Substance P Content Research Articles

Alteration in the brain content of substance P (1–7) during withdrawal in morphine-dependent rats

Previous studies have shown that substance P (SP) may modulate the abstinence reaction to opioid withdrawal. Its N-terminal fragment SP 1–7 may inhibit the intensity of the withdrawal reactions in morphine dependent mice. This study was designed to determine whether the endogenous concentrations of the SP 1–7 fragment in the brain are affected during naloxone-precipitated withdrawal in the male rat. The amounts of the peptide was assessed by a specific radioimmunoassay in extracts of discrete brain regions (including the cerebral cortex, hippocampus, hypothalamus, nucleus accumbens, striatum, substantia nigra, ventral tegmental area and the spinal cord) during morphine tolerance and withdrawal. The results indicated that the concentrations of SP 1–7 were significantly elevated in the ventral tegmental area both in morphine tolerant rats and during naloxone-precipitated withdrawal. During morphine withdrawal significant increases in the peptide concentration were also observed in the hypothalamus and the spinal cord. It was concluded that the enhanced content of SP 1–7 may also indicate the involvement of the SP system during opioid withdrawal in the rat. The enhanced production of SP 1–7 may reflect an increased release and/or metabolism of SP, which, in turn, counteracts the withdrawal.

HYPERREFLEXIA OF THE URINARY BLADDER: POSSIBLE ROLE OF THE EFFERENT FUNCTION OF THE CAPSAICIN SENSITIVE PRIMARY AFFERENTS

Purpose Capsaicin sensitive primary afferents (CSPA) have been implicated in the pathogenesis hyperreflexia after spinalization. In this study we investigated the role of the efferent function of these fibers in detrusor hyperreflexia and its effect on detrusor physiology and pharmacology. Materials and Methods Four groups of female Sprague Dawley rats were included in our study. These groups were normal controls, capsaicin treated normal rats, spinalized rats and capsaicin treated spinalized rats. Six weeks following spinalization, animals were subjected to cystometric study, and bladders were obtained for either in vitro detrusor contractility study or substance P (SP), neurokinin A (NKA) and calcitonin gene related peptide (CGRP) quantification by radioimmunoassay. Results Spinalized animals consistently developed hyperreflexia after spinalization in the form of uninhibited contractions more than 15 cm. water in amplitude. This was accompanied by increased urinary bladder total content of the neuropeptides but without any change in the detrusor contractility or neurokinin receptor pharmacology as shown by responses to KCl, electric field stimulation and neurokinin receptor selective agonists in vitro study. In the control group, urinary bladder total content of SP, NKA and CGRP was 0.19 +/− 0.03, 0.15 +/− 0.01 and 0.84 +/− 0.1 rho mol/bladder respectively. In contrast, in the spinalized animals, these were 0.44 +/− 0.07, 0.21 +/− 0.03 and 2.28 +/− 0.34 rho mol/bladder for the same peptides, respectively. Capsaicin treatment abolished hyperreflexia, which corresponded with the decrease in the neuropeptide content of the urinary bladder. The number and amplitude of the uninhibited contractions decreased dramatically. SP, NKA and CGRP reached 0.06 +/− 0.01, 0.07 +/− 0.01 and 0.44 +/− 0.18 rho mol/bladder 2 weeks after capsaicin treatment in spinalized animals. This was associated with the occurrence of detrusor super-sensitivity to both neurokinin receptor selective agonists. Conclusion This study demonstrates the importance of the efferent function of the CSPA in the pathogenesis of hyperreflexia. On the other hand, detrusor changes were shown to be a non-crucial factor in the development of hyperreflexia.

Intraduodenal neuropeptide levels, but not plasma levels, vary in a cyclic fashion with the migrating motor complex.

