The cardiovascular response to epicardial application of neurotensin in guinea pigs

Topical application of picomoles of neurotensin (NT) on the surface of the left ventricle (epicardial application) of anesthetized guinea pigs evoked dose-dependent pressor effects and tachycardia. The pressor response to epicardial NT was attenuated by pentolinium, a mixture of phentolamine and propranolol, or by guanethidine. However it was not affected by indomethacin, atropine or by a mixture of mepyramine and cimetidine. The tachycardia caused by epicardial NT was not modified by any of the aforementioned drugs. Both the pressor effects and tachycardia elicited by epicardial application of NT were markedly inhibited by chronic treatment of guinea pigs with capsaicin, and by topical application of lidocaine or tetrodotoxin to the surface of the left ventricle. Epicardial application of calcitonin gene-related peptide (CGRP), substance P (SP) or capsaicin also elicited tachycardia and either a decrease (CGRP and SP) or increase of blood pressure (capsaicin) in anesthetized guinea pigs. Epicardial application of NT, CGRP, or capsaicin in isolated, perfused hearts of guinea pigs also caused tachycardia. Together, these results suggest that the pressor responses to topical application of NT on the surface of the left ventricle in anesthetized guinea pigs are partially reflex in nature and likely to result from the stimulation by NT of cardiac sympathetic, capsaicin-sensitive, sensory nerve endings, whereas the tachycardia caused by epicardial NT appears to be due both to direct and indirect effects of NT on ventricular muscle cells. The possible participation of CGRP and/or SP in the chronotropic effect of NT applied on the epicardium, and their putative role as neurotransmitter of cardiac, capsaicin-sensitive, sensory neurons are discussed.     

Sensory innervation of the ear drum and middle-ear mucosa: Retrograde tracing and immunocytochemistry

Summary The distribution and origin of nerve fibers of presumed sensory nature in the ear drum and middle-ear mucosa of the rat were studied by a retrograde tracing technique in combination with immunocytochemistry.Application of True Blue (TB) on the ear drum or on the middle-ear mucosa labeled nerve cell bodies in the jugular, trigeminal, geniculate and cervical dorsal root ganglia (C₂–C₄). Judging from the number of TB-labeled nerve cell bodies the jugular and trigeminal ganglia contributed the major component to the sensory innervation of the ear drum and the middle-ear mucosa, while the contribution from the geniculate and cervical dorsal root ganglia was relatively minor.The majority of the TB-labeled nerve cell bodies contained calcitonin gene-related peptide (CGRP), whereas minor populations stored substance P (SP) and neurokinin A (NKA). Nerve fibers containing SP, NKA and CGRP were moderate in number in the middle-ear mucosa and few in the ear drum. Double immunostaining revealed that SP invariably coexisted with NKA in nerve cell bodies in the ganglia examined. The SP/NKA-containing nerve cell bodies constituted a subpopulation of those storing CGRP.The findings indicate that several ganglia project to the ear drum and middle-ear mucosa and that many neuropeptides are involved in the mediation of middle-ear sensitivity.     

Participation of capsaicin-sensitive neurons in the cardiovascular effects of neurotensin in guinea pigs

Intravenous (IV) infusions of neurotensin (NT) in anesthetized guinea pigs elicited dose-dependent pressor effects and tachycardia. Both effects were significantly reduced or abolished in guinea pigs given a chronic treatment with the neurotoxin capsaicin. In guinea pig isolated atria NT evoked a positive inotropic and chronotropic effect. Both effects were completely abolished in atria derived from capsaicin-treated guinea pigs. The positive inotropic and chronotropic effects of NT in guinea pig atria were mimicked by capsaicin and calcitonin gene-related peptide (CGRP). These results were interpreted as an indication that NT produces its cardiovascular effects in guinea pigs by activating capsaicin-sensitive sensory neurons.     

