Histamine release and vascular changes induced by neuropeptides

The acetylcholine-induced flare response in evaluation of small fiber dysfunction

We iontophoresed acetylcholine on the dorsum of the foot and simultaneously measured flare and sweat responses using laser Doppler and sudorometric techniques, respectively. We compared these responses with those induced by histamine. Both acetylcholine and histamine produced dose-dependent flare, but only acetylcholine produced sweat responses. Responses to acetylcholine and histamine were blocked by hexamethonium chloride and pyrilamine maleate, respectively (p less than 0.01). We compared flare and sweat responses in 26 control subjects, 21 asymptomatic diabetic patients and 41 patients (17 diabetic, 24 nondiabetic) with pain symptoms suggestive of small fiber neuropathy and normal sensation (n = 15) or mild to moderate (n = 19) or severe (n = 7) sensory loss. No patient had trophic foot lesions. Basal skin blood flow and maximal flare responses were not significantly different among the various subgroups (Control subjects, 49 +/- 7.4; asymptomatic diabetic patients, 29 +/- 4; patients with small fiber neuropathy and normal sensation, 34 +/- 6; with neuropathy and mild to moderate sensory loss, 29 +/- 4.8; and with neuropathy and severe sensory loss, 35 +/- 5 ml/100 gm, for flare response, respectively). Flare responses lower than the lowest found in control subjects occurred in 5 of 21 asymptomatic diabetic patients, 4 of 15 patients with small fiber neuropathy and normal sensation, 5 of 19 with neuropathy and mild to moderate sensory loss, and 1 of 7 with neuropathy and severe sensory loss.(ABSTRACT TRUNCATED AT 250 WORDS)

Neuropeptides enhance irritant and allergic contact dermatitis

It is supposed that neuropeptides participate in the regulation of delayed-type hypersensitivity (DTH) reactions. However, their function in this kind of immune response is not known presently. Therefore, in vivo studies were initiated to test the effect on allergic (ACD) and irritant contact dermatitis (ICD) of the neuropeptides substance P (SP), calcitonin gene-related peptide (CGRP), and somatostatin (SOM), which are released from afferent neurons in the skin. Each neuropeptide was applied topically at the site of contact with the allergen (oxazolone) or irritant (croton oil) during the challenge and sensitization phase of contact dermatitis. The intensity of the inflammation was measured as an increase of ear-swelling response, which represents the degree of plasma extravasation in the early phase of inflammation. Neuropeptides alone led only to a distinct vasodilation. All three neuropeptides were equally able to increase allergic and irritant inflammation. Even minor irritant stimuli were enhanced. Beyond that, CGRP was able to boost sensitization, whereas SOM and SP did not show any effects on the sensitization process. The results presented demonstrate that neuropeptides increase plasma extravasation independent of the pathogenesis of inflammation and may act as priming substances for other mediators of increased vascular permeability. In addition, CGRP enhances the sensitization process.

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.

Substance P innervation of spleen in rats: nerve fibers associate with lymphocytes and macrophages in specific compartments of the spleen

We investigated the distribution of SP+ nerve fibers in the spleen of adult male Fischer 344 rats. SP+ nerve fibers entered the spleen with the splenic artery in the hilar region, arborized along the venous sinuses, and extended from these larger plexuses into trabeculae and the surrounding red pulp. In the white pulp, SP+ nerve fibers were found in the marginal zone, and in the outer regions of the PALS among T lymphocytes. No SP+ nerve fibers were observed in association with the splenic capsule, the central arteries of the white pulp, or the follicles. SP levels in rat spleen were 5.7 +/- 0.4 ng/g wet wt. On the basis of the present findings of SP presence in nerve fibers in the spleen, and published evidence for SP receptors on lymphocytes and macrophages, we suggest that SP derived from nerve fibers in the spleen can act as a neurotransmitter with cells of the immune system as targets. These SP nerve fibers may be an important neural link between the nervous system and the immune system and may participate in modulation of immune reactivity and inflammatory responses.

Trigeminal sensory fiber stimulation induces morphological changes reflecting secretion in rat dura mater mast cells

Mast cells are involved in allergic reactions, but may also participate in neurogenic inflammation. The morphology of mast cells in rat dura mater and tongue was evaluated by histochemistry, as well as by scanning and transmission electron microscopy following unilateral trigeminal ganglion stimulation (5 min, 5 Hz, 5 ms, and 0.02, 0.1 or 1.0 mA). Mast cells in dura and tongue of normal animals were numerous, perivascular and often in close proximity to nerve fibers. After 5 min of electrical stimulation, mast cells contralateral to the stimulation showed histochemical characteristics of normal peripheral tissue mast cells (Safranin-positive), and by electron microscopy appeared homogeneous with numerous intact electron-dense granules. On the stimulated side, however, the staining characteristics of mast cells showed changes indicating progressive intracellular loss of their granular content. In addition, the total number of stainable mast cells decreased at all three stimulus intensities, but reached significance only at 0.1 and 0.02 mA. Ultrastructural evidence of granule changes consistent with secretion were observed although degranulation was not observed until 20 min after stimulation. There were no mast cell changes after electrical trigeminal stimulation in adult rats treated as neonates with capsaicin to destroy small caliber sensory afferent axons. These results suggest that mast cells may secrete in response to electrical stimulation of trigeminal axons, possibly mediated by antidromic release of neuropeptides, and may participate in the development of neurogenic inflammation.

