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ABSTRACT: The effects of intracerebroventricular (icv) administration of adrenomedullin (AM) and proadrenomedullin NH2-terminal 20 peptide (PAMP) on the expression of Fos in the central nervous system (CNS) were examined in conscious rats, using immunohistochemistry. Fos-like immunoreactivity (LI) was detected in various brain areas of the rats, including the supraoptic nucleus, the paraventricular nucleus, the locus coeruleus, the area postrema and the nucleus of the tractus solitarius 90 min after icv administration of AM. Few cells with Fos-LI were found in the CNS 90 min after icv administration of saline. Fos-LI was also detected in the various hypothalamic areas after icv administration of PAMP. These results suggest that centrally administered AM and PAMP may cause physiological responses through the activation of a neural network in the hypothalamus and the brainstem.
Peptides 12/2001; 22(11):1817-24. · 2.43 Impact Factor
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ABSTRACT: Urocortin-like immunoreactivity (Ucn-LI) in the supraoptic nucleus (SON) of Dahl rats was examined. Dahl salt-sensitive (S) rats fed with a high salt diet developed hypertension. Numbers of Ucn-LI neurons in the SON in Dahl S on a high salt diet were markedly increased, compared with those in Dahl salt-resistant (R) rats on the same. Sporadic Ucn-LI neurons were found in the SON of both Dahl S and R on a normal diet. Numbers of Ucn-LI neurons in the SON of spontaneously hypertensive rat (SHR) and stroke-prone SHR, genetic models of hypertension, and control rats (Sprague-Dawley and Wistar-Kyoto) were similar. These results suggest that Ucn in the SON is associated with salt loading-induced hypertension rather than spontaneous hypertension.
Neuroscience Letters 02/2000; 279(1):17-20. · 2.11 Impact Factor
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R Serino,
Y Ueta,
Y Hara,
M Nomura,
Y Yamamoto,
I Shibuya, Y Hattori,
K Kitamura,
K Kangawa,
J A Russell,
H Yamashita
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ABSTRACT: The effects of intracerebroventricular (i.c.v.) administration of adrenomedullin (AM) on plasma oxytocin (OXT), c-Fos protein (Fos), and c-fos messenger RNA (mRNA) in the paraventricular (PVN) and supraoptic nuclei (SON) of the rat were investigated using RIA for OXT, immunohistochemistry for Fos, and in situ hybridization histochemistry for c-Fos mRNA. Central administration of AM caused a significant increase in the plasma OXT level. Intracerebroventricular administration of AM caused a marked induction of Fos-like immunoreactivity (LI) in the PVN and in the dorsal parts of the SON. In the PVN and SON, OXT-LI cells predominantly exhibited nuclear Fos-LI in comparison with arginine vasopressin-LI cells. In situ hybridization histochemistry revealed that the induction of c-fos mRNA in the PVN and SON was increased in a dose-related manner 30 min after i.c.v. administration of AM. This induction was reduced by pretreatment with the AM receptor antagonist, human AM-(22-52)-NH2. These results suggest that central AM is responsible for activating the neurosecretory cells in the PVN and SON via selective AM receptors, and that AM stimulates the secretion of OXT by activating hypothalamic OXT-producing cells.
Endocrinology 06/1999; 140(5):2334-42. · 4.46 Impact Factor
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ABSTRACT: 1. The expression, distribution and function of P2X purinoceptors in the supraoptic nucleus (SON) were investigated by reverse transcription-polymerase chain reaction (RT-PCR), in situ hybridization, and Ca2+-imaging and whole-cell patch-clamp techniques, respectively. 2. RT-PCR analysis of all seven known P2X receptor mRNAs in circular punches of the SON revealed that mRNAs for P2X2, P2X3, P2X4, P2X6 and P2X7 receptors were expressed in the SON, and mRNAs for P2X3, P2X4 and P2X7 were predominant. 3. In situ hybridization histochemistry for P2X3 and P2X4 receptor mRNAs showed that both mRNAs were expressed throughout the SON and in the paraventricular nucleus (PVN). 4. ATP caused an increase in [Ca2+]i in a dose-dependent manner with an ED50 of 1.7 x 10-5 M. The effects of ATP were mimicked by ATPgammaS and 2-methylthio ATP (2MeSATP), but not by AMP, adenosine, UTP or UDP. alphabeta-Methylene ATP (alphabetaMeATP) and ADP caused a small increase in [Ca2+]i in a subset of SON neurones. 5. The P2X7 agonist 2'- & 3'-O-(4-benzoylbenzoyl)-ATP (BzATP) at 10-4 M increased [Ca2+]i, but the potency of BzATP was lower than that of ATP. In contrast, BzATP caused a more prominent [Ca2+]i increase than ATP in non-neuronal cells in the SON. 6. The effects of ATP were abolished by extracellular Ca2+ removal or by the P2 antagonist pyridoxal phosphate-6-azophenyl-2',4'-disulphonic acid (PPADS), and inhibited by extracellular Na+ replacement or another P2 antagonist, suramin, but were unaffected by the P2X7 antagonist oxidized ATP, and the inhibitor of Ca2+-ATPase in intracellular Ca2+ stores cyclopiazonic acid. 7. Two patterns of desensitization were observed in the [Ca2+]i response to repeated applications of ATP: some neurones showed little or moderate desensitization, while others showed strong desensitization. 8. Whole-cell patch-clamp analysis showed that ATP induced cationic currents with marked inward rectification. The ATP-induced currents exhibited two patterns of desensitization similar to those observed in the [Ca2+]i response. 9. The results suggest that multiple P2X receptors, including P2X3, are functionally expressed in SON neurones, and that activation of these receptors induces cationic currents and Ca2+ entry. Such ionic and Ca2+-signalling mechanisms triggered by ATP may play an important role in the regulation of SON neurosecretory cells.