The neurohormonal control of the migrating motor complex (MMC) is not fully understood. The hypothesis of the present study was that neuropeptide levels might vary with the different phases of the MMC and that a similar variation might be found in the secretions of the gastrointestinal tract. Thus, plasma and intraduodenal concentrations of vasoactive intestinal peptide (VIP), somatostatin (SOM), substance P (SP) and neurokinin A (NKA) were determined by radioimmunoassay every 10 min during two complete MMC cycles in eight male subjects. For comparison, plasma motilin (MOT) concentrations were measured. Plasma concentrations of MOT (mean peak value +/- SEM; 39 +/- 6 pmol L-1), but none of the neuropeptides studied, showed a cyclic variation in plasma with the different phases of the MMC. Peak intraduodenal concentrations of VIP (79 +/- 23 pmol L-1), SOM (2437 +/- 432 pmol L-1) and SP (718 +/- 326 pmol L-1) occurred at or at the time point before the onset of phase III of the MMC. No such correlation was observed for NKA. These results demonstrate that intraduodenal but not plasma concentrations of the neuropeptides VIP, SOM and SP show an association with phase III of the MMC. The biological relevance of this finding is yet unclear, but the results raise the possibility that gut neuropeptides may regulate fasting motility through a luminal release.

Hydroxyzine inhibits neurogenic bladder mast cell activation

Increased numbers of activated mast cells have been documented close to substance P (SP) containing nerve endings in the bladders of patients with interstitial cystitis (IC), a painful, sterile bladder disorder occurring primarily in females. Many of these patients also suffer from allergies, but common antihistamines do not help. In line with the fact that IC symptoms worsen under stress, we recently showed that bladder mast cells could be activated by the stable acetylcholine (Ach) analogue carbachol and by immobilization stress. Preliminary data from open label studies indicated that the heterocyclic histamine-1 receptor antagonist (H-1r α) hydroxyzine reduces IC symptoms. We, therefore, investigated whether hydroxyzine could inhibit carbachol-induced bladder mast cell activation. Methods: Bladder pieces from male Sprague–Dawley rats were perfused with 10 −5 M carbachol, 10 −5 M SP, or 100 μg\\ml compound 48\\80 (C48\\80), with or without preincubation with the designated concentrations of the H-1r α. Mast cell activation was assessed by release of exogenous 3H-serotonin and morphological evidence of secretion by light microscopy. Results: Carbachol at 10 −5 M triggered rat bladder mast cell serotonin release which represented a 65% increase over control. Equimolar concentrations of SP caused a 32% increase, while C48\\80 had no effect. The heterocyclic piperazine H-1r α hydroxyzine reduced carbachol-induced serotonin release by 25% at 10 −6 M and 34% at 10 −5 M, both of which were statistically significant ( P < 0.05). On the contrary, the well known H-1r α diphenhydramine had no inhibitory effect, while the mixed H-1r α and 5-hydroxytryptamine-receptor antagonist (5-HTr α) azatadine actually caused an 11% increase. Conclusion: Hydroxyzine reduced carbachol-induced serotonin release from rat bladder in vitro through a mechanism which was unrelated to its H-1 receptor antagonistic properties. The ability of hydroxyzine to inhibit bladder mast cell activation by neurogenic stimuli along with its anticholinergic, anxiolytic and analgesic properties, may explain the clinical efficacy of this drug in reducing IC symptoms. Other, non-sedating, hydroxyzine analogues able to inhibit bladder mast cell activation may provide potentially new therapeutic approaches for IC.

Change in substance P in a firearm wound and its significance

The present study was designed to detect the change of substance P (SP) in firearm wounds and its relationship with wound healing. Twenty two rabbits were randomly divided into two groups, one with firearm wounds created by steel balls shooting rabbits’ thighs and another with stab wounds created by knife. The experimental design did not include direct injury to femora major peripheral nerve trunks or blood vessels. SP content in wound tissue of both groups was measured with radioimmunoassay (RIA). Histologic examination was performed on the wound and the saphenous and sciatic nerves away from the wound-track edges. It was found that both types of injuries caused an increase of SP content in the wound compared with normal tissue. At three to 10 days after injury, SP content was lower in firearm wounds than that in stab wounds. Pathomorphologic observation showed the indirect injuries to the saphenous and sciatic nerves in the rabbits with firearm wounds were more severe than those with stab wounds. Meanwhile, wound healing in the firearm wounds was poor compared with that in the stab wounds. The results suggest that the change in SP in firearm wounds differs from that in cold weapon wounds as a result of the presence of indirect injuries to major peripheral nerve trunks created by laceration shock wave and cavity effects, and SP in vivo may participate in wound healing as a growth factor. Therefore, the improvement of neuropeptide metabolism in firearm wound may be an important measure for accelerating wound healing.

