Hypoxia activates SREBP2 through Golgi disassembly in bone marrow-derived monocytes for enhanced tumor growth

Bone marrow-derived cells (BMDCs) infiltrate hypoxic tumors at a pre-angiogenic state and differentiate into mature macrophages, thereby inducing pro-tumorigenic immunity. A critical factor regulating this differentiation is activation of SREBP2-a well-known transcription factor participating in tumorigenesis progression-through unknown cellular mechanisms. Here, we show that hypoxia-induced Golgi disassembly and Golgi-ER fusion in monocytic myeloid cells result in nuclear translocation and activation of SREBP2 in a SCAP-independent manner. Notably, hypoxia-induced SREBP2 activation was only observed in an immature lineage of bone marrow-derived cells. Single-cell RNA-seq analysis revealed that SREBP2-mediated cholesterol biosynthesis was upregulated in HSCs and monocytes but not in macrophages in the hypoxic bone marrow niche. Moreover, inhibition of cholesterol biosynthesis impaired tumor growth through suppression of pro-tumorigenic immunity and angiogenesis. Thus, our findings indicate that Golgi-ER fusion regulates SREBP2-mediated metabolic alteration in lineage-specific BMDCs under hypoxia for tumor progression.

Acidic extracellular pH drives accumulation of N1-acetylspermidine and recruitment of protumor neutrophils

An acidic tumor microenvironment plays a critical role in tumor progression. However, understanding of metabolic reprogramming of tumors in response to acidic extracellular pH has remained elusive. Using comprehensive metabolomic analyses, we demonstrated that acidic extracellular pH (pH 6.8) leads to the accumulation of N1-acetylspermidine, a protumor metabolite, through up-regulation of the expression of spermidine/spermine acetyltransferase 1 (SAT1). Inhibition of SAT1 expression suppressed the accumulation of intra- and extracellular N1-acetylspermidine at acidic pH. Conversely, overexpression of SAT1 increased intra- and extracellular N1-acetylspermidine levels, supporting the proposal that SAT1 is responsible for accumulation of N1-acetylspermidine. While inhibition of SAT1 expression only had a minor effect on cancer cell growth in vitro, SAT1 knockdown significantly decreased tumor growth in vivo, supporting a contribution of the SAT1-N1-acetylspermidine axis to protumor immunity. Immune cell profiling revealed that inhibition of SAT1 expression decreased neutrophil recruitment to the tumor, resulting in impaired angiogenesis and tumor growth. We showed that antineutrophil-neutralizing antibodies suppressed growth in control tumors to a similar extent to that seen in SAT1 knockdown tumors in vivo. Further, a SAT1 signature was found to be correlated with poor patient prognosis. Our findings demonstrate that extracellular acidity stimulates recruitment of protumor neutrophils via the SAT1-N1-acetylspermidine axis, which may represent a metabolic target for antitumor immune therapy.

Phosphoethanolamine Accumulation Protects Cancer Cells under Glutamine Starvation through Downregulation of PCYT2

Tolerance to severe tumor microenvironments, including hypoxia and nutrient starvation, is a common feature of aggressive cancer cells and can be targeted. However, metabolic alterations that support cancer cells upon nutrient starvation are not well understood. Here, by comprehensive metabolome analyses, we show that glutamine deprivation leads to phosphoethanolamine (PEtn) accumulation in cancer cells via the downregulation of PEtn cytidylyltransferase (PCYT2), a rate-limiting enzyme of phosphatidylethanolamine biosynthesis. PEtn accumulation correlated with tumor growth under nutrient starvation. PCYT2 suppression was partially mediated by downregulation of the transcription factor ELF3. Furthermore, PCYT2 overexpression reduced PEtn levels and tumor growth. In addition, PEtn accumulation and PCYT2 downregulation in human breast tumors correlated with poor prognosis. Thus, we show that glutamine deprivation leads to tumor progression by regulating PE biosynthesis via the ELF3-PCYT2 axis. Furthermore, manipulating glutamine-responsive genes could be a therapeutic approach to limit cancer progression.

