Biomedical subjects

Masayasu Kojima

Publications and source records attributed to Masayasu Kojima.

At least 19 recordsLinked to original sources

PubMed2005

Maternal ghrelin plays an important role in rat fetal development during pregnancy.

Ghrelin, an acylated peptide serving as an endogenous ligand for GH secretagogue receptor (GHS-R), was originally isolated from rat and human stomach. In this study, we report the critical role of maternal ghrelin in fetal development. High levels of ghrelin receptor (GHS-R) mRNA were detected in various peripheral fetal tissues beginning at embryonic d 14 and lasting until birth. Fetal GHS-R expression was also confirmed in fetal tissues by immunohistochemistry. Autoradiography revealed that both des-acyl ghrelin and acyl ghrelin bind to fetal tissues. Chronic treatment of mothers with ghrelin resulted in a significant increase in birth weight in comparison to newborns from saline-treated mothers. Even when maternal food intake after ghrelin treatment was restricted through paired feeding, significant stimulation of fetal development still occurred. Conversely, active immunization of mothers against ghrelin decreased fetal body weight during pregnancy. A single ghrelin injection into the mother increased circulating ghrelin levels in the fetus within 5 min of injection, suggesting that maternal ghrelin transits easily to the fetal circulation. High levels of des-acyl ghrelin were detected in fetal blood and amniotic fluid. Both acylated and des-acyl ghrelin increased [3H]thymidine and 5-bromo-2'-deoxyuridine incorporation of cultured fetal skin cells in a dose-dependent manner, and calcium-imaging analysis revealed that acyl and des-acyl ghrelin increased the Ca2+ influx in discrete cultured fetal skin cells, respectively. These results indicate that maternal ghrelin regulates fetal development during the late stages of pregnancy.

Amniotic Fluid↗

PubMed2005

The neuropeptide neuromedin U promotes inflammation by direct activation of mast cells.

Neuromedin U (NMU) is a neuropeptide that is expressed in the gastrointestinal tract and central nervous system. NMU interacts with two G protein-coupled receptors, NMU-R1 and NMU-R2. Whereas NMU-R2 localizes predominantly to nerve cells, NMU-R1 is expressed in peripheral tissues including lymphocytes and monocytes, suggesting a role of NMU in immunoregulation. However, the functions of NMU in peripheral tissues have not been clarified. In this study, using NMU-deficient mice, we first demonstrated that NMU plays an important role in mast cell-mediated inflammation. Complete Freund's adjuvant-induced mast cell degranulation as well as edema and neutrophil infiltration, which occurred weakly in mast cell-deficient WBB6F(1)-W/W(v) mice, did not occur in NMU-deficient mice. Moreover, intraplantar injection of NMU into paws induced early inflammatory responses such as mast cell degranulation, vasodilation, and plasma extravasation in WT mice but not in WBB6F(1)-W/W(v) mice. NMU-R1 was highly expressed in primary mast cells, and NMU induced Ca(2+) mobilization and degranulation in peritoneal mast cells. These data indicate that NMU promotes mast cell-mediated inflammation; therefore, NMU receptor antagonists could be a novel target for pharmacological inhibition of mast cell-mediated inflammatory diseases.

Animals↗

PubMed2005

Purification, cDNA cloning, and characterization of ghrelin in channel catfish, Ictalurus punctatus.

The ghrelin peptide and cDNA encoding precursor protein were isolated from the stomach of a channel catfish, Ictalurus punctatus. Catfish ghrelin is a 22-amino acid peptide with a sequence of GSSFLSPTQKPQNRGDRKPPRV. The third serine residue has been modified by n-decanoic acid and unsaturated fatty acids; however, an octanoylated form could not be identified. The carboxyl end of the peptide possessed an amide structure. A Gly-extended, non-amidated 23-amino acid ghrelin (ghrelin-Gly) was also isolated. Real-time quantitative PCR analysis revealed high levels of gene expression in the stomach and moderate levels in the pancreas and gall bladder. Intraperitoneal (IP) injection of ghrelin increased plasma GH levels in the catfish, but the effect of ghrelin-Gly was more potent than that of amidated ghrelin. Furthermore, IP injection with both amidated ghrelin and ghrelin-Gly caused a significant increase in pituitary GH mRNA expression over a 3-h period. These results indicate that ghrelin is present in catfish and stimulates GH gene expression and GH release in channel catfish.

