Peptides (v.22, #1)
Aggregational behavior of aqueous dispersions of the antifungal lipopeptide iturin A 1 1 Abbreviations: CF, 5,6-carboxyfluorescein; CMC, critical micellar concentration; Kav, distribution coefficient; Vo, void volume; Ve, elution volume; Vt, total volume; Vm, matrix or stationary phase volume; Mr, molecular weight; Rs, Stokes radius by Alicia Grau; Juan C. Gómez-Fernández; Françoise Peypoux; Antonio Ortiz (1-5).
Iturin A, a lipopeptide isolated from Bacillus subtilis, posses a strong antifungal activity, and has been devoted to a great deal of attention. Since iturin is an amphiphilic compound with a great propensity to self-associate in solution as well as inside the membrane, the question arises to whether its aggregational behavior is dependent on the concentration of the lipopeptide. In order to test this, the ability of iturin suspensions to encapsulate water-soluble molecules has been examined. Iturin was dispersed at different concentrations above its critical micellar concentration, in a buffer containing the water-soluble dye 5,6-carboxyfluorescein. For iturin A micelles, a Stokes radius of 1.3 nm and an aggregational number of 7 was obtained. The results shown in this work clearly demonstrate that iturin dispersions in water, at concentrations of 0.7, 1.4 and 3 mM, i.e. far above the critical micellar concentration (40 μM), are capable of encapsulating carboxyfluorescein, probably by adopting a type of aggregate different from the micelle. Negative-staining electron microscopy shows the presence of vesicles with an average size of 150 nm. By using 14C-iturin, it is shown that, at 3 mM concentration, 40% of the iturin molecules adopt this vesicular state. It is proposed that iturin molecules form a fully interdigitated bilayer, where each hydrocarbon tail span the entire hydrocarbon width of the bilayer, resulting in multilamellar vesicles capable of encapsulating an aqueous compartment. The possible implications of these results to the membrane destabilizing effect of iturin A, are discussed according to the dynamic cone-shape of the iturin molecule.
Keywords: Lipopeptides; Iturin; Interdigitated bilayers;
Structure-activity relationships of 18 endogenous neuropeptides on the motornervous system of the nematode Ascaris suum by Ralph E Davis; Antony O.W Stretton (7-23).
Neuropeptides play an important role in all nervous systems and structure-activity studies of related peptides is one approach to understanding this role. This study of the motornervous system of the parasitic nematode Ascaris suum describes the physiological effects of a family of 18 endogenous Ascaris FMRFamide-like peptides (AF peptides) on the membrane potential and input resistance of the dorsal excitatory type 2 (DE2) and dorsal inhibitory (DI) motorneurons. These motorneurons are part of the final common output pathway from the motornervous system to the somatic muscle cells responsible for locomotion. AF peptide effects on the frequency of excitatory postsynaptic potentials (EPSPs) in DE2 motorneurons were also measured to infer peptide effects on central presynaptic spiking neurons. AF peptide injections into intact worms were made to assess their qualitative effects on behavior, providing a context for interpreting motorneuron data. One category of AF peptides, N-terminally extended -FIRFa peptides (AF5, AF7 and AF1), has pronounced behavioral effects and qualitatively similar, but quantitatively different effects on DE2 and DI motorneurons. A second category of AF peptides (AF2, AF9, and AF8) also produces dramatic behavioral effects and strong electrophysiological effects on DE2 and/or DI motorneurons. A third category of AF peptides, consisting of six members of the -PGVLRFa group (which are encoded by the same gene and have closely related sequences) and peptide AF11, have pronounced behavioral effects, but relatively weak or negligible effects on DE2 and DI motorneurons. A fourth category of AF peptides, also consisting of structurally unrelated members, has pronounced behavioral effects and, as individual peptides, similar effects on both DE2 and DI motorneurons; AF15 is excitatory, while AF17 and AF19 are inhibitory, on both motorneuron types. Finally, two AF peptides (AF6, AF16) are relatively weak or inactive in producing behavioral or motorneuronal effects. Based on comparisons of the effects of AF peptides on DE2 and DI motorneurons, a tentative list of 5 major response-types is proposed as a working hypothesis to guide the search for AF peptide receptors. The findings attest to the potential complexity of neurosignaling in this comparatively simple nervous system.
