In vitro and in vivo ACTH-releasing activity of ovine CRF,sauvagine and urotensin I

The ability of three homologous peptides, ovine corticotropin-releasing factor (CRF), sauvagine and urotensin I, to release ACTH was examined in vitro and in vivo. All three peptides exhibit statistically equivalent potencies to stimulate ACTH secretion both by cultured pituitary cells and in pharmacology blocked rats. These results suggest that all three peptides evolved from a common mammalian precursor that possessed high hypophysiotropic potency.     

The distribution of corticotropin-releasing factor-immunoreactive neurons and nerve fibers in the brain of the snake,Natrix maura

Summary The anatomical distribution of neurons and nerve fibers containing corticotropin-releasing factor (CRF) has been studied in the brain of the snake, Natrix maura, by means of immunocytochemistry using an antiserum against rat CRF. To test the possible coexistence of CRF with the neurohypophysial peptides arginine vasotocin (AVT) and mesotocin (MST) adjacent sections were stained with antisera against the two latter peptides. CRF-immunoreactive (CRF-IR) neurons exist in the paraventricular nucleus (PVN). In some neurons of the PVN, coexistence of CRF with MST or of CRF with AVT has been shown. Numerous CRF-IR fibers run along the hypothalamo-hypophysial tract and end in the outer layer of the median eminence. In addition, some fibers reach the neural lobe of the hypophysis. CRF-IR perikarya have also been identified in the following locations: dorsal cortex, nucleus accumbens, amygdala, subfornical organ, lamina terminalis, nucleus of the paraventricular organ, nucleus of the oculomotor nerve, nucleus of the trigeminal nerve, and reticular formation. In addition to all these locations CRF-IR fibers were also observed in the lateral septum, supraoptic nucleus, habenula, lateral forebrain bundle, paraventricular organ, hypothalamic ventromedial nucleus, raphe and interpeduncular nuclei.     

High affinity binding sites for somatostatin to rat pituitary

Binding sites for somatostatin (SS) are described in rat pituitary membranes using either [¹²⁵I-Tyr¹¹]-SS-14 or [Leu⁸, D-Trp²², ¹²⁵I-Tyr²⁵]-SS-28 as radioligands; in each case saturable and high affinity binding sites with K_D's for SS of 1.09 and 0.95 nM respectively have been characterized. The binding capacity is 100 f mols/mg protein. The potencies of various SS analogs measured in the radioreceptor assay are in agreement with the potencies in a bioassay measuring inhibition of growth hormone release; in particular, SS-28 is slightly less potent than SS-14. A comparison of these data with those describing SS binding in brain and pancreas suggests that some pharmacological differences may exist between pituitary, brain and pancreas binding sites for SS.     

Physiological changes in rat hypothalamic CRF: Circadian,stress and steroid suppression

Hypothalamic CRF-like immunoreactivity was measured in the a.m. and p.m., after systemic dexamethasone administration or after either stress in adult male rats. Measurement of plasma corticosterone levels revealed the expected circadian rhythmicity, suppression after dexamethasone administration and increase after ether stress. The hypothalamic content of CRF-like immunoreactivity was significantly decreased in the p.m. and after dexamethasone administration. However, no change in hypothalamic CRF-like immunoreactivity was observed after ether stress. The results are consistent with an increased release in the p.m. and decreased synthesis of hypothalamic CRF after systemic dexamethasone administration. The observation that there is no change in content of hypothalamic CRF-like immunoreactivity after ether stress could be due to the fact that the animals were stressed by handling. The results show that this immunoreactivity present in the hypothalamus is altered by changes in the hypothalamic-pituitaryadrenal axis and thus suggest that this peptide is a physiologically significant CRF in the rat.     

Hypothalamic CRF-like immunoreactivity in the rat after hypophysectomy or adrenalectomy

Hypothalamic CRF-like immunoreactivity was measured in normal, hypophysectomized or adrenalectomized adult male rats. As expected, adrenalectomy resulted in decreased levels in plasma corticosterone and increased plasma levels of ACTH; hypophysectomy resulted in decreased levels in both corticosterone and ACTH. The hypothalamic content of CRF-like immunoreactivity in animals two weeks post-hypophysectomy or adrenalectomy was approximately seven times greater than that found in intact animals. At one week, post-surgery, small but statistically significant decreases in content of CRF-like immunoreactivity were observed. The results at one week are consistent with removal of feedback effects of ACTH and corticosterone causing increased release of CRF and decreased content. The increase in CRF-like immunoreactivity two weeks post-surgery is probably not related to direct feedback effects on release but may be due to increased synthesis secondary to long term removal of feedback inhibition.     