Schizophrenia-like phenotypes in mice with NMDA receptor ablation in intralaminar thalamic nucleus cells and gene therapy-based reversal in adults

In understanding the mechanism of schizophrenia pathogenesis, a significant finding is that drug abuse of phencyclidine or its analog ketamine causes symptoms similar to schizophrenia. Such drug effects are triggered even by administration at post-adolescent stages. Both drugs are N-methyl-d-aspartate receptor (NMDAR) antagonists, leading to a major hypothesis that glutamate hypofunction underlies schizophrenia pathogenesis. The precise region that depends on NMDAR function, however, is unclear. Here, we developed a mouse strain in which NMDARs in the intralaminar thalamic nuclei (ILN) were selectively disrupted. The mutant mice exhibited various schizophrenia-like phenotypes, including deficits in working memory, long-term spatial memory, and attention, as well as impulsivity, impaired prepulse inhibition, hyperlocomotion and hyperarousal. The electroencephalography analysis revealed that the mutant mice had a significantly reduced power in a wide range of frequencies including the alpha, beta and gamma bands, both during wake and rapid eye movement (REM) sleep, and a modest decrease of gamma power during non-REM sleep. Notably, restoring NMDARs in the adult ILN rescued some of the behavioral abnormalities. These findings suggest that NMDAR dysfunction in the ILN contributes to the pathophysiology of schizophrenia-related disorders. Furthermore, the reversal of inherent schizophrenia-like phenotypes in the adult mutant mice supports that ILN is a potential target site for a therapeutic strategy.

Ethos in Fukushima and the ICRP dialogue seminars

Ethos in Fukushima, a non-profit organisation, participated in 10 of the 12 International Commission on Radiological Protection (ICRP) dialogue seminars over the past 4 years. The slides and videos that were shown at the seminars are recorded on the Ethos in Fukushima website ( http://ethos-fukushima.blogspot.jp/p/icrp-dialogue.html ). I would like to introduce the activities of Ethos in Fukushima to date, and explain why the ICRP dialogue materials have come to be published on its website.

Increase of Galanin in Trigeminal Ganglion during Tooth Movement

It is known that nerve fibers containing neuropeptides such as galanin increase in the periodontal ligament during experimental tooth movement. However, the origin of galanin-containing nerve fibers in the periodontal ligament remains unclear. This study was conducted to examine our hypothesis that the increased galanin nerve fibers have a sensory neuronal origin, and that the peptide is associated with pain transmission and/or periodontal ligament remodeling during experimental tooth movement. In control rats, galanin-immunoreactive trigeminal ganglion cells were very rare and were observed predominantly in small ganglion cells. After 3 days of experimental tooth movement, galanin-immunoreactive trigeminal ganglion cells significantly increased, and the most marked increase was observed at 5 days after experimental tooth movement. Furthermore, their cell size spectrum also significantly changed after 3 and 5 days of movement: Medium-sized and large trigeminal ganglion cells began expressing, and continued to express, galanin until 14 days after experimental tooth movement. These findings suggest that the increase of galanin in the periodontal ligament during experimental tooth movement at least partially originates from trigeminal ganglion neurons and may play a role in pain transmission and/or periodontal remodeling.

Reclaiming Our Lives in the Wake of a Nuclear Plant Accident

Ryoko Ando lives and works in Iwaki-shi, which is located in the coastal area of Fukushima Prefecture. On 11 March 2011, Iwaki was hit by the Great East Japan Earthquake and tsunami. Then the nuclear plant accident at Fukushima No. 1 nuclear power plant, also located in the coastal area of Fukushima Prefecture, added to the woes of Iwaki residents. Although Iwaki-shi is outside of the ‘restricted area’ set up by the government in the 20 km radius around the nuclear power plant, some municipalities in Iwaki-shi lie within the 30 km radius zone. The residents of Iwaki were naturally concerned about the effects of radioactive contamination. On top of these, they had to confront a wide range of issues, including confusion and miscommunication, reputation risk and infrastructural constraints due to the influx of residents from the ‘restricted area’.