Formation of Neuromuscular Junctions and Synthesis of Sensory Neuropeptides in the Co-cultures of Dorsal Root Ganglion and Cardiac Myocytes

Aim The interactions between primary sensory neurons and cardiac myocytes are still unclear. In the present study, the co-culture model of dorsal root ganglion (DRG) explant and cardiac myocytes was used to characterize the morphological relationship between primary sensory nerve endings and cardiac myocytes and to investigate whether cardiac myocytes could induce substance P (SP) and calcitonin gene-related peptide (CGRP) synthesis in DRG neurons and release from DRG neurons in the neuromuscular co-cultures. Methods The formation of neuromuscular junctions was observed with scanning electron microscopy (SEM). SP and CGRP expression were detected by immunocytochemistry. Basal SP and CGRP release and capsaicin-evoked SP and CGRP release were analyzed by radioimmunoassay (RIA). Results In this study, neuromuscular junctions were observed in the co-cultures of DRG explant and cardiac myocytes. SP-immunoreactive (IR) and CGRP-IR neurons were detected in both neuromuscular co-cultures and DRG explant cultures, but the number of SP-IR and CGRP-IR neurons migrating from DRG explant was significantly increased in neuromuscular co-cultures. Capsaicin-evoked SP and CGRP release but not basal SP and CGRP release in neuromuscular co-cultures increased significantly as compared with that in the cultures of DRG explant alone. Conclusions The results implicated that the morphological relationship between sensory nerve terminal and cardiac myocyte is much more close in vitro than it is in vivo. Cardiac myocytes may induce sensory neuropeptide synthesis and capsaicin-evoked neuropeptide release in neuromuscular co-cultures. Further experiment needs to be performed about the significance of neuropeptide synthesis and capsaicin-evoked neuropeptide release induced by target cardiac myocytes. Zhen Liu and Huaxiang Liu contributed equally to this article.     

神经肽Y、钙基因相关肽和P物质在甲状腺中的分布及其在甲亢状态下的变化(英文)

以往的研究表明,甲状腺中分布有肽能神经,包括神经肽Y(NPY)能神经、P物质(SP)能神经和脑肠肽(VIP)能神经.这些神经纤维的终末与血管和甲状腺的滤泡接触.一般认为,甲状腺的功能活动主要受下丘脑-垂体-甲状腺轴的调节,有关神经肽的调节,尤其是在甲亢状态下的调节尚不清楚.本研究以SD大鼠为实验动物,通过T4注射建立甲亢动物模型.使用免疫组化技术对NPY、CGRP和SP 在实验与对照动物的分布进行形态学研究,使用放射免疫测定技术对模型动物与对照动物甲状腺中的NPY、CGRP和SP进行定量研究.免疫组化技术发现NPY阳性神经纤维密集环绕小血管,其末端与血管内皮紧密联系,一些NPY阳性神经走行于滤泡间的结缔组织中,其末端与滤泡上皮接触;有SP阳性神经纤维走行于滤泡间的结缔组织中,其末端与滤泡上皮接触;CGRP阳性细胞分布于滤泡间的结缔组织中,或滤泡上皮细胞之间.放射免疫测定表明甲亢大鼠NPY、SP水平高于对照大鼠,CGRP水平低于对照大鼠.结果表明,在甲亢状态下,机体通过血管收缩介质NPY、SP的增多与血管舒张介质CGRP的减少,控制甲状腺素进入血液循环,这是机体在病理过程中的自稳机制之一.     

Calcitonin gene-related peptide coexists with substance P in capsaicin sensitive neurons and sensory ganglia of the rat

Immunohistochemical and radioimmunoassay studies revealed that both CGRP- and SP-like immunoreactivity in the caudal spinal trigeminal nucleus and tract, the substantia gelatinosa and the dorsal cervical spinal cord as well as in cell bodies of the trigeminal ganglion and the spinal dorsal root ganglion is markedly depleted by capsaicin which is known to cause degeneration of a certain number of primary sensory neurons. Higher brain areas and the ventral spinal cord were not affected by capsaicin treatment. Furthermore CGRP and substance P-like immunoreactivity were shown to be colocalized in the above areas and to coexist in cell bodies of the trigeminal ganglion and the spinal dorsal root ganglia. It is suggested that CGRP, like substance P, may have a neuromodulatory role on nociception and peripheral cardiovascular reflexes.     