Keywords: FMRFamide-like; Neuropeptide; Endogenous neuropeptide; Neuromodulation; Nematode; Ascaris; Electrophysiology; Structure-activity;
Designing of an orally active complement C3a agonist peptide with anti-analgesic and anti-amnesic activity by Yunden Jinsmaa; Yasuuki Takenaka; Masaaki Yoshikawa (25-32).
Complement C3a is an anti-opioid peptide, having anti-analgesic and anti-amnesic effects after intracerebroventricular administration. However, the peptide is inactive after oral administration. Orally active C3a agonist peptide was designed based on the structure of oryzatensin, a C3a agonist peptide derived from rice albumin. Tyr-Pro-Leu-Pro-Arg, a pentapeptide at the carboxyl terminus of oryzatensin is the minimally essential structure for exerting C3a activity. Due to the affinity for μ-opioid receptor, both oryzatensin and Tyr-Pro-Leu-Pro-Arg showed analgesia after intracerebroventricular administration in mice which was blocked by the opioid antagonist naloxone. Tyr-Pro-Leu-Pro-Arg lost opioid activity by substitution the amino terminus tyrosine with other hydrophobic residues. Among the newly designed peptides, Trp-Pro-Leu-Pro-Arg was found to possess the strongest C3a activity. The peptide antagonized morphine-induced analgesia at 300 mg/kg after oral administration and also improved scopolamine- and ischemia-induced amnesia in a step-through passive avoidance test.
Keywords: Analgesia; Anti-opioid; Complement C3a; Learning;
Role of the delta-opioid receptor in (1DMe)NPYF mediated antinociception by Mei Xu; Vesa K. Kontinen; Pertti Panula; Eija Kalso (33-38).
A selective δ-opioid antagonist, naltrindole, was used to study the role of the δ-opioid receptor in the antinociceptive actions of a synthetic NPFF analog, (1DMe)NPYF. I.t. (1DMe)NPYF (5 nmol) produced antinociception in the tail flick test and (1DMe)NPYF (0.5 nmol) potentiated the antinociceptive effect of i.t. morphine 7.8 nmol. (1DMe)NPYF (5 nmol) had an antihyperalgesic effect in carrageenan inflammation and it significantly reduced mechanical allodynia in the spinal nerve ligation model. All these effects were prevented or significantly reduced by pretreatment with naltrindole (28 nmol) (P < 0.01–0.001). These data suggest that activation of spinal δ-opioid receptors plays an important role in mediating the spinal antinociceptive effects of (1DMe)NPYF.
Keywords: δ-Opioid antagonist; Neuropeptide FF analog; Carrageenan inflammation; Neuropathic pain; Spinal nociception;
Age dependent endothelin contribution to NOC/oFQ induced impairment of NMDA cerebrovasodilation after brain injury by William M. Armstead (39-46).
