Gastric distension-induced release of 5-HT stimulates c-fos expression in specific brain nuclei via 5-HT3 receptors in conscious rats

We examined c-fos expression in specific brain nuclei in response to gastric distension and investigated whether 5-HT released from enterochromaffin (EC) cells was involved in this response. The role of 5-HT3 receptors in this mechanism was also addressed. Release of 5-HT was examined in an ex vivo-perfused stomach model, whereas c-fos expression in brain nuclei induced by gastric distension was examined in a freely moving conscious rat model. Physiological levels of gastric distension stimulated the vascular release of 5-HT more than luminal release of 5-HT, and induced c-fos expression in the nucleus of the solitary tract (NTS), area postrema (AP), paraventricular nucleus (PVN), and supraoptic nucleus (SON). The c-fos expression in all these brain nuclei was blocked by truncal vagotomy as well as by perivagal capsaicin treatment, suggesting that vagal afferent pathways may mediate this response. Intravenous injection of 5-HT3 receptor antagonist granisetron blocked c-fos expression in all brain nuclei examined, although intracerebroventricular injection of granisetron had no effect, suggesting that 5-HT released from the stomach may activate 5-HT3 receptors located in the peripheral vagal afferent nerve terminals and then induce brain c-fos expression. c-fos Positive cells in the NTS were labeled with retrograde tracer fluorogold injected in the PVN, suggesting that neurons in the NTS activated by gastric distension project axons to the PVN. The present results suggest that gastric distension stimulates 5-HT release from the EC cells and the released 5-HT may activate 5-HT3 receptors located on the vagal afferent nerve terminals in the gastric wall leading to neuron activation in the NTS and AP and subsequent activation of neurons in the PVN and SON.     

Involvement of tachykinin NK(1) and NK(2) receptors in changes in lung mechanics and airway microvascular leakage during the early phase of endotoxemia in Guinea pigs

We investigated the role of tachykinins in airway neurogenic responses occurring in the early phase of endotoxemia. Forty-eight anesthetized guinea pigs were evenly divided into six groups pretreated with either saline vehicle, CP-96,345 (a tachykinin NK(1) receptor antagonist), SR-48,968 (a tachykinin NK(2) receptor antagonist) or CP-96,345 and SR-48,968 in combination. Animals then received an intravenous injection of either saline (the vehicle for endotoxin) or endotoxin (30 mg/kg). Total lung resistance (R(L)) and dynamic lung compliance (C(dyn)) were continuously measured before and 30 min after administration of saline or endotoxin. Airway microvascular leakage was assessed at the end of the observation period. Endotoxin significantly increased R(L) and decreased C(dyn) 10 min after intravenous endotoxin injection. Plasma extravasation significantly increased in the trachea, main bronchi and intrapulmonary airways with endotoxin administration. These changes in lung mechanics were abolished by SR-48,968, but were unaffected by CP-96,345. The plasma extravasation was largely attenuated by CP-96,345 and/or SR-48,968. We conclude that (1) endogenous tachykinins play an important role in producing changes in lung mechanics and airway microvascular leakage during the early phase of endotoxemia and (2) activation of tachykinin NK(2) receptors is responsible for the former response, while activation of both tachykinin NK(1) and NK(2) receptors is involved in the latter response.     

Functional and molecular characterization of tachykinins and tachykinin receptors in the mouse uterus

