Morphologic maturation of tachykinin peptide-expressing cells in the postnatal rabbit retina

Tachykinin (TK) peptides, which include substance P, neurokinin A, two neurokinin A-related peptides and neurokinin B, are widely present in the nervous system, including the retina, where they act as neurotransmitters/modulators as well as growth factors. In the present study, we investigated the maturation of TK-immunoreactive (IR) cells in the rabbit retina with the aim of further contributing to the knowledge of the development of transmitter-identified retinal cell populations. In the adult retina, the pattern of TK immunostaining is consistent with the presence of TK peptides in amacrine, displaced amacrine, interplexiform and ganglion cells. In the newborn retina, intensely immunostained TK-IR somata are located in the ganglion cell layer (GCL) and in the inner nuclear layer (INL) adjacent to the inner plexiform layer (IPL). They are characterized by an oval-shaped cell body originating a single process without ramifications. TK-IR processes are occasionally observed in the IPL and in the outer plexiform layer (OPL). Long TK-IR fiber bundles are observed in the ganglion cell axon layer. TK-IR profiles resembling small somata are rarely observed in the INL adjacent to the OPL. At postnatal day (PND) 2, some TK-IR cells display more complex morphologic features, including processes with secondary ramifications. Long TK-IR processes in the IPL are often seen to terminate with growth cones. Between PND 6 and PND 11 (eye opening), there is a dramatic increase in the number of immunolabeled processes with growth cones both in the IPL and in the OPL and the mature lamination of TK-IR fibers in laminae 1, 3 and 5 of the IPL is established. TK-IR cells attain mature morphological characteristics and the rare, putative TK-IR somata in the distal INL are no longer observed. After eye opening, growth cones are not present and the pattern typical of the adult is reached. These observations indicate that the development of TK-IR cells can be divided into an early phase (from birth to PND 6) in which these cells establish their morphological characteristics, and a later phase (from PND 6 to eye opening) in which they are involved in active growth of their processes and likely in synapse formation. Since TK peptides are thought to play neurotrophic actions in the developing nervous system and they are consistently present in the retina throughout postnatal development, they may also act as growth factors during retinal maturation.

Characterization of antisera specific to NK1, NK2, and NK3 neurokinin receptors and their utilization to localize receptors in the rat gastrointestinal tract

Understanding the physiological role of tachykinins requires precise cellular and subcellular localization of their receptors. We raised antisera by immunizing rabbits with peptides corresponding to portions of the intracellular tails of the rat neurokinin 1, 2, and 3 receptors (NK1-R, NK2-R, NK3-R). Receptors were localized by immunofluorescence and confocal microscopy. NK1-R, NK2-R, and NK3-R were detected at the plasma membrane of transfected cells with minimal intracellular stores. Staining was abolished by preabsorption of the antisera with the peptides used for immunization. Nontransfected cells were unstained. Each antiserum only stained cells transfected with the appropriate receptor and did not stain cells transfected with the other receptors. Therefore, the antisera are specific and do not cross-react with other neurokinin receptors. We examined the distribution of the neurokinin receptors in the gastrointestinal tract of the rat. NK1-R was detected in myenteric and submucosal neurons and in interstitial cells of Cajal. NK2-R was localized to circular and longitudinal muscle cells and to nerve endings in the plexuses. NK3-R was detected in numerous myenteric and submucosal neurons. Some neurons expressed both NK1-R and NK3-R. Receptors were detected at the plasma membrane and in endosomes. Cells expressing the receptors were closely associated with tachykinin-containing nerve fibers. Thus, NK1-R and NK3-R mediate neurotransmission by tachykinins within enteric nerve plexuses, and NK1-R and NK2-R mediate the effects of tachykinins on interstitial and smooth muscle cells, respectively.

Calretinin immunoreactivity of motor neurons in the guinea-pig distal colon and taenia coli

Calretinin is a calcium-binding protein which occurs in neurons and endocrine cells, including neurons throughout the gastrointestinal tract. Calretinin-immunoreactive (IR) neurons innervate the circular muscle in the guinea-pig distal colon and have descending as well as ascending projections. This suggests that calretinin-IR is in motor neurons, but whether it might be in excitatory or inhibitory motor neurons or both was previously undetermined. The presence of calretinin-IR in neurons innervating the taenia coli has not been previously reported. Numerous fibres in the circular muscle of the distal colon and in the taenia coli displayed immunoreactivity for calretinin. Tachykinin (TK), vasoactive intestinal peptide (VIP), calretinin, and gamma-aminobutyric acid (GABA) immunoreactivity was also in fibres innervating these targets. The abundances of these fibres was estimated to be TK > VIP > calretinin > GABA. Double label immunohistochemistry revealed the presence in both tissues of populations of calretinin-IR fibres which were also TK-IR, and fibres with calretinin and GABA-IR in the colon, but calretinin-IR fibres were never VIP-IR. TK- and VIP-IR were in separate populations of nerve fibres as were GABA- and TK-IR. It is concluded that calretinin-IR does not provide a definitive labelling of a physiologically known subgroup of motor neurons, either in the distal colon or in the taenia coli, but that calretinin is most likely to be in excitatory motor neurons.