Activation of Protein Kinase C Augments Peptide Release from Rat Sensory Neurons

Abstract: To determine whether protein kinase C (PKC) mediates release of peptides from sensory neurons, we examined the effects of altering PKC activity on resting and evoked release of substance P (SP) and calcitonin gene-related peptide (CGRP). Exposing rat sensory neurons in culture to 10 or 50 n M phorbol 12,13-dibutyrate (PDBu) significantly increased SP and CGRP release at least 10-fold above resting levels, whereas the inactive 4α-PDBu analogue at 100 n M had no effect on release. Furthermore, 100 n M bradykinin increased peptide release approximately fivefold. Down-regulation of PKC significantly attenuated the release of peptides evoked by either PDBu or bradykinin. PDBu at 1 n M or 1-oleoyl-2-acetyl- sn -glycerol at 50 µ M did not alter resting release of peptides, but augmented potassium- and capsaicin-stimulated release of both SP and CGRP approximately twofold. This sensitizing action of PKC activators on peptide release was significantly reduced by PKC down-regulation or by pretreating cultures with 10 n M staurosporine. These results establish that activation of PKC is important in the regulation of peptide release from sensory neurons. The PKC-induced enhancement of peptide release may be a mechanism underlying the neuronal sensitization that produces hyperalgesia.     

Pathway-specific patterns of the co-existence of substance P,calcitonin gene-related peptide,cholecystokinin and dynorphin in neurons of the dorsal root ganglia of the guinea-pig

Summary The co-existence of immunoreactivities to substance P (SP), calcitonin gene-related peptide (CGRP), cholecystokinin (CCK) and dynorphin (DYN) in neurons of the dorsal root ganglion (DRG) of guinea-pigs has been investigated with a double-labelling immunofluorescence procedure. Four main populations of neurons could be identified that contained different combinations of these peptides and had distinctive peripheral projections: (1) Neurons that contained immunoreactivity to SP, CGRP, CCK and DYN were distributed mainly to the skin. (2) Neurons with immunoreactivity to SP, CGPR and CCK, but not DYN, were distributed mainly to the small blood vessels of skeletal muscles. (3) Neurons with immunoreactivity to SP, CGRP and DYN, but not CCK, were distributed mainly to pelvic viscera and airways. (4) Neurons containing immunoreactivity to SP and CGRP, but not CCK and DYN, were distributed mainly to the heart, systemic blood vessels, blood vessels of the abdominal viscera, airways and sympathetic ganglia. Other small populations of DRG neurons containing SP, CGRP or CCK alone also were detected. Perikarya containing these combinations of neuropeptides were not found in autonomic ganglia. The peripheral axons of neurons containing immunoreactivity to at least SP and CGRP were damaged by chronic treatment with capsaicin. However, some sensory neurons containing CCK alone were not affected morphologically by capsaicin.These results clearly show that individual DRG neurons can contain many different neuropeptides. Furthermore, the combination of neuropeptides found in any particular neuron is related to its peripheral projection.     

Light- and electron-microscopic study of synaptic connections in the paracervical ganglion of the female rat: special reference to calcitonin gene-related peptide-, galanin- and tachykinin (substance P and neurokinin A)-immunoreactive nerve fibers and terminals

Nerve fibers and varicosities in the pelvic paracervical ganglia (PG) are immunoreactive for the neuropeptides calcitonin gene-related peptide, galanin, and the tachykinins substance P and neurokinin A. Many of these fibers and varicosities are capsaicin-sensitive, originate in dorsal root ganglia and, thus, are considered to be primary afferent fibers. Numerous immunoreactive varicosities are pericellular to principal neurons in the PG. The present study examines the ultrastructure of calcitonin gene-related peptide-, galanin-, substance P-, and neurokinin A-immunoreactive nerve fibers and varicosities in the ganglia to determine their relationships to principal neurons and their synaptic connectivity. Paracervical ganglia of female rats were processed for light-microscopic immunohistochemistry using antisera against synapsin I, as a nerve terminal marker, and microtubule-associated protein-2 to define soma and dendrites. The rationale for performing this co-immunohistochemical analysis was to reveal the relationship between nerve endings and principal neurons. Synapsin I endings were predominantly axosomatic with fewer being axodendritic. Other ganglia were processed for electron-microscopic immunohistochemistry using both standard immunogold and peroxidase-anti-peroxidase procedures. Unmyelinated fibers and varicosities immunoreactive for calcitonin gene-related peptide, galanin, and the tachykinins were routinely observed in the interstitium between neuron somas. Numerous immunoreactive axon profiles were present in small groups that were ensheathed by Schwann cells. Immunoreactive fibers and varicosities were also observed within the satellite-cell sheath of the neuron soma and often intimately associated with the membrane of the soma, somal protrusions, or with the proximal part of a dendrite. Membrane specializations, indicative of synaptic contacts, between the fibers and the principal neurons were observed. It is suggested that these peptide-immunoreactive sensory fibers and varicosities are involved in regulation of activity in the PG.     

