Immunohistochemical Localization and Radioimmunoassay of Corticotropin-Releasing Factor in the Forebrain and Hypophysis of the Frog <i>Rana ridibund</i><i>a</i>

Abstract

The distribution of immunoreactive corticotropin-releasing hormone (CRF) in the forebrain and pituitary of the frog Rana ridibunda was studied by means of specific radioimmunoassay and immunohistochemistry using the indirect immunofluorescence and the peroxidase-antiperoxidase techniques. Relatively high concentrations of CRF-like material were found in both chiasmatic and infundibular regions of the hypothalamus (352 ± 11 and 422 ± 36 pg, respectively). Large amounts of CRF were also found in neurointermediate lobe extracts. Standard curves of synthetic CRF and the dilution curves for hypothalamic or neurointermediate lobe extracts were parallel. After Sephadex G-75 gel filtration, CRF-like immunoreactivity eluted in a single peak, in the same position as synthetic ovine CRF. Reversed-phase high-performance liquid chromatography of the material purified on Sephadex G-75 revealed 5 components with CRF-like immunoreactivity. The major peak had a retention time of 22 min as compared to 25.4 min for ovine CRF and 36 min for rat CRF. The detection of CRF-like immunoreactivity in neurons was facilitated by colchicine pretreatment of the frogs. The great majority of the CRF-positive perikarya were seen in the ventral region of the preoptic nucleus. A few scattered perikarya were also observed in the dorsal preoptic nucleus and in the retrochiasmatic region. Immunoreactive fibers were found in the infundibular nucleus and in various extrahypothalamic zones. CRF-containing neurons were apparently distinct from mesotocinergic and vasotocinergic neurons. A large number of immunoreactive nerve fibers were observed in the median eminence in close contact with the capillaries of the pituitary portal plexus and in the neural lobe. A few CRF-positive fibers were detected in the intermediate lobe, whereas the distal lobe was totally negative. These results show that the diencephalon and pars intermedia-nervosa of the frog contain a peptide immunologically related to mammalian CRF.

Molecular cloning, pharmacological characterization, and histochemical distribution of frog vasotocin and mesotocin receptors

“…The occurrence of VTR mRNA in the distal lobe of the pituitary is consistent with a role of VT in the control of ACTH secretion (Tonon et al 1986). Previous studies have shown that the intermediate lobe of the pituitary is innervated by MTcontaining fibers (Dierickx & Vandesande 1976, Tonon et al 1985, Lamacz et al 1989. The fact that MTR mRNA is actively expressed in the pars intermedia strongly suggests that MT controls the activity of pituitary melanotrophs.…”

Amphibian Melanotrope Subpopulations Respond Differentially to Hypothalamic Secreto-Inhibitors

“…Immunocytochemical studies have shown that nerve terminals reaching melanotrope cells contain, in addition to dopamine [10, 13]and TRH [14, 15, 16, 17], the classical neurotransmitters γ-aminobutyric acid (GABA) [18, 19, 20]and serotonin [21, 22], as well as the neuropeptides mesotocin [17, 23], corticotropin-releasing factor [24, 25]and neuropeptide Y (NPY) [13, 20, 26, 27, 28, 29]. Double-labeling experiments also revealed that a single neuron may contain more than one factor.…”

Corticotropin-Releasing Factor-Like Immunoreactivity, Arginine Vasopressin-Like Immunoreactivity and ACTH-Releasing Bioactivity in Hypothalamic Tissue from Fetal and Neonatal Sheep

“…231-0607) against oCRFi_4i as described previously [19] except that I251-oC R F i_4| was purified by chromatography on a Biogel P10 (100-200 mesh) column (0.9 x 60 cm) and eluted with phos phate buffer 0.05 M, pH 7.6 containing 0.3% bovine serum albu-…”