Cytological evidence for activation of neuroendocrine cells in the parvocellular preoptic nucleus of the goldfish hypothalamus following pharmacological adrenalectomy

Summary The nucleus preopticus (NPO) of the goldfish hypothalamus is composed of parvocellular (NPOpc) and magnocellular (NPOmc) neurosecretory neurons. The cytology of NPOpc and NPOmc neurons was examined with light and electron microscopy following pharmacological adrenalectomy with the adrenocortical inhibitor, metopirone. After five days of metopirone administration, light microscopy revealed a significant increase in nuclear area of NPOpc, but not of NPOmc, neurons.Ultrastructural examination of NPOpc neurons revealed two cell types, PC 1 and PC 2 neurons, which could be distinguished by the relative abundance and the size of the neurosecretory granules in the cytoplasm. The ultrastructural appearance of the NPOmc neurons revealed a single cell type containing abundant neurosecretory granules. Following five days of metopirone administration, the ultrastructural appearance of the PC 1 neurons indicated a state of enhanced secretory activity. Metopirone had no observable effect on the appearance of the PC 2 or NPOmc neurons. These observations demonstrate that PC 1 neurons are activated under the conditions of pharmacological adrenalectomy and suggest that the secretory activity of these neurons is inhibited by adrenocorticosteroids.     

Immunohistochemical investigation of urotensins in the caudal spinal cord of four species of elasmobranchs and the lamprey,Lampetra japonica

Summary In the four species of elasmobranchs examined (Triakis scyllia, Heterodontus japonicus, Scyliorhinus torazame, Dasyatis akajei), all identifiable caudal neurosecretory cells and their corresponding neurohemal areas showed urotensin II (UII)-immunoreactivity with varied intensity. To localize urotensin I (UI) in the caudal neurosecretory system of the dogfish, Triakis scyllia, h-CRF (1–20) antiserum that cross-reacts with UI was used in place of UI antiserum. CRF/UI-immunoreactivity was demonstrated in the neurosecretory cells and neurohemal areas. A considerable number of neurons showed both UII- and CRF/UI-immunoreactivities, suggesting that UII and UI are produced in the same neurosecretory cells. However, some neurons exhibited UII-immunoreactivity, but no CRF/UI-immunoreactivity. Cells immunoreactive only to CRF antiserum were not detected. At least two populations of neurons exist in the dogfish caudal neurosecretory system: (i) cells immunoreactive for both CRF/UI and UII, and (ii) cells immunoreactive for UII. The dorsal cells of the lamprey, Lampetra japonica, did not react with either UII or CRF antiserum.     

CRF-containing neurons of the rat hypothalamus

Summary The immunoreactive CRF-neurons of the rat hypothalamus have been examined immunohistochemically employing anti-rat CRF serum. These neurons are confined to the paraventricular nucleus, dorsomedial-lateral hypothalamic area, and suprachiasmatic nucleus, and are, respectively, also immunoreactive to anti-Met-enk, -alpha-MSH, and -VIP sera. Intraventricular administration of colchicine (50 g/5 l/rat) induces a dramatic enhancement of the immunostainability of the cell somata, and also accelerates the development of immunoreactivity of other stored peptides, especially in the paraventricular nucleus.The CRF-neurons respond to adrenalectomy by showing increased immunoreactivity and an increase in the number of cell bodies; in the dorsomedial-lateral area and suprachiasmatic nucleus, there is also an enhanced immunoreactivity for alpha-MSH and VIP, respectively. CRF-cells in the paraventricular nucleus become markedly hypertrophied, but do not show any enhanced immunoreactivity for Met-enk. Since the axons of the paraventricular neurons run to the median eminence, it is probable that they are involved with the endocrine control of hypophysial ACTH release. It is concluded that the CRF-containing neurons in rat hypothalamus consist of three types which are functionally and morphologically different.     

模拟高原低氧对不同性别新生大鼠下丘脑 CRF和AVP水平的影响

目的:探讨高原低氧对雌雄新生大鼠下丘脑-腺垂体-肾上腺皮质轴中枢部位肽能神经元发育的影响.方法:在低压氧舱中模拟高海拔低氧,用放免法测定精氨酸加压素(AVP)和下丘脑促肾上腺皮质激素释放激素(CRF)含量.结果:无论是在2 300 m对照海拔,还是在5 000 m模拟海拔,雌雄生后大鼠具相同的发育模式.低氧下发育至21 d时,CRF水平显著低于对照;相反,21 d及28 d时,低氧组AVP水平高于对照.结论:下丘脑CRF和AVP神经元间不同的发育模式可能与它们的功能及发育阶段特性相异有关.     

第三脑室注射组织胺增强五肽促胃液素诱导的胃酸分泌的作用机制

本文探讨中枢组织胺增强胃酸分泌的作用机制。雄性ＳＤ大鼠重２００－３００ｇ,用３７℃生理盐水做恒速,连续胃灌流。膈下迷走神经切除后,观察第三脑室或外周给药对五肽促胃激素诱导的胃酸分泌及对血交涉以质酮水平的影响。结果如下：１．第三脑室注射１．０μｇ组织胺增强Ｇ－５诱导的胃酸分泌,这作用可为预先肌肉注射苯海拉明８．０μｇ听阻断。２．脑注射促肾上腺皮质激素释放因子增强因酸分泌,且呈量效关系。３．脑室注射组