Amino Acid Sequence↗

PubMed2005

Molecular forms of hypothalamic ghrelin and its regulation by fasting and 2-deoxy-d-glucose administration.

Ghrelin, an endogenous ligand for the GH secretagogue receptor, is a hormone expressed in stomach and other tissues, such as hypothalamus, testis, and placenta. This hormone acts at a central level to stimulate GH secretion and food intake. Little is known, however, about the molecular forms and physiological roles of ghrelin within the hypothalamus. In this report, we detail the molecular forms, mRNA expression patterns, and peptide contents of ghrelin within the rat hypothalamus. Using the combination of reverse-phase HPLC and ghrelin-specific RIA, we determined that the rat hypothalamus contains both n-octanoyl-modified and des-acyl ghrelins. Fasting for 24 and 48 h significantly decreased ghrelin mRNA expression in the hypothalamus to 24% and 28% of control values, respectively. Both n-octanoyl-modified and des-acyl ghrelin content in the hypothalamus decreased after 24 and 48 h of fasting. These results contrast the changes in gastric ghrelin after fasting, which decreased in content despite increased mRNA expression. Two hours after injection of 2-deoxy-d-glucose (2-DG), a selective blocker of carbohydrate metabolism, ghrelin peptide levels also decreased. Thus, induction of glucoprivic states, such as fasting and 2-DG treatment, decreased ghrelin gene expression and peptide content within the hypothalamus.

Animals↗

PubMed2005

Effects of ghrelin on growth hormone secretion in vivo in ruminants.

Ghrelin, a novel endogenous growth hormone (GH) secretagogue, has been shown to exert very potent and specific GH-releasing activity in rats and humans. However, little is known about its GH-releasing activity and endocrine effects in domestic animals. To clarify the effect of ghrelin on GH secretion in vivo in ruminants, plasma GH responses to intra-arterial and intra-hypothalamic injections of rat ghrelin (rGhrelin) were examined in goats and cattle. The intra-arterial injection of 1 microg/kg BW of rGhrelin in ovariectomized goats failed to stimulate GH release, however, a dosage of 3 microg/kg BW significantly increased plasma GH concentrations (P<0.05). GH levels peaked at 15 min after the injection, then decreased to basal concentrations within 1 h after the injection. However, the secretory response to 3 microg/kg BW of rGhrelin was weaker than that of growth hormone-releasing hormone (GHRH) (0.25 microg/kg BW) (P<0.05). An infusion of 10 nmol of ghrelin into the medial basal hypothalamus (arcuate nucleus) significantly stimulated the release of GH in male calves (P<0.05). GH levels began to rise just after the infusions and peaked at 10 min, then decreased to the basal concentrations within 1 h after the injection. The present results show that ghrelin stimulates GH release in ruminants.

Animals↗

PubMed2005

Developmental changes in the pattern of ghrelin's acyl modification and the levels of acyl-modified ghrelins in murine stomach.

Ghrelin is an acylated peptide hormone secreted primarily from endocrine cells in the stomach. The major active form of ghrelin is a 28-amino acid peptide with an n-octanoyl modification at Ser(3) (n-octanoyl ghrelin), which is essential for its activity. In addition to n-octanoyl ghrelin, other forms of ghrelin peptide exist, including des-acyl ghrelin, which lacks an acyl modification, and other minor acylated ghrelin species, such as n-decanoyl ghrelin, whose Ser(3) residue is modified by n-decanoic acid. Multiple reports have identified various physiological functions of ghrelin. However, until now, there have been no reports that explore the process of ghrelin acyl modification, and only a few studies have compared the levels of des-acyl, n-octanoyl, and/or other minor populations of acylated ghrelin peptides. In this study we report that the amount of n-octanoyl ghrelin in murine stomachs increases gradually during the suckling period to a maximal level at 3 wk of age and falls sharply after the initiation of weaning. However, the concentration (picomoles per milligram of wet weight tissue) of total ghrelin, which includes des-acyl and all acylated forms of ghrelin peptides with intact C termini in murine stomach, remains unchanged across this suckling-weaning transition. Prematurely weaned mice exhibited a significant decrease in the amount of n-octanoyl or n-decanoyl ghrelin in the stomach. Orally ingested glyceryl trioctanoate, a medium-chain triacylglyceride rich in milk lipids, significantly increased the level of n-octanoyl-modified ghrelin in murine stomach. Fluctuations in the proportion of this biologically active, acyl-modified ghrelin could contribute to or be influenced by the change in energy metabolism during the suckling-weaning transition.