Alterations in receptors for sensory neuropeptides in human inflammatory bowel disease

Glutamate and several neuropeptides are synthesized and released by subpopulations of primary afferent neurons. These sensory neurons play a role in regulating the inflammatory and immune responses in peripheral tissues. We have explored what changes occur in the location and concentration of receptor binding sites for sensory neurotransmitters in two human inflammatory diseases, ulcerative colitis and Crohn's disease, using quantitative receptor autoradiography. The sensory neurotransmitter receptors included bombesin, calcitonin gene-related peptide-alpha, cholecystokinin, galanin, glutamate, somatostatin, neurokinin A (substance K), substance P, and vasoactive intestinal polypeptide. Of the nine receptor binding sites examined only binding sites for substance P and vasoactive intestinal peptide were significantly altered in the inflamed tissue. These data suggest that substance P is involved in regulating the inflammatory and immune responses in human inflammatory diseases and indicate a specificity of efferent action for each sensory neurotransmitter in peripheral tissues.

Rat mast cells inhibit platelet aggregation by releasing a nitric oxide-like factor: influence of histamine release

In th present paper we report the ability of rat serosal mast cells (MC) to release a nitric oxide (NO)-like factor by the inhibition of platelet aggregation and the effect of sodium nitroprusside (NaNP, a NO-generating drug) on MC histamine release by different stimuli.

Comparison of the enzymatic and edema-producing activities of two venom phospholipase A2 enzymes

The edema-producing activity of NNAVPLA2, an acidic phospholipase A2 (PLA2) enzyme from Naja naja atra venom (NNAV), was less potent than that of TMVPLA2 II, a basic PLA2 from Trimeresurus mucrosquamatus venom (TMV). These edema-forming effects were greatly suppressed by pretreatment of rats with diphenhydramine/methysergide or compound 48/80, which reduced the tissue content of histamine and serotonin. Heparin abolished and suppressed the paw edema caused by protamine and TMVPLA2 II, respectively, but had no effect on the NNAVPLA2-induced response. In isolated rat peritoneal mast cells, both PLA2 concentration dependently induced the release of histamine and beta-glucuronidase. Again, TMVPLA2 II was more potent than NNAVPLA2. This degranulation effect of mast cells caused by TMVPLA2 II and protamine was inhibited by heparin, while that caused by NNAVPLA2 was unaffected. The edema-forming and mast cell degranulation effects were greatly decreased in both PBPB-modified NNAVPLA2 and PBPB-modified TMVPLA2 II, in which the catalytic activity of the enzymes was completely lost. PBPB-modified TMVPLA2 II-induced paw edema was also suppressed by heparin. Furthermore, this edematous response was totally reversed in rat pretreated with aspirin in combination with diphenhydramine and methysergide. These results suggest that the edema-forming effect of PLA2 is probably dependent on the presence of catalytic, positive charge and pharmacological sites on its molecule.

Substance P innervation of the rat thymus

Immunohistochemistry for substance P (SP) in the rat thymus revealed fine varicose neural profiles in specific regions of the thymus. Thymic SP innervation was abundant within the capsule and interlobular septa. The majority of SP+ nerve fibers within the septa were free of vascular association, although some fibers were associated with the vasculature deep within the septa. SP+ nerve fibers entered the thymic cortex from the septa and distributed among cortical thymocytes and mast cells. Along the corticomedullary junction, SP+ nerve fibers were found in association with the vasculature. The medullary region of the thymus received only a sparse innervation of SP+ fibers. In addition, SP+ nerve fibers coursed adjacent to OX-8+ cells and mast cells in the extrathymic connective tissue surrounding the thymus. The present study provides evidence that SP is present in nerve fibers in the thymus, and may be available to interact with thymocytes, mast cells, and other cells in the thymus, and affect their development and function.

Substance P immunoreactivity in periodontal tissues during orthodontic tooth movement

Neurotransmitters, such as substance P (SP), may mediate the biological response to mechanical stress applied to teeth during orthodontic treatment. This hypothesis was investigated immunohistochemically on maxillae of cats which had one maxillary canine tipped distally for a period of time ranging from 1 h to 14 days. Horizontal histological sections 5 microns thick, collected on adhesive tape while still frozen, then freeze-dried, were stained by an immunoglobulin-enzyme bridge method using rabbit anti-SP polyclonal antibodies. The specificity of the staining was evaluated either by using the serum of non-immunized rabbits in lieu of anti-SP serum, or by pre-incubating the anti-SP serum with the antigen. Only sparse SP-like immunoreactivity was detected in the dental pulp, near or in the walls of blood vessels, or in the periodontal ligament (PDL) of unstressed canines. However, the density of neuronal elements exhibiting positive staining for SP appeared to increase markedly after application of an orthodontic force. This phenomenon occurred rapidly (3 h) in the dental pulp, but later in the PDL (24 h to 14 days), mainly at compression sites. These results demonstrate that the stimulation of periodontal nerve terminals by means of orthodontic forces may induce the peripheral release of the neurotransmitter SP, suggesting that it may be an initial trigger for a biochemical cascade which comprises the activation of various types of PDL cells.

