Several mediators appear to interact in neurogenic inflammation

Plasma protein extravasation was studied in the rat abdominal skin. Substance P (SP), neurokinin A (NKA) and B (NKB) were found to induce extravasation with a threshold dose of about 1 pmol. Calcitonin gene-related peptide (CGRP) caused no or little extravasation alone but it potentiated the action of SP, NKA, NKB, and physalaemin. The potentiation of the SP-induced extravasation was unaffected by pretreatment with capsaicin, indomethacin or compound 48/80, it was reduced by neuropeptide Y or pretreatment with mepyramine plus cimetidine, and was abolished in streptozotocin diabetic rats. CGRP augmented extravasation induced by histamine, reduced the effect of ATP or adenosine and did not alter extravasation by serotonin, bradykinin or neurotensin. These results indicate that in addition to SP the novel mammalian tachykinins NKA and NKB may be considered as mediator candidates for neurogenic plasma extravasation. CGRP is a possible mediator of antidromic vasodilation. Furthermore, CGRP potentiates the extravasation caused by coexisting tachykinins and could thereby augment neurogenic inflammation. The diverse interactions of CGRP with other inflammatory mediators suggest multiple sites of action.     

Algesia and local responses induced by neurokinin A and substance P in human skin and temporal muscle

Neurokinin A (NKA), substance P (SP) and the two peptides combined (SP + NKA) were injected intracutaneously on the forearm and into the temporal muscle of healthy volunteers. Pain intensity, cutaneous wheal and flare responses and tenderness of the temporal muscle were quantitated. SP but not NKA induced cutaneous pain. This relates the algesic effect of SP to the specific N-terminal amino acid sequence of the peptide, not shared by NKA. NKA, however, potentiated the algesic effect of SP as SP + NKA induced a significantly prolonged cutaneous pain sensation. Both peptides induced wheals, but only SP induced flare. These results confirm previous studies relating wheal formation to the identical C-terminal amino acid sequence of the two peptides and flare reaction to the N-terminal part of SP. Injections into the temporal muscle did not cause pain or tenderness.     

Effects of neurokinin A and calcitonin gene-related peptide on mucociliary activity in rabbit maxillary sinus

Substance P (SP) released from sensory C-fibers in the airways increases the mucociliary (m.c.) activity in the rabbit maxillary sinus. The purpose of the present study was to investigate the m.c. effects of two other neuropeptides, coexisting with SP in sensory neurones, neurokinin A (NKA) and calcitonin gene-related peptide (CGRP). NKA increased the m.c. activity dose-dependently (dose range 0.1-10.0 micrograms/kg, 88 pmol to 8.8 nmol/kg), the maximum increase being 41.9 +/- 2.6%. The effect was inhibited by pretreatment with the tachykinin antagonist (D-Pro2,D-Trp7,9)SP, but not with atropine or hexamethonium. Thus NKA released from sensory C-fibers may contribute to the non-cholinergic increase of m.c. activity observed after C-fiber stimulation. In contrast CGRP did not influence the m.c. activity. Neither did it influence the responses to NKA or SP. It is concluded that CGRP is unlikely to be involved in the control of m.c. function.     

Effects of neuropeptides on growth of cultivated rat molar pulp fibroblasts

The effect of the neuropeptides substance P (SP), neurokinin A (NKA), calcitonin gene-related peptide (CGRP), neuropeptide Y (NPY) and vasoactive intestinal polypeptide (VIP) on DNA synthesis of dental pulp cells was investigated in cells grown from molar tooth bud explants from 4–6 days old rat pups. A concentration response-assay of the proliferative response of pulpal cells was performed with SP, NPY, NKA, CGRP and VIP (0.01 to 1 nM) in the presence of EGF (10 ng/ml), hydrocortisone (0.4 μg/ml) and 3% FCS, using [³H]thymidine incorporation. The results showed that SP, NKA and CGRP, but not NPY and VIP, increased the cell number in a concentration-dependent manner, with maxima at 10⁻¹⁰ – 10⁻⁹ M (SP, NKA) and 10⁻⁷ M (CGRP). No potentiating effect was noted when cells are simultaneously stimulated with SP and CGRP. The finding that SP, NKA and CGRP have growth regulatory properties on pulpal cells in vitro suggests that sensory neuropeptides may be involved during pulpal development or in wound healing after pulpal injury.     