The aim of this study was to analyze the function and expression of tachykinins, tachykinin receptors, and neprilysin (NEP) in the mouse uterus. A previous study showed that the uterotonic effects of substance P (SP), neurokinin A (NKA), and neurokinin B (NKB) in estrogen-treated mice were mainly mediated by the tachykinin NK1 receptor. In the present work, further contractility studies were undertaken to determine the nature of the receptors mediating responses to tachykinins in uteri of late pregnant mice. Endpoint and real-time quantitative RT-PCR were used to analyze the expression of the genes that encode the tachykinins SP/NKA, NKB, and hemokinin-1 (HK-1) (Tac1, Tac2, and Tac4); and the genes that encode tachykinin NK1 (Tacr1), NK2 (Tacr2), and NK3 (Tacr3) receptors in uteri from pregnant and nonpregnant mice. The data show that the mRNAs of tachykinins (particularly NKB and HK-1), tachykinin receptors, and NEP are locally expressed in the mouse uterus, and their expression changes during the estrous cycle and during pregnancy. The tachykinin NK1 receptor is the predominant tachykinin receptor in the nonpregnant and early pregnant mouse and may mediate tachykinin-induced uterine contractions in the nonpregnant mouse. The tachykinin NK2 receptor is predominant in the late pregnant mouse and is the main receptor mediating uterotonic responses to tachykinins at late pregnancy. The tachykinin NK3 receptor is expressed in considerable amounts only in uteri from nonpregnant diestrous animals, and its physiological significance remains to be clarified.     

Role of tachykinins in the bronchoconstriction induced by HCl intraesophageal instillation in the rabbit

Gastroesophageal acid reflux (GER) is a common disorder associated with the exacerbation of asthma. In this study we investigated the effects on the airways of intraoesophageal HCl instillation in the rabbit and the role of tachykinins in these effects. In anaesthetized New Zealand rabbits bronchopulmonary functions [total lung resistance (R(L)) and dynamic compliance (C(dyn))] were calculated before and after HCl intraoesophageal instillation. Infusion of HCl induced a significant bronchoconstriction (P < 0.05) in the terms of R(L) and C(dyn) changes, that were increased by phosphoramidon pre-treatment and reduced by capsaicin pre-treatment. Moreover, a pre-treatment with SR 48968, a tachykinin NK2 receptor antagonist, or SR 140333, a NK1 receptor antagonist, significantly inhibited the bronchoconstriction induced by intraoesophageal HCl infusion in terms of R(L) and C(dyn)changes. Finally, the HCl induced bronchoconstriction was unaffected by SR 142801, a tachykinin NK3 receptor antagonist.In conclusion these results suggest that bronchoconstriction induced by intraoesophageal HCl infusion is mainly dependent on the release of tachykinins and that both NK1 and NK2 tachykinin receptors are involved.     

Binding sites for tachykinin peptides in the brain and stomach of the dogfish, Scyliorhinus canicula.

In membranes of dogfish brain and stomach, two binding sites for tachykinins were identified. One site specifically bound [125I]-Bolton-Hunter substance P (BH-SP) and the rank potency of tachykinins to compete for BH-SP binding revealed similarities with the rank potency of an NK1 receptor. The pharmacology of the other site, which specifically bound [125I]-Bolton-Hunter scyliorhinin II (BH-Scy II), did not resemble any of the mammalian tachykinin receptors. The rank potency to inhibit BH-Scy II binding to this second site was: scyliorhinin II approximately scyliorhinin I greater than eledoisin approximately substance P approximately neurokinin A greater than phyllomedusin approximately physalaemin greater than [Sar9Met(O2)11]substance P. Neurokinin B and senktide did not displace BH-Scy II binding. In addition, nucleotide analogues inhibited BH-SP binding but not BH-Scy II binding. Our binding data suggest the existence of a mammalian-like NK1 receptor and of a nonmammalian tachykinin receptor in the dogfish.     

Inhibitory activity of nociceptin/orphanin FQ on capsaicin-induced bronchoconstriction in the guinea-pig