Serotonin modulates substance P-induced plasma extravasation and vasodilatation in rat skin by an action through capsaicin-sensitive primary afferent nerves

Using a blister model of inflammation in the rat hind footpad, the present study was undertaken to examine the ability of serotonin (5-HT) to modulate an inflammatory reaction manifested as plasma extravasation and vasodilatation induced by the neuropeptide substance P (SP). In addition, the role of primary afferent sensory nerve fibres in these modulatory effects was studied in capsaicin pretreated rats. Using a protocol of simultaneous perfusion of amine and peptide over the blister base, no major modulatory effect was observed. On the other hand, using a protocol of sequential perfusion, 5-HT was found to extend the plasma extravasation and vasodilatation responses to SP. 5-HT maintained the plasma extravasation response to SP after cessation of stimulation (during the post-stimulation period). On the other hand, it extended the vasodilatation response to SP during the actual stimulation period by preventing the occurrence of tachyphylaxis. These modulatory effects were absent in capsacin-pretreated rats. The present study provides evidence for the first time in vivo to suggest that serotonin can modulate an inflammatory response to SP via a mechanism that involves capsaicin-sensitive sensory fibres.

Synthesis of a nitric oxide-like factor from L-arginine by rat serosal mast cells: stimulation of guanylate cyclase and inhibition of platelet aggregation

Rat serosal mast cells were tested for their ability to generate a nitric oxide-like factor by two bioassay systems: inhibition of platelet aggregation and stimulation of mast cell guanylate cyclase. Incubation of rat serosal mast cells with human washed platelets resulted in an inhibition of thrombin-induced platelet aggregation proportional to the number of cells. The inhibition was potentiated by superoxide dismutase (SOD) and reversed by oxyhaemoglobin (oxyHb). The inhibitory activity of mast cells was also prevented by NG-monomethyl-L-arginine (MeArg), an effect reversed by co-incubation with L-Arg but not D-Arg. When mast cells alone were stirred at 1,000 rpm, a time-dependent increase in the levels of their cGMP but not cAMP was observed. This increase was reduced by pretreatment with MeArg. The inhibitory effect of MeArg was reversed by L-Arg but not D-Arg. These results demonstrate that rat mast cells release a factor with the same pharmacological profile as NO, and that this NO-like factor is derived from L-arginine.

Spantide II, an effective tachykinin antagonist having high potency and negligible neurotoxicity

Spantide (D-Arg1-Pro2-Lys3-Pro4-Gln5-Gln6-D-Trp7-Phe8-D-Trp9-++ +Leu10-Leu11-NH2) was introduced as a tachykinin antagonist in 1984 and has served as a starting point in the design of new antagonists that have proven to be more effective and have exhibited no neurological side effects. The most remarkable and unpredictable structural change that significantly increased potency was deletion of a methylene group by changing Gln6 to Asn6. On the basis that D-Arg1 and Lys3 of spantide contribute to neurological side effects, many new designs led to D-Lys(Nic)1-Pro2-Pal(3)3-Pro4-D-Phe(Cl2)5-Asn6-D-Trp7-Phe8-D-Trp9- Leu10-Nle11- NH2 [spantide II, where D-Lys(Nic) is N epsilon-nicotinoyllysine, Pal(3) is 3-(3-pyridyl)alanine, D-Phe(Cl2) is 3,4-dichloro-D-phenylalanine, and Nle is norleucine], which is a potent antagonist without neurotoxicity. Spantide II, an undecapeptide, has a total of seven substitutions in the sequence of substance P, consisting of two natural L amino acids, and one unnatural L amino acid, and four unnatural D amino acids. The pi- and sigma-bond amino acid substituents of substance P and spantide II are compared toward a future understanding of the essential substituents for mechanism and inhibition binding. Spantide II has five pi-bond and six sigma-bond amino acid moieties, and substance P has two pi-bond and nine sigma-bond moieties.

Recombinant enkephalinase effectively inhibits substance P-induced miosis in the rabbit eye cup model

Enkephalinase (EC 3.4.24.11) is a naturally occurring, membrane-bound peptidase that degrades substance P in vivo and in vitro. Addition of this neutral endopeptidase to a rabbit eye cup model partially inhibits substance P-induced contraction of the iris sphincter muscle. Inactivation of substance P is reversed by thiorphan, a specific inhibitor of enkephalinase. These results show that enkephalinase degradation of substance P produces metabolites that are physiologically inactive in iris contraction. We also observed that atropine acts synergistically with enkephalinase to completely abolish substance P-induced iris contraction suggesting that the action of substance P on the iris contains an acetylcholine-stimulatory effect which is not lost by enkephalinase treatment.

Substance P induces the expression of an endothelial-leukocyte adhesion molecule by microvascular endothelium

Leukocyte trafficking in normal and diseased skin appears to be initially governed by endothelial surface glycoproteins that promote adhesive interactions with circulating leukocytes. In a separate study, we have demonstrated that one of these glycoproteins, endothelial-leukocyte adhesion molecule-1 (ELAM-1), is rapidly induced on postcapillary dermal venules as a direct consequence of experimentally-elicited degranulation of adjacent mast cells (Proc Natl Acad Sci USA 86:8972-8976, 1989). A principle endogenous mediator of mast cell degranulation is the neuropeptide substance P. In this study, we exposed organ cultures of neonatal human foreskins for 45 min to substance P or to a substance P analogue (D-pro4, D-trp7,9)SP(4-11) that binds to the identical mast cell surface receptor but which does not provoke histamine release. Dermal mast cells were uniformly degranulated only in explants exposed to substance P, as judged by ultrastructural analysis. After subsequent culture in medium alone for 6 h, superficial venules of explants exposed to substance P showed evidence of ELAM-1 induction, as documented histochemically using H4/18 monoclonal antibody. ELAM-1 was not induced by substance P analogue. Furthermore, preincubation of explants with analogue or with the mast cell inhibitor, cromolyn sodium, abrogated the ability of substance P to induce ELAM-1. From these results we suggest that substance P endogenously released by dermal nerve fibers upon physiologic or electrical stimulation may be important in the regulation of endothelial-leukocyte interactions in vivo. This concept provides further evidence for a neurogenic and psychogenic modulation of the immune response, and may be relevant to the course of naturally occurring dermatoses (e.g., psoriasis) that are commonly exacerbated by emotional stress.