Effect of sensory neuropeptides on canine bronchial and pulmonary vessels in vitro

Sensory neuropeptides may be important in the noncholinergic component of parasympathetic vasodilation in the tracheobronchial circulation. We studied the effects of substance P (SP), neurokinin A (NKA), neurokinin B (NKB) and calcitonin gene-related peptide (CGRP) on the isolated canine bronchial artery and used pulmonary artery and vein of similar size for comparison. CGRP (10pM-300nM) was a potent relaxant of the bronchial and pulmonary arteries, and the pulmonary vein with equal potency in all vessels. SP in low concentrations (10pM-100nM) caused vasodilation of the precontracted bronchial artery and in high concentration (10-100 microM) contracted the vessel from resting tone. SP also relaxed the pulmonary artery and vein. NKA and NKB caused relaxation in all three vessels. All of the vascular effects of the sensory neuropeptides were concentration-dependent. The order of potency of the neuropeptides in the bronchial and pulmonary artery was SP greater than NKA greater than CGRP greater than NKB. In the pulmonary vein NKB caused a much larger relaxation than SP and NKA but it was less potent than either NKA or CGRP. Capsaicin (1 microM) caused a large contraction of the bronchial artery, similar in magnitude to the contraction caused by high dose of SP. Neuropeptide Y was also studied and found to cause no consistent constriction of any of the vessels studied. In conclusion, CGRP is a universal dilator of the bronchial and pulmonary blood vessels. SP and NKA exert their main effect on arterial vasomotor tone, whereas NKB is the only tachykinin producing marked dilation of the pulmonary vein.     

Occurrence and effects of multiple tachykinins; substance P, neurokinin A and neuropeptide K in human lower airways

In the present work we have studied the occurrence of different tachykinins (substance P (SP), neurokinin A (NKA) and neuropeptide K (NPK)) in human distal bronchi and pulmonary arteries by means of radioimmunoassay (RIA) and high performance liquid chromatography (HPLC). We have also compared the biological effects of different tachykinins on isolated human bronchi and pulmonary arteries in vitro. The concentration of immunoreactive SP using antiserum SP2 in the pulmonary arteries was higher (1.34 +/- 0.15 pmol/g) than in the bronchi (0.56 +/- 0.05 pmol/g). The contents of other tachykinins than SP measured using antiserum K12 was on the other hand considerably higher in the bronchi (0.33 +/- 0.14 pmol/g) than in pulmonary arteries (0.13 +/- 0.02 pmol/g). Immunoreactive materials corresponding to SP, NKA and NPK were identified in bronchial extracts by RIA combined with HPLC, which also indicated the presence of an eledoisin (ELE)-like component. In vitro studies showed that NKA was the most potent of the tachykinins as a bronchoconstrictor agent, being several hundred-fold more active than SP, acetylcholine and histamine. NPK had an intermediate potency. The bronchoconstrictor effect of NKA was unaffected by atropine, mepyramine and cimetidine. The tachykinins SP and NKA had on the other hand, a rather equal potency in inducing relaxation of serotonin precontracted pulmonary arteries. In conclusion, multiple tachykinins are present in lower airways of man. These peptides exert different biological activities whereby NKA is a very active bronchoconstrictor agent compared to SP while both NKA and SP have rather similar relaxatory activities of vascular smooth muscle.     