Acylation↗

PubMed2005

Analysis of rat insulin II promoter-ghrelin transgenic mice and rat glucagon promoter-ghrelin transgenic mice.

We developed and analyzed two types of transgenic mice: rat insulin II promoter-ghrelin transgenic (RIP-G Tg) and rat glucagon promoter-ghrelin transgenic mice (RGP-G Tg). The pancreatic tissue ghrelin concentration measured by C-terminal radioimmunoassay (RIA) and plasma desacyl ghrelin concentration of RIP-G Tg were about 1000 and 3.4 times higher than those of nontransgenic littermates, respectively. The pancreatic tissue n-octanoylated ghrelin concentration measured by N-terminal RIA and plasma n-octanoylated ghrelin concentration of RIP-G Tg were not distinguishable from those of nontransgenic littermates. RIP-G Tg showed suppression of glucose-stimulated insulin secretion. Arginine-stimulated insulin secretion, pancreatic insulin mRNA and peptide levels, beta cell mass, islet architecture, and GLUT2 and PDX-1 immunoreactivity in RIP-G Tg pancreas were not significantly different from those of nontransgenic littermates. Islet batch incubation study did not show suppression of insulin secretion of RIP-G Tg in vitro. The insulin tolerance test showed lower tendency of blood glucose levels in RIP-G Tg. Taking lower tendency of triglyceride level of RIP-G Tg into consideration, these results may indicate that the suppression of insulin secretion is likely due to the effect of desacyl ghrelin on insulin sensitivity. RGP-G Tg, in which the pancreatic tissue ghrelin concentration measured by C-RIA was about 50 times higher than that of nontransgenic littermates, showed no significant changes in insulin secretion, glucose metabolism, islet mass, and islet architecture. The present study raises the possibility that desacyl ghrelin may have influence on glucose metabolism.

Animals↗

PubMed2005

Ingested medium-chain fatty acids are directly utilized for the acyl modification of ghrelin.

Ghrelin, an acylated brain and gut peptide, is primarily produced by endocrine cells of the gastric mucosa for secretion into the circulation. The major active form of ghrelin is a 28-amino-acid peptide containing an n-octanoyl modification at serine that is essential for activity. Studies have identified multiple physiological functions for ghrelin, including GH release, appetite stimulation, and metabolic fuel preference. Until now, there has not been any report detailing the mechanism of ghrelin acyl modification. Here we report that ingestion of either medium-chain fatty acids (MCFAs) or medium-chain triacylglycerols (MCTs) increased the stomach concentrations of acylated ghrelin without changing the total (acyl- and des-acyl-) ghrelin amounts. After ingestion of either MCFAs or MCTs, the carbon chain lengths of the acyl groups attached to nascent ghrelin molecules corresponded to that of the ingested MCFAs or MCTs. Ghrelin peptides modified with n-butyryl or n-palmitoyl groups, however, could not be detected after ingestion of the corresponding short-chain or long-chain fatty acids, respectively. Moreover, n-heptanoyl ghrelin, an unnatural form of ghrelin, could be detected in the stomach of mice after ingestion of either n-heptanoic acid or glyceryl triheptanoate. These findings indicate that ingested medium-chain fatty acids are directly used for the acylation of ghrelin.

Acylation↗

PubMed2005

Identification of neuromedin S and its possible role in the mammalian circadian oscillator system.

The discovery of neuropeptides has resulted in an increased understanding of novel regulatory mechanisms of certain physiological phenomena. Here we identify a novel neuropeptide of 36 amino-acid residues in rat brain as an endogenous ligand for the orphan G protein-coupled receptor FM-4/TGR-1, which was identified to date as the neuromedin U (NMU) receptor, and designate this peptide 'neuromedin S (NMS)' because it is specifically expressed in the suprachiasmatic nuclei (SCN) of the hypothalamus. NMS shares a C-terminal core structure with NMU. The NMS precursor contains another novel peptide. NMS mRNA is highly expressed in the central nervous system, spleen and testis. In rat brain, NMS expression is restricted to the core of the SCN and has a diurnal peak under light/dark cycling, but remains stable under constant darkness. Intracerebroventricular administration of NMS in rats activates SCN neurons and induces nonphotic type phase shifts in the circadian rhythm of locomotor activity. These findings suggest that NMS in the SCN is implicated in the regulation of circadian rhythms through autocrine and/or paracrine actions.