This study was designed to characterize the role of endothelin-1 (ET-1) in nociceptin/orphanin FQ (NOC/oFQ) induced impairment of NMDA cerebrovasodilation after fluid percussion brain injury (FPI) as a function of age in newborn (1–5 days old) and juvenile (3–4 weeks old) pigs equipped with a closed cranial window. Previous studies have observed that NOC/oFQ is released into CSF and contributes to impaired NMDA induced pial artery dilation following FPI to a greater extent in newborn vs juvenile pigs. Topical ET-1 (10−10 M), a concentration approximating that observed in CSF following FPI in the newborn, increased CSF NOC/oFQ from 67 ± 4 to 119 ± 7 pg/ml under non FPI conditions. CSF NOC/oFQ was elevated within 60 min of FPI (70 ± 3 to 444 ± 51 pg/ml) but such release was attenuated by the ET-1 antagonist BQ123 in the newborn (66 ± 3 to 145 ± 10 pg/ml). CSF ET-1 and NOC/oFQ were not elevated as greatly in the juvenile following FPI and BQ123 correspondingly did not attenuate CSF NOC/oFQ release as much as in the newborn. Under non injury conditions, ET-1 (10−10 M) coadministered with NMDA attenuated pial dilation to this excitatory amino acid. Following FPI in the newborn, NMDA (10−8, 10−6 M) induced pial artery dilation was reversed to vasoconstriction and both NOC/oFQ and ET-1 receptor antagonists partially prevented such alterations (9 ± 1 and 16 ± 1, sham control; −7 ± 1 and −12 ± 1, FPI; −2 ± 1 and −3 ± 1, FPI-NOC/oFQ antagonist; and 2 ± 1 and 5 ± 1%, FPI-ET-1 antagonist). NMDA induced pial dilation was only attenuated following FPI in the juvenile and modestly restored by NOC/oFQ and ET-1 receptor antagonists. These data show that ET-1, in concentrations present in CSF following FPI, contributes to the release of CSF NOC/oFQ following such an insult. The greater release of such ET-1 following FPI in the newborn contributes to the corresponding greater release of NOC/oFQ in the newborn vs the juvenile. Moreover, ET-1 also contributes to the impairment of NMDA cerebrovasodilation after brain injury to a greater extent in newborns vs juveniles. These data suggest that ET-1 contributes to NOC/oFQ induced impairment of NMDA cerebrovasodilation after brain injury in an age dependent manner.
Keywords: Newborn; Excitatory amino acids; Endothelin; Opioids; Cerebral circulation; Brain injury;
Pharmacological characterization of recombinant rat corticotropin releasing factor binding protein using different sauvagine analogs by Olaf Jahn; Klaus Eckart; Sabine Sydow; Bernhard A. Hofmann; Joachim Spiess (47-56).
Little is known on the structural ligand requirements for corticotropin-releasing factor binding protein (CRFBP) of the rat used as an important experimental animal. To obtain such information recombinant rat CRFBP was produced in stably transfected HEK 293 cells. The primary structure and posttranslational processing of purified rat CRFBP was established by peptide mapping using HPLC combined with mass spectrometric analysis. Rat CRFBP was pharmacologically characterized employing a competition binding assay with tritium-labeled rat urocortin. The rank order of declining affinity of various CRF analogs was urotensin-I, human/rat CRF (h/rCRF), rat urocortin, sauvagine (Svg), and ovine CRF in agreement with the rank order found for human CRFBP. In contrast to astressin, the CRF receptor 2-selective antagonist anti-sauvagine-30 did not show any detectable specific binding to rat CRFBP. The significance of residues 10 to 12 and 21 to 24 of Svg for its low affinity binding was established by changing these residues of Svg to those of h/rCRF. The corresponding residues 22 to 25 of h/rCRF represented the ARAE motif determined to be crucial for binding in agreement with reported data on human CRFBP. Residues 11 to 13 of CRF introduced into Svg also enhanced the affinity to rat CRFBP.
Keywords: Corticotropin-releasing factor (CRF); CRF binding protein (CRFBP); Sauvagine (Svg); Anti-sauvagine-30; CRF receptor antagonist; HPLC-mass spectrometry; HEK 293 cells;
Bombesin-induced HPA and sympathetic activation requires CRH receptors by Pam Kent; Tania Bédard; Samir Khan; Hymie Anisman; Zul Merali (57-65).
Central administration of bombesin (BN) (into the ventricular system) increased circulating levels of ACTH, corticosterone, epinephrine, norepinephrine and glucose, indicating that this peptide activates the hypothalamic-pituitary-adrenal (HPA) axis and sympathetic nervous system. We then assessed the potential contribution of corticotropin-releasing hormone (CRH) system, in the mediation of these BN effects. Blockade of CRH receptors with αh-CRF (10 μg) attenuated or blocked the BN-induced rise in plasma ACTH, epinephrine, norepinephrine, glucose and corticosterone levels. These findings support the notion that BN-induced HPA axis and sympathetic activation are mediated, at least in part, via activation of CRH neurons.