A possible role for saliva as a diagnostic fluid in patients with chronic pain

Objectives: The focus of this review was on proteins and peptides found in saliva. Of greatest interest were those neuropeptides relevant to nociception and to the pathogenesis of chronic pain syndromes. An additional goal was to develop a standardized protocol to collect saliva for laboratory assessment. Methods: Data were obtained through discussion with experts at the medical schools in San Antonio and Heidelberg and a Medline literature search involving all relevant studies from 1966 to 1997. The literature search was based on the following key terms: saliva, serotonin, neuropeptide, substance P (SP), calcitonin gene-related peptide (CGRP), and nerve growth factor (NGF). Results: The mean concentration of SP in the saliva of healthy normal controls ranged from 9.6 to 220 pg/mL. Generally, the concentration of SP was approximately three times higher in saliva than in plasma. In a number of painful conditions, particularly tension headache, substantial elevations of salivary SP were found. Mean values for salivary CGRP in healthy controls were approximately 22 pmol/L and were significantly elevated in patients with migraine attacks or cluster headache. There were no data to indicate prior quantitative determination of NGF in human saliva. Conclusions: After sampling and processing techniques have been standardized,measurement of neuropeptides in human saliva could provide a valuable tool for the study of patients with chronic painful disorders such as rheumatoid arthritis, osteoarthritis, and even fibromyalgia syndrome.

Corrigenda

CORRIGENDACorrigendaPublished Online:01 Apr 1998https://doi.org/10.1152/jappl.1998.84.4.1/aOriginal articleMoreSectionsPDF (14 KB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInEmailWeChat Volume 83, August 1997 Page 522, Abstract: In line 20 of the Abstract, “arterial Po 2” was mistakenly printed instead of “arterial Pco 2.” The corrected Abstract is reprinted below. Waters, Karen A., André Laferrière, Julie Paquette, Cynthia Goodyer, and Immanuela R. Moss. Curtailed respiration by repeated vs. isolated hypoxia in maturing piglets is unrelated to NTS ME or SP levels. J. Appl. Physiol. 83(2): 522–529, 1997.—In early development, respiratory disorders can produce recurring hypoxic episodes during sleep. To examine possible effects of daily repeated vs. isolated hypoxic hypoxia, cardiorespiratory functions and central, respiratory-related neuromodulator levels in 21- to 32-day-old, chronically instrumented, unsedated piglets were compared between a fifth sequential daily hypoxia and an isolated hypoxia (10% O2-90% N2 for 30 min). Diaphragmatic electromyographic activity, heart rate and arterial pressure, and pH and gas tensions were measured. In vivo microdialysis, via chronically implanted guides, served to sample interstitial substance P (SP) and methionine-enkephalin (ME) at the level of the respiratory-related nucleus tractus solitarii (NTS). Compared with an isolated hypoxia, repeated hypoxia resulted in 1) lower respiratory frequency (f), ventilation equivalent, and arterial pH, higher arterial Pco 2 during hypoxia, and lower f in recovery from hypoxia; and 2) increased SP concentrations but no change in ME concentrations. We conclude that, in these maturing swine, repeated vs. isolated hypoxic exposure curtails respiratory responses to hypoxia by a mechanism(s) unrelated to SP or ME levels at the NTS.This article has no references to display. Download PDF Back to Top Next FiguresReferencesRelatedInformationRelated articlesCurtailed respiration by repeated vs. isolated hypoxia in maturing piglets is unrelated to NTS ME or SP levels 01 Aug 1997Journal of Applied Physiology More from this issue > Volume 84Issue 4April 1998Pages 1a-1a Copyright & PermissionsCopyright © 1998 the American Physiological Societyhttps://doi.org/10.1152/jappl.1998.84.4.1/aHistory Published online 1 April 1998 Published in print 1 April 1998 Metrics Downloaded 56 times

A modulatory role for substance P on the regulation of luteinizing hormone secretion by cultured porcine gonadotrophs.