The Journal of Physiology 02/1999; 514 ( Pt 2):351-67. · 4.72 Impact Factor
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Y Ueta,
Y Hara,
V S Setiadji,
T Isse,
I Shibuya,
K Kitamura,
K Kangawa,
H Matsuo,
T Eto, Y Hattori,
H Yamashita
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ABSTRACT: Adrenomedullin-like immunoreactivity in the hypothalamo-neurohypophysial tract in colchicine-treated and hypophysectomized rats was examined by immunohistochemistry. Adrenomedullin-like immunoreactive (AM-LI) neurons were localized in the hypothalamic areas, including the paraventricular nuclei and the supraoptic nuclei. Abundant AM-LI fibers and varicosities were found in the hypothalamoneurohypophysial tract and the internal zone of the median eminence in the colchicine-treated and hypophysectomized rats, whereas in control rats few AM-LI fibers were observed. These results suggest that the axons of the AM-LI neurons in the hypothalamus may terminate in the neurohypophysis.
Peptides 02/1999; 20(2):199-204. · 2.43 Impact Factor
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ABSTRACT: Plasma arginine vasopressin (AVP) is known to be elevated in patients with uncontrolled insulin-dependent diabetes mellitus who have plasma hyperosmolality with hyperglycaemia. Although osmotic stimuli cause an increase in nitric oxide synthase (NOS) activity as well as synthesis of AVP and oxytocin in the paraventricular (PVN) and supraoptic nuclei (SON), it is not known whether NOS activity in the hypothalamus changes in the diabetic patients who have plasma hyperosmolality with hyperglycaemia caused by insulin deficiency. Expression of the neuronal (n) NOS gene in the PVN and SON in streptozotocin (STZ)-induced diabetic rats was investigated by using in situ hybridization histochemistry and NADPH-diaphorase histochemical staining. Four weeks after intraperitoneal (i. p.) administration of STZ, male Wistar rats developed hyperglycaemia and plasma hyperosmolality. The expression of nNOS gene and NADPH-diaphorase staining in the PVN and SON remarkably increased in STZ-induced diabetic rats compared to control rats. Three weeks after administration of STZ, the diabetic rats were subcutaneously treated with insulin for 1 week, which resulted in significant suppression of the induction of nNOS, AVP and oxytocin gene expression in the PVN and SON. Furthermore, the induction of nNOS gene expression in the PVN and SON was suppressed in STZ-induced diabetic rats treated with phlorizin and diet to normalize hyperglycaemia without insulin treatment. These results suggest that upregulation of nNOS gene expression as well as AVP and oxytocin gene expression in the PVN and SON in STZ-induced diabetic rats may be associated with hyperglycaemia and plamsa hyperosmolality.