Capsaicin pretreatment modifies hydrogen sulphide-induced pulmonary injury in rats

One of the major target organs of hydrogen sulphide gas is the lung. Exfoliation of upper respiratory epithelia and pulmonary edema are prominent effects. Various neuropeptides contained in afferent C-fibres are intimately associated with the epithelia of the conducting airways and are liberated upon exposure to noxious gases. We sought to determine their role in the pathogenesis of hydrogen-sulphide-induced pulmonary injury by pretreating rats with the neurotoxin, capsaicin, which is known to ablate a subpopulation of vagal afferent C-fibres. Groups of capsaicin and saline (control) pretreated Fischer 344 rats were exposed to an edemogenic concentration of hydrogen sulphide (525-559 mg/m3) for 4 hr. Mortality was significantly greater (p less than 0.01) in the capsaicin treated rats (12/12) compared to the control animals (2/12). Pulmonary injury was also more severe in the capsaicin pretreated animals as assessed by lung water content, histological grade of pulmonary edema and protein in the broncho-alveolar fluid. Animals depleted of substance P exhibited a significantly greater (p less than 0.01) degree of bronchial epithelial cell exfoliation and ulceration following exposure to hydrogen sulphide. These experiments indicate that capsaicin sensitive sensory nerves may play a major role in pulmonary defense against the effects of inhaled toxic gases such as hydrogen sulphide.

A retrospective clinical and neuroimmunohistochemical study of rheumatoid arthritic patients with atlanto-axial subluxation

In a retrospective study of 87 RA patients with radiographically documented anterior atlanto-axial subluxation (AAS) in flexion-extension radiographs, 40 had been studied radiographically before they developed AAS. Of these 40 patients, 34 had had occipitocervical pain already before the subluxation. This shows that pain early in the course of the rheumatoid cervical spine is not caused by or associated with AAS itself. In a separate operatively treated group of 5 patients, ligament neuroanatomy in AAS was more closely studied, using specific heteroantisera to cytoskeletal neurofilaments and various transmitter neuropeptides as neural markers and the highly sensitive avidin-biotin-peroxidase complex (ABC) immunohistochemical staining procedure. These specimens were obtained from the ligamentous structures between the posterior arch of the atlas and the spinous process of C2, corresponding to the C1-C2 interspinal non-inflammatory ligament, during atlanto-axial stabilizing operations. This ligamentous tissue contained, in addition to focal inflammatory cell infiltrates, neurofilament and/or neuropeptide immunoreactive neural elements. This finding may suggest that pain early in anterior AAS could be caused not only by synovitis, for example, but also by local ligamentary involvement leading to irritation of local neural elements. This phenomenon may have contributed to the local occipitocervical pain experienced by 34/40 patients who later developed AAS.

Substance P-induced augmentation of cutaneous vascular permeability and granulocyte infiltration in mice is mast cell dependent

The undecapeptide substance P is thought to mediate both vasodilatation and augmented vascular permeability when released from sensory nerve endings in the skin. Substance P also induces mast cell degranulation in vitro or in vivo. However, the extent to which substance P-induced changes in vascular permeability are mast cell-dependent is unclear. We investigated this issue by injecting substance P and certain related peptides (substance P1-4, substance P4-11) into the skin of genetically mast cell-deficient WBB6F1-W/W or WCB6F1- SI/SId mice the congenic normal (+/+) mice, and W/W mice which had undergone selective local repair of their mast cell deficiency by intradermal injection of IL-3-dependent mast cells generated in vitro from the bone marrow cells of the congenic +/+ mice. Substance P induced significant augmentation of vascular permeability and significant cutaneous swelling when injected into normal mice at doses as low as 2 pmol i.d. Substance P also induced granulocyte infiltration, although the infiltrate were modest and were seen at doses of peptide from 5 to more than 20-fold higher than those required for induction of tissue swelling. The effects of substance P on tissue swelling, vascular permeability, and granulocyte infiltration were virtually entirely mast cell dependent. By contrast, substance P1-4 was inactive in our assays at 25 nmol/site, and substance P4-11 induced modest augmentation of vascular permeability, which was at least in part mast cell independent.

Vasodepression ex vivo after administration of inflammatory mediators in vivo in the rat

When rats were pretreated by intraplantar or i.v. injection of various inflammatory mediators, the vasopressor effect of i.a. norepinephrine in the subsequently isolated perfused hindlegs of the rats was found to be partly depressed. This vasodepression could also be detected if mediators were directly co-perfused in the isolated hindlegs. The vasodepressor effect was strongest following histamine pretreatment and co-perfusion, respectively, whereas endotoxin 0111:B4, PAF-acether, PGE1, and LTD4 were less effective. Only weak or no vasodepression could be induced by bradykinin, serotonin, lysolecithin, and substance P (1-11). The significance of the results is discussed with respect to anaphylactic disorders.