Substance P (SP) has been suggested to regulate gonadotroph function both directly and indirectly in different species. In pigs, the possible role of hypothalamic and pituitary SP in the control of LH release has not been examined. Here, we investigated SP effects on basal and GnRH-stimulated LH secretion by porcine gonadotrophs in vitro, in both static and dynamic culture systems. SP concentrations of 100 nM or above stimulated LH release from monolayer cultures without affecting intracellular LH content. In the same cultures, SP potentiated GnRH (10 nM)-stimulated LH release and reversed the GnRH-induced decrease of gonadotroph LH stores. The GnRH, but not the SP, effect was completely blocked by the potent GnRH-receptor antagonist antide. In superfused pituitary fragments, three successive pulses of SP or GnRH also stimulated LH release, yet the combined administration of both factors did not result in a synergistic stimulation. These results demonstrate that SP acts directly on porcine gonadotrophs to stimulate LH release, and to maintain the levels of hormonal stores, through a GnRH receptor-independent mechanism. Furthermore, our findings suggest that continuous exposure of gonadotrophs to SP would potentiate GnRH-stimulated LH secretion, thus supporting a possible role of SP as modulator of porcine gonadotroph function.

Tachykinin receptors are present on human monocytes and play a role in rheumatoid arthritis

Mammalian tachykinins such as substance P (SP) and neurokinin A (NKA) play a significant role in inflammatory and immune diseases by interacting with different cell populations 1-3. Mononuclear phagocytes, either circulating blood monocytes or tissue macrophages, largely participate in host defense responses: we previously demonstrated that human and guinea-pig alveolar macrophages possess NK2 and NK1 receptors and that in vitro stimulation by SP, NKA and NK2 selective agonists results in superoxide anion (O2 ) production 4,5. Lotz et al 6 reported that low concentrations of SP or NKA (the former less active) induce the release of inflammatory cytokines (e.g., TNF-α, IL-1 and IL-6) from human monocytes, whereas Kavelaars et al 7 observed IL-6 release only after high micromolar concentrations of SP and described “a non-neurokinin substance P receptor” on human monocytes. Different experimental approaches suggest a role for mammalian tachykinins in the onset and development of rheumatoid arthritis (RA): SP contributes to the severity of experimental arthritis, induces PGE2 and collagenase release from human synoviocytes and has been demonstrated to be significantly enhanced in joint fluids from rheumatoid patients 8-10. Therefore, we decided to evaluate whether or not mammalian tachykinins and synthetic selective agonists could exert a stimulatory effect on monocytes obtained from healthy donors or rheumatoid patients.

Cell trafficking, mediator release, and articular metabolism in acute inflammation of innervated or denervated isolated equine joints

SUMMARY Objectives To describe the acute cellular response, inflammatory mediator release, and effect on chondrocyte metabolism of interleukin 1β (IL-1β) in isolated innervated or denervated equine metacarpophalangeal joints. Animals One metacarpophalangeal joint of 24 adult horses. Procedures The metacarpophalangeal joint was isolated for 6 hours in a pump-perfused, auto-oxygenated, innervated or denervated metacarpophalangeal joint preparation. Isolated joints were assigned to 4 groups: control, control-denervated, inflamed, and inflamed-denervated, and inflammation was induced by intra-articular injection of IL-1β. Synovial fluid was collected for cytologic examination and determination of IL (IL)-1β, (IL-6), prostaglandin E2 (PGE2), and substance P (SP) values. Synovial membrane was immunostained with SP and nerve-specific enolase (NSE) antibodies. Cartilage was collected for determination of proteoglycan (PG) synthesis and degradation. Results IL-1β induced significant neutrophilic leukocytosis in synovial fluid and synovial membrane. IL-1β concentration had returned to baseline by 5.5 hours, but IL-6 concentration significantly increased throughout the study. Total SP content was significantly higher in inflamed joints. There was a significant increase in 24- and 48-hour PG degradation in inflamed innervated joints. Conclusion Cellular response to IL-1β was rapid and sustained; joint clearance of IL-1β was rapid, and endogenous production of IL-1β did not follow. The IL-6 and PGE2 concentrations significantly increased, and SP content was increased in association with inflammation but not denervation. A degradative response of cartilage to IL-1β was observed, and was enhanced by innervation. This model was useful for investigation of the articular response to acute inflammation and the influence of denervation in modulating this response. (Am J Vet Res 1998;59:88–100)