Keywords: Gastrin-releasing peptide; ACTH; Corticosterone; Norepinephrine; Epinephrine; Glucose;
Arginine vasopressin in the cytoplasm and nuclear fraction of lymphocytes from healthy donors and patients with depression or schizophrenia by Rolf Ekman; Johan Gobom; Rita Persson; Patrizia Mecocci; Carol L. Nilsson (67-72).
We investigated whether cytoplasmic or nuclear extracts of human peripheral blood lymphocytes contain AVP in samples from healthy controls and patients diagnosed as depressed or schizophrenic. Both the cytoplasmic and nuclear extracts contained AVP as determined by radioimmunoassay. AVP and other peptides were detected in the purified samples by matrix-assisted laser desorption/ionization time of flight mass spectrometry. It is the first time that AVP has been characterized in human lymphocytes of patients with depression or schizophrenia. This finding demonstrates the presence of another important component within the potential regulatory loop between immune and neuro-endocrine tissues.
Keywords: Arginine vasopressin; Lymphocytes; Radioimmunoassay; High-performance liquid chromatography (HPLC); Mass spectrometry;
Biological effects after percutaneous absorption of thyrotropin-releasing hormone and its analogue M-TRH by B.M. Magnusson; L.-O.D. Koskinen; M. Koch; K. Karlsson (73-79).
Besides its well known endocrinological effects, thyrotropin-releasing hormone (TRH) has potential clinical value in the treatment of neurotrauma and various neurologic and psychiatric disorders. The aim of this study was to assess if transdermal delivery of TRH and its analogue, M-TRH, in the presence of enhancers, is an effective means for administration of the peptides. Using the in vitro diffusion cell method, the effect of ethanol and a terpene on the transdermal penetration of the peptides across full-thickness rat skin were studied. Steady-state permeability values for TRH and M-TRH were 8.7 ± 2.2 and 6.7 ± 1.4 μg/cm2 h, respectively. The addition of 3% terpene in combination with 47% ethanol increased the penetration of TRH and M-TRH to 16.2 ± 1.7 and 14.6 ± 2.1 μg/cm2 h, respectively. Rats were studied in vivo for release of thyroid-stimulating hormone (TSH) as a biologic effect after transdermally delivered peptide. Topical application of TRH and M-TRH induced an increase in TSH serum concentration from 0.32 ± 0.09 ng/ml to 32.6 ± 5.0 and 22.9 ± 7.6 ng/ml, respectively, after 30 min. The addition of terpene and ethanol in combination with TRH or M-TRH, increased the TSH release to 43.0 ± 3.8 and 48.4 ± 4.0 ng/ml, respectively. It is concluded that, in the rat, peptides can be absorbed through the skin with retained biologic activity, and in amounts sufficient to elicit a physiological response.
Keywords: Transdermal delivery; In vivo; In vitro; Peptides; TRH; Penetration enhancer;
Central TRH receptor 1 antisense blocks cold-induced gastric emptying but not brain c-Fos induction by Vicente Martı́nez; Lixin Wang; Yvette Taché (81-90).
We studied whether TRH receptor 1 (TRH-R1) antisense oligodeoxynucleotides injected intracisternally, impaired acute cold-induced c-Fos expression in the brain and vagally mediated stimulation of gastric emptying in conscious rats. Cold exposure (4–6°C, 90 min) increased gastric emptying and the number of c-Fos positive cells in the paraventricular nucleus of the hypothalamus, supraoptic nucleus, raphe pallidus, dorsal motor nucleus of the vagus, nucleus of the solitary tract and area postrema compared with rats at room temperature. TRH-R1 antisense abolished cold-induced stimulation of gastric transit but not c-Fos expression in the brain. TRH-R1 mismatch did not alter the gastric response to cold. These data indicate that central activation of TRH-R1 mediates cold-induced stimulation of gastric emptying but does not influence the induction of c-Fos expression in the brain.
Keywords: TRH; TRH receptors; mRNA antisense; Oligodeoxynucleotides; c-Fos immunoreactivity; Cold exposure; Medulla; Paraventricular nucleus of the hypothalamus; Nucleus tractus solitarius; Dorsal vagal complex; Raphe pallidus; Gastric emptying;
Effects of VIP and NO on the motor activity of vascularly perfused rat proximal colon by Kimitsuka Kumano; Masaki Fujimura; Shin-ichi Oshima; Hiroshi Yamamoto; Naoki Hayashi; Takaaki Nakamura; Mineko Fujimiya (91-98).