Relationships between permeable vessels, nerves, and mast cells in rat cutaneous neurogenic inflammation

Electrical stimulation of rat sensory nerves produces cutaneous vasodilation and plasma protein extravasation, a phenomenon termed "neurogenic inflammation". Rat skin on the dorsum of the paw developed neurogenic inflammation after electrical stimulation of the saphenous nerve. In tissue sections, the extravasation of the supravital dye monastral blue B identified permeable vessels. Mast cells were identified by toluidine blue stain. Permeable vessels were significantly more dense in the superficial 120 microns of the dermis than in the deeper dermis, whereas mast cells were significantly more frequent in the deeper dermis. The relationships between nociceptive sensory nerve fibers, permeable vessels, and mast cells were examined by indirect immunohistochemistry for calcitonin gene-related peptide (CGRP), neurokinin A (NKA), and substance P (SP). CGRP-, NKA-, and SP-containing nerves densely innervated the superficial dermis and appeared to innervate the vessels that became permeable during neurogenic inflammation. In contrast, mast cells were not associated with either permeable vessels or nerve fibers. These data suggest that electrical stimulation of rat sensory nerves produces vascular permeability by inducing the release of neuropeptides that may directly stimulate the superficial vascular bed. Mast cells may not be involved in this stage of cutaneous neurogenic inflammation in rat skin.     

Effects of trigeminal neurotransmitters on piglet pial arterioles.

We investigated effects of calcitonin gene-related peptide (CGRP), substance P (SP), and neurokinin A (NKA) on pial arterioles in newborn pigs. Pial arteriolar diameter was determined using a closed cranial window and intravital microscopy. Initial diameters were approximately 100 microns. Calcitonin-gene related peptide dilated pial arterioles by 22 +/- 8% at 10(-9)M and by 34 +/- 6% at 10(-8)M (n = 8), and this response was not significantly altered by prior administration of indomethacin (5mg/kg, iv) (n = 6) or administration of NG-methyl-L-arginine (5mg/kg, iv, and 10(-3)M in CSF) (n = 10). Substance P dilated arterioles at 10(-10)M through 10(-5)M (maximal response = 23 +/- 3%) (n = 6), and this response was unaffected by indomethacin administration (n = 6). In contrast, NG-methyl-L-arginine blocked much of the pial arteriolar dilation to SP. Unlike the other two peptides, NKA did not change pial arteriolar diameter. Radioimmunoassay determinations indicated that cerebrospinal fluid levels of 6-keto-prostaglandin F1 and prostaglandin E2 did not change appreciably during application of CGRP or SP. We conclude that CGRP and SP but not NKA are dilator stimuli in the piglet pial circulation. Dilation by CGRP probably involves direct activation of receptors on vascular smooth muscle, while SP probably partially dilates pial arterioles via release of an endothelium-dependent relaxing factor.     

Release of calcitonin gene-related peptide and tachykinins from the rat trachea.

The release of calcitonin gene-related peptide (CGRP), neurokinin A (NKA) and substance P (SP) from intralumenally perfused rat trachea was examined in vitro. In accord with the relative tissue levels of the respective peptides, capsaicin (10(-8) to 10(-5) M) and K+ (120 mM) added to the perfusate resulted in a concentration-dependent increase in the levels of CGRP and NKA, and to a minor extent SP, in the perfusates. Sequential exposure of the trachea to capsaicin revealed a concentration-dependent tachyphylaxis of CGRP release. Thus, 40 min after the application with capsaicin 10(-5) M, a second exposure to capsaicin at the same concentration, or K+ 120 mM, did not evoke CGRP release. In contrast, prior stimulation with K+ 120 mM significantly enhanced the CGRP release induced by a second stimulation with K+ 120 mM or capsaicin 10(-5) M. Capsaicin- and K(+)-induced peptide release was diminished or abolished in the absence of Ca2+. HPLC analysis of CGRP in release materials revealed that there was a single peak which eluted in the same fraction as synthetic rat CGRP. These data demonstrate that CGRP, NKA and SP exist in releasable, capsaicin-sensitive pools in terminals which lie within the proximal lumen of the trachea.     