In vivo studies were conducted in the guinea-pig to investigate the activity of the selective ORL1 receptor agonist nociceptin/orphanin FQ against capsaicin-induced bronchoconstriction, a response mediated by the release of tachykinins from pulmonary sensory nerves. Anesthetized guinea-pigs were ventilated with a rodent ventilator and placed in a whole-body plethysmograph, and pulmonary resistance (R(L)) and dynamic lung compliance (C(Dyn)) were monitored. Intravenous administration of nociceptin/orphanin FQ (0.3 mg/kg) inhibited the capsaicin-induced bronchoconstriction. The new nonpeptide ORL1 receptor antagonist 1-[(3R,4R)-1-cyclooctylmethyl-3-hydroxymethyl-4-piperidyl]-3-ethyl-1,3-dihydro-2H-benzimidazol-2-one (J-113397) administered intravenously (1 mg/kg) produced a significant blockade of the inhibitory effect of nociceptin/orphanin FQ (0.3 mg/kg) on capsaicin-induced bronchoconstriction, whereas the nonselective opioid receptor antagonist naloxone (1 mg/kg) had no effect. Nociceptin/orphanin FQ (0.3 mg/kg) did not affect the bronchoconstriction induced exogenously by the tachykinin NK2 receptor agonist [beta-ala8]-neurokinin A (4-10). We conclude that nociceptin inhibits in vivo capsaicin-evoked tachykinin release from sensory nerve terminals in the guinea-pig by a prejunctional mechanism. This inhibitory action does not involve activation of opioid receptors.     

侧脑室注射肾上腺髓质素增加大鼠心血管相关核团中c-fos的表达并激活脑内一氧化氮神经元

本研究利用Fos蛋白和一氧化氮合酶(nNOS)双重免疫组化方法,观察侧腑脑室注射肾上腺髓质素(adrenomedullin,ADM)对大鼠心血管相关核中c-fos表达及一氧化氮神经元的影响,以探讨ADM在中枢的作用部位并研究其在中枢的作用是否有NO神经元参与。侧脑室注射ADM(1nmol／kg,3nmol／kg)诱发脑干的孤束核、最后区、蓝斑核、臂旁核和外侧巨细胞旁核,下丘脑的室旁核、视上核才腹内侧核以及前脑的中央杏仁核和外侧缰核等多个部位的心血管中枢出现大量Fos样免疫反应神经元。侧脑室注射ADM(3nmol／kg),引起脑干的孤束核、外侧巨细胞旁核,下丘脑的室旁核、视上核内的Fos-nNOS双标神经元增加;ADM(1nmol／kg)亦可引起室旁核、视上核内的Fos-nNOS双标神经元增加,而对孤束核、外侧巨细胞旁核内的Fos-nNOS双标神经元无影响。降钙素基因相关肽(calcitonin gene—related peptide,CGRP)受体拈抗剂CGRP8-37(30nmol／kg)可明显减弱此效应。以上结果表明,ADM可兴奋脑内多个心血管相关核闭的神经元并激活室旁核、视上核、孤束核及外侧巨细胞核内一氧化氮神经元,此效应可能部分山CGRP受体介导。     

Tachykinin receptors mediating airway macromolecular secretion.

Three tachykinin receptor types, termed NK1, NK2, and NK3, can be distinguished by the relative potency of various peptides in eliciting tissue responses. Airway macromolecular secretion is stimulated by the tachykinin substance P (SP). The purposes of this study were to determine the tachykinin receptor subtype responsible for this stimulation, and to examine the possible involvement of other neurotransmitters in mediating this effect. Ferret tracheal explants maintained in organ culture were labeled with 3H-glucosamine, a precursor of high molecular weight glycoconjugates (HMWG) which are released by airway secretory cells. Secretion of labeled HMWG then was determined in the absence and presence of the tachykinins SP, neurokinin A (NKA), neurokinin B (NKB), physalaemin (PHY), and eledoisin (ELE). All the tachykinins tested stimulated HMWG release to an approximately equal degree. Stimulation was concentration-related, with log concentrations giving half-maximal effects (EC50) as follows: SP -9.47, NKA -7.37, NKB -5.98, PHY -8.08, and ELE -7.68. This rank order of potency (SP greater than PHY greater than or equal to ELE greater than or equal to NKA greater than NKB) is most consistent with NK1 receptors. To evaluate the possible contribution of other mediators, tachykinin stimulation was examined in the presence of several receptor blockers. The potency of SP was not diminished by pretreatment with atropine, propranolol, or chlorpheniramine, and atropine actually increased the magnitude of the secretory response. The SP receptor antagonist [D-Arg1,D-Phe5, D-Trp7,9, Leu11]-SP blocked SP-induced secretion. These findings indicate that SP is a potent stimulus of airway macromolecular secretion. This effect occurs through the action of NK1 receptors, and is not dependent upon cholinergic, beta-adrenergic, or H-1 histamine receptors. The facilitation by atropine of SP stimulation suggests the existence of a mechanism of cholinergic inhibition of SP-induced stimulation.     

