beta-Endorphin-like immunoreactivity in the brain of the lizard, Lacerta muralis

Ontogeny of a novel decapeptide derived from POMC-A in the brain and pituitary of the rainbow trout

Trout POMC-A exhibits a unique C-terminal extension of 25-amino acids which is processed in the pituitary and hypothalamus to generate two novel decapeptides, EQWGREEGEE and ALGERKYHFQ-NH(2). The fibers containing these two decapeptides are widely distributed in the brain, suggesting that they may exert neurotransmitter or neuromodulator activities. In the present study, we have investigated the ontogeny of the decapeptide EQWGREEGEE in the trout pituitary and brain. In the pituitary of 29-day embryos and 33-day alevins, EQWGREEGEE-immunoreactive material was observed in a cluster of cells located in the central and rostral region of the gland, respectively. In 47-day alevins, a second group of cells exhibiting EQWGREEGEE-like immunoreactivity was detected in the caudal region of the pituitary and the intensity of labeling in these cells increased in 61-day fry. In the brain, EQWGREEGEE immunoreactivity was detected in 47-day alevins. In 47- and 61-day larvae, immunoreactive elements were mainly detected in the diencephalon. Characterization of the immunoreactive material by reversed-phase high-performance liquid chromatographic analysis combined with radioimmunoassay detection revealed the existence of two major forms which exhibited different retention times than synthetic EQWGREEGEE. The present study indicates that EQWGREEGEE-related peptides are present in the trout pituitary early during ontogeny and appear in the brain only later, and that processing of the C-terminal extension of POMC-A generates distinct molecular species at different developmental stages. These data suggest that alternative processing of the C-terminal domain of POMC-A gives rise to various peptide products that may exert specific activities during trout development.

Beta-endorphin-like immunoreactivity in the forebrain and pituitary of the teleost Clarias batrachus (Linn.)

The organization of beta-endorphin-like immunoreactivity in the olfactory system, forebrain, and pituitary of the teleost Clarias batrachus was investigated. Immunoreactivity was prominently seen in the sensory neurons and basal cells in the olfactory epithelium and in some cells in the periphery and center (granule cells) of the olfactory bulb. Immunoreactive fibers in the olfactory nerve enter the olfactory nerve layer of the olfactory bulb and branch profusely to form tufts organized as spherical neuropils in the glomerular layer. While fascicles of immunoreactive fibers were seen in the medial olfactory tracts, the lateral olfactory tracts showed individual immunoreactive fibers. Immunoreactive fibers in the medial olfactory tract extend into the telencephalon and form terminal fields in discrete telencephalic and preoptic areas; some immunoreactive fibers decussate in the anterior commissure, while others pass into the thalamus. While neurons of the nucleus lateralis tuberis revealed weak immunoreactivity, densely staining somata were seen at discrete sites along the wall of the third ventricle. Although a large population of immunoreactive cells was seen in the pars intermedia of the pituitary gland, few were seen in the rostral pars distalis and proximal pars distalis; immunoreactive fibers were seen throughout the pituitary gland.

In vivo and in vitro studies on effects of beta-endorphin and naloxone on sex steroids in the water frog, Rana esculenta

The effects of beta-endorphin and its receptor antagonist, naloxone, on progesterone, androgens, and oestradiol-17 beta release in male and female Rana esculenta were studied in vivo and in vitro. In the in vivo experiments the frogs underwent hypophysectomy, gonadectomy or both, or were left intact; the animals were injected with beta-endorphin or naloxone and killed after 15, 30, 90 and 240 min. In the in vitro experiments inter-renal, testis and ovary, all with and without added pituitary, were incubated with beta-endorphin or naloxone for 10, 20, 40 and 80 min. The in vivo and in vitro data from males and females were in agreement. In vivo beta-endorphin increased progesterone in all experimental groups and oestradiol in intact and hypophysectomized frogs, while it decreased androgens in all experimental groups. In vitro beta-endorphin increased progesterone in inter-renal and gonadal tissue, and oestradiol in gonads only, while it decreased androgens in inter-renals and gonads. In vivo and in vitro naloxone induced opposite effects to beta-endorphin. These data suggest that in Rana esculenta, opioids are involved in the modulation of hypothalamo-pituitary-inter-renal and gonadal axes. In particular, the data indicate a direct effect of opioids on inter-renal and gonadal sex steroid production.