Role of capsaicin-sensitive afferents and sensory neuropeptides in endotoxin-induced airway inflammation and consequent bronchial hyperreactivity in the mouse

Substance P (SP) and calcitonin gene-related peptide (CGRP) released from capsaicin-sensitive afferents induce neurogenic inflammation via NK(1), NK(2) and CGRP1 receptor activation. This study examines the role of capsaicin-sensitive fibres and sensory neuropeptides in endotoxin-induced airway inflammation and consequent bronchial hyperreactivity with functional, morphological and biochemical techniques in mice. Carbachol-induced bronchoconstriction was measured with whole body plethysmography 24 h after intranasal lipopolysaccharide administration. SP and CGRP were determined with radioimmunoassay, myeloperoxidase activity with spectrophotometry, interleukin-1beta with ELISA and histopathological changes with semiquantitative scoring from lung samples. Treatments with resiniferatoxin for selective destruction of capsaicin-sensitive afferents, NK(1) antagonist SR 140333, NK(2) antagonist SR 48968, their combination, or CGRP1 receptor antagonist CGRP(8-37) were performed. Lipopolysaccharide significantly increased lung SP and CGRP concentrations, which was prevented by resiniferatoxin pretreatment. Resiniferatoxin-desensitization markedly enhanced inflammation, but decreased bronchoconstriction. CGRP(8-37) or combination of SR 140333 and SR 48968 diminished neutrophil accumulation, MPO levels and IL-1beta production, airway hyperresponsiveness was inhibited only by SR 48968. This is the first evidence that capsaicin-sensitive afferents exert a protective role in endotoxin-induced airway inflammation, but contribute to increased bronchoconstriction. Activation of CGRP1 receptors or NK(1)+NK(2) receptors participate in granulocyte accumulation, but NK(2) receptors play predominant role in enhanced airway resistance.     

Neuropeptides of the primary sensory neurones in rat skin: an ontogenic study.

Cutaneous primary sensory neurones contain a number of biologically-active peptides, including substance P (SP), neurokinin A (NKA) and calcitonin gene-related peptide (CGRP). However, little information is available on ontogenic changes in the tissue concentrations of these neuropeptides. In this study, the concentrations of these neuropeptides have been assessed in dorsal and ventral abdominal rat skin at various stages of development from foetal, early neonatal, late neonatal, weaner to adult, using sensitive and specific radioimmunoassays. In addition, the levels of peptide histidine isoleucine (PHI), a peptide found in non-sensory cutaneous nerves, were assessed to control the study. The levels of PHI and NKA immunoreactivity did not change significantly at any stage of development. However, the levels of SP and CGRP immunoreactivity were significantly elevated in the early neonate with CGRP remaining elevated in the late neonate. The levels of both SP and CGRP were not significantly different between other developmental groups. Significant elevations in cutaneous SP and CGRP concentrations in early neonatal life in the rat, at a time when the pups are blind and naked, may be related to control of cutaneous sensitivity, which during this period of development, has positive survival value for the pups.     

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.     

Capsaicin-induced bronchoconstriction and neuropeptide release in guinea pig perfused lungs.

In the guinea pig isolated perfused lung, we have examined the relationship between the effects of capsaicin and neuropeptide release and the possible existence of an axon reflex arrangement. Bolus injections into the pulmonary artery of capsaicin (1-100 pmol), substance P (10-1,000 pmol), and neurokinin (NK) A (10-100 pmol) produced a concentration-dependent bronchoconstriction, whereas calcitonin gene-related peptide (CGRP, 20-40 nmol) was without effect. Repeated administration of capsaicin at 40- to 60-min intervals was not associated with tachyphylaxis. These data support the presence of a NK2- (or NKA) type of tachykinin receptor in the guinea pig airways. Tetrodotoxin (0.3-3 microM) inhibited the effect of capsaicin, indicating that an axon reflex was operant. Capsaicin increased overflow of CGRP-like immunoreactivity (-LI) and NKA-LI, the latter only during concurrent infusion of the enkephalinase inhibitor phosphoramidon (3 microM). Phosphoramidon also increased overflow of CGRP-LI, suggesting that both NKA and CGRP were catabolized by a similar enzyme. The purine nucleoside adenosine did not cause any detectable overflow of CGRP-LI, indicating that neuropeptides may not be involved in adenosine-evoked bronchoconstriction and that bronchoconstriction per se does not induce neuropeptide overflow. Capsaicin and NKA had only minor effects on buffer flow, whereas substance P produced pulmonary vasoconstriction. These data clearly demonstrate that capsaicin acts via an axon reflex in the guinea pig airways. Supramaximal concentrations of capsaicin are needed to detect neuropeptide overflow, but the possibility exists that released neuropeptides mediate its effects.     