Reduction of food intake by cholecystokinin requires activation of hindbrain NMDA-type glutamate receptors

Intraperitoneal injection of CCK reduces food intake and triggers a behavioral pattern similar to natural satiation. Reduction of food intake by CCK is mediated by vagal afferents that innervate the stomach and small intestine. These afferents synapse in the hindbrain nucleus of the solitary tract (NTS) where gastrointestinal satiation signals are processed. Previously, we demonstrated that intraperitoneal (IP) administration of either competitive or noncompetitive N-methyl-d-aspartate (NMDA) receptor antagonists attenuates reduction of food intake by CCK. However, because vagal afferents themselves express NMDA receptors at both central and peripheral endings, our results did not speak to the question of whether NMDA receptors in the brain play an essential role in reduction of feeding by CCK. We hypothesized that activation of NMDA receptors in the NTS is necessary for reduction of food intake by CCK. To test this hypothesis, we measured food intake following IP CCK, subsequent to NMDA receptor antagonist injections into the fourth ventricle, directly into the NTS or subcutaneously. We found that either fourth-ventricle or NTS injection of the noncompetitive NMDA receptor antagonist MK-801 was sufficient to inhibit CCK-induced reduction of feeding, while the same antagonist doses injected subcutaneously did not. Similarly fourth ventricle injection of d-3-(2-carboxypiperazin-4-yl)-1-propenyl-1-phosphoric acid (d-CPPene), a competitive NMDA receptor antagonist, also blocked reduction of food intake following IP CCK. Finally, d-CPPene injected into the fourth ventricle attenuated CCK-induced expression of nuclear c-Fos immunoreactivity in the dorsal vagal complex. We conclude that activation of NMDA receptors in the hindbrain is necessary for the reduction of food intake by CCK. Hindbrain NMDA receptors could comprise a critical avenue for control and modulation of satiation signals to influence food intake and energy balance.     

辣椒素引起脑干内心血管活动相关核团中c-fos的表达

在１６只切断两侧缓冲神经的大鼠,观察颈总动脉注射辣椒素对脑干内心血管活动相关核团ｃ－ｆｏｓ原癌基因表达的影响。在剂对照组大鼠脑干,仅见少数Ｆｏｓ蛋白样免疫反应（ＦＬＩ）神经元。与对照组相比,颈总动脉注射辣椒素（１０μｍｏｌ,０．１ｍｌ）时,脑干内巨细胞旁外侧核（ＰＧＬ）、蓝斑（ＬＣ）、最后区（ＡＰ）和孤束核（ＮＴＳ）等部位的ＦＬＩ神经元显著增加,而中脑中央灰质（ＰＡＧ）和中缝核群（ＲＮ）的ＦＬＩ神     

The new neurokinin 1-sensitive receptor mediates the facilitation by endogenous tachykinins of the NMDA-evoked release of acetylcholine after suppression of dopaminergic transmission in the matrix of the rat striatum