Measuring, discussing, and living together: lessons from 4 years in Suetsugi

Cooperating with radiological protection experts and taking radiation measurements, the residents of Suetsugi, Iwaki City, Fukushima have been striving to reshape their lives since the accident at Fukushima Daiichi nuclear power plant. Suetsugi lies within 30 km of the power plant, so the residents have had serious reservations about continuing their lives there since the accident. Today, radiation remains a 'line' dividing their lives, with any dose measurements directly affecting their daily decision making. Assisted by medical and scientific specialists, the residents faced this challenging situation by measuring exposures individually and then discussing the results among themselves. Since 2012, the residents of Suetsugi have been using personal dosimeters, made village-wide trips for whole-body counter tests, and measured food contamination throughout the village. The results have been shared openly between the residents. Obtaining and discussing their own data were crucial to gain understanding of various results and to practice radiological protection in their daily routine. These 4 y of experience in Suetsugi demonstrate cooperation between various stakeholders, which should be a lesson for the future.

Heat-moisture treatment of high-amylose corn starch increases dietary fiber content and lowers plasma cholesterol in ovariectomized rats

The effect of dietary high-amylose corn starch (HACS) of varying dietary fiber (DF) content on plasma cholesterol was examined in ovariectomized (OVX) rats. Gelatinized normal corn starch (G-CS) was used as a reference. OVX rats were fed a fiber-free purified diet containing G-CS, HACS, gelatinized high-amylose corn starch (G-HACS), or heat-moisture treated HACS (HM-HACS) at 400 g starch/kg diet for 21 d. The DF content of G-CS, HACS, G-HACS, and HM-HACS measured by the AOAC method was 0.1, 19.3, 2.4, and 64.5 g/100 g, respectively. The dry weight of cecal contents, cecal wall weight, the amount of short chain fatty acids in cecal contents, the amount of bile acids in small intestinal contents, and fecal excretion of neutral sterols increased logarithmically with increasing DF, while total plasma cholesterol concentration decreased. On the other hand, hepatic CYP7A1 activity, fecal dry weight, and fecal excretion of bile acids increased linearly with increasing DF, while body weight gain decreased. The hypocholesterolemic effect of HACS in OVX-rats appeared to be more effective by heat-moisture treatment.

Characteristics of propofol-evoked vascular pain in anaesthetized rats

BACKGROUND

In this study we have assessed vascular pain caused by the i.v. anaesthetic agent, propofol, using the flexor reflex response and compared this with that of capsaicin in anaesthetized intact rats.

METHODS

Experiments were performed on 133 male Sprague-Dawley rats weighing 280-340 g. The animals were anaesthetized with urethane (1.3 g kg(-1), i.p.), and an arterial cannula was inserted to the level of the bifurcation of the femoral artery. The magnitude of the flexor reflex was examined by recording the electromyogram from the posterior biceps femoris/semitendinosus muscles.

RESULTS

Our data show that the flexor reflexes evoked by intra-arterial (i.a.) injection of propofol (1%, 25-100 microl) and capsaicin (0.05-0.2 microg) were dose dependent. An initial i.a. injection of procaine (2%, 200 microl) blocked both responses. Furthermore, the flexor reflex induced by these chemical stimuli were inhibited by morphine (5 mg kg(-1), s.c.) and restored with naloxone (1.5 mg kg(-1), s.c.). Pre-treatment with capsazepine (20 microg, i.a.), a selective VR1 antagonist, inhibited the capsaicin-evoked response, but not that of propofol. Indomethacin (10 mg kg(-1), i.p.), a non-selective cyclo-oxygenase inhibitor, inhibited only the propofol-evoked response and this recovered with arterial PGE2 (5 microg).

CONCLUSIONS

Collectively our data suggest that propofol-evoked vascular pain is mainly initiated by prostanoids.

An assessment of vascular pain using the flexor reflex in anesthetized rats

This study assessed the flexor reflex induced by intraarterial algogenic drugs in anesthetized rats. The experiments were performed on male Sprague Dawley rats weighing 290-350 g. The animals were anesthetized with urethane (1.3 g/kg i.p.) and an arterial cannula was inserted to the level of the bifurcation of the femoral artery. The magnitude of the flexor reflex was examined by recording the electromyograph from the posterior biceps femoris/semitendinous muscles. Results showed that the flexor reflex evoked by intra-arterial injection of capsaicin (0.05-0.5 microg) was dose-dependent. A similar reflex resulted from pinching the toe of the hindlimb. These responses were inhibited by morphine (5 mg/kg s.c.) and restored with naloxone (1.5 mg/kg s.c.). Intraarterial preinjection of procaine (2%, 200 microl) and capsazepine (20 microg), which is a selective vanilloid receptor antagonist, inhibited the capsaicin-evoked response, but not that of pinching. These results indicate that the flexor reflex is a useful tool for assessing vascular pain in anesthetized animals.