The effects of vasoactive intestinal polypeptide (VIP) and nitric oxide (NO) on the motor activity of the rat proximal colon were examined in an ex vivo model of vascularly perfused rat proximal colon. VIP reduced motor activity and this inhibitory effect was not altered by either atropine, hexamethonium, tetrodotoxin (TTX) nor TTX plus acetylcholine (ACh), but was completely antagonized by NO synthase inhibitor NG-nitro-L-arginine (L-NA) and by VIP receptor antagonist, VIP(10–28). These results suggest that VIP may exert a direct inhibitory effect on the motor activity of the rat proximal colon via a VIP receptor located on the smooth muscle and this effect is mediated by NO but not by cholinergic pathways. Atropine and hexamethonium reduced but ACh stimulated motor activity and the effect of ACh was not changed by TTX, suggesting that the cholinergic pathway may exert a direct stimulatory effect on motor activity. Single injection of TTX, VIP(10–28) or L-NA induced a marked increase in motor activity, suggesting that the motor activity of rat proximal colon is tonically suppressed by VIP and NO generating pathways, and elimination of inhibitory neurotransmission by TTX may induce an abnormal increase of the motor activity. The interaction between VIP and NO in regulation of motor activity was further examined by a measurement of NO release from vascularly perfused rat proximal colon. Results showed that NO release was significantly increased during infusion of VIP and this response was reversed by L-NA. These results suggest that VIP generating neurons may inhibit colonic motility by stimulating endogenous NO production in either smooth muscle cells or nerve terminals.
Keywords: VIP; NO; Rat proximal colon; Isolated vascular perfusion; Motility; Dialysis; NO release;
Distribution of vasoactive intestinal polypeptide, neuropeptide-Y and substance P and their effects on insulin secretion from the in vitro pancreas of normal and diabetic rats☆ by E Adeghate; A.S Ponery; D.J Pallot; J Singh (99-107).
This study examined the pattern of distribution of vasoactive intestinal polypeptide (VIP), neuropeptide-Y (NPY) and substance P (SP) in the pancreas of diabetic rat to determine whether there are changes in the number and pattern of distribution of these neuropeptides after the onset of diabetes. Moreover, the effect of VIP, NPY and SP on insulin secretion from the pancreas of normal and diabetic rats was also examined. Diabetes mellitus (DM) was induced by a single dose of streptozotocin (STZ) given intraperitoneally (i.p.) (60 mg kg body weight−1). Four weeks after the induction of DM, diabetic (n = 6) and normal (n = 6) rats were anesthetized with chloral hydrate and their pancreases removed and processed for immunohistochemistry and insulin secretion. The number of insulin-positive cells in the islets of Langerhans was reduced while that of VIP and NPY increased significantly after the onset of diabetes. The pattern of distribution of VIP, NPY and SP in the nerves innervating the pancreas was similar in both normal and diabetic rats. VIP-evoked large and significant (P < 0.02) increases in insulin secretion from the pancreas of normal and diabetic rats. NPY also induced a marked (P < 0.005) increase in insulin release from pancreatic tissue fragments of normal rat. Stimulation of pancreatic tissue fragments of diabetic rat with NPY resulted in a slight but not significant increase in insulin release. SP induced a large and significant (P < 0.005) increase in insulin secretion from the pancreas of normal rat but inhibited insulin secretion significantly (P < 0.03) from isolated pancreas of diabetic rat. In summary, VIP and NPY can stimulate insulin secretion from the pancreas after the onset of diabetes. The stimulatory effect of SP on insulin secretion is reversed to inhibitory in diabetic rats.
Keywords: VIP; NPY; SP; Insulin secretion; Radioimmunoassay; Immunohistochemistry; Pancreas; Diabetes mellitus; Rat;
SR48692 is a neurotensin receptor antagonist which inhibits the growth of small cell lung cancer cells by Terry W Moody; Jessica Chiles; Marchessini Casibang; Elizabeth Moody; Daniel Chan; Thomas P Davis (109-115).