Using an in vitro microsuperfusion procedure, the NMDA-evoked release of [3H]ACh was studied after suppression of dopamine (DA) transmission (alpha-methyl-p-tyrosine) in striatal compartments of the rat. The effects of tachykinin neurokinin 1 (NK1) receptor antagonists and the ability of appropriate agonists to counteract the antagonist responses were investigated to determine whether tachykinin NK1 classic, septide-sensitive and/or new NK1-sensitive receptors mediate these regulations. The NK1 antagonists, SR140333, SSR240600, GR205171 but not GR82334 and RP67580 (0.1 and 1 microM) markedly reduced the NMDA (1 mm + D-serine 10 microM)-evoked release of [3H]ACh only in the matrix. These responses unchanged by coapplication with NMDA of NK2 or NK3 agonists, [Lys5,MeLeu9,Nle10]NKA(4-10) or senktide, respectively, were completely counteracted by the selective NK1 agonist, [Pro9]substance P but also by neurokinin A and neuropeptide K (1 nM each). According to the rank order of potency of agonists for counteracting the antagonist responses ([Pro9]substance P, 0.013 nM > neurokinin A, 0.15 nM > substance P(6-11) 7.7 nM = septide 8.7 nM), the new NK1-sensitive receptors mediate the facilitation by endogenous tachykinins of the NMDA-evoked release of ACh in the matrix, after suppression of DA transmission. Solely the NK1 antagonists having a high affinity for these receptors could be used as indirect anti-cholinergic agents.     

Substance P stimulates Growth Hormone (GH) and GH-Releasing Hormone (GHRH) secretions through tachykinin NK2 receptors in sheep

Substance P is ubiquitous undecapeptide belonging to the tachykinins family. It has been found in the hypothalamus and is involved in the hypothalamo-hypophysial axis in several mammals, including human. Previous studies have shown that substance P increases GH secretions in rats and human. In this study, we have shown that intravenously infused substance P in sheep caused an increased level of Growth Hormone (GH) and GH-Releasing Hormone (GHRH), and decreased Somatotropin Release Inhibiting Hormone (SRIH) secretions. GH was obtained from peripheral blood. GHRH and SRIH were directly collected from hypophysial portal blood, using a trans-nasal surgery technique in a vigil sheep that allowed accessing to hypothalamo-hypophysial portal vessels. Hormones assays were performed by radioimmunoassay (RIA). Moreover, we showed that substance P-induced GH and GHRH secretion appears to be mediated by NK2 tachykinin receptors, since it is specifically blocked by a non peptidic tachykinin NK2 receptor antagonist (SR48968, Sanofi, Montpellier, France) whereas a non peptidic tachykinin NK1 antagonist (SR140333, Sanofi, Montpellier, France) failed to modify GH and GHRH hormones secretions.     

Delta9-tetrahydrocannabinol selectively acts on CB1 receptors in specific regions of dorsal vagal complex to inhibit emesis in ferrets

The aim of this study was to investigate the efficacy, receptor specificity, and site of action of Delta9-tetrahydrocannabinol (THC) as an antiemetic in the ferret. THC (0.05-1 mg/kg ip) dose-dependently inhibited the emetic actions of cisplatin. The ED50 for retching was approximately 0.1 mg/kg and for vomiting was 0.05 mg/kg. A specific cannabinoid (CB)1 receptor antagonist SR-141716A (5 mg/kg ip) reversed the effect of THC, whereas the CB2 receptor antagonist SR-144528 (5 mg/kg ip) was ineffective. THC applied to the surface of the brain stem was sufficient to inhibit emesis induced by intragastric hypertonic saline. The site of action of THC in the brain stem was further assessed using Fos immunohistochemistry. Fos expression induced by cisplatin in the dorsal motor nucleus of the vagus (DMNX) and the medial subnucleus of the nucleus of the solitary tract (NTS), but not other subnuclei of the NTS, was significantly reduced by THC rostral to obex. At the level of the obex, THC reduced Fos expression in the area postrema and the dorsal subnucleus of the NTS. The highest density of CB1 receptor immunoreactivity was found in the DMNX and the medial subnucleus of the NTS. Lower densities were observed in the area postrema and dorsal subnucleus of the NTS. Caudal to obex, there was moderate density of staining in the commissural subnucleus of the NTS. These results show that THC selectively acts at CB1 receptors to reduce neuronal activation in response to emetic stimuli in specific regions of the dorsal vagal complex.     