Contribution of brominated organic disinfection by-products to the mutagenicity of drinking water

The activity inducing chromosomal aberrations of the mixture of brominated disinfection by-products (DBPs) was approximately three times higher than that of the chlorinated counterparts for the same hypohalous acid dose. With the combination of chromosomal aberration test and a new analytical technique to differentiate total organic chlorine (TOCl) and total organic bromine (TOBr), it was found that TOBr was correlated to the mutagenicity of chlorinated waters. It was also implied that for a bromide-to-TOC ratio of 0.1 (mg/mg C), brominated DBPs could account for at least 29% of the total toxicity of DBPs formed during chlorination. On the other hand, bromate ion, a major ozonation DBP, was not a major contributor to the activity inducing chromosomal aberrations of the water treated with an ozone/chlorine sequential process. Therefore, ozonation is one possible option to reduce the health risk caused by DBPs even in the presence of bromide.

Differential effects of yohimbine, naloxone and 8-OH-DPAT on ejaculatory response in male dogs

The aim of this study was to compare the effects of the alpha(2)-adrenergic-receptor antagonist yohimbine, the 5-HT(lA)-receptor agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) and the opioid-receptor antagonist naloxone (all of which have been shown to stimulate male sexual arousal/motivation in rats) on sexual responses in male dogs. Sexual responses (i.e., ejaculation, penile erection and pelvic thrusting behavior) were elicited by manual penile stimulation. Systemic administration of yohimbine (0.03-1.0 mg/kg) produced a biphasic dose response curve for the amount of ejaculated semen collected during genital stimulation (for 5 min), whereas 8-OH-DPAT (0.03-0.3 mg/kg) dose-dependently decreased the amount of ejaculated semen. Thus, yohimbine increased the amount of ejaculated semen at lower doses (0.03-0.3 mg/kg), but decreased it at the highest dose (1.0 mg/kg). The highest dose of yohimbine (1.0 mg/kg) and 8-OH-DPAT (0.3 mg/kg) also produced a significant delay of onset in both ejaculation and penile erection latency (time from starting the stimulation to the first ejaculation and full erection), and a decrease in the incidence of pelvic thrusting behavior. In contrast, administration of naloxone (0.03-1.0 mg/kg) did not affect the sexual responses elicited by genital stimulation. These results indicate that yohimbine and 8-OH-DPAT, but not naloxone, affect sexual responses, particularly ejaculation, and that the drugs which stimulate the mechanisms regulating sexual arousal/motivation in male rats do not show identical effects for sexual function in male dogs. The present findings also confirm our previous observations that the ejaculatory capacity in dogs can be stimulated by lower doses of yohimbine, as evidenced by an increase in the amount of ejaculated semen.

The nephroblastoma overexpressed gene (NOV/ccn3) protein associates with Notch1 extracellular domain and inhibits myoblast differentiation via Notch signaling pathway

We demonstrate a novel interaction of the nephroblastoma overexpressed gene (NOV), a member of the CCN gene family, with the Notch signaling pathway. NOV associates with the epidermal growth factor-like repeats of Notch1 by the CT (C-terminal cysteine knot) domain. The promoters of HES1 and HES5, which are the downstream transducers of Notch signaling, were activated by NOV. Expressions of NOV and Notch1 were concomitant in the presomitic mesoderm and later in the myocytes and chondrocytes, suggesting their synergistic effects in mesenchymal cell differentiation. In C2/4 myogenic cells, elevated expression of NOV led to down-regulation of MyoD and myogenin, resulting in inhibition of myotube formation. These results indicate that NOV-Notch1 association exerts a positive effect on Notch signaling and consequently suppresses myogenesis.

Association of beta-fibrinogen and factor VII polymorphism with plasma fibrinogen and factor VII levels, and no association of PAI-1 polymorphism with plasma PAI-1 levels in hemodialysis patients

AIMS

Recent studies have stressed the roles of genetic factors on the plasma levels of hemostatic markers and on cardiovascular complications. We investigated the association of DNA polymorphisms for beta-fibrinogen, factor VII, and PAI-1 with plasma levels of these factors and with ischemic heart disease (IHD) and cerebral infarction (CI) in patients undergoing hemodialysis (HD).