Distribution and Quantity of Neuroendocrine Markers in Allergic Rhinitis

Neuroendocrine components exist in the human nasal mucosa. However, the pathophysiological and neuroimmunological roles of the regulatory peptides in allergic rhinitis (AR) require further investigation. To analyse the functional morphology and quantify the tissue concentration of regulatory peptides in the nasal mucosa of AR subjects, human inferior turbinate mucosa specimens from 25 patients with AR, 20 patients with non-allergic rhinitis and 10 patients without any nasal diseases were investigated. Using immunohistochemistry and radioimmunoassays, we detected the presence, distribution and concentrations of various neuropeptides [vasoactive intestinal peptide (VIP), neuropeptide Y (NPY), substance P (SP) and calcitonin gene-related peptide (CGRP)] and general neuroendocrine markers (neuron-specific enolase and chromogranin A). Quantitative analysis of the stained fibres and cells was performed using a graphic AutoCAD program. The presence and distribution of NPY, CGRP and SP nerve fibres and neuroendocrine cells were similar among the three subject groups. AR subjects had significantly higher tissue concentrations of VIP and SP. AR subjects had increased numbers of VIP fibres which predominantly innervated vessels. Thus, VIP and SP play important neuroimmunological roles in the pathogenesis of AR.

Dopamine D1 receptor antagonist inhibits swallowing reflex in guinea pigs.

To determine whether dopamine D1 receptor antagonist impairs the swallowing reflex and reduces substance P (SP) in the peripheral organs, the swallowing reflex in terms of the number of swallows elicited by injections of three different volumes (0.2, 0.4, and 0.6 ml) of distilled water into the pharynx through a catheter was examined in anesthetized guinea pigs pretreated with Sch-23390. Animals were pretreated with either subcutaneous Sch-23390 (200 micrograms/kg) or a vehicle of Sch-23390 every 12 h for 7 days. The number of swallows was counted by submental electromyographic activity and visual observation of characteristic laryngeal movement. Injections of distilled water caused a volume-dependent increase in the number of swallows in animals without Sch-23390 treatment. Sch-23390 significantly decreased and exogenously administered SP increased the number of swallows elicited by all volumes of distilled water. FK-888 (10(-5) M, 1 ml), a specific inhibitor of the NK1 receptor, reduced the number of swallows to a greater degree than Sch-23390. Sch-23390 significantly reduced SP content in the laryngeal and pharyngeal mucosa compared with control. These results suggest that inhibition of the dopamine D1 receptor may impair the swallowing reflex and reduce SP content in the peripheral organs.

A substance P receptor antagonist (FK 888) modifies gut alterations induced by ionizing radiation

Purpose: We previously reported disturbances of ileal substance P (SP) levels and of characteristics of specific receptors after ionizing radiation associated with disorders of intestinal motility. The aim of this study was to investigate the effect of a SP receptor blockade by FK 888 on gut SP levels and contractile properties after rat irradiation. Materials and methods: Rats were exposed to 6 Gy whole-body gamma irradiation and injected 1 h post-irradiation with FK 888 for 3 days (0.1mg/kg/day). Plasma and ileal SP concentrations, ileal muscle SP receptor binding and SP-induced contractions in isolated ileum were investigated 3 and 14 days post-irradiation and FK 888 treatment. Results: Irradiation induced an increase of total SP binding site number at day 3 (1.3-fold) and day 14 (1.6-fold). FK 888 had no effect on SP receptor characteristics in irradiated animals. In contrast, FK 888 treatment caused a reduction of endogenous ileal SP level in mucosal (29%) and muscularis (40%) layers at day 3 and these decreases were greater at day 14, 88% in mucosal and 61% in muscularis layers. FK 888 treatment decreased efficacy of ileal contraction in both the control and irradiated rat but surprisingly it increased potency at day 3 and decreased it at day 14 in the irradiated rat. Conclusions: The findings demonstrate that a SP receptor antagonist could be effective on intestine contractility alteration induced several days after ionizing radiation exposure but not at 3 days after irradiation.