Diabetologia 07/1998; 41(6):640-8. · 6.81 Impact Factor
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ABSTRACT: In the present study, the effects of glutamate and of agonists for ionotropic and metabotropic glutamate receptors on intracellular Ca2+ concentration ([Ca2+]i) were investigated in neurons of the rat supraoptic nucleus (SON). We used the intracellular Ca2+ imaging technique with fura-2, in single magnocellular neurons dissociated from the SON of rats. Glutamate (10(-6)-10(-4) M) evoked a dose-dependent increase in [Ca2+]i. The glutamate agonists exerted similar effects, although with some differences in the characteristics of their responses. The [Ca2+]i response to NMDA was smaller than those of glutamate or the non-NMDA receptor agonists, AMPA and kainate, but was significantly enhanced by the removal of extracellular Mg2+. Glutamate, as well as quisqualate, an agonist for both ionotropic and metabotropic glutamate receptors, evoked a [Ca2+]i increase in a Ca2+-free condition, suggesting Ca2+ release from intracellular Ca2+ stores. This was further evidenced by [Ca2+]i increases in response to a more selective metabotropic glutamate receptor agonist, t-ACPD, in the absence of extracellular Ca2+. Furthermore, the quisqualate-induced Ca2+ release was abolished by the selective metabotropic glutamate receptor antagonist, (S)-4-carboxyphenylglycine. The results suggest that metabotropic glutamate receptors as well as non-NMDA and NMDA receptors are present in the SON neurons, and that activation of the first leads to Ca2+ release from intracellular Ca2+ stores and the activation of the latter two types induces Ca2+ entry. These dual mechanisms of Ca2+ signalling may play a role in the regulation of SON neurosecretory cells by glutamate.
Journal of Neuroendocrinology 06/1998; 10(5):383-9. · 3.14 Impact Factor
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ABSTRACT: We have examined the effects of isotonic hypovolemia on the expression of the neuronal nitric oxide synthase (nNOS) gene in the paraventricular (PVN) and supraoptic nuclei (SON) of the rat, using in situ hybridization histochemistry with a 35S-labelled oligodeoxynucleotide probe complementary to nNOS mRNA. Intraperitoneal (i.p.) administration of polyethylene glycol (PEG) (MW 4000, 20 ml/kg body weight) dissolved in 0.9% saline (20% w/v) induced isotonic hypovolemia. The expression of the nNOS gene in the PVN and SON 6 h after i.p. administration of PEG was increased significantly in comparison with controls. The dual staining for NADPH diaphorase activity and Fos-like immunoreactivity (Fos-LI) showed that at 3 and 6 h after i.p. administration of PEG, a subpopulation of NADPH diaphorase-positive cells in the PVN and SON exhibited nuclear Fos-LI. These results suggest that NO in the PVN and SON may be involved in the neuroendocrine and autonomic responses to non-osmotic hypovolemia.
Brain Research 05/1998; 790(1-2):25-32. · 2.73 Impact Factor
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ABSTRACT: Pituitary adenylate cyclase activating polypeptide (PACAP)-like immunoreactivity and its receptor mRNA have been reported in the supraoptic and the paraventricular nucleus (SON and PVN, respectively) and PACAP has been implicated in the regulation of magnocellular neurosecretory cell function. To examine the site and the mechanism of the action of PACAP in the neurosecretory cells, we measured AVP release from SON slice preparations and the cytosolic Ca2+ concentration ([Ca2+]i) from single dissociated SON neurons. PACAP at concentrations from 10(-12) to 10(-7) M increased [Ca2+]i in dissociated SON neurons in a dose-dependent manner. The patterns of the PACAP-induced [Ca2+]i increase were either sustained increase or cytosolic Ca2+ oscillations. PACAP (10[-7] M) increased [Ca2+]i in 27 of 27 neurons and glutamate (10[-4] M) increased [Ca2+]i in 19 of 19 SON neurons examined, whereas angiotensin II (10[-7] M) increased [Ca2+]i in only 15 of 60 SON neurons examined. PACAP at lower concentrations (10[-10] to 10[-8] M) increased [Ca2+]i in 70-80% of neurons examined. Although the onset and recovery of the PACAP-induced [Ca2+]i increase were slower than those observed with glutamate, the spatial distribution of the [Ca2+]i increases in response to the two ligands were similar: [Ca2+]i increase at the proximal dendrites was larger and faster and that at the center of the soma was smaller and slower. The PACAP-induced [Ca2+]i responses were abolished by extracellular Ca2+ removal, the L-type Ca2+-channel blocker, nicardipine, or by replacement of extracellular Na+ with N-methyl D-glucamine, and were partially inhibited by the Na+-channel blocker, tetrodotoxin. The N-type Ca2+-channel blocker, omega-conotoxin GVIA did not significantly inhibit the PACAP-induced [Ca2+]i responses. Furthermore, PACAP (10[-7] M) as well as glutamate (10[-4] M) increased AVP release from SON slice preparations, and extracellular Ca2+ removal or nicardipine inhibited the AVP release in response to PACAP. These results indicate that PACAP enhances Ca2+ entry via voltage-gated Ca2+ channels and increases [Ca2+]i, which, in turn, stimulates somatodendritic vasopressin release by directly activating PACAP receptors on SON neurons. The results also suggest that PACAP in the SON may play a pivotal role in the control of the neurohypophyseal function at the level of the soma or the dendrites.