Tachykinin-induced vasodilatation in rat skin measured with a laser-Doppler flowmeter: evidence for receptor-mediated effects

Vasodilatation was induced by perfusion of the tachykinins substance P (SP), neurokinin A and neurokinin B and the analogues [Glp6, D-Pro9]SP-(6-11) and [Glp6, L-Pro9]SP-(6-11) over the base of vacuum-induced blisters on the rat footpad. Vasodilatation was measured as change in blood flow using a laser-Doppler flowmeter. The tachykinins induced vasodilatation in a dose-response manner with a threshold of approximately 3 pmol and pD2's of 6.48, 6.13 and 6.21 for SP, neurokinin A and neurokinin B respectively. The D- and L-Pro analogues of [Glp6, Pro9]SP-(6-11) also induced vasodilatation in a dose-dependent manner. The L-Pro analogue was more potent than the D-Pro analogue (D/L ratio of the EC50's = 21) which suggests the involvement of an NK-1 type receptor in the mediation of small vessel vasodilatation. The vasodilatation to SP was reduced by 64% and 59% in capsaicin- and antihistamine-pretreated animals respectively, demonstrating the involvement of capsaicin-sensitive primary afferent nerves and mast cells in the vasodilatation component of the neurogenic inflammatory response.

Edematous response caused by [Thi5,8,D-Phe7]bradykinin, a B2 receptor antagonist, is due to mast cell degranulation

[Thi5,8,D-Phe7]bradykinin caused hind-paw edema and degranulation of isolated peritoneal mast cells in a dose-dependent manner. Pretreatment with diphenhydramine/methysergide or compound 48/80 completely suppressed the edematous response caused by [Thi5,8,D-Phe7]bradykinin, whereas bradykinin-induced hind-paw swelling was only partially inhibited by diphenhydramine and methysergide pretreatment; the residual response was significantly further depressed by [Thi5,8,D-Phe7]bradykinin. Neither the bradykinin- nor [Thi5,8,D-Phe7]bradykinin-induced edematous response was significantly affected by aspirin or BW755C. The mast cell degranulation caused by [Thi5,8,D-Phe7]bradykinin and bradykinin was inhibited by gangliosides but not by heparin. These results suggest that the edematous response elicited by [Thi5,8,D-Phe7]bradykinin was mainly due to the actions of mediators released by the degranulation of mast cells. Unlike bradykinin, [Thi5,8,D-Phe7]bradykinin was devoid of a direct exudation-promoting effect but exerted an antagonistic effect on the direct effect of kinin. If the influence of mast cells degranulation could be minimized, [Thi5,8,D-Phe7]bradykinin could be used as a tool to evaluate the role of kinin in the edematous response in inflammation.

Peripheral patterns of calcitonin-gene-related peptide general somatic sensory innervation: cutaneous and deep terminations

The distribution of calcitonin-gene-related peptide (CGRP) immunoreactivity (IR) was studied in peripheral tissues of rats. The ganglionic origin, somatosensory nature, and anatomic relations of this thin-axon population were evaluated with particular emphasis on possible nociceptive roles. In animals untreated with colchicine, CGRP-IR is found in a vast proportion of small- and medium-diameter sensory ganglion cells that give rise to numerous thinly myelinated and unmyelinated axons that display CGRP-IR throughout the body. The integumentary innervation consists, in part, of an extensive subpapillary network largely traced to dermal blood vessels, sweat glands, and "free" nerve endings, some of which are found within regions containing only mast cells, fibroblasts, and collagen. Dermal papillae contain CGRP-IR axons surrounding each vascular loop; other papillary axons end freely or occasionally surround Meissner corpuscles. Intraepithelial axons enter glabrous epidermal pegs, branching and exhibiting terminals throughout the stratum spinosum. A similar pattern is found in hairy skin with additional innervation entering the base and surrounding the lower third of each hair follicle, but apparently not supplying sebaceous glands and arrector pili muscle. Axons innervating nonkeratinized oral epithelium are similar or greater in number and distribution compared to epidermis, often with more extensive branching. The high density of intraepithelial CGRP-IR innervation does not appear to correlate with the sensitive mechanoreceptor-based increase in spatial sensory discriminative capacities in the distal portions of the limb. In deep somatic tissues, CGRP-IR is principally related to vasculature and motor end plates of striated muscle, but there is an extensive network of thin axons within bone, principally in the periosteum, and focally in joint capsules, but not in relation to muscle spindles or tendon organs. These findings, together with the distribution in cranial tissues described in an accompanying paper (Silverman and Kruger: J. Comp. Neurol. 280:303-330, '89), are considered in the context of a "noceffector" concept incorporating the efferent role of these sensory axons in various tissues. It is suggested that involvement in tissue maintenance and renewal during normal function, as well as following injury, may predominate over the relatively infrequent nociceptive role of this peptidergic sensory system.