Recognition of neurokinin 1 receptor (NK1-R): an antibody to a peptide sequence from the third extracellular region binds to brain NK1-R

Substance P (SP) can produce cytokine-like responses by astrocytes and mononuclear cells. In an effort to identify neurokinin-1-receptors (NK1-R), an antibody to NK1-R was generated by using a linear peptide sequence from the deduced third extracellular region (ECR) corresponding to the seven transmembrane rat brain NK1-R. The ECR-3 peptide was coupled to keyhole-limpet hemocyanin and the antisera produced in rabbits was purified by binding to a peptide-affinity matrix. The specificity for the anti-peptide antibody was shown by its reactivity to the ECR-3 peptide by ELISA. The anti-ECR-3 peptide antibody could detect, by Western blot analysis of SDS-PAGE-separated rat brain membranes, a single band with an apparent molecular weight (MW) of 53-54 kDa. An affinity matrix made from the anti-ECR-3 antibody was used to isolate NK1-R from rat brain membranes which exhibited two products on SDS-PAGE with apparent MW of 54 and 44 kDa. The C6 astrocytes were shown to express NK1-R as determined by [125I]Bolten-Hunter SP binding to intact cells with a Kd = 0.32 nM. These C6 cells did not co-express either NK2-R or NK3-R when analyzed at the mRNA level. The anti-ECR-3 peptide antibody could inhibit [125I]Bolten-Hunter SP binding to intact C6 astrocytes and CHO cells expressing NK1-R by greater than 95% when compared to normal rabbit IgG which failed to inhibit radiolabeled SP binding. Thus, an antibody which recognizes surface determinants to the NK1-R could be generated upon immunization with an NK1-R peptide.

GABA and nitric oxide synthase immunoreactivities are colocalized in a subset of inhibitory motor neurons of the guinea-pig small intestine

Simultaneous immunofluorescence labelling was used to determine the patterns of colocalization of immunoreactivity for gamma-aminobutyric acid (GABA-IR) with immunoreactivity for nitric oxide synthase (NOS), vasoactive intestinal peptide (VIP) and tachykinins (TK) in nerve cells and fibres of the guinea-pig small intestine. GABA-IR nerve cell bodies were located in the myenteric plexus and varicose fibres innervated the circular and longitudinal muscle, but did not form pericellular endings in the myenteric ganglia. GABA-IR nerve cells comprised 4-5% of all nerve cells in the myenteric ganglia. Of GABA-IR myenteric nerve cells, about 85% had NOS-IR and of GABA-IR nerve fibres in both muscle layers, about 75% were NOS-IR. Conversely, 20% of NOS-IR nerve cells were GABA-IR. About 6% of GABA-IR nerve fibres innervating the circular muscle, but none innervating the longitudinal muscle, were TK-IR. Most GABA-IR fibres supplying the circular muscle, but none of those supplying the longitudinal muscle, were VIP-IR. From this study, and previous studies of projections of enteric neurons, it is concluded that most GABA-IR neurons in the guinea-pig small intestine are inhibitory motor neurons that also contain NOS-IR. A small proportion represents anally directed excitatory motor neurons that innervate the circular muscle and are also immunoreactive for TK.

Immunoreactive tachykinins in 24-h collections of urine from patients with carcinoid tumours: characterization and correlation with plasma concentrations

Tachykinins are a family of peptides that may be present in and secreted from carcinoid tumours of mid-gut origin. They are likely to play a role in the pathogenesis of, e.g. the flush, dyspnoea and valvular heart disease seen in the carcinoid syndrome. Since tachykinins are secreted from the tumour into the circulation in bursts, coinciding with flushing attacks, and have short half-lives, we anticipated that analysis of 24-h urine excretion of immunoreactive tachykinin metabolites might prove to be a more sensitive and stable parameter for monitoring than tachykinin-like immunoreactivity in plasma. The study included 48 patients hospitalized for treatment of advanced carcinoid tumours and 32 healthy controls. The urine excretion of tachykinin-like immunoreactive metabolites in the carcinoid patients (median 27.5 pmol 24 h-1, interquartile range (IQR) 8.5-51.0 pmol 24 h-1) was significantly (p<0.001) higher than that in the 32 healthy subjects (median 3.0 pmol 24 h-1, IQR 0.9-4.20 pmol 24 h-1). Of the patients, 38 (79%) had elevated 24-h urine excretion of tachykinin-like immunoreactive metabolites while 31 (64%) had elevated plasma concentrations of tachykinin-like immunoreactive metabolites. Of the patients, 27 (56%) had elevated concentrations of tachykinin-like immunoreactive metabolites both in plasma and urine, 12 (25%) had elevated concentrations only in urine excretion, 3 (6%) had elevated concentrations of only plasma tachykinin-like immunoreactive metabolites and 7 (14%) had elevation of neither plasma nor urine concentrations. Analysis by means of different column chromatographic techniques indicated that the immunoreactive material was heterogeneous, with some components co-eluting with oxidized neurokinin A (NKA) and neuropeptide K (NPK). The urine tachykinin-like immunoreactivity correlates well with that of plasma, but is a slightly more sensitive indicator of elevated tachykinin-like immunoreactivity, probably since levels of urine tachykinin-like immunoreactive metabolites reflect the overall amount of the latter secreted into the circulation during 24 h.