Transient receptor potential vanilloid 1, calcitonin gene-related peptide, and substance P mediate nociception in acute pancreatitis

The mechanism of pancreatitis-induced pain is unknown. In other tissues, inflammation activates transient receptor potential vanilloid 1 (TRPV1) on sensory nerves to liberate CGRP and substance P (SP) in peripheral tissues and the dorsal horn to cause neurogenic inflammation and pain, respectively. We evaluated the contribution of TRPV1, CGRP, and SP to pancreatic pain in rats. TRPV1, CGRP, and SP were coexpressed in nerve fibers of the pancreas. Injection of the TRPV1 agonist capsaicin into the pancreatic duct induced endocytosis of the neurokinin 1 receptor in spinal neurons in the dorsal horn (T10), indicative of SP release upon stimulation of pancreatic sensory nerves. Induction of necrotizing pancreatitis by treatment with L-arginine caused a 12-fold increase in the number of spinal neurons expressing the proto-oncogene c-fos in laminae I and II of L1, suggesting activation of nociceptive pathways. L-arginine also caused a threefold increase in spontaneous abdominal contractions detected by electromyography, suggestive of referred pain. Systemic administration of the TRPV1 antagonist capsazepine inhibited c-fos expression by 2.5-fold and abdominal contractions by 4-fold. Intrathecal, but not systemic, administration of antagonists of CGRP (CGRP(8-37)) and SP (SR140333) receptors attenuated c-fos expression in spinal neurons by twofold. Thus necrotizing pancreatitis activates TRPV1 on pancreatic sensory nerves to release SP and CGRP in the dorsal horn, resulting in nociception. Antagonism of TRPV1, SP, and CGRP receptors may suppress pancreatitis pain.     

Neurokinin A in cerebral vessels: characterization, localization and effects in vitro

Nerve fibres displaying neurokinin A (NKA)-immunoreactivity (IR) were seen in trigeminal nerve cell bodies and around cerebral blood vessels. NKA-positive fibres had the same general distribution as those displaying substance P (SP)-IR. Double or sequential immunostaining revealed coexistence of NKA- and SP-IR in a population of small nerve cell bodies in the trigeminal ganglion and in perivascular nerve fibres of brain vessels; both tachykinins were also noted to coexist with calcitonin gene-related peptide (CGRP)-IR. The presence of NKA- and SP-IR in cerebral vessels from guinea pig was verified by high-performance liquid chromatography and radioimmunochemistry. The levels NKA-IR were higher than those of SP-IR in cerebral vessels of rat, guinea pig and rabbit. In cat, pig, cow and human brain vessels, the levels of NKA- and SP-IR were equal. Major cerebral vessels at the base of the brain contained higher levels of NKA- and SP-IR than pial vessels on the cerebral convexities. Only low levels of NKA-IR and SP-IR were measured in choroid plexus and dura mater. Precontracted isolated arterial segments of middle cerebral (cat), basilar (rabbit, guinea pig and rat) and pial arteries (man) relaxed following the in vitro administration of NKA and SP. The responses occurred in the same concentration range; the IC50 value for NKA was, however, about 10 times higher than that for SP, while the maximum relaxation was equal. In basilar arteries from guinea pig, the peptides NKA, SP and CGRP all induced strong and potent relaxations. There was no evidence that one of the peptides might potentiate the relaxant effects in vitro of another. The present data suggest that NKA, SP and CGRP are costored and can be released together and cooperate in the mediation of vascular reactions in response to activation of the trigemino-cerebrovascular pathway.     