SP和CGRP在炎症性肠病大鼠结肠中的表达规律

目的通过研究P物质（SP）和降钙素基因相关肽（CGRP）在炎症性肠病（IBD）大鼠结肠中的表达规律来探讨二者在IBD发生发展过程中发挥的作用。方法采用三硝基苯磺酸（TNBS）化学诱导建立IBD大鼠动物模型,应用real-time RT-PCR方法来检测SP和CGRP mRNA在模型不同时期结肠中的表达变化。结果随着炎症性肠病病理变化的加剧（第3、7天）,sP和CGRP在结肠组织中的表达水平显著升高;随着疾病的恢复（第21、28天）,其表达水平逐渐降低并趋向于正常水平。从总体来看,在IBD大鼠结肠组织中,SP和CGRP mRNA水平的变化与IBD的发生、发展呈正相关。结论神经递质SP和CGRP在IBD炎症和修复中起重要的神经免疫信号传导作用。     

Immunohistochemical evidence for different pathways immunoreactive to substance P and calcitonin gene-related peptide (CGRP) in the guinea-pig stellate ganglion

The colocalization of immunoreactivities to substance P and calcitonin gene-related peptide (CGRP) in nervous structures and their correlation with other peptidergic structures were studied in the stellate ganglion of the guinea pig by the application of double-labelling immunofluorescence. Three types of fibre were distinguished. (1) Substance P⁺/CGRP⁺ fibres, which sometimes displayed additional immunoreactivity for enkephalin, constituted a small fibre population of sensory origin, as deduced from retrograde labelling of substance P⁺/CGRP⁺ dorsal root ganglion cells. (2) Substance P⁺/CGRP^– fibres were more frequent; some formed baskets around non-catecholaminergic perikarya that were immunoreactive to vasoactive intestinal polypeptide (VIP). (3) CGRP⁺/substance P^– fibres were most frequent and were mainly distributed among tyrosine hydroxylase (TH)-immunoreactive cell bodies. The peptide content of fibre populations (2) and (3) did not correspond to that of sensory ganglion cells retrogradely labelled by tracer injection into the stellate ganglion. Therefore, these fibres are throught to arise from retrogradely labelled preganglionic sympathetic neurons of the spinal cord, in which transmitter levels may have been too low for immunohistochemical detection of substance P or CGRP. CGRP-immunoreactivity but no substance P-immunolabelling was observed in VIP-immunoreactive postganglionic neurons. Such cell bodies were TH-negative and were spared by substance P-immunolabelled fibre baskets. Retrograde tracing with Fast Blue indicated that the sweat glands in the glabrous skin of the forepaw were the targets of these neurons. The streptavidin-biotin-peroxidase method at the electron-microscope level demonstrated that immunoreactivity to substance P and CGRP was present in dense-cored vesicles of 50–130 nm diameter in varicosities of non-myelinated nerve fibres in the stellate ganglion. No statistically significant difference in size was observed between vesicles immunolabelled for substance P and CGRP. Immunoreactive varicosities formed axodendritic and axosomatic synaptic contacts, and unspecialized appositions to non-reactive neuronal dendrites, somata, and axon terminals. Many varicosities were partly exposed to the interstitial space. The findings provide evidence for different pathways utilizing substance P and/or CGRP in the guinea-pig stellate ganglion.     

Calcitonin gene-related peptide immunoreactivity in the biliary pathway and liver of the guinea-pig: distribution and colocalization with substance P

Summary Calcitonin gene-related peptide immunoreactivity was localized immunohistochemically in nerve fibers innervating the biliary pathway and liver of the guinea-pig. Immunoreactive fibers are present in all layers of the gallbladder and biliary tract and are particularly numerous around blood vessels. In the liver, immunoreactive processes are usually restricted to the interlobular space and porta hepatis, and only a few, very thin, beaded processes were observed in the hepatic parenchyma. A rich innervation is also associated with the vena portae. Positive ganglion cell bodies were not visualized within the ganglionated plexus of the biliary system, whereas they were found in the myenteric and submucosal plexus in the cranial portion of the duodenum corresponding to the sphincter of Oddi. The vast majority, if not all, of calcitonin gene-related peptide-immunoreactive fibers contain substance P immunoreactivity; however, there are some substance P-containing fibers lacking calcitonin gene-related peptide immunoreactivity. The lack of co-occurrence of calcitonin gene-related peptide and substance P immunoreactivities in intrinsic ganglion cells suggests that these two peptides are coexpressed in the extrinsic component of the innervation of the hepatobiliary system.     