Detection of Met-enkephalin and Leu-enkephalin in the brain of the hagfish, Eptatretus stouti, and the lamprey, Petromyzon marinus

Acid extracts of the brain of the pacific hagfish, Eptatretus stouti, and the marine lamprey, Petromyzon marinus, were each fractionated by gel filtration chromatography and aliquots of column fractions were screened with radioimmunoassays (RIAs) specific for pro-dynorphin-related end products and for pro-enkephalin-related end products. Only pro-enkephalin-related immunoreactive forms were detected. The enkephalin-sized immunoreactive material, isolated for each species, was separately fractionated by reverse-phase high-performance liquid chromatography (HPLC). Aliquots of column fractions were screened with RIAs specific for Met-enkephalin, Leu-enkephalin, Met-enkephalin-Arg-Phe, and Met-enkephalin-Arg-Gly-Leu. In the hagfish brain, immunoreactive forms with the same retention times as synthetic Met-enkephalin and Leu-enkephalin were detected in a ratio of approximately 2:1. In addition, an immunoreactive form was detected with the Met-enkephalin-Arg-Phe-specific RIA. This form had the same chromatographic properties as synthetic Met-enkephalin-Arg-Phe. Analyses with the Met-enkephalin-Arg-Gly-Leu RIA were negative. HPLC analysis of the lamprey enkephalin-related material revealed the presence of authentic Met-enkaphalin and Leu-enkephalin in a molar ratio of 3:1. C-terminally extended forms of Met-enkaphalin were not detected in the lamprey extracts. Collectively these observations indicate that pro-enkephalin-related opioid peptides are present in the brain of cyclostomes.

Proopiomelanocortin (POMC)-related peptides in the brain of the rainbow trout, Salmo gairdneri

We have investigated the presence of ACTH, alpha-MSH and beta-endorphin, three peptides which derive from the multifunctional precursor protein proopiomelanocortin (POMC) in the brain of the rainbow trout Salmo gairdneri. Using both the indirect immunofluorescence and peroxidase-antiperoxidase techniques, a discrete group of positive cells was identified in the hypothalamus, within the anterior part of the nucleus lateralis tuberis. alpha-MSH-containing neurons represented the most abundant immunoreactive subpopulation. Coexistence of alpha-MSH, ACTH and beta-endorphin was observed in the lateral part of the nucleus. ACTH- and beta-endorphin-containing cells were mainly distributed in the rostral and caudal regions of the nucleus. In the medial portion of the nucleus lateralis tuberis, numerous cells were only stained for alpha-MSH. Moderate to dense plexuses of immunoreactive fibers were observed in the ventral thalamus and the floor of the hypothalamus. Some of these fibers projected towards the pituitary. The concentrations of ACTH, alpha-MSH and beta-endorphin-like immunoreactivities were measured in microdissected brain regions by means of specific radioimmunoassays. Diencephalon, mesencephalon and medulla oblongata extracts gave dilution curves which were parallel to standard curves. The highest concentrations of POMC-derived peptides were found in the diencephalon (alpha-MSH: 4.28 +/- 0.43 ng/mg prot.; ACTH: 1.08 +/- 0.09 ng/mg prot.; beta-endorphin: 1.02 +/- 0.1 ng/mg prot.), while lower concentrations were detected in the mesencephalon, medulla oblongata and telencephalon. The present results demonstrate that various peptides derived from POMC coexist within the same cell bodies of the fish hypothalamus. Taken together, these data suggest that expression and processing of POMC in the fish brain is similar to that occurring in pituitary melanotrophs.