Role of sensory innervation and mast cells in neurogenic plasma protein exudation into the airway lumen.

Neurogenic inflammation in the airways involves both mucosal oedema and plasma protein exudation into the airway lumen. We aimed to investigate the mechanism of exudation of plasma proteins into the airway lumen. Neurogenic inflammation was induced in anaesthetized Sprague-Dawley rats by electrical stimulation of both vagal nerves at 20 V, 10 Hz, 5 ms. Vascular permeability was measured as 125I-albumin extravasation into both the airway wall and tracheobronchial lavage fluid. Following vagal stimulation, tracheobronchial lavages were analysed for albumin, total protein, histamine, immunoreactive substance P (SP), and immunoreactive calcitonin gene-related peptide (CGRP). Vagal stimulation rapidly increased vascular permeability in the airway mucosa and induced exudation of plasma proteins into the tracheobronchial fluid. Pre-treatment with capsaicin inhibited both neurogenic vascular permeability and movement of albumin into the airway lumen. SP and CGRP were detectable in basal lavages (1.37+/-0.12 ng/mL and 2.17+/-0.21 ng/mL, respectively) and the concentration of SP fell by 43% following treatment with capsaicin. Following vagal stimulation, concentrations of both SP and CGRP decreased significantly. Although basal tracheobronchial lavages contained histamine, vagal stimulation did not increase the histamine concentration. These results indicate that both neurogenic vascular permeability and plasma protein exudation into the airway lumen results from activation of capsaicin-sensitive sensory nerves and the reaction is not associated with mast cell activation.

Visceral afferent stimulation-evoked changes in the release of peptides into the parabrachial nucleus in vivo

Previous investigations have demonstrated that the peptides substance P (SP), calcitonin gene-related peptide (CGRP), cholecystokinin (CCK), neurotensin (NT) and somatostatin (SOM) significantly modulate the glutamate-mediated transmission of visceral information through the parabrachial nucleus (PBN) to the ventrobasal thalamus. In addition, we have shown that the staining intensity of SOM, CCK and NT in the PBN decreases significantly following 2 h of vagal stimulation as visualized using immunohistochemistry. As well, the staining intensity of both SP and CGRP in the PBN were shown to increase under similar conditions. The present investigation was done to determine whether the altered peptide staining intensity of these peptides observed following 2 h of vagal stimulation was the result of an altered peptide release from terminals within the PBN. Male Sprague-Dawley rats were anesthetized with sodium thiobutabarbitol and instrumented to record blood pressure and heart rate and for the stimulation of the cervical vagus nerve. A push–pull perfusion cannula was lowered into the region of the PBN for the continuous sampling of extracellular fluid. Radioenzymatic quantification of the perfusates for peptide content revealed that the extracellular fluid concentration of CGRP and SP increased significantly during the 2 h of vagal stimulation. When the vagal stimulation was terminated, the release of both CGRP and SP decreased significantly below prestimulated values for approximately 30 min before returning to prestimulated levels shortly thereafter. In contrast, there was a significant decrease in the release of CCK, SOM and NT into the PBN during the period of vagal stimulation. Extracellular perfusate levels of these peptides returned to normal upon termination of stimulation. These results demonstrate that terminal release of CGRP and SP is significantly increased and terminal release of CCK, SOM and NT is significantly decreased in the PBN during 2 h of vagal stimulation. These results are consistent with our previous finding that the immunohistochemical staining intensity of CGRP and SP is increased while that of CCK, SOM and NT is decreased following vagal stimulation.