Endogenous histamine excites neurones in the guinea-pig superior cervical ganglion in vitro

1. Intracellular recordings were obtained from neurones in the guinea-pig superior cervical ganglion (SCG) in vitro to study the electrophysiological effects of endogenously released histamine. 2. Guinea-pigs were actively sensitized to the specific antigen, ovalbumin. SCG removed from these animals rapidly released a significant proportion of their endogenous histamine stores into the extracellular space upon exposure to the sensitizing antigen. Several observations indicated that the released histamine was derived from ganglionic mast cells. 3. The electrophysiological effects produced by antigen challenge in a neurone mimicked qualitatively and quantitatively those effects produced by exogenously applied histamine in the same neurone. Under current clamp the membrane effects of antigen and histamine included a transient depolarization, an increase in input resistance and transient blockade of a long-duration component of the spike after-hyperpolarization. In voltage clamp histamine and antigen produced an inward current and decreased membrane conductance. 4. Histamine H1, but not H2 or H3 receptor antagonists prevented the membrane depolarization to both histamine and antigen treatments. 5. These convergent biochemical, physiological and pharmacological data demonstrate that a sufficient quantity of endogenous histamine is released by an antigenic stimulus in SCG from sensitized guinea-pigs to affect specific electrophysiological characteristics of neurones. Histamine may thus be involved in mediating interactions between the mammalian immune system and the peripheral sympathetic nervous system.

Antagonists of luteinizing hormone releasing hormone bind to rat mast cells and induce histamine release

It was reported previously that administration of certain synthetic antagonists of LHRH to rats produced allergy-like symptoms that were attributed to their histamine releasing action. In the present study the interaction of LHRH analogs with rat peritoneal mast cells was investigated in vitro. Potent antagonists of LHRH showed strong in vitro histamine releasing activity from rat peritoneal mast cells. Membrane preparations of rat pituitary glands showed specific binding of radioiodinated LHRH antagonist as well as LHRH agonist. However, rat peritoneal mast cells and membrane preparations from those cells bound antagonist but not the agonist. Furthermore, the LHRH antagonist did not bind to membranes prepared from tissues such as prostate, liver, kidney, and brain. Competitive displacement curves of the [125I]-antagonist with different LHRH analogs showed that the ability of the analogs to compete for binding sites on mast cells was related to their histamine releasing activity. We conclude that histamine release from rat mast cells induced by LHRH analogs is mediated by specific binding of the active peptides to cell membranes. Furthermore, using rat mast cells, the binding assay in conjunction with histamine releasing assay may be utilized to predict the in vivo histamine releasing potential of new LHRH peptides which are of clinical importance.

Study of the effect of some neuropeptides and endogenous opioid peptides on in vitro histamine release from human lung mast cells and peripheral blood basophils

In the present study we investigated the effect of substance P, bombesin, beta lipotropin, alpha and gamma endorphins, and metionin and leucin enkephalins on in vitro histamine release from partially purified human lung mast cells and peripheral blood basophils. In the concentration range of 10-100 microM, these neuropeptides and endogenous opioid peptides neither elicited a significant histamine secretions from human lung mast cells and blood basophils, nor influenced the anti-IgE-induced histamine release. These data indicate that human lung mast cells and blood basophils are resistant to the activity of substance P, bombesin, beta lipotropin, alpha and gamma endorphins, and metionin and leucin enkephalins, and confirm the functional heterogeneity of mast cells, depending on the species and the tissue origin.

Receptor binding sites for substance P and substance K in the canine gastrointestinal tract and their possible role in inflammatory bowel disease

The mammalian tachykinins, substance P, substance K (neurokinin A) and neuromedin K (neurokinin B), are putative peptide neurotransmitters in both the brain and peripheral tissues. We used quantitative receptor autoradiography to localize and quantify the distribution of binding sites for radiolabeled substance P, substance K and neuromedin K in the canine gastrointestinal tract. Substance P binding sites were localized to smooth muscle cells in the muscularis mucosa and muscularis externa, the smooth muscle and endothelium of arterioles and venules, neurons in the myenteric plexus, mucosal epithelial cells, exocrine cells and lymph nodules. Substance K binding sites were distributed in a pattern distinct from substance P binding sites and were localized to smooth muscle cells in the muscularis mucosa and muscularis externa, the smooth muscle and endothelium of arterioles and venules, and neurons of the myenteric plexus. Neuromedin K binding sites were not observed in any area of the canine gastrointestinal tract although they were localized with high specific/non-specific binding ratios in the canine spinal cord. These results indicate that there are at least two distinct types of tachykinin receptor binding sites in the canine gastrointestinal tract, one of which probably recognizes substance P and the other substance K as endogenous ligands. In correlation with previous physiological data, these substance P and substance K receptor binding sites appear to be involved in the regulation of a variety of gastrointestinal functions including gastric motility, mucosal ion transport, hemodynamics, digestive enzyme secretion and neuronal excitability. In addition these results demonstrate that receptor binding sites for substance P and substance K are expressed by cells involved in mediating inflammatory and immune responses. These data, together with our studies on surgical specimens from patients with inflammatory bowel disease, suggest that in a pathophysiological state tachykinins and their receptors may play a role in inflammatory bowel disease and should permit a rational approach to designing neuropeptide antagonists which may prove effective in treating inflammatory diseases.

Pathophysiological significance of the distribution of histamine receptor sub-types: a proposed dual role for histamine in inflammation and type I hypersensitivity reactions

The pathophysiological significance of histaminergic receptors located on the membranes of immunocompetent cells is reviewed. H2-receptor agonists decrease the immunological histamine release from isolated serosal mast cells and from isolated hearts taken from actively sensitised guinea-pigs. Histamine and H2-receptor agonists inhibit the generation of superoxide anion from human neutrophils activated by FMLP and by substance P. These observations lend further support to the hypothesis of an immunodepression exerted by the activation of H2-receptors, which can be converted to immunostimulation by treatment with H2-receptor antagonists.