Abundant distribution of locustatachykinin-like peptide in the nervous system and intestine of the cockroach Leucophaea maderae

An antiserum raised to the locust neuropeptide locustatachykinin I (LomTK I) was used for analysis of the distribution of tachykinin-related peptide in the cockroach Leucophaea maderae. Extracts of dissected brains, suboesophageal ganglia, thoracic ganglia and midguts were separated by high performance liquid chromatography and the fractions analysed in enzyme-linked immunosorbent assay with use of the LomTK antiserum. Each of the tissues was found to contain LomTK-like immunoreactive (LomTK-LI) components with retention times corresponding approximately to synthetic LomTK I and II and callitachykinins I and II. The LomTK antiserum was also used for immunocytochemical mapping of peptide in the nervous system and intestine of L. maderae. A large number of LomTK-LI interneurons were detected in the proto-, deuto- and tritocerebrum of the brain and in the suboesophaegeal ganglion. The immunoreactive neurons supply processes to most parts of the brain: the central body, protocerebral bridge, mushroom body calyces, antennal lobes, optic lobe and most regions of the non-glomerular neuropil. A few protocerebral neurons send LomTK-LI processes to the glandular lobe of the corpora cardiaca. In each of the thoracic ganglia there are six LomTK-LI interneurons and in each of the unfused abdominal ones there are two interneurons. The fused terminal ganglion contains some additional cell bodies in the posterior neuromers. LomTK-LI cell bodies were detected in the frontal ganglion and fibres were seen in this ganglion as well as in the hypocerebral ganglion. The frontal ganglion supplies LomTK-LI processes to the muscle layer of the pharynx. The muscle layer of the midgut is innervated by LomTK-LI fibres from the stomatogastric system (oesophageal nerve and associated ganglia). Additionally the midgut contains numerous LomTK-LI endocrine cells. A number of the pharyngeal dilator muscles were also found to be innervated by LomTK-LI fibres, probably derived from cell bodies in the suboesophageal ganglion. All the LomTK-LI neurons of the central nervous system appear to be interneurons, suggesting a neuromodulatory role of the endogenous tachykinins. The tachykinin-like peptides from peripheral ganglia may be involved in the control of foregut and midgut contractility and possibly the peptide of the endocrine cells in the midgut has additional actions related to intestinal function.

Multiple molecular forms of tachykinins in rat spinal cord: a study comparing different extraction methods

Various procedures for extraction at acid, neutral and alkaline pH were compared with regard to the yield of different tachykinins and tachykinin-like substances from rat spinal cord. Reverse phase high performance liquid chromatography (RP-HPLC) and radioimmunoassay with various C-terminally directed tachykinin antisera and a newly developed N-terminally directed substance P (SP)-antiserum (SPN 1) were used. Antiserum SPN 1 fully reacts with SP-analogues modified at the C-terminal end (SP free acid and SP-Gly-Lys) and also (77%) with SP(1-9) but not with C-terminal SP-fragments lacking 2 or more N-terminal amino acids. The highest levels of SP-like immunoreactivity (LI) and neurokinin A (NKA)-LI were measured after combined water and acetic acid extraction procedures. Also when measuring cholecystokinin-like immunoreactivity the highest level was obtained following this extraction procedure. RP-HPLC revealed a major component of SP-LI at the position of synthetic SP irrespectively of the extraction method and if the C- or N-terminally directed antiserum was used. Neutral water extracts contained a late eluting component detected with the C-terminally, but not with the N-terminally, directed antiserum. Acid and alkaline extracts, in contrast, contained components which could be detected with the N-terminally, but not with the C-terminally, directed SP-antiserum. Immunoreactive components eluting at the position of NKA and NKB were found in all types of extracts with NKA-, kassinin- and eledoisin-antisera. The NKB- and neuropeptide K (NPK)-components were more prominent in acid than in neutral and alkaline extracts. In conclusion, the present results indicate that rat spinal cord may contain molecular forms of tachykinin-like immunoreactivity in addition to those previously described and illustrate the importance of the choice of extraction method in immunochemical studies. Combined extraction in water and acetic acid appears to be a suitable method when the content of peptides with different chemical properties are to be measured in a tissue sample.

A study of tachykinin-immunoreactivity in the cat visual cortex

The localization of tachykinin-immunoreactivity in the cat visual cortex (area 17) was investigated using immunohistochemical methods. Strong laminar specificity was observed, with immunoreactivity highest in layer V, followed by layers I, VI, II and III, and the lowest density in layer IV. Most of the immunoreactive product was localized in neuronal processes. A few immunopositive cell bodies were also present. The immunopositive neurons were non-pyramidal, multipolar, or bipolar in shape, and mostly found in layer V. There were particularly dense immunopositive fibers and varicosities around somata in layer V. These may represent tachykinin-containing presynaptic terminals (boutons). The results provide anatomical evidence that tachykinins may primarily affect layer V neurons in the cat visual cortex.