Activated eosinophils elicit substance P release from cultured dorsal root ganglion neurons.

This study was performed to test the hypothesis that activated eosinophils or their secretory products can directly stimulate sensory neurons to release their neuropeptides. Neurons derived from neonatal rat dorsal root ganglia (DRG), which synthesize and store sensory neuropeptides, were placed in primary cell culture and were exposed to eosinophils or their bioactive mediators. The resultant release of substance P (SP) was measured by enzyme-linked immunosorbent assay and was expressed as a percent (mean +/- SE) of total neuronal SP content. Eosinophils were isolated from human volunteers with a history of allergic rhinitis and/or mild asthma and were activated by incubation with cytochalasin B (5 micrograms/ml) and N-formyl-methionyl-leucyl-phenylalanine (FMLP, 1 microM). Activated eosinophils [6 x 10(6)/ml, suspended in Hanks' buffered salt solution (HBSS)] applied to cultured DRG neurons for 30 min increased basal SP release 2.4-fold compared with HBSS-exposed neurons (activated eosinophils 11.10 +/- 2.48% vs. HBSS 4.59 +/- 0.99%; P = 0.002), whereas neither nonactivated eosinophils nor cytochalasin B and FMLP in HBSS influenced SP release. Additional cultured DRG neurons were exposed to soluble products made by eosinophils. Compared with SP release under control conditions (2.37 +/- 0.34%), major basic protein (MBP) increased release in a concentration-related fashion (e.g., 3 microM MBP: 6.23 +/- 0.67%, P = 0.006 vs. control), whereas neither eosinophil cationic protein (3 microM), eosinophil-derived neurotoxin (3 microM), leukotriene D4 (500 nM), platelet-activating factor (100 nM), nor H2O2 (100 microM) affected SP release. These studies demonstrate that activated eosinophils can stimulate cultured DRG neurons directly and suggest that MBP may be the responsible mediator.

Effects of experimental Mycoplasma pulmonis infection on sensory neuropeptides and airway mucosa in the rat

The effect of airway infection on neurogenic inflammation is not known. The present study examines the effect of Mycoplasma pulmonis infection on the sensory neuropeptides substance P (SP) and calcitonin gene-related peptide (CGRP) in the trigeminal ganglion and in the mucosa of the nose and trachea in rats. We compared germ-free (GF), conventionally raised (CV) and specific pathogen-free (SPF) rats. The concentrations of SP and CGRP in the nasal mucosa were assessed with immunohistochemistry, and their prohormonal transcripts in the trigeminal ganglion were assessed with Northern blot. Mucosa was also processed for light microscopy and electron microscopy. SP-like immunoreactivity was greater in the nasal mucosa of infected animals than in uninfected controls. CGRP-like immunoreactivity was greater in the nasal septum, but not in the nasal turbinate, of infected than uninfected animals. In contrast, no change was evident in the expression levels of the prohormonal transcripts in the trigeminal ganglion. Infected nasal and tracheal mucosa was oedematous and locally infiltrated with inflammatory cells. In the nose of uninfected GF rats, subepithelial lymphoid aggregations were scarce and appeared inactive. We conclude that Mycoplasma pulmonis infection results in increased immunoreactivity of substance P, probably within nerves. There was no clear evidence of increased synthesis of the precursors of substance P and calcitonin gene-related peptide.

Substance P stimulates vascular endothelial cellular reducing capacity in the presence of insulin and human plasma factors