Structural requirements for mast cell triggering by substance P-like peptides

Experiments were based on the hypothesis that the histamine releasing action of substance P and some other neuropeptides is not due to the interaction of the neuropeptide with a specific membrane receptor. Rather, this may be a property of many amphiphilic compounds having a minimal number of positives charges and a hydrophobic chain which is not necessarily a peptide. According to this hypothesis, 18 substance P derivatives and fragments were synthesized and tested on rat and hamster peritoneal mast cells, among them five compounds which contain a non-peptide chain instead of the C-terminal substance P heptapeptide. The results are in accord with the above hypothesis.

Substance P-induced bronchoconstriction in the guinea pig. Enhancement by inhibitors of neutral metalloendopeptidase and angiotensin-converting enzyme

We tested the effects of the neutral metalloendopeptidase (NEP) inhibitor, thiorphan (0.17, 0.5, and 1.7 mg i.v), and the angiotensin-converting enzyme (ACE) inhibitor, captopril (0.5, 1.7, and 5.0 mg i.v.), on the bronchoconstrictor response to rapid intravenous infusions of substance P (0.1 to 30 nmol/kg) in anesthetized, mechanically ventilated guinea pigs. The decreases in pulmonary conductance and dynamic compliance caused by substance P were greater in animals treated with either thiorphan or captopril than in control animals. Thiorphan (0.5 mg) had no effect on airway responsiveness to intravenously administered methacholine, whereas captopril (1.7 mg) caused a small increase in methacholine responsiveness. Both drugs significantly increased the recovery of immunoreactive substance P in arterial plasma after exogenous administration of the peptide. We conclude that degradation of substance P by both NEP and ACE is important for determining the magnitude of the bronchoconstriction caused by intravenous administration of this neuropeptide. These data suggest that conditions associated with diminished peptidase activity could result in enhanced responses to stimuli which cause the release of endogenous substance P.

Substance-P-like levels in inflammatory exudates

Levels of SP-like immunoreactivity were assessed by enzyme immunoassay in exudates induced in the rat by intrapleural injection of either calcium pyrophosphate (CaPP) or carrageenan. SP-like levels increased during the first hour, up to approximately 2 ng/ml, and remained significantly higher than control values from 1 to 6 h after the induction of pleurisy by CaPP. With carrageenan as the irritant, SP-like levels rose during the first 4 h, up to 3 ng/ml, and remained significantly higher than control values from 4 to 24 h. In terms of the total volume of exudate induced by carrageenan, total amounts increased up to 8 ng/rat at 16 h after the beginning of the reaction. Our data demonstrate a detectable release of SP-like material in these pleural exudates and suggest its involvement in the inflammatory response, either directly, or through other mediators, or simply by acting on nociceptive fibers and inducing vascular changes.

Airway responses to substance P and substance P fragments in the guinea pig

Airway responses to rapid intravenous infusions of substance P (SP), selected carboxy terminal fragments (SP3-11, SP5-11, SP7-11, and SP9-11), and an amino terminal fragment (SP1-9) were measured in anesthetized, mechanically ventilated guinea pigs. The dose of each peptide required to decrease pulmonary conductance (GL) to 50% of baseline value was calculated in each animal. The order of ED50GL was: SP5-11 less than SP3-11 less than SP less than SP7-11. SP9-11 and SP1-9 were inactive at doses up to 1000 nmol/kg i.v. The effects of the neutral metalloendopeptidase (NEP) inhibitor, thiorphan, and the angiotensin converting enzyme (ACE) inhibitor, captopril, on airway responses to SP5-11 were examined in order to test the hypothesis that differences in degradation of SP and SP5-11 contribute to the difference in airway responsiveness to the two peptides. Thiorphan (0.5 mg/animal, i.v.) caused a significant decrease in ED50GL for SP5-11, as has been previously noted for SP. In contrast, captopril (1.7 mg/animal i.v.) had no effect on ED50GL for SP5-11, although it has a substantial effect on SP responses. These results indicate that while the carboxy terminal of SP is essential for peptide bronchoactivity, loss of amino terminal peptides (up to four residues) actually enhances bronchoconstrictor responses to the peptide. Part of this enhancement appears to result from differences in the degradation of SP and SP5-11 by ACE. The data suggest that cleavage of SP by dipeptidyl aminopeptidases could enhance its bioactivity.

Neuropeptide regulation of immediate and delayed hypersensitivity

Peptide mediators of sensory nerves that are released in tissues by noxious stimuli or inflammatory reactions rapidly elicit local and systemic responses similar to those of immediate hypersensitivity. These sensory neuropeptides affect functions of smooth muscles, blood vessels, leukocytes, and epithelial glands both directly and indirectly, through the actions of mediators released from mast cells stimulated by the peptides. Stereospecific receptors transduce the effects of neuropeptides of the peripheral nervous system (PNS) and central nervous system (CNS) on diverse functions of human, murine and guinea pig mononuclear and polymorphonuclear leukocytes, mast cells, and basophils in vitro and in vivo. Stimulatory and inhibitory effects of neuropeptides on leukocytes are attained in vitro at concentrations which are similar to those in the circulation and in tissues. The dissociation constant (KD) for the binding of a neuropeptide to its leukocyte receptor is within the range of concentrations that evoke cellular responses critical to immunity and hypersensitivity. Neuropeptides exhibit both cellular and stimulus specificities, as exemplified by the greater potency of substance P in activating mucosal than connective tissue mast cells and the capacity of somatostatin to inhibit the release of mediators from basophils challenged by IgE-dependent mechanisms, but not by basic peptides or ionophores. The selective release of distinct neuropeptides from different subsets of sensory nerve endings, the specificity of neuropeptide recognition by mast cells, basophils, lymphocytes, and other target cells, and the diversity of relevant activities of the neuropeptides suggest that the nervous system may initiate and modulate immediate and delayed hypersensitivity by unique mechanisms.