Amino Acid Sequence↗

PubMed2005

Different effects of peripheral and central ghrelin on regulation of food intake in the Japanese quail.

When rat or human ghrelin is administered to chickens or rats it stimulates the release of growth hormone, however, its effects on food intake differ between the two species. To investigate this discrepancy, we measured plasma ghrelin concentrations before and after food intake, and determined the effects of central (intracerebroventricular, icv) and peripheral (intraperitoneal, ip) injections of various ghrelin doses on food intake and body temperature in the Japanese quail. In control quails, plasma ghrelin levels were significantly increased in the fasting state; subsequent feeding produced a reduction, suggesting that ghrelin may act as an orexigenic signal in Japanese quails as well as mammals. Food intake was stimulated by ip, but not icv, injections of small doses of ghrelin, whereas both ip and icv injections of larger doses inhibited feeding. A large dose of ghrelin also increased body temperature. These results suggest that an increase in peripheral ghrelin may act as a hunger signal to induce food intake through stimulation of the afferent vagal nerve in the Japanese quail, as in rats, whereas central ghrelin may inhibit feeding in different ways in the two species.

Animals↗

PubMed2005

Ghrelin: structure and function.

Small synthetic molecules called growth hormone secretagogues (GHSs) stimulate the release of growth hormone (GH) from the pituitary. They act through the GHS-R, a G protein-coupled receptor whose ligand has only been discovered recently. Using a reverse pharmacology paradigm with a stable cell line expressing GHS-R, we purified an endogenous ligand for GHS-R from rat stomach and named it "ghrelin," after a word root ("ghre") in Proto-Indo-European languages meaning "grow." Ghrelin is a peptide hormone in which the third amino acid, usually a serine but in some species a threonine, is modified by a fatty acid; this modification is essential for ghrelin's activity. The discovery of ghrelin indicates that the release of GH from the pituitary might be regulated not only by hypothalamic GH-releasing hormone, but also by ghrelin derived from the stomach. In addition, ghrelin stimulates appetite by acting on the hypothalamic arcuate nucleus, a region known to control food intake. Ghrelin is orexigenic; it is secreted from the stomach and circulates in the bloodstream under fasting conditions, indicating that it transmits a hunger signal from the periphery to the central nervous system. Taking into account all these activities, ghrelin plays important roles for maintaining GH release and energy homeostasis in vertebrates.

Amino Acid Sequence↗

PubMed2005

Influencing the between-feeding and endocrine responses of plasma ghrelin in healthy dogs.

OBJECTIVES: Ghrelin has recently been isolated from rat and human stomach as an endogenous ligand for the growth hormone (GH) secretagog receptor. Using beagle dogs, we investigated the distribution of ghrelin in the stomach and its possible role. METHODS: We examined: (i) GH release in response to ghrelin injection (0.5 or 5 microg/kg, i.v.), (ii) gastric localization of ghrelin-immunostained cells, (iii) changes in daily food consumption after ghrelin injection (3, 10, and 20 microg/kg, i.v.), (iv) plasma ghrelin levels under regular, but restricted feeding conditions, and (v) variations in plasma ghrelin levels in relatively lean, normal and obese dogs. RESULTS: Administration of ghrelin to dogs promptly increased circulating GH concentrations, although this effect was transitory and was maintained for only 20 min. Ghrelin was localized in the stomach fundus and body, but none was detected in either the pylorus or cardia. Administration of ghrelin at a dose of 20 microg/kg increased the daily food intake of beagle dogs. Plasma ghrelin levels peaked just before meal times, and then returned to basal levels. Obese dogs had higher plasma ghrelin levels than did normal and lean dogs. CONCLUSIONS: These results indicate that ghrelin is a potent GH secretagog in dogs. The distribution of ghrelin-immunoreactive cells in the canine stomach resembles that of both the murine and human stomach. Ghrelin participates in the control of feeding behavior and energy homeostasis in dogs and may, therefore, be involved in the development of obesity.

Animals↗

PubMed2004

Ghrelin directly regulates bone formation.