Immunohistochemical identification of calcitonin gene-related peptide and substance P in nerves of the bovine parathyroid gland

Summary Although peptide neurotransmitters have been shown to modulate hormone secretion in many glands, there are very few studies of neurotransmitters in the parathyroid gland. Bovine parathyroid glands were collected at a local abattoir, fixed with paraformaldehyde, sectioned using a cryostat, and stained by indirect immunohistochemistry for calcitonin gene-related peptide and substance P. We were able to positively identify both neuropeptides. Nerve fibres containing calcitonin gene-related peptide and substance P were identified in contact with the tunica media of arteries and arterioles and dispersed throughout the stroma of the gland. While many of the fibres encircled parenchymal lobules, no intimate contact with the peripheral chief cells was observed. All immunoreactive fibres were found to contain both neuropeptides. Since calcitonin gene-related peptide and substance P are vasodilators, they may increase blood flow within the gland. In addition, the neuropeptides may diffuse from perilobular nerve fibres into the parenchyma, thereby modulating secretion of parathyroid hormone.     

Effects of capsaicin in rat and pigeon on peripheral nerves containing substance P and calcitonin gene-related peptide

Summary Substance P and calcitonin gene-related peptide were immunohistochemically identified in axons innervating the cornea and the ureter of adult rats and pigeons. The two neuropeptides were similarly distributed in both species. Capsaicin pretreatment induced depletion of the immunoreactivity; this was quantitatively and qualitatively different in rats and pigeons. Topical application of capsaicin (1%) reduced the immunoreactivity in the cornea in both species by 50%. Systemic capsaicin treatment completely depleted both peptides from the corneal innervation of rats but reduced the peptide content only by 50% in the cornea of pigeons. In the ureter of rats, capsaicin pretreatment completely depleted the peptide immunoreactivity. In pigeons the peptide depletion was only complete in the outer longitudinal muscle layer. Whereas only a few immunoreactive fibres were observed in the circular muscle layer, about 50% of the peptide remained in the inner longitudinal muscle layer. The results demonstrate that peptidergic afferents in the cornea and ureter of pigeons are sensitive to capsaicin, although birds do not show nociceptive responses to local administration of the drug. The long-term depletion of substance P and calcitonin gene-related peptide by capsaicin is discussed with regard to the possibility that functionally capsaicin receptors may exist in the axon but not at nerve endings.Part of the thesis of Gerhard Harti, to be presented to the Fachbereich Biologie, Justus-Liebig-Universität, Giessen     

慢性肾缺血致心功能不全时大鼠心肌组织降钙素基因相关肽含量的变化

目的观察慢性肾缺血导致心功能不全时心肌组织降钙素基因相关肽（CGRP）含量变化,并分析变化的机制。方法将40只Wistar大鼠分为,狭窄对照组（n=15）和狭窄治疗组（n=15）,均采用两肾动脉之间腹主动脉缩窄术造成单侧慢性肾缺血。假手术组（n=10）仅分离腹主动脉。至术后16周狭窄治疗组给予阿魏酸钠40mg／kg腹腔内注射,狭窄对照组和假手术组均给予同等剂量生理盐水。治疗2周后,测定颈动脉压、左心功能,处死大鼠后测定心肌组织CGRP、ET-1和NO含量,分别测定心肌和脊髓背根神经节CGRP mRNA表达。结果狭窄对照组和狭窄治疗组心功能均下降,但狭窄治疗组心脏舒张功能优于狭窄对照组。狭窄对照组心肌内ET-1含量明显增加,CGRP含量明显下降。狭窄治疗组心肌内ET-1含量较对照组减少,CGRP含量略增高。各组心肌CGRP mRNA表达无明显差异。狭窄治疗组脊髓背根神经节CGRP mRNA表达较假手术组增加。结论大鼠慢性肾缺血导致心脏组织ET-1持续激活,CGRP、NO合成受损,与心功能下降密切相关。心功能不全时,脊髓背根神经节CGRP mRNA表汰代偿件增高,但心脏血管内皮绢织受损可能是心脏CGRP含量下降的主要因素。     