Substance P receptor-dependent responses of leukocytes in pulmonary inflammation

Pulmonary immunologic responses may be mediated and modulated in part by neuropeptides released from the endings of nerve fibers that innervate the airways. Bronchoconstriction, mucosal edema, and increased airway secretions may be mediated by multiple locally generated neuropeptides. The neuropeptides affect directly and indirectly through other mediators the functions of endothelial cells, smooth muscle cells, blood vessels, and leukocytes. The high content of diverse potent neuropeptides in the ganglionated plexuses close to pulmonary smooth muscle bundles, along blood vessels, and in neural projections into the bronchial epithelium and regions containing acini of mucus glands provide tissue concentrations well within the range required to attain such biologic effects. The airway responses mediated principally by neuropeptides exhibit unique mechanisms of specificity attributable to the selective distribution of each neuropeptide in a distinct subset of nerve fibers that react differently to each stimulus and to the target cell specificity of the neuropeptides. At physiologically relevant in vitro concentrations, many of the neuropeptides have different effects on mast cells, basophils, monocytes, and lymphocytes. The direct actions of substance P (SP) and the capacity to initiate and modulate leukocyte responses are described in relation to the physiologic and pathopharmacologic consequences of pulmonary nerve stimulation. Selected cellular and molecular characteristics of the interactions of SP with mast cells, basophils, lymphocytes, endothelial cells, and smooth muscle cells also will be presented in order to define the functionally critical properties of receptors for the neuropeptide and to expose possible means of specifically modifying the interactions.

Effects of substance P, neurokinin A and calcitonin gene-related peptide in human skin and their involvement in sensory nerve-mediated responses

The effects evoked by intradermal injections of substance P (SP), neurokinin A (NKA) or calcitonin gene-related peptide (CGRP) were studied in 51 non-atopic subjects. SP and NKA produced flare and weal, and CGRP produced an indurated erythema. The reactions to SP were strong, the flare being maximal 3-5 min after injection and the weal after 10-15 min. NKA evoked a much weaker flare and a slightly weaker weal than did SP. CGRP produced a prominent long-lasting, indurated erythema with pseudopodia surrounded by a pallor edge. The mode of action of the three peptides was studied by pretreatment of the skin with the histamine-releasing compound 48/80, the H1-antagonist mepyramine or the local anesthetic xylocaine. The results suggest that mast-cell histamine and an intact sensory nerve supply are essential for the flare response to both SP and NKA. The weal response to SP was somewhat reduced by pretreatment with either 48/80 or xylocaine. The weal response to NKA, however, did not seem to depend upon either mast cells or sensory nerve fibres. The erythema evoked by CGRP was not suppressed by pretreatment with xylocaine, compound 48/80 or mepyramine, suggesting a direct action of CGRP on the blood vessels. The interaction between SP and CGRP was studied in subjects receiving a low dose of CGRP and increasing doses of SP or a low dose of SP and increasing doses of CGRP. CGRP did not potentiate the SP-evoked flare and weal and SP did not seem to enhance the response to CGRP.

Mast cell activation--a receptor-independent mode of substance P action?

Substance P is a representative of a group of amphiphilic neuropeptides which act as mast cell secretagogues. Our experiments with some new substance P derivatives suggest that these effects are dependent on two structural elements: (i) a hydrophobic chain which is not essentially a peptide, and (ii) a hydrophilic part with two positively charged amino acids. The mast cell triggering effect is unlikely to be mediated by a selective substance P receptor, but has strong similarities to the mode of action of polycations.

Sympathetic innervation of the cornea from the superior cervical ganglion. An HRP study in the cat

Horseradish peroxidase (HRP) was applied to the cornea in cats using a variety of methods. Small numbers of labeled neurons were observed in the superior cervical ganglion (SCG), the majority were located in the rostral half. This confirms previous histofluorescence data which indicated the SCG was the likely source of adrenergic fibers to the cornea.

Investigation of the vagally induced changes in transmural potential difference in the ferret jejunum in vivo

This study was designed to determine whether the non-cholinergic, non-adrenergic rise in transmural potential difference (PD), induced by vagal nerve stimulation is an efferent effect or one caused by the antidromic stimulation of afferent fibers. Unilateral left supranodose vagotomy was performed, which caused degeneration of efferent fibers within the vagus nerve, leaving the nodose ganglion, and consequently afferent cell bodies, undamaged. After stimulating the unoperated nerve there was an increase in jejunal motility, a rise in transmural PD and a fall in systemic blood pressure. Although cholinergic blockade with atropine and adrenergic blockade with or a combination of phentolamine and propranolol abolished this vagally induced motor activity and fall in systemic blood pressure, the transmural PD response induced by stimulation of the unoperated nerve was only partially inhibited. However, the subsequent administration of the nicotinic ganglionic blocker, hexamethonium, abolished this transmural PD response. In contrast, stimulation of the operated vagus nerve failed to produce these effects. Therefore, cholinergic and non-cholinergic efferent fibers are responsible for the vagally induced rise in transmural PD and thus fluid secretion in the ferret jejunum.