Tachykinergic synaptic inputs to neurons of the medial preoptic region which project to the rat arcuate nucleus

Anatomical relationships between tachykinin-containing terminals and neurons of the medial preoptic area that innervate the arcuate nucleus were studied using silver staining of the retrograde tracer wheat germ agglutinin-apoperoxidase-gold (WGA-ApoHRP-gold) complex injected in the arcuate nucleus and pre-embedding immunocytochemistry for neurokinin A (NKA). At the histological level, retrogradely labeled cells not stained for NKA were seen to be surrounded by numerous NKA-immunopositive punctate profiles, in particular in the dorsal part of the medial preoptic area. At the ultrastructural level, retrogradely labeled cell bodies and dendritic profiles displayed highly electron-dense silver particle accumulations over the cytoplasm. The were seen in synaptic contact with one or several NKA-immunoreactive axon terminals containing small clear vesicles and dense-cored vesicles. Such synapses were either symmetrical or asymmetrical. The occurrence of synaptic contacts between tachykinin terminals and cells innervating the arcuate nucleus in the medial preoptic region provides a morphological support for a tachykinergic regulation of preoptic afferences to the arcuate nucleus. These results suggest that tachykinins are implicated in the indirect control of neuronal activity in the arcuate nucleus notably via the preoptic area. Consequently, tachykinins are potentially able to regulate indirectly numerous neuroendocrine events involving the tuberoinfundibular system.

Locustatachykinin immunoreactivity in the blowfly central nervous system and intestine

An antiserum raised against locustatachykinin I, one of four myotropic peptides that have been isolated from the locust brain and corpora cardiaca, was characterized by enzyme-linked immunosorbent assay (ELISA) and used for immunocytochemical detection of neurons and endocrine cells in the nervous system and intestine of the blowfly Calliphora vomitoria. The ELISA characterization indicated that the antiserum recognizes the common C-terminus sequence of the locustatachykinins I-III. Hence, the cross reaction with locustatachykinin IV is less, and in competitive ELISAs no cross reaction was detected with a series of vertebrate tachykinins tested. It was also shown that the antiserum recognized material in extracts of blowfly heads, as measured in ELISA. In high-performance liquid chromatography the extracted locustatachykinin-like immunoreactive (LomTK-LI) material eluted in two different ranges. A fairly large number of LomTK-LI neurons was detected in the blowfly brain and thoracicoabdominal ganglion. A total of about 160 LomTK-LI neurons was seen in the proto-, deuto-, and tritocerebrum and subesophageal ganglion. Immunoreactive processes from these neurons could be traced in many neuropil regions of the brain: superior and dorsomedian protocerebrum, optic tubercle, fan-shaped body and ventral bodies of the central complex, all the glomeruli of the antennal lobes, and tritocerebral and subesophageal neuropil. No immunoreactivity was seen in the mushroom bodies or the optic lobes. In the fused thoracicoabdominal ganglion, 46 LomTK-LI neurons could be resolved. The less evolved larval nervous system was also investigated to obtain additional information on the morphology and projections of immunoreactive neurons. In neither the larval nor the adult nervous systems could we identify any efferent or afferent immunoreactive axons or neurosecretory cells. The widespread distribution of LomTK-LI material in interneurons suggests an important role of the native peptide(s) as a neurotransmitter or neuromodulator within the central nervous system. Additionally a regulatory function in the intestine is indicated by the presence of immunoreactivity in endocrine cells of the midgut.

Bradykinin-induced airway inflammation. Contribution of sensory neuropeptides differs according to airway site

We examined the mechanisms of bradykinin-induced airway microvascular leakage in guinea pig airways by measuring extravasation of Evans blue dye. Animals were pretreated with propranolol (1 mg/kg, intravenous) and atropine (1 mg/kg, intravenous) to block the beta-adrenergic and muscarinic responses, respectively. Bradykinin (250 nmol) instillation into airways significantly increased the leakage of dye in the trachea, main bronchi, and intrapulmonary airways to the same degree. The bradykinin B2-receptor antagonist HOE140 (500 nmol/kg, intravenous) did not alter basal leakage but almost completely inhibited bradykinin-mediated leakage. By contrast, the neurokinin NK1 antagonist FK888 (10 mg/kg, intravenous) partially inhibited bradykinin-induced leakage in trachea (p < 0.01) and main bronchi (p < 0.01), but had no significant effect on intrapulmonary airways. Indomethacin (5 mg/kg, intravenous) had no effect on the plasma leakage after instilled bradykinin. We concluded that the airway inflammatory response to bradykinin administered directly into the airways is mediated by bradykinin B2 receptors and partially mediated by tachykinin release from sensory nerve terminals, whereas cyclooxygenase products have no important role in the response. In the central airways, the contribution of sensory neuropeptides to the bradykinin response is greater than that caused by direct stimulation of the B2 receptor on the endothelium at the postcapillary venule of the bronchial circulation. In contrast, in the peripheral airways, the contribution of direct B2-receptor stimulation on the airway vasculature is greater than that involving sensory neuropeptides.

