fmol/mg protein) were found in 5 nuclei: ventral premamillary nucleus, anterior hypothalamic nucleus, dorsomedial nucleus, arcuate nucleus, and medullary reticular nuclei. Moderate concentrations of the peptide (between 120 and 240 fmol/mg protein) were found in 55 brain nuclei such as septal and amygdaloid nuclei, most diencephalic structures, mesencephalic nuclei, pons and medulla oblongata nuclei and others. Low concentrations of ir-Dyn A 1–8(< 120fmol/mg protein) were found in 16 regions, e.g. frontal cortex, hippocampus, caudate-putamen cortical amygdaloid nucleus, several thalamic nuclei, mamillary body superior and inferior colliculi, cerebellar nuclei and others. The posterior thalamic nucleus has the lowest ir-Dyn A 1–8 concentration (62.0 fmol/mg protein). The neurointermediate lobe of the pituitary gland is extremely rich in ir-Dyn A 1–8 (4063.0 fmol/mg protein).