The distribution of immunoreactive FMRF-amide, neurotensin, and galanin in the brain and pituitary gland of three species of Xiphophorus from birth to sexual maturity.

This report seeks to extend the existing information on the relationship of regulatory neuropeptides to neuroendocrine and pituitary function through a longitudinal study of the distribution of FMRF-amide, galanin (GAL), and neurotensin (NT) in the brain and pituitary gland of three species of Xiphophorus from birth to sexual maturity. In the pituitary gland, immunoreactive (ir)-NT and -GAL were localized in the three regions of the adenohypophysis; ir-FMRF-amide was found in the neurohypophsis and in cells of the rostral pars distalis, but the immune reaction to this antisera in the pituitary was of very low intensity. Ir-GAL was found to colocalize with growth hormone, prolactin, and somatolactin in pituitary cells. In the brain, ir-GAL was found in the posterior nucleus lateralis tuberis (NLT), nucleus preopticus (NPO), and in the nucleus preopticus periventricularis (NPP). Ir-NT was localized in the anterior NLT. Ir-FMRF-amide was localized in the nucleus olfactoretinalis (NOR) where it was colocalized with gonadotropin releasing hormone, as well as in tracts that appeared to extend from the NOR, through the NPO and NPP, to the NLT. The NLT and the NOR have been previously implicated in the pituitary regulation of reproductive function. The above-cited localizations suggest that these peptides are involved in the neuroendocrine regulation of growth and reproduction in this genus.