Effect of subchronic administration of tachykinin antagonists on response of guinea-pigs to mild and severe stress

The effects of subchronic subcutaneous treatment with tachykinin receptor antagonists over nine days on the repeated mild stress response induced by daily subcutaneous injections and on the severe acute stress induced by morphine withdrawal were investigated in guinea-pigs. The NK(1) receptor antagonist, L733,060, 0.25mg/kg, significantly increased locomotor activity of guinea-pigs compared with animals subjected to repeated injection of the inactive enantiomer, but inhibited Fos-like immunoreactivity (Fos-LI) in the hypothalamus. In animals subjected to the acute severe stress of naltrexone-induced morphine withdrawal, treatment with the NK(1) antagonist, L733,060, produced reductions in Fos-LI in the spinal dorsal horn, whereas those treated with the NK(3) antagonist, SSR146,977, 0.3mg/kg, had reduced Fos-LI in the dorsal horn, adrenal medulla, nucleus accumbens, ventral tegmental area and periaqueductal grey. Those animals treated with both NK(1) and NK(3) antagonists also had reduced Fos-LI in the amygdala and paraventricular nucleus of the thalamus. It was concluded that the NK(1) antagonist reduced the hypothalamic response to mild stress but the NK(3) antagonist was more effective in reducing the severe stress response to morphine withdrawal. Furthermore, combination of NK(1) and NK(3) antagonists was more effective than either antagonist in reducing the Fos-LI response to morphine withdrawal.     

颈动脉注射辣椒素对脑干心血管相关核团一氧化氮合酶和Fos表达的影响

实验采用NADPH－d组化技术和Fos蛋白免疫组化技术相结合的方法,观察了颈动脉注射辣椒不时,大鼠脑干心血管相关核团内NOS和Fos蛋白的分布以及两者的共存关系。结果显示：（1）颈动脉注射辣椒不可诱发脑干中最后区（AP）、孤束核（NTS）、巨细胞旁外侧核（PGL）和蓝斑（LC）等多个部位Fos样免疫反应（FLI)神经元显著增加 中脑中央灰质（PAG）和中缝核群（RN）的FLI神经元无明显改变。（2）PGL和NTS内NO合成神经元以及PGL内双标神经元数量也明显增加,而AG和RN中NO合成神经元无明显变化,在LC和AP仅偶见或未见NO合成神经元。（3）预先应用辣椒素受体阻断剂钌红或NMDA受体阻断剂MK－801,则明显减弱辣椒素的上述效应,以上结果表明,颈动脉注射辣椒素可兴奋脑干心血管活动相关核团神经元,NO在脑干核团对辣椒素的反应中发挥间接的调制作用,辣椒素的效应由香草酸受体（辣椒素受体）介导并有谷氨酸参与。     

NK(1) receptor and its interaction with NMDA receptor in spinal c-fos expression after lower urinary tract irritation

The role of neurokinin 1 (NK(1)) receptor and possible interaction between NK(1) and N-methyl-D-aspartic acid (NMDA) glutamatergic receptors were investigated on spinal c-fos expression after lower urinary tract irritation with acetic acid infusion in rats. At both levels of the first (L(1)) and sixth lumbar (L(6)) spinal cord, where most of hypogastric nerve and pelvic nerve afferent terminals project, respectively, the selective NK(1) receptor antagonist CP-99,994 dose dependently reduced the total number of c-fos protein (Fos)-positive cells. However, CP-100,263, the enantiomer of CP-99,994 with a very low affinity for NK(1) receptor, did not have any effect on the total number of Fos-positive cells. Coadministration of a low dose (1 mg/kg) of CP-99,994 and NMDA receptor antagonist (MK-801), either of which alone did not affect c-fos expression, significantly inhibited c-fos expression at both levels of the spinal cord. Regarding regional differences, the number of Fos-positive cells decreased significantly at all regions of the L(6) level, but only at the dorsal horn of the L(1) level. These results indicate that NK(1) receptor is involved in spinal c-fos expression after lower urinary tract irritation and that NK(1) and NMDA receptors have a synergistic interaction in the spinal processing of nociceptive input from the lower urinary tract.