METHODS

beta-fibrinogen G/A-455, factor VII R353Q and PAI-1 4G/5G polymorphisms were determined by PCR-RFLP in 149 HD patients and in 100 controls. The plasma levels of fibrinogen, factor VII and PAI-1 were also measured.

RESULTS

The allele frequencies and the genotype frequencies of these 3 polymorphisms were not different between HD patients and controls. In HD patients, plasma fibrinogen levels were significantly lower in the GG genotype than in the GA genotype, and plasma factor VII activity was significantly higher in the RR genotype than in the RQ genotype. Multiple regression analysis disclosed that CRP and beta-fibrinogen polymorphism were the significant determinants of fibrinogen levels. Plasma PAI-1 levels were not different among the 3 genotypes. The frequency of the A-455 allele was significantly higher in HD patients with CI than in those without CI, and the genotype distribution for beta-fibrinogen differed significantly between the 2 groups. Between the same 2 groups, however, significant differences were found neither in the frequency of the 353Q or 4G allele nor in the genotype distribution for factor VII and PAI-1. No significant differences in the frequency of the G-455, 353Q or 4G alleles, or in the genotype distribution for beta-fibrinogen, factor VII and PAI-1 were observed between patients with IHD and those without IHD. Multiple logistic regression analysis demonstrated that neither polymorphism was associated with CI or IHD.

CONCLUSIONS

In HD patients, beta-fibrinogen and factor VII polymorphisms affected plasma levels of fibrinogen and factor VII, respectively. Beta-fibrinogen polymorphism was not an independent but a possible risk factor for CI in HD patients. Further study will be needed to confirm the precise role of 5-fibrinogen polymorphisms in the pathogenesis of CI in HD patients.

3-(Arylacetylamino)-N-methylbenzamides: a novel class of selective anti-Helicobacter pylori agents

After chemical modification preceded by the random screening of our chemical library, a novel class of selective anti-Helicobacter pylori agents was generated. Consequently, the 3-(arylacetylamino)-N-methylbenzamides, which were quite easy to prepare, showed potent inhibitory activity against Helicobacter pylori but exhibited no inhibitory activity against other sorts of bacteria and fungi, e.g., Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, Bacteroides fragilis, and Candida albicans. These compounds showed potent anti-H. pylori activity under acidic conditions, whereas amoxicillin and clarithromycin decreased activity. The 3-(3-arylpropionylamino)-N-methylbenzamides, 3-(aryloxyacetylamino)-N-methylbenzamides, and (3-methylcarbamoylphenyl)carbamic acid 1-arylmethyl esters also exhibited potent anti-H. pylori activity. Finally, we selected 7n (BAS-118) as a candidate compound for further evaluation.

Interaction of corticotropin-releasing factor and glucagon-like peptide-1 on behaviors in chicks

Both corticortropin-releasing factor (CRF) and glucagon-like peptide-1 (GLP-1) inhibit food intake of chicks, but they also produce other behaviors. The present experiments were undertaken to clarify the interaction of CRF and GLP-1 regarding their anorectic actions as well as other behaviors. In Experiment 1, birds were injected intracerebroventricularly (i.c.v.), following a 3-h fast, with either saline, 0.1 microg of CRF, 0.1 microg of CRF+0.1 microg of GLP-1 or 0.1 microg of CRF+1 microg of GLP-1, and food intake was measured for 2 h. The injection of CRF decreased food intake, and CRF injected with GLP-1 suppressed food intake for up to 2 h. Birds were treated similarly in Experiment 2 in which the doses of CRF and GLP-1 were reversed. GLP-1 strongly suppressed food intake, and this effect was augmented by coadministration of CRF. In Experiment 3, the behaviors of chicks injected with saline, CRF (0.1 microg), GLP-1 (0.1 microg) or CRF (0.1 microg)+GLP-1 (0.1 microg) were monitored for the numbers of steps, vocalization and locomotion. Chicks were excited, moved more and vocalized loudly following injection of CRF, whereas an opposite response was seen with GLP-1. The behaviors were intermediate following the coinjection of the two peptides. In conclusion, CRF and GLP-1 interact in the chick brain, but the response depends on the behavior being measured.