Neurotensin (NT) is an autocrine growth factor for some small cell lung cancer (SCLC) cells. In this communication, the effects of a non-peptide NT receptor antagonist, SR48692, were investigated using SCLC cells. 3H-SR48692 bound with high affinity (IC50 = 20 nM) to NCI-H209 cells. Also, NT and SR48692 inhibited specific 125I-NT binding with high affinity (IC50 values of 2 and 200 nM). In contrast, the NT2 receptor agonist, levocabastine, had little effect on specific 125I-NT binding, second messenger production and proliferation using NCI-H209 cells. SR48692 (5 μM) antagonized the ability of NT (10 nM) to cause elevated cytosolic Ca2+ in Fura-2 AM loaded NCI-H209 cells. SR48692 antagonized the ability of NT to cause elevation of c-fos mRNA in these cells. Using a MTT proliferation assay, SR48692 inhibited NCI-H209 and H345 proliferation in a concentration-dependent manner. Using a clonogenic assay, 1 μM SR48692, reduced NCI-H209 colony number. Also, SR48692 (0.4 mg/kg per day) inhibited NCI-H209 xenograft proliferation in nude mice. These results suggest that SR48692 is a NT1 receptor antagonist which inhibits SCLC growth.
Keywords: Lung cancer; SR48692; Receptor binding; Cytosolic Ca2+; C-fos mRNA; Proliferation;
Endothelins stimulate aldosterone secretion from dispersed rat adrenal zona glomerulosa cells, acting through ETB receptors coupled with the phospholipase C-dependent signaling pathway by Paola G. Andreis; Cinzia Tortorella; Ludwik K. Malendowicz; Gastone G. Nussdorfer (117-122).
Compelling evidence indicates that endothelins (ETs) stimulates aldosterone secretion from rat zona glomerulosa (ZG) cells, acting through the ETB receptor subtype. We have investigated the mechanisms transducing the aldosterone secretagogue signal elicited by the pure activation of ETB receptors. Aldosterone response of dispersed rat ZG cells to the selective ETB-receptor agonist BQ-3020 was not affected by inhibitors of adenylate cyclase/protein kinase (PK)A, tyrosine kinase-, mitogen-activated PK-, cyclooxygenase- and lipoxygenase-dependent pathways. In contrast, the inhibitor of phospholipase C (PLC) U-73122 abrogated, and the inhibitors of PKC, phosphatidylinositol trisphosphate (IP3)-kinase and calmodulin (calphostin-C, wortmannin and W-7, respectively) partially prevented aldosterone response to BQ-3020. When added together, calphostin-C and wortmannin or W-7 abolished the secretagogue effect of BQ-3020. BQ-3020 elicited a marked increase in the intracellular Ca2+ concentration ([Ca2+]i) in dispersed rat ZG cells, and the effect was abolished by the Ca2+-release inhibitor dantrolene. The Ca2+ channel blocker nifedipine affected neither aldosterone nor Ca2+ response to BQ-3020. Collectively, our findings suggest that (1) ETs stimulate aldosterone secretion from rat ZG cells through the activation of PLC-coupled ETB receptors; (2) PLC stimulation leads to the activation of PKC and to the rise in [Ca2+]i with the ensuing activation of calmodulin; and (3) the increase in [Ca2+] is exclusively dependent on the stimulation of IP3-dependent Ca2+ release from intracellular stores.
Keywords: Endothelins; Adrenal zona glomerulosa; Aldosterone secretion; Rat;
Orexin-A immunoreactive neurons in the rat hypothalamus do not contain neuronal nitric oxide synthase (nNOS) by David J. Cutler; Richard Morris; Martyn L. Evans; Ron A. Leslie; Jonathan R.S. Arch; Gareth Williams (123-128).