Calretinin-immunoreactivity in trigeminal neurons innervating the nasal mucosa of the rat

Trigeminal primary neuronal cell bodies were labeled by retrograde transport of Fluoro-gold (FG) from the nasal mucosa of rats. The trigeminal ganglion containing the labeled cell bodies were processed for double stain for calretinin- and tachykinin-immunoreactivities (CR- and TK-irs). Except for a few contralateral cells, all the cells that innervated the nasal mucosa (NM cells) were confined to the ophthalmo-maxillary division of the trigeminal ganglion ipsilateral to the FG application. In the dorsal two-thirds of the ganglion, NM cells formed a cluster in the rostromedial part of ophthalmo-maxillary division (the rostromedial cluster). In the ventral third, the number of cells in the rostromedial cluster markedly decreased. Instead, numerous NM cells were found in the caudolateral part of the ophthalmo-maxillary division (the caudoventrolateral cluster). CR- and TK-irs were detected in 18% and 54% of overall population of NM cells, respectively. Virtually all of CR-immunoreactive (-ir) NM cells coexpressed TK. Although the proportion of TK-ir cells, irrespective of CR-ir, was similar for both clusters, CR-ir cells were more frequent in the caudoventrolateral cluster than in the rostromedial cluster. In the dorsal 1/3 of the ganglion where all the NM cells belonged to the rostromedial cluster, only 8.4% exhibited CR-ir. On the other hand, as much as 30.1% of NM cells expressed CR-ir in the ventral 1/3 where most NM cells were found in the caudoventrolateral cluster. Trigeminal cell bodies innervating the cornea and conjunctivum were located in the rostromedial part of the ophthalmo-maxillary division.(ABSTRACT TRUNCATED AT 250 WORDS)

Insect myotropic peptides: differential distribution of locustatachykinin- and leucokinin-like immunoreactive neurons in the locust brain

Locustatachykinin I is one of four closely related myotropic neuropeptides isolated from brain and corpora-cardiaca complexes of the locust Locusta migratoria. Antiserum was raised against locustatachykinin I for use in immunocytochemistry. It was found that the antiserum recognizes also locustatachykinin II and hence probably also the other two locustatachykinins due to their similarities in primary structure. Locustatachykinin-like immunoreactive (LomTK-LI) neurons were mapped in the brain of the locust, L. migratoria. A total of approximately 800 LomTK-LI neurons were found with cell bodies distributed in the proto-, deuto- and tritocerebrum, in the optic lobes and in the frontal ganglion. Processes of these neurons innervate most of the synaptic neuropils of the brain and optic lobes, as well as the frontal ganglion and hypocerebral ganglion. The widespread distribution of LomTK-LI neurons in the locust brain indicates an important role of the locustatachykinins in signal transfer or regulation thereof. As a comparison neurons were mapped with an antiserum against the cockroach myotropic peptide leucokinin I. This antiserum, which probably recognizes the native peptide locustakinin, labels a population of about 140 neurons distinct from the LomTK-LI neurons (no colocalized immunoreactivity). These neurons have cell bodies that are distributed in the proto- and tritocerebrum and in the optic lobe. The processes of the leucokinin-like immunoreactive (LK-LI) neurons do not invade as large areas in neuropil as the LomTK-LI neurons do and some neuropils, e.g. the mushroom bodies, totally lack innervation by LK-LI fibers. In some regions, however, the processes of the LomTK-LI and LK-LI neurons are superimposed: most notably in the central body and optic lobes. A functional relation between the two types of neuropeptide in the locust brain can, however, not be inferred from the present findings.

Androgen concentration by a sexually dimorphic population of tachykinin-immunoreactive neurons in the rat ventral premammillary nucleus

Strong connections with sexually dimorphic nuclei suggest that the ventral premammillary nucleus (PMv) may be involved in the mediation of reproductive behavior. Steroid autoradiography and immunohistochemistry were used to show that: (1) there is a sex difference in the numbers of PMv neurons that contain tachykinin peptides, (ii) dihydrotestosterone concentrating cells are densely distribution in the PMv and about a quarter of these also contain immunoreactive tachykinin and, (iii) size of the immunoreactive tachykinin population does not respond to alterations in levels of gonadal steroids in adulthood. Thus the PMv appears to make a contribution to the regulation of sexual behavior through androgen-concentrating, tachykinin-containing pathways that are anatomically distinct from estrogen receptive circuitry.

