Localization and characterization of diazepam-binding inhibitor (DBI)-like peptides in the brain and pituitary of the trout (Salmo gairdneri).

The distribution of diazepam-binding inhibitor (DBI)-like peptide(s) in the brain and pituitary of the trout was determined by the indirect immunofluorescence technique using an antiserum raised against synthetic rat octadecaneuropeptide (ODN). Numerous immunoreactive perikarya and processes were observed in the basal hypothalamus, within the pars lateralis of the nucleus lateralis tuberis. In the pituitary, ODN-immunoreactive processes were visualized in the neurohypophysial tract, projecting into the pars intermedia, and the pars distalis. Reverse-phase high-performance liquid chromatography combined to radioimmunoassay quantification was used to characterize the DBI-related material in tissue extracts. In both pituitary and hypothalamic extracts, the major immunoreactive form eluted with a retention time higher than that of rat ODN. In the hypothalamus, a minor peak co-eluting with the synthetic ODN standard was also resolved. The existence of peptides related to mammalian DBI in the hypothalamo-hypophysial complex of the trout suggests these neuropeptides may participate in the control of pituitary hormone release.