The lateral hypothalamic area (LHA), a key site involved in the central control of feeding and energy homeostasis, contains populations of neurons that produce the orexin peptides or nitric oxide, two chemical factors that increase food intake. In this study, we used immunohistochemistry to investigate the possibility that rat LHA neurons co-express orexin-A and neuronal nitric oxide synthase (nNOS). The orexin-A and nNOS cell populations in the LHA showed extensive overlap without co-localization, and no evidence of direct anatomic contact was found. The finding that LHA neurons do not co-localize orexin-A and nNOS may suggest that the actions of the orexins and nitric oxide on food intake are mediated via independent mechanisms, however, nitric oxide is a diffusible molecule and could potentially affect the activity of orexin neurons via a non-synaptic mechanism.
Keywords: Orexin; Nitric oxide; Nitric oxide synthase; Lateral hypothalamic area; Feeding; Immunohistochemistry; Hypocretin;
Paraventricular hypothalamic α-melanocyte-stimulating hormone and MTII reduce feeding without causing aversive effects by Michelle M Wirth; Pawel K Olszewski; Carolyn Yu; Allen S Levine; Silvia Q Giraudo (129-134).
α-Melanocyte-stimulating hormone (α-MSH) appears to play a tonic inhibitory role in feeding and energy storage. MTII, a specific synthetic MC3-R/MC4-R agonist, has similar effects on feeding in rats. The current studies demonstrate that PVN administration of α-MSH or MTII decreases nocturnal and NPY-stimulated food intake without causing aversive effects. Co-administration with NPY of 600 pmol α-MSH or 1 pmol MTII into the PVN caused a significant decrease in NPY-induced feeding. PVN administration of MTII or α-MSH at doses effective to suppress feeding did not cause conditioned taste aversion (CTA). ICV administration of α-MSH, however, did cause weak CTA. These results indicate that the potent effects on feeding of MC3-R and MC4-R agonists when injected into the PVN are not due to aversive effects.
Keywords: Paraventricular nucleus of the hypothalamus (PVN); α-melanocyte-stimulating hormone (α-MSH); MTII; Neuropeptide Y (NPY); Food intake; Conditioned taste aversion; Melanocortin-4 receptor (MC4-R); Melanocortins;
The effect of melanotropic peptides on binding of [3H]dihydroalprenolol-hydrochloride to hypothalamic membranes by Ruth Stutz; Mónica Sanchez; Nancy A. Salvatierra; Teresa Scimonelli (135-138).
In the present work we studied the interaction of α-melanocyte-stimulating hormone (α-MSH) and ACTH-(1–24) with β-adrenergic receptors in hypothalamic membranes from rat brain. Saturation curves for [3H]dihydroalprenolol-hydrochloride ([3H]DHA) binding in the presence of the peptides revealed a decreased binding capacity (Bmax). The dissociation constant (Kd) was, however, not affected by α-MSH or ACTH-(1–24). These data indicate a non competitive interaction between these melanocortin peptides and [3H]DHA on β-adrenergic receptors in hypothalamic membranes.
Keywords: α-MSH; ACTH-(1–24); β-Adrenergic receptor; [3H]DHA; Hypothalamic membranes;
Immunoreactive orexin-A in human plasma by Zenei Arihara; Kazuhiro Takahashi; Osamu Murakami; Kazuhito Totsune; Masahiko Sone; Fumitoshi Satoh; Sadayoshi Ito; Toraichi Mouri (139-142).
Orexin-A and orexin-B are newly discovered neuropeptides which are implicated in feeding behavior and arousal state. We studied immunoreactive(IR)-orexin-A concentrations in human plasma by radioimmunoassay. IR-orexin-A concentrations in plasma obtained from 17 healthy subjects in the morning were 1.94 ± 0.24 pmol/liter (mean ± SEM). IR-orexin-A levels in the plasma obtained at night were not significantly different from those obtained in the morning in 9 female subjects. The HPLC analysis of the plasma extract showed two immunoreactive peaks; one peak eluting in an identical position to synthetic orexin-A, and one eluting earlier. This study has shown for the first time the presence of orexin-A in human plasma.
Keywords: Orexin-A; Plasma; Diurnal variation; Radioimmunoassay;
Erratum to ‘Effects of supraspinal orphanin FQ/nociceptin’ by Judith E. Grisel; Jeffrey S. Mogil (143).