Activation of human neutrophils by tachykinins: effect on formyl-methionyl-leucyl-phenylalanine- and platelet-activating factor-stimulated superoxide anion production and antibody-dependent cell-mediated cytotoxicity

This study examines the contribution of tachykinins to the processes of inflammation. Neurokinin A (NKA), neurokinin B (NKB) and eledoisin (E) but not kassinin (K) have similar effects to substance P (SP) in priming neutrophils for increased superoxide anion (O2-) production in response to formyl-methionyl-leucyl-phenylalanine (FMLP). This similarity in activity may be due to the carboxy amino acid terminal end of these tachykinins being highly conserved. This was confirmed by demonstrating that SP fragment 7-11 (SP7-11) had the same priming effect as the whole molecule, whereas, the amino end fragment 1-4 (SP1-4) inhibited the response to FMLP. The priming effect of tachykinins was not confined to a single stimulus, such as FMLP, since NKA, NKB and SP also enhanced O2- production stimulated by platelet-activating factor (PAF), an important mediator of inflammation but a weak stimulus of O2- production on its own. In addition, all the tachykinins studied increased neutrophil antibody-dependent cell-mediated cytotoxicity (ADCC) towards opsonized target cells. In contrast to their effects on FMLP-induced O2- production, both SP fragments, SP1-4 and SP7-11, stimulated neutrophil ADCC and had a synergistic effect when used together.

Mass spectrometric analysis of opioid and tachykinin neuropeptides in non-secreting and ACTH-secreting human pituitary adenomas

In a study to test the hypothesis that defects in the metabolism of neuropeptides might be a contributing factor to human anterior pituitary tumor formation, the proenkephalin A, proopiomelanocortin (POMC), and tachykinin systems, which produce methionine enkephalin (ME), beta-endorphin (BE), and substance P (SP), respectively, were measured in patients who had a wide variety of pituitary tumors. Mass spectrometry was used to optimize the level of molecular specificity of the ME and BE analytical measurements, and radioimmunoassay was used to measure SP-like immunoreactivity (SP-li). Compared to data obtained from pituitaries from post-mortem controls, the non-secreting tumors contained a significantly lower amount of the POMC neuropeptide, BE. The lower ME level was not significant. However, two adrenocorticotrophic hormone (ACTH)-secreting tumors contained ME, BE, and SP-li amounts that were much higher than both the controls and nonsecreting tumors. These data suggest that a hypometabolism of the POMC precursor may be operating in non-secreting tumors, and that a hypermetabolism of the proenkephalin A, POMC, and tachykinin precursors may be operating in two ACTH-secreting tumors. These data demonstrate that mass spectrometry plays a critical role in the study of human pituitary tumors.

Immunochemical characterisation of tachykinin immunoreactivity in the nervous system of the garden snail, Helix aspersa

1. Circumoesophageal ganglia and foot muscle of the garden snail, Helix aspersa, were subjected to immunocytochemistry using antisera to the tachykinins, substance P (SP), neurokinin A (NKA), kassinin (KAS) and eledoisin (ELE). 2. Immunoreactivity in neuronal somata and fibres was detected only with the SP antiserum. 3. SP and NKA radioimmunoassays were performed on extracts of circumoesophageal ganglia. In common with immunocytochemistry, immunoreactivity was only detected with the SP antiserum. 4. Gel permeation chromatography of extracts resolved a single peak of immunoreactivity eluting slightly later than synthetic mammalian SP. Reverse-phase HPLC of immunoreactive fractions resolved two immunoreactive peptides representing oxidised and reduced forms of a single peptide. 5. These data suggest that the nervous system of H. aspersa contains a single tachykinin with C-terminal structural characteristics similar to mammalian SP.

Insect tachykinin-like peptide: distribution of leucokinin immunoreactive neurons in the cockroach and blowfly brains

Antisera were raised against leucokinin I, a cockroach myotropic neuropeptide with some resemblance to vertebrate tachykinins. These antisera were used for immunocytochemical mapping of neurons and neurosecretory cells in the brains of a cockroach and a blowfly species. The leucokinin immunoreactive cells are distinct from neurons that can be labeled with antisera against vertebrate type tachykinins. It is suggested that leucokinin-like peptides may have roles as neurohormones and neuromodulators in the insect nervous system.

Modulation of the immune response by tachykinins

Neuro-immunology is becoming an increasingly important discipline of immunology. This review has examined the immunomodulatory function of one group of neuropeptides, the TK, particularly SP and NKA. These peptides are localized in primary afferent nerves which have been shown to innervate several immune organs. In addition, binding sites for the TK have been demonstrated in thymus, spleen and lymph node. Several immune cell types also express neurokinin receptors including human circulating lymphocytes with binding to the Th/i class predominating, murine T and B cells, a human T lymphoblastoid cell line, human monocytes, rabbit polymorphonuclear leucocytes and guinea-pig macrophages. The apposition of nerves with immune cells and receptors for neuropeptides thus produces an environment for interaction between the nervous and immune systems. Studies in vitro and, more recently, in vivo have examined how the TK regulate immune cell responses. The TK stimulate proliferation of T cells, enhance mitogen-induced release of cytokines including IFN-gamma, TNF-alpha, IL-1 and IL-6 from mononuclear cells and macrophages, enhance immunoglobulin secretion and affect cellular chemotaxis and phagocytosis. Studies in vivo have shown a role for TK in lymphocyte recirculation of sheep lymph nodes, reversal of stress-induced thymic involution and Ig production in both rat and mouse. Many of these effects appear to be mediated via NK-2 type receptors. To date, most of the work has involved studies in vitro, but the results from these are now being validated by studies in vivo where both the immune system and neuropeptides are able to interact at many anatomical sites. The complexities of the immune and the nervous systems mean that only a small number of potential interactions has been examined. Future studies can be expected to amplify these observations, especially with respect to the understanding of inflammatory and immune diseases in humans.