Intracerebroventricular injection of exendin (5-39) increases food intake of layer-type chicks but not broiler chicks

To clarify the involvement of endogenous glucagon-like peptide-1 (GLP-1) on feeding in chicks, we examined the central effect of GLP-1 antagonist, exendin (5-39) on food intake. Intracerebroventricular co-injection of exendin (5-39) with GLP-1 attenuated the anorexigenic effect of GLP-1 in layer-type chicks. Furthermore, exendin (5-39) enhanced food intake of layer-type chicks under ad libitum feeding. However, this effect was not observed in broiler chicks. Therefore, endogenous GLP-1 may be important in the regulation of feeding in layer-type chicks but not in broiler chicks.

Intracerebroventricular injection of pipecolic acid inhibits food intake and induces sleeping-like behaviors in the neonatal chick

It has been demonstrated that L-pipecolic acid (L-PA), a major metabolic intermediate of L-Lysine (L-Lys) in the brain, is involved in the functioning of Gamma-aminobutyric acid. In the present work the effect of intracerebroventricular (i.c.v.) administration of L-PA, and its relatives, on food intake and behavior in neonatal chicks was investigated. The i.c.v. injection of 1 mg of L-PA and D-PA significantly inhibited food intake during the 2 h following injection, whereas greater than 2 mg of L-Lys was required to inhibit food intake. In behavioral tests, the i.c.v. injection of L-PA reduced active wakefulness and feeding behavior while inducing sleeping-like behavior in chicks. These results suggest that L-PA has an important role for the regulation of behaviors in the neonatal chick after conversion from L-Lys in the brain.

Feeding responses to several neuropeptide Y receptor agonists in the neonatal chick

Neuropeptide Y is one of the most potent neuropeptides known to induce feeding in animals, and has been suggested to be a physiological signal for food intake. It has been also reported that intracerebroventricular injection of neuropeptide Y stimulates feeding behavior of the neonatal chick. There are many neuropeptide Y receptor agonists that have not been investigated in feeding response of the neonatal chick. The aim of this study is to elucidate whether central injection of several neuropeptide Y receptor agonists stimulates feeding of the neonatal chick over 2 h. We found that central injections of [Leu(31), Pro(34)]neuropeptide Y, peptide YY, human pancreatic polypeptide and rat pancreatic polypeptide significantly stimulated food intake of neonatal chicks throughout the 2-h post-injection period. Neuropeptide Y-(13-36) significantly stimulated feeding at 30 min, but not thereafter. [D-Trp(32)]neuropeptide Y stimulated feeding at 60 and 120 min, but not 30 min, post-injection. Central administration of rat pancreatic polypeptide, which does not increase food intake in rats, stimulated feeding in chicks. This result reflects structural differences of the neuropeptide Y receptor subtypes and/or differences in mechanisms stimulating feeding behavior between mammals and chickens. In conclusion, neuropeptide Y receptor agonists, except for neuropeptide Y-(13-36), are potent stimulators of food intake in the neonatal chick.

Suppression of food intake induced by corticotropin-releasing factor family in neonatal chicks

Corticotropin-releasing factor (CRF), urocortin and urotensin I share amino acid sequences, and they inhibit food intake in mammals. CRF plays a potent role in decreasing food intake in avian species, but the effects of urocortin and urotensin I have not been investigated. Therefore, the effect of these three peptides on food intake in the neonatal chick was compared. In Experiment 1, birds were injected intracerebroventricularly (i.c.v.) with either 0, 0.01, 0.1 or 1 microg of urocortin following a 3-h fast, and food intake was measured for 2 h post-injection. Food intake was suppressed in a dose-dependent manner. Using a similar design in Experiment 2, the effect of urotensin I was investigated. Urotensin I appeared to suppress food intake in neonatal chicks more than urocortin did. In Experiment 3, the efficacy of CRF, urocortin and urotensin I was directly compared using one dose, 0.1 microg. The results indicated that the suppressive effect on food intake was strongest for CRF followed by urotensin I, then urocortin. These results suggest that the structure of receptors for the CRF family in chicks may be somewhat different than in mammals.