Cyclic AMP Regulates the Expression of Neurokinin1 Receptors by Neonatal Rat Spinal Neurons in Culture

Neurokinin1 (NK1) receptors are up-regulated in the spinal cord during peripheral inflammation, but the biochemical mediators regulating this change have not been resolved. The promoter region of the gene encoding the NK1 receptor contains a cyclic AMP (cAMP)-responsive element. Therefore, we used primary cultures of neonatal rat spinal cord to test whether increasing intracellular cAMP can increase expression of NK1 receptors. Treatment with dibutyryl-cAMP (dbcAMP) resulted in a time-dependent increase in 125I-Bolton-Hunter-substance P (BHSP) binding in the cultures; treatment with dibutyryl-cyclic GMP did not. Treatment with forskolin plus 3-isobutyl-1-methylxanthine mimicked the increase in binding, providing further evidence for the involvement of cAMP in this effect. Scatchard analyses indicated that the increase in BHSP binding was due to an increase in binding capacity. The cAMP-induced increase in BHSP binding was preceded by an increase in levels of mRNA for NK1 receptor and was attenuated by pretreatment with cycloheximide. These data indicate that the cAMP-induced increase in binding was due to increased synthesis of NK1 receptors. Comparison of substance P (SP)-induced production of inositol phosphates between cultures pretreated with dbcAMP and controls suggested that increased expression of NK1 receptors did not result in increased generation of second messenger by NK1 receptor activation. Together, these data indicate that a persistent increase in intracellular cAMP increases expression of NK1 receptors. Because NK1 receptor activation contributes to increased excitability of spinal neurons, the increased expression of NK1 receptors may be important in maintaining responsiveness of spinal neurons to SP in central mechanisms underlying hyperalgesia.     

Innervation of lower airways and neuropeptide effects on bronchial and vascular tone in the pig

Summary The occurrence and distribution of peptide-containing nerve fibres [substance P (SP), calcitonin gene-related peptide (CGRP), vasoactive intestinal polypeptide (VIP), peptide histidine isoleucine (PHI), neuropeptide Y (NPY)] and noradrenergic nerve fibres [tyrosine hydroxylase (TH)- and dopamine beta hydroxylase (DBH)-positive] in the airways of the pig were studied by means of immunohistochemistry. SP- and CGRP-immunoreactive (-IR) nerve fibres were present close to and within the lining respiratory epithelium, around blood vessels, within the tracheobronchial smooth muscle layer and around local tracheobronchial ganglion cells. The content of CGRP- and neurokinin A (NKA)-like immunoreactivity (-LI) measured by radioimmunoassay (RIA) was twice as high in the trachea compared to that in the peripheral bronchi. SP was a more potent constrictor agent than NKA on pig bronchi in vitro. CGRP had a relaxant effect on precontracted pig bronchi. On blood vessels CGRP exerted a relaxant effect that was more pronounced on pulmonary arteries than on bronchial arteries. VIP/PHI-IR fibres were seen in association with exocrine glands and in the tracheobronchial smooth muscle layer. VIP-positive nerve fibres were abundant around blood vessels in the trachea but sparse or absent around blood vessels in the peripheral bronchi. This histological finding was supported by RIA; it was shown that the content of peptides displaying VIP-like immunoreactivity (-LI) was 18 times higher in the trachea compared to peripheral bronchi. VIP was equally potent as CGRP in relaxing precontracted pig bronchi in vitro. Both bronchial and pulmonary arteries were relaxed by VIP. NPY was colocalized with VIP in tracheal periglandular nerve fibres and in nerve fibres within the tracheobronchial smooth muscle layer. NPY was also present in noradrenergic (DBH-positive) vascular nerve fibres. The content of NPY was much higher (15-fold) in the trachea compared to small bronchi. NPY caused a contraction of both pulmonary and bronchial arteries. The bronchial smooth muscle contraction to field stimulation in vitro was purely cholinergic. A non-cholinergic relaxatory effect following field stimulation was observed after bronchial precontraction. Capsaicin had no effect on pig bronchi in vitro.     