Light microscopic immunoenzyme and electron microscopic immunogold cytochemistry reveal tachykinin immunoreactivity in Merkel cells of pig skin

Light microscopic (LM) immunoenzyme and electron microscopic (EM) immunogold cytochemistry were used to demonstrate the presence and subcellular distribution of tachykinin (substance P)-like immunoreactivity in Merkel cells of pig skin. Merkel cells of sinus hair follicles were strongly immunoreactive for tachykinins. In contrast, tachykinin-like immunoreactivity was absent from or very weak in epidermal Merkel cells while subepidermal and some intraepidermal nerve fibres were clearly immunopositive for tachykinins. Postembedding immunogold cytochemistry on the EM level revealed that tachykinin-like immunoreactivity was confined to the secretory granules in Merkel cells. Tachykinin immunoreactivity was clearly absent from the axon of the Merkel cell-axon complex. The selective presence of tachykinin immunoreactivity in secretory granules strongly suggests that tachykinins are synthesized in cutaneous Merkel cells, at least of pig. This is a further indication for the concept that the Merkel cell is a member of the diffuse neuroendocrine system. However, the functional role of tachykinins like substance P and neurokinin A and of other peptides present in Merkel cells remains enigmatic.

Tachykinin and calcitonin gene-related peptide immunoreactivities and mRNAs in the mammalian enteric nervous system and sensory ganglia

Tachykinins and CGRP label two distinct populations of neurons innervating the digestive system: intrinsic and extrinsic, afferents. The bulk of SP/tachykinin innervation originates from intrinsic neurons, even though a minor component of this innervation derives from afferent neurons, which are mostly located in dorsal root ganglia. Afferent SP/tachykinin fibers are mainly confined to a perivascular location and to the submocosa in the gut, but are distributed also to the hepatobiliary pathway and pancreas. On the contrary, the extrinsic CGRP-containing afferents form a major component of the sensory innervation of the alimentary tract, including the rich CGRP innervation of the esophagus, stomach, hepatobiliary tract, pancreas, and vasculature, as well as a portion of non-vascular fibers distributed to the intestinal wall. Tachykinin and CGRP immunoreactivities appear to be colocalized in a population of nerve fibers, which are likely to be extrinsic, afferent, since colocalization of these peptide immunoreactivities has not been reported in intrinsic neurons. The presence of SP/NKA-encoding transcripts in the enteric nervous system and sensory ganglia and the lack of hybridization signal with RNA probes complementary to NKB mRNA indicate that the PPT I gene, but not the PPT II gene, is transcribed in these structures. This observation, along with receptor binding sites and radioimmunoassay data, which have failed to detect NKB receptor binding sites or immunoreactivity (Eysselein et al., 1990; Maggio, 1988; Mantyh et al., 1988; 1989) in the intestine of several mammals, is consistent with a differential expression of the two PPT genes in the periphery and in the central nervous system (Brecha et al., 1989; Warden and Young, 1988). A differential expression of the tachykinin-encoding genes, the existence of multiple tachykinin receptor subtypes (Mantyh et al., 1988; 1989), and the findings that tachykinins can be differentiated on the basis of the potency of their activities (Galligan et al., 1987; Maggio, 1988), support the possibility that each tachykinin is expressed in separate, and perhaps functionally distinct neuronal systems. alpha- and beta-CGRP genes also are differentially expressed according to the neuronal populations: alpha-CGRP mRNA is the most prominent form in sensory ganglia, and beta-CGRP mRNA is the only form detected in enteric neurons (Mulderry et al., 1988; Sternini and Anderson, 1990). In addition, distinct distributions of mRNAs generated from the two CGRP genes have been reported in the central nervous system (Amara et al., 1985). The differential expression patterns of alpha- and beta-CGRP mRNAs are consistent with a differential regulation of the alpha- and beta-CGRP genes.(ABSTRACT TRUNCATED AT 400 WORDS)

A microcolumnar structure of monkey cerebral cortex revealed by immunocytochemical studies of double bouquet cell axons

