The presence of corticotropin-like and opiate-like activities in tissues of adult sea lamprey, Petromyzon marinus L

Ovarian opioids and the reproductive cycle of the frog Rana esculenta

In mammals, proopiomelanocortin-related peptides are involved in reproductive processes both at the hypothalamo-pituitary and ovarian levels. Using immunocytochemical, biochemical and physiological "in vitro" studies, we provide here evidence for a diffuse POMC-related opioid system in the frog Rana esculenta. Ovarian beta-endorphin (beta-EP) is expressed in thecal cells and changes during the reproductive cycle in an inverse relationship with follicular development. Seasonal changes in the ovary are different to those in the brain or in the pituitary. The ratio of acetylated vs native beta-EP in the ovary also changes over the reproductive period, affecting the biological activity of the peptide. During both the reproductive spring period and the summer post-reproductive phase pMol amounts of beta-EP stimulate follicular androgen secretion in vitro, in a naloxone-reversible way. In either period, an inhibition of estradiol, possibly mediated via other factors, is the result of opioid action. In conclusion, these data demonstrate for the first time the widespread presence of beta-EP-related peptides in the frog Rana esculenta. Both immunocytochemical and biochemical evidence, as well as in vitro responses, support a physiological role for beta-EP in ovarian seasonality during the reproductive cycle of this amphibian.

Corticotropin-like immunoreactivity in the brain and pituitary of three teleost species (goldfish, trout and eel)

Immunostaining of brain and pituitary sections of three teleost species (goldfish, trout and eel) with antisera to porcine and human ACTH 1-39 revealed the presence of an ACTH (adrenocorticotropic hormone)-like peptide in the ventral hypothalamus. Perikarya were localized in the rostral, median and posterior portions of the nucleus lateralis tuberis (NLT); some were in contact with the cerebrospinal fluid. A dense network of immunoreactive (ir) fibers occurred in the peri-infundibular region and extended into the periventicular tissue, around the lateral and posterior recesses. Rostrally directed ir-fibers reached the telencephalon either ventrally or mediodorsally; some were observed in the olfactory lobe. In the mesencephalon, ir-fibers penetrated into the optic tectum of the goldfish. In the pituitary, both antisera intensely labeled rostral ACTH cells. Small groups of labeled cells were scattered in the rostral pars distalis and the proximal pars distalis. A gradient of activity was evident among ACTH cells: those located along the rostral neurohypophysis containing corticotropin-releasing factor nerve terminals were larger and often more marked than those farther away from the neural tissue. ACTH-like peptide in the brain may act as a neuromodulator, mainly in the NLT and the preoptic nucleus, and around the nuclei of the ventricular recesses containing serotonin and catecholamines.