UNLABELLED: To clarify the role of ghrelin in bone metabolism, we examined the effect of ghrelin in vitro and in vivo. Ghrelin and its receptor, GHS-R1a, were identified in osteoblasts, and ghrelin promoted both proliferation and differentiation. Furthermore, ghrelin increased BMD in rats. Our results show that ghrelin directly affects bone formation. INTRODUCTION: Ghrelin is a gut peptide involved in growth hormone (GH) secretion and energy homeostasis. Recently, it has been reported that the adipocyte-derived hormone leptin, which also regulates energy homeostasis and opposes ghrelin's actions in energy homeostasis, plays a significant role in bone metabolism. This evidence implies that ghrelin may modulate bone metabolism; however, it has not been clarified. To study the role of ghrelin in skeletal integrity, we examined its effects on bone metabolism both in vitro and in vivo. MATERIALS AND METHODS: We measured the expression of ghrelin and growth hormone secretagogue receptor 1a (GHS-R1a) in rat osteoblasts using RT-PCR and immunohistochemistry (IHC). The effect of ghrelin on primary osteoblast-like cell proliferation was examined by recording changes in cell number and the level of DNA synthesis. Osteoblast differentiation markers (Runx2, collagen alpha1 type I [COLI], alkaline phosphatase [ALP], osteocalcin [OCN]) were analyzed using quantitative RT-PCR. We also examined calcium accumulation and ALP activity in osteoblast-like cells induced by ghrelin. Finally, to address the in vivo effects of ghrelin on bone metabolism, we examined the BMD of Sprague-Dawley (SD) rats and genetically GH-deficient, spontaneous dwarf rats (SDR). RESULTS: Ghrelin and GHS-R1a were identified in osteoblast-like cells. Ghrelin significantly increased osteoblast-like cell numbers and DNA synthesis in a dose-dependent manner. The proliferative effects of ghrelin were suppressed by [D-Lys(3)]-GHRP-6, an antagonist of GHS-R1a, in a dose-dependent manner. Furthermore, ghrelin increased the expression of osteoblast differentiation markers, ALP activity, and calcium accumulation in the matrix. Finally, ghrelin definitely increased BMD of both SD rats and SDRs. CONCLUSIONS: These observations show that ghrelin directly stimulates bone formation.

Adipocytes↗

PubMed2004

Isolation and characterization of four VIP-related peptides from red-bellied newt, Cynops pyrrhogaster.

Four novel bioactive peptides were isolated from the red-bellied newt, Cynops pyrrhogaster, using a bioassay system monitoring the rectum contraction of the Japanese quail, Coturnix japonica. As these peptides are structurally related to vasoactive intestinal polypeptide (VIP), we termed these peptides newt VIP-related peptides 1, 2, 3, and 4 (NVRP-1, -2, -3, and -4). The primary sequences of these peptides were determined to be HSDAVFTDNYSRLLGKTALKNYLDGALKKE (NVRP-1), HSDAVFTDNYSRLLAKTALKNYLDGALKKE (NVRP-2), HSDAVFT-DNYSRLLGKIALKNYLDEALKKE (NVRP-3), and HSDAVFTDNYSRLLGKT-ALKNYLDSALKKE (NVRP-4). The N-terminal regions of these NVRPs possessed homology at the amino-acid level to various VIP, while the NVRP C-termini differed from VIPs significantly. All of the VIP consist of 28 amino-acid residues with amidated forms at the C-termini, whereas NVRPs possess 30 amino-acid residues and have free forms at the C-termini. NVRPs exert relaxant activities on isolated quail rectums in a dose-dependent manner, with threshold concentrations between 1 x 10(-8) and 3 x 10(-8) M. NVRPs also exhibited potent relaxant activities acting on the newt duodenum at 3 x 10(-8) M. As yet, this is the first isolation of biologically active VIP-related peptides from urodele.

Amino Acid Sequence↗

PubMed2004

Neuromedin U is involved in nociceptive reflexes and adaptation to environmental stimuli in mice.