Immunocytochemical methods were used to study 28,000 mol. wt calbindin and tachykinin immunoreactivity in the monkey cerebral cortex. Calbindin and tachykinin immunoreactivity give rise to a generally different pattern of staining of cell bodies and terminal-like puncta. However, the staining of long, vertically-oriented bundles of processes--identical to classical double bouquet cell axonal arborizations--is the most prominent feature of the pattern of both calbindin- and tachykinin-immunoreactive staining. These bundles form a widespread and regular columnar system descending from layer II to layers III-V. The bundles are most evident in layer III where, in tangential sections, they have a density of 7-15 bundles/10,000 microns 2 with a center-to-center spacing of 15-30 microns. The distribution of immunoreactive bundles through the cortex is not homogeneous; somatic sensory, auditory, and visual areas display a large number of calbindin-immunoreactive bundles while tachykinin-immunoreactive bundles are only numerous in the auditory areas and in area 18 of the visual cortex. In the motor cortex (area 4) few or no immunoreactive bundles are visualized with either antibody. Correlative light and electron microscope analysis of tachykinin immunoreactive bundles in the primary auditory cortex shows that the tachykinin-positive axons of the bundles form symmetrical synaptic contacts with dendritic shafts (57%) and spines (43%). Frequently, several immunoreactive boutons that arise from the same fiber are seen climbing along the surfaces of vertically-oriented, non-immunoreactive processes which include myelinated and unmyelinated axons and probably glial processes. The same ultrastructural features and a similar synaptic distribution were found in a previous study [DeFelipe et al. (1989) Brain Res. 503, 49-54] of calbindin-positive bundles in the somatic sensory cortex (areas 3a and 1). Despite the virtually identical morphological features of tachykinin- and calbindin-immunoreactive bundles, colocalization studies demonstrate little coexistence of the two antigens in somata and none in the axonal bundles of double bouquet cells. These data suggest that the double bouquet cell is a chemically heterogeneous, but ubiquitous morphological type of cortical interneuron, whose uniquely bundled axonal system, which is probably GABAergic, imposes a fundamental microcolumnar organization upon the cerebral cortex.

Identification of immunoreactive neuropeptide-gamma in human placenta: localization, secretion, and binding sites

The aim of the present study was to evaluate the possible presence of immunoreactive neuropeptide-gamma (irNPY) in human placenta. Acidic extracts of human placental tissue collected at term pregnancy contained high irNPY concentrations. The extracted irNPY eluted from HPLC with the same retention time as synthetic NPY. The presence of the peptide in placental cells was confirmed by immunohistochemical findings showing numerous cells of the cytotrophoblast layer positively staining for NPY. Further supporting local production of the peptide, primary cultures of human placental cells released irNPY into the culture medium and the addition of high K+ concentrations increased the release of the peptide. The finding of irNPY in human placenta stimulated the characterization of binding sites of NPY in the same tissue. Using autoradiographic techniques we showed specific binding of [125I]NPY in human placental tissue. The binding of [125I]NPY to the placental receptors was saturable and widely distributed within the placental tissue. Finally, the addition of NPY to the medium of cultured placental cells increased the release of immunoreactive CRF, suggesting a possible role of NPY in placental hormone production. The effect of NPY was dose related and augmented by the addition of norepinephrine (10 nM). These results showed that human placenta produces and secretes irNPY and that NPY receptors are present in placental tissue. Moreover, the evidence that NPY stimulated the release of immunoreactive CRF from cultured placental cells suggests an action of NPY in placental hormonogenesis.

Reduced numbers of calcitonin gene-related peptide-(CGRP-) and tachykinin-immunoreactive sensory neurones associated with greater enkephalin immunoreactivity in the dorsal horn of a mutant rat with hereditary sensory neuropathy

The mutilated foot rat is a mutant with autosomal recessive sensory neuropathy and frequent mutilation of the hindlimbs. Decreased numbers of dorsal root ganglion cells and diminished sensitivity to painful stimuli are characteristics of these animals. By use of immunocytochemistry, changes in the distributions of peptides involved in sensory and/or autonomic regulation, i.e., calcitonin gene-related peptide (CGRP), tachykinins, enkephalin and neuropeptide Y in spinal cord, dorsal root ganglia and skin of these animals, were studied. In comparison with normal litter-mate controls, the dorsal horn of mutilated foot rats contained substantially fewer CGRP- and tachykinin-immunoreactive fibres but more fibres immunoreactive for enkephalin. Many enkephalin-immunoreactive cell bodies were also found in the dorsal horn of the mutants, by contrast none were visible in control animals. Neuropeptide Y immunoreactivity was, however, unchanged in the spinal cord of the mutants. In the dorsal root ganglia of the mutants, the number of CGRP- or tachykinin-immunoreactive cells and their proportion to total neuronal numbers were significantly less in comparison with normal controls. The diameter range of CGRP- and tachykinin-immunoreactive cells shifted from small (15-25 microns) to medium size (25-45 microns) as revealed by frequency distribution histograms. The skin from the affected fore- and hindlimbs of the mutant rats, in keeping with fewer CGRP- and tachykinin-immunoreactive cells in the dorsal root ganglia, contained substantially less fibres immunoreactive for CGRP and tachykinins; a difference that was not seen in skin of unaffected areas (whiskers and snout). By contrast, neuropeptide Y-immunoreactive fibres showed a normal distribution around blood vessels and sweat glands of mutilated foot rats. The data suggest that diminished pain perception in the mutilated foot rat is related to loss of peptide-containing sensory neurones. Furthermore, the intraspinal increase of enkephalinergic neurons in the dorsal horn, concomitant with the decreased number of primary sensory neurones, may also play a contributory rôle in reducing pain thresholds.