Alpha 2-adrenoceptor antagonists: effects on ejaculation, penile erection and pelvic thrusting behavior in dogs

We previously reported that systemic administration of yohimbine, an alpha2-adrenoceptor antagonist, exerts a biphasic effect (stimulating and suppressing) on ejaculation in dogs, when this function is analyzed using the amount of ejaculated semen in response to genital stimulation. To clarify the effect of alpha2-adrenoceptor blockade on male sexual function, we investigated the effects of four selective alpha2-adrenoceptor antagonists, rauwolscine, idazoxan, RX821002 and mydaglizole, on sexual responses (ejaculation, penile erection and pelvic thrusting behavior) elicited by manual penile stimulation in dogs. Rauwolscine (intraperitoneal, 30 min before the testing) caused a biphasic effect on ejaculation; the amount of ejaculated semen produced by the stimulation was significantly increased by the lower doses (0.1 and 0.3 mg/kg), whereas it was decreased by the higher doses (1.0 and 2.0 mg/kg). The higher doses of rauwolscine also markedly inhibited both penile erection and pelvic thrusting behavior. Idazoxan and RX821002, at doses of 0.1 and 0.3 mg/kg, caused a significant increase in the amount of ejaculated semen without affecting other sexual functions. RX821002 (2.0 mg/kg), but not idazoxan (2.0 mg/kg), moderately inhibited both penile erection and pelvic thrusting behavior. Mydaglizole, a peripherally acting alpha2-adrenoceptor antagonist, did not affect the sexual responses at any doses (0.1-4.0 mg/kg). In the ejaculatory declining test, all alpha2-adrenoceptor antagonists (0.1 mg/kg), except for mydaglizole, completely prevented the decrease in ejaculatory capacity produced by antecedent ejaculation. These results indicate that, though the range of the effective dose is narrow, the alpha2-adrenoceptor antagonists that can block the central alpha2-adrenoceptors have the stimulatory effects on ejaculatory function. The difference of the sexual effects may be based on the action except for the alpha2-adrenoceptor blockade.

Intracerebroventricular injection of agouti-related protein attenuates the anorexigenic effect of alpha-melanocyte stimulating hormone in neonatal chicks

It is well known that alpha-melanocyte stimulating hormone (alpha-MSH) inhibits feeding via melanocortin receptor-4 (MC4R) in the mammalian brain. The anorexigenic effect of alpha-MSH is attenuated by agouti-related protein (AGRP), an antagonist for MC4R. Present studies were carried out to clarify whether human AGRP (86-132) antagonizes the anorexigenic effect of alpha-MSH in broiler chicks. Intracerebroventricular injection of AGRP attenuated the anorexigenic effect of alpha-MSH. Furthermore, AGRP stimulated food intake of layer-type chicks under an ad libitum feeding condition but not broiler chicks, suggesting that the orexigenic effect of AGRP is different between two breeds. These also imply that the extent of the anorexigenic effect of endogenous alpha-MSH is different among two breeds. This may be a part of the difference in food intake between two breeds.

Intracerebroventricular injection of ghrelin and growth hormone releasing factor inhibits food intake in neonatal chicks

Growth hormone releasing factor (GRF) is known to stimulate feeding of rats. Ghrelin, a novel growth hormone (GH)-releasing acylated peptide, was recently isolated from rat stomach. It also stimulates the release of GH from the anterior pituitary through the GH secretagogue receptor (GHS-R) and feeding in the rat. We have investigated the effects of ghrelin and GRF on food intake of the neonatal chick. In Experiment 1, 0, 1.25, 2.5 and 5 microg of ghrelin were administered intracerebroventricularly (i.c.v.) to ad libitum fed birds. In Experiment 2, the effect of (i.c.v.) injection of 0, 1.25, 2.5 and 5 microg of GRF was investigated. Both peptides strongly inhibited food intake of the chick during the 2-h post-injection period. In the third experiment, 0, 0.5, 1 and 2 microg of ghrelin was injected i.c.v. in chicks previously deprived of food for 3 h. Food intake was again inhibited by ghrelin in a dose-dependent manner. These results suggest that the mechanisms for feeding of the neonatal chick through GH release are different from mammals.