Following our recent observations of inactivity and slowed movement in neuromedin U knockout (NMU KO) mice, we compared nociceptive reflexes and environmental adaptation in NMU KO and wild-type mice. Hot plate and formalin tests revealed that reflexes to heat and pain were significantly decreased in NMU KO mice. Conversely, intracerebroventricular injection of NMU into wild-type mice stimulated nociceptive reflexes in a dose-dependent manner. After NMU injection, increased c-Fos expression was observed in a wide range of locations in hypothalamus, brainstem, and spinal cord. NMU mRNA expression increased in the spinal cord, but not in the hypothalamus, 2 and 4 h after formalin injection. When their light-dark cycle was advanced or retarded by 5 h, NMU KO mice required a longer time to re-entrain into the new light-dark cycle than did wild-type mice. Wild-type mice displayed increased blood pressure after their environmental temperature was changed from 23 to 37 degrees C, whereas no such increase was observed in NMU KO mice. Blood corticosterone levels were significantly increased after 10 min of immobilization stress in wild-type mice, but not in NMU KO mice. These results suggest that endogenous NMU may be involved in reflexes and adaptation to environmental stimuli.

Adaptation, Physiological↗

PubMed2004

Neuromedin U has a novel anorexigenic effect independent of the leptin signaling pathway.

Neuromedin U (NMU) is a hypothalamic neuropeptide that regulates body weight and composition. Here we show that mice lacking the gene encoding NMU (Nmu(-/-) mice) develop obesity. Nmu(-/-) mice showed increased body weight and adiposity, hyperphagia, and decreased locomotor activity and energy expenditure. Obese Nmu(-/-) mice developed hyperleptinemia, hyperinsulinemia, late-onset hyperglycemia and hyperlipidemia. Notably, however, treatment with exogenous leptin was effective in reducing body weight in obese Nmu(-/-) mice. In addition, central leptin administration did not affect NMU gene expression in the hypothalamus of rats. These results indicate that NMU plays an important role in the regulation of feeding behavior and energy metabolism independent of the leptin signaling pathway. These characteristic functions of NMU may provide new insight for understanding the pathophysiological basis of obesity.

Adipose Tissue↗

PubMed2004

Presynaptic modulation by neuromedin U of sensory synaptic transmission in rat spinal dorsal horn neurones.

Neuromedin U (NMU) is a brain-gut peptide first isolated from the spinal cord. Recent studies on NMU and its receptors have suggested a role of NMU in sensory transmission. Here we report on the localization of NMU in sensory neurones, and the actions of NMU in the substantia gelatinosa (SG) and the deep layer of the dorsal horn (laminae III-V) in adult rat spinal cord slices using the patch-clamp technique. An immunohistochemical study revealed that NMU peptide was present in most of the dorsal root ganglion neurones. In the spinal cord, NMU-immunoreactive neurones were located in the deep layer (laminae III-V), but not in the SG. However, NMU-positive axon terminals were observed in the SG as well as the deep layer. Bath-applied NMU (10 microm) increased the frequency, but not amplitude, of miniature excitatory postsynaptic currents (mEPSCs) in the SG and deep layer neurones by 146 +/- 14% (P < 0.01, n = 17) and 174 +/- 21% (P < 0.01, n = 6), respectively, without inducing any postsynaptic membrane currents recorded in tetrodotoxin. On the other hand, NMU did not affect miniature inhibitory postsynaptic currents recorded in tetrodotoxin. These findings, taken together, suggest that NMU acts on the presynaptic terminals of the primary afferent fibres working as an autocrine/paracrine neuromodulator to increase mEPSC frequency of the SG and deep layer neurones. This may account for the spinal mechanisms of the NMU-induced hyperalgesia reported previously.

Animals↗

PubMed2004

The gut-brain peptide neuromedin U is involved in the mammalian circadian oscillator system.

Immunohistochemical analysis revealed the presence of a gut-brain peptide, neuromedin U (NMU), in the suprachiasmatic nucleus (SCN), which is the site of the master circadian oscillator. The expression of NMU mRNA exhibited a circadian rhythm, with the peak expression in the SCN occurring at CT4-8h. The two NMU-binding receptors (NMU-R1 and NMU-R2) were also expressed in the SCN, but their phase angles were different. Intracerebroventricular injection (ICV) of NMU induced the expression of Fos protein in the SCN cells and caused a phase-dependent phase shift of the circadian locomotor activity rhythm. The magnitude of the phase shift was dose dependent. This NMU-induced phase shift was of the nonphotic type. Quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) analysis revealed increases in the expression in the SCN of immediate early genes, such as c-fos, NGFI-A, NGFI-B, and JunB. Furthermore, ICV injection of NMU increased the expression of Per1, but not Per2, in the SCN. These results indicate that NMU may play some important role in the circadian oscillator by exerting an autocrine or paracrine action in the SCN.

Animals↗