Neurogenic inflammation in mice deficient in heparin-synthesizing enzyme

Mast cell activation, or neurogenic inflammation, is known to induce lowering of interstitial fluid pressure (P(if)) and plasma protein extravasation (PPE) in several tissues from both rats and mice. To examine a possible role of connective tissue mast cells (CTMCs) in these inflammatory responses, we used mice with dysfunctional CTMCs due to lack of the N-deacetylase/N-sulfotransferase-2 enzyme (NDST-2(-/-)). P(if) and PPE were measured after challenge with compound 48/80 (C48/80), and P(if) alone was measured after treatment either with capsaicin, substance P (SP), or calcitonin gene-related peptide (CGRP). Measurements of P(if) in anesthetized (fentanyl/fluanison and midazolam, 1:1) mice were performed in paw skin with glass capillaries connected to a servo-controlled counterpressure system. PPE was measured with microdialysis by using hollow plasmapheresis fibers (cutoff at 3,000 kDa) placed subcutaneously on the back. Intravenous administration of C48/80 lowered P(if) significantly (P < 0.05) in NDST-2(-/-) mice (-1.67 +/- 0.42 mmHg) compared with vehicle (-0.57 +/- 0.17 mmHg) but the lowering was significantly (P < 0.05) less compared with that of the NDST-2(+/+) mice (-2.31 +/- 0.47 mmHg). PPE was increased 300% after treatment with C48/80 in NDST-2(+/+) mice, whereas there was no increase in PPE in NDST-2(-/-) mice. Capsaicin, SP, and CGRP lowered P(if) significantly (P < 0.05) compared with vehicle and to the same extent in both NDST-2(+/+) and NDST-2(-/-) mice. We can conclude that although NDST-2(-/-) mice demonstrate an altered response in P(if) after mast cell activation, there was no similar alteration after neurogenic inflammation. Therefore, we suggest that neurogenic inflammation in mouse skin is not exclusively dependent on intact CTMCs.     

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.     

Tracheal smooth muscle responses to substance P and neurokinin A in the piglet.

The tachykinins substance P (SP) and neurokinin A (NKA) have been shown to induce airway smooth muscle contraction in mature animals, and the enzyme neutral endopeptidase (NEP) modulates this effect. We evaluated maturation of SP- and NKA-induced tracheal smooth muscle contraction and modulation of their effects by NEP in anesthetized, paralyzed, and artificially ventilated piglets less than 4 days, 2-3 wk, and 10 wk of age. Tracheal smooth muscle tension was measured in vivo from an open tracheal segment by use of a force transducer. Intravenous SP caused a dose-dependent increase in tracheal tension in all three age groups; however, the response in less than 4-day-old piglets was significantly weaker than in 2- to 3- and 10-wk-old piglets. NKA caused a dose-dependent increase in tracheal tension only in 2- to 3- and 10-wk-old piglets. The response of tracheal tension to NKA was weaker than the response to SP in all age groups. Atropine (2 mg/kg) significantly diminished the responses of tracheal tension to SP and NKA, indicating a cholinergic contribution to these responses at all ages. Intravenous thiorphan, a known NEP inhibitor, potentiated the effects of SP only in 2- to 3- and 10-wk-old piglets and did not affect the response of tracheal tension to NKA at any age. Biochemical analyses demonstrated a significant increase in tracheal NEP activity in comparably aged piglets over the first 10 wk of life.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effect of a chromogranin A-derived peptide (CgA4-16) in the writhing nociceptive response induced by acetic acid in rats

The nociceptive effects of i.p administration of a synthetic peptide (CgA4-16) derived from chromogranin A (CgA) were studied on a model of inflammatory (somato-visceral) pain. Inflammatory mediators participate in controlling the activity of enterochromaffin cells that store and release chromogranins. Adult male Wistar rats were injected i.p with diluted acetic acid (AA) to induce abdominal writhes. Pharmacological agents were injected prior to CgA4-16 and/or AA together. While i.p CgA4-16 alone did not produce any effect, the peptide increased the number of abdominal constrictions induced by i.p AA administration in a dose-related manner. To determine the possible mechanisms involved in CgA4-16 produced pronociceptive effect, i.p diltiazem or indomethacin were tested. The pronociceptive effect induced by CgA4-16 was blocked by pretreatment of either substance. I.p administration of CGRP, substance P (SP) or capsaicin evoked dose-related abdominal writhing. CgA4-16, 20 min prior to CGRP or capsaicin, potentiated the nociceptive effects induced by CGRP or capsaicin, but not those induced by SP. Taken together, these data suggest for the first time that a CgA-derived peptide may modulate inflammatory pain.     

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.