Nerve growth factor receptor-like immunoreactivity in primary and permanent canine tooth pulps of the cat

Summary The distribution of nerve growth factor receptor (NGF receptor)-like immunoreactivity in pulps of developing primary and mature permanent cat canine teeth was examined, by use of a monoclonal antibody against NGF receptor detected by fluorescence immunohistochemistry and pre-embedding immunocytochemical light- and electron microscopy. Both primary and permanent pulps contained a vast number of NGF receptor-like immunoreactive nerves. Immunolabelling appeared to be localized both to axons and Schwann cells. In addition, many blood vessel walls in immature primary tooth pulps showed NGF receptor-like immunoreactivity, in contrast to permanent pulps where blood vessels rarely were NGF receptor-immunoreactive. Double-labelling immunofluorescence experiments revealed that in the permanent pulp a majority of the NGF receptor-positive nerves also showed calcitonin gene-related peptide (CGRP)-like immunoreactivity, and many showed substance P-like immunoreactivity. However, nerve fibers with neuropeptide Y-like immunoreactivity lacked NGF receptor-like immunoreactivity. In developing primary tooth pulps fewer NGF receptor-positive nerves were CGRP-like immunoreactive or substance P-like immunoreactive, as compared to the permanent pulp. Neuropeptide Y-like immunoreactive nerve fibers were not detected in the primary tooth pulp. The results suggest a role for nerve growth factor in both developing and mature sensory nerves of the tooth pulp.     

Tachykinins Potentiate N-Methyl-D-Aspartate Responses in Acutely Isolated Neurons from the Dorsal Horn

Abstract: Substance P and neurokinin A both potentiated N -methyl- d -aspartate (NMDA)-induced currents recorded in acutely isolated neurons from the dorsal horn of the rat. To elucidate the mechanism underlying this phenomenon, we measured the effects of tachykinins and glutamate receptor agonists on [Ca²⁺]_i in these cells. Substance P, but not neurokinin A, increased [Ca²⁺]_i in a subpopulation of neurons. The increase in [Ca²⁺]_i was found to be due to Ca²⁺ influx through voltage-sensitive Ca²⁺ channels. Substance P and neurokinin A also potentiated the increase in [Ca²⁺]_i produced by NMDA, but not by α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid, kainate, or 50 m M K⁺. Phorbol esters enhanced the effects of NMDA and staurosporine inhibited the potentiation of NMDA effects by tachykinins. It is concluded that activation of protein kinase C may mediate the enhancement of NMDA effects by tachykinins in these cells. However, the effects of tachykinins on [Ca²⁺]_i can be dissociated from their effects on NMDA receptors.     

Resveratrol improves cognitive function in mice by increasing production of insulin-like growth factor-I in the hippocampus

We examined whether resveratrol increases insulin-like growth factor-I (IGF-I) production in the hippocampus by stimulating sensory neurons in the gastrointestinal tract, thereby improving cognitive function in mice. Resveratrol increased calcitonin gene-related peptide (CGRP) release from dorsal root ganglion (DRG) neurons isolated from wild-type (WT) mice. Increases in tissue levels of CGRP, IGF-I, and IGF-I mRNA and immunohistochemical expression of IGF-I were observed in the hippocampus at 3 weeks after oral administration of resveratrol in WT mice. Significant enhancement of angiogenesis and neurogenesis was observed in the dentate gyrus of the hippocampus in these animals (P<.01). Improvement of spatial learning in the Morris water maze was observed in WT mice after administration of resveratrol. None of the effects of resveratrol observed in WT mice were seen after resveratrol administration in CGRP-knockout (CGRP^−/−) mice. Although red wine containing 20 mg/L of resveratrol produced effects similar to those of resveratrol administrationl in WT mice, neither red wine containing 3.1 mg/L of resveratrol nor white wine exhibited such effects in WT mice. Resveratrol was undetectable in the hippocampus of WT mice administered resveratrol and red wine containing 20 mg/L of resveratrol. These observations strongly suggest that resveratrol increases hippocampal IGF-I production via sensory neuron stimulation in the gastrointestinal tract, thereby improving cognitive function in mice.