Substance P (SP) is an important tachykinin in vascular wall biology. In previous studies [Villablanca et al. (1994): Circ Res 75:1113-1120], the authors have demonstrated that SP is a stimulus for endothelial cell growth and proliferation in serum-free culture conditions with cell quiescent in the G0-G1 phase of the cell cycle. As mitogenic and metabolic activity may interrelate, the purpose of this study was to determine the effects of the vasoactive perivascular neuropeptide SP on changes in the metabolic function of endothelial cells, and to characterize the response, by studying cellular reducing capacity in aortic vascular endothelial cells. In addition, interactions between SP and other growth factors (insulin and non-platelet plasma factors) were investigated and compared to the responses to SP alone. Metabolic effects were determined by evaluating cellular reducing capacity by the conversion of (3-[4,5-dimethylthiazole-2-yl]-2,5-diphenyltetrazolium bromide) to formazan (the MTT assay). The findings demonstrated that SP alone (10 pg/ml-25 micrograms/ml) inhibited cellular reducing capacity in vascular endothelial cells. In contrast, SP in the presence of insulin (10 micrograms/ml) stimulated endothelial reducing capacity, as compared to SP alone, by twofold on average. The effect of SP and insulin was additive at < or = 0.001 microgram/ml SP, and synergistic at SP concentrations ranging within 0.01-1.0 microgram/ml. SP in the presence of human platelet-poor plasma (HPPP, 5%) stimulated endothelial reducing capacity, as compared to SP alone, by threefold on average. The effect of SP and HPPP was additive at < or = 0.01 microgram/ml SP and synergistic at SP concentrations of 0.1-25 micrograms/ml. Lastly, SP in the presence of insulin and HPPP stimulated endothelial metabolic activity, as compared to SP alone, by 14-fold on average. An additive response to SP, insulin, and HPPP was observed at the lowest SP concentration studied (10 pg/ml). At all other SP concentrations studied (0.0001-25 micrograms/ml), the responses to insulin, HPPP, and SP were synergistic. Our studies indicate that the vasoactive neuropeptide substance P may synergize with insulin and HPPP in regulating endothelial cell metabolism. In addition, our findings suggest that the mechanisms by which SP stimulates cellular metabolism are different from the mechanisms by which it stimulates cell growth.

Curtailed respiration by repeated vs. isolated hypoxia in maturing piglets is unrelated to NTS ME or SP levels.

In early development, respiratory disorders can produce recurring hypoxic episodes during sleep. To examine possible effects of daily repeated vs. isolated hypoxic hypoxia, cardiorespiratory functions and central, respiratory-related neuromodulator levels in 21- to 32-day-old, chronically instrumented, unsedated piglets were compared between a fifth sequential daily hypoxia and an isolated hypoxia (10% O2-90% N2 for 30 min). Diaphragmatic electromyographic activity, heart rate and arterial pressure, and pH and gas tensions were measured. In vivo microdialysis, via chronically implanted guides, served to sample interstitial substance P (SP) and methionine-enkephalin (ME) at the level of the respiratory-related nucleus tractus solitarii (NTS). Compared with an isolated hypoxia, repeated hypoxia resulted in 1) lower respiratory frequency (f), ventilation equivalent, and arterial pH, higher arterial PO2 during hypoxia, and lower f in recovery from hypoxia; and 2) increased SP concentrations but no change in ME concentrations. We conclude that, in these maturing swine, repeated vs. isolated hypoxic exposure curtails respiratory responses to hypoxia by a mechanism(s) unrelated to SP or ME levels at the NTS.

Decreased substance P content in the rectal mucosa of diabetics with diarrhea and constipation

Substance P (SP), vasoactive intestinal polypeptide (VIP), and somatostatin content in rectal mucosa were determined by radioimmunoassay (RIA) in 38 diabetic patients (12 with normal bowel function, 13 with diabetic diarrhea, and 13 with constipation) and in 10 nondiabetic crontrols with normal bowel funciton. SP content (picograms per milligram) in the rectal mucosa of diabetics with normal bowel funciton was significantly higher than that of nondiabetic controls ( P < .05). SP content in the rectal mucosa of diabetics with diabetic diarrhea and constipation was significantly lower than in diabetics with normal bowel habits and nondiabetic controls ( P < .05). No differences were found in the rectal mucosa content of VIP and somatostatin between the different groups of diabetics and controls. Diabetic diarrhea is a condition with an intermittent nature and frequently alternates with constipation. Our findings showing low levels of rectal mucosa SP in both conditions suggest a possible common role of SP in the pathogenesis of diabetic diarrhea and constipation.