Journal of Neuroendocrinology 01/1998; 10(1):31-42. · 3.14 Impact Factor
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ABSTRACT: The existence of PTH-related peptide (PTHrP) in the hypothalamus was examined by immunohistochemistry in colchicine-treated rats. Two days after intracerebroventricular administration of colchicine dense PTHrP-like immunoreactivity (LI) was observed in the external zone of the median emminence (ME). PTHrP-LI cells were found in the paraventricular nucleus, the supraoptic nucleus and the periventricular region of the third ventricule. The effects of PTHrP on intracellular Ca2+ concentrations ([Ca2+]i) were examined by a Ca2+ imaging method using fura-2 in perifused preparations of isolated rat anterior pituitary cells. The rise in [Ca2+]i induced by PTHrP was found in approximately 17% of the cells examined. These results suggest that PTHrP-LI cells in the hypothalamus may project to the ME and contribute to the anterior pituitary function.
Brain Research 12/1997; 774(1-2):216-20. · 2.73 Impact Factor
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ABSTRACT: The effects of dehydration and food deprivation on urocortin-like immunoreactivity (Ucn-IR) in the rat supraoptic nucleus (SON) and the paraventricular nucleus (PVN) were examined by immunohistochemistry. Water deprivation for 48 h caused a significant increase in the number of Ucn-IR neurons in the SON, compared with control. Ucn-IR fibers and varicosities in the SON and the internal zone of the median eminence (ME) were increased, but a few and faint Ucn-IR neurons and fibers were observed in the PVN. On the other hand, food deprivation for 48 h caused a significant decrease in the number of Ucn-IR neurons in the SON, compared with control. Ucn-IR fibers and varicosities in the SON and the ME were fewer than those in controls. Ucn-IR neurons and fibers in the PVN were not detected after food deprivation. These results suggest that Ucn in the SON may be involved in the central regulation of water balance and nutrient homeostasis.
Neuroscience Letters 07/1997; 229(1):65-8. · 2.11 Impact Factor
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ABSTRACT: The effect of chronic salt loading on urocortin-like immunoreactivity (Ucn-IR) was investigated in the rat hypothalamo-neurohypophysial system. In control rats a few Ucn-IR neurons were observed scattered throughout the supraoptic nucleus (SON) and few in the paraventricular nucleus (PVN). A small number of Ucn-IR fibers were observed scattered in the median eminence (ME) and the posterior pituitary. However, after 5 days of chronic administration of 2% saline, a marked increase in the number of Ucn-IR perikarya and fibers was observed in the PVN and the SON. Additionally, Ucn-IR varicosities and fibers were found in the internal zone of the ME and in the posterior pituitary. To confirm the findings and examine the possible involvement of anterior pituitary function in synthesis of Ucn, surgical hypophysectomized rats were used. Five days after hypophysectomy, a marked increase in Ucn-IR was observed in the PVN, the SON, and both the internal and the external zone of the ME. These results suggest that Ucn in the hypothalamo-neurohypophysial system may be involved in the regulation of salt balance, and possibly in the stimulation of ACTH release from the anterior pituitary.
Neuroscience Letters 06/1997; 227(2):127-30. · 2.11 Impact Factor
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ABSTRACT: The effects of angiotensin II (A II) and ANP on spontaneously active neurons in the subfornical organ (SFO), anteroventral third ventricle (AV3V) and supraoptic (SON) and paraventricular nucleus (PVN) were investigated using slice preparations and extracellular recordings. Application of A II (10(-7)M) excited the neural activity of 66% of the SFO neurons, 28% of the AV3V neurons and 44% of the SON neurons. The threshold concentration to produce responses in SFO and AV3V neuron was less than 10(-10)M, while that in SON neurons was 10(-9)M. The excitatory effects of A II were reversibly antagonized by saralasin and persisted after synaptic blockade in a low Ca2+ and high Mg2+ medium. Application of ANP (10(-7)M) inhibited the neural activity of 41% of the AV3V neurons, 22% of the PVN neurons and only 14% of the SFO neurons but had no effect on SON neurons. The threshold concentration for ANP in the AV3V was 10(-11)M. Interestingly, ANP inhibited A II induced excitation in most of the SFO neurons (87%), while ANP had little effects on their spontaneous firing rates. These results show that both peptides of A II and ANP have direct central actions on hypothalamic neurons although ANP can not directly influence magnocellular neurons, suggesting that these blood borne peptides are detected in the SFO and AV3V and that they are acting as a neurotransmitter or a neuromodulator in the central nervous system to regulate water homeostasis.
Archives of Histology and Cytology 02/1989; 52 Suppl:121-7. · 0.57 Impact Factor
