Neuromedin L: a novel mammalian tachykinin identified in porcine spinal cord

Capsaicin induced release of multiple tachykinins (substance P, neurokinin A and eledoisin-like material) from guinea-pig spinal cord and ureter

The release of tachykinins from isolated slice preparations of the guinea-pig spinal cord and ureter was studied in vitro. Capsaicin (10 microM) caused release of substance P, neurokinin A and an eledoisin-like component from both the spinal cord and ureter. The release of tachykinins induced by capsaicin or potassium (60 mM) was calcium dependent. No detectable release of neurokinin B or neuropeptide K, an N-terminally extended form of neurokinin A, was induced by capsaicin. No detectable release of tachykinins could be demonstrated after exposure to agents which are known to activate C-fibre afferents, such as histamine, bradykinin, serotonin, prostaglandins E1, E2 or acetylcholine. Protein extravasation in the ureter, as determined by the Evans Blue extravasation technique was used as a functional correlate to the tachykinin release. Protein extravasation was induced in vivo by local intraluminal injections of capsaicin at several hundred-fold lower concentrations than those required to induce a detectable release of tachykinins in vitro. The difference may, however, partly depend on the experimental conditions and the detection limit of the tachykinin assay used. The protein extravasation response to capsaicin was absent after systemic capsaicin pretreatment, which causes a marked depletion of tachykinins in the ureter. In conclusion, capsaicin evokes release of several tachykinins from both central and peripheral endings of primary afferent neurons. The peptides released from sensory nerves in the periphery may induce effects such as protein extravasation and smooth muscle contraction.

Scyliorhinin I and II: two novel tachykinins from dogfish gut

Two peptides with tachykinin-like ability to contract longitudinal muscle from the guinea pig ileum were isolated from the intestine of the common dogfish, Scyliorhinus caniculus. The amino acid sequence of scyliorhinin I was established as Ala-Lys-Phe-Asp-Lys-Phe-Tyr-Gly-Leu-Met-NH2 and this peptide cross-reacted with antisera directed against the C-terminal region fo substance P. The amino acid sequence of scyliorhinin II was established as Ser-Pro-Ser-Asn-Ser-Lys-Cys-Pro-Asp-Gly-Pro-Asp-Cys-Phe-Val-Gly-Leu-Met- NH2 and this peptide cross-reacted with antisera directed against the C-terminal region of neurokinin A. The mammalian peptides substance P and neurokinin A were absent from the dogfish intestinal tissue.

Neuroleptic treatment induces region-specific changes in levels of neurokinin A and substance P in rat brain

The effects of 10 days treatment with haloperidol or sulpiride on tissue levels of neurokinin A-like and substance P-like immunoreactivity (NKA-LI and SP-LI) in various regions of rat brain were studied using reversed phase HPLC and radioimmunoassay. The most marked effect was a decrease in NKA-LI levels in n.accumbens after treatment with both sulpiride and haloperidol. Striatal NKA-LI and SP-LI levels were not clearly affected. NKA-LI levels but not SP-LI levels were decreased in substantia nigra by haloperidol. A low dose of sulpiride increased both NKA-LI and SP-LI levels in ventral tegmental area/n.interpeduncularis. In conclusion, region-specific changes of NKA-LI and SP-LI were seen after subchronic treatment with neuroleptics. It seems likely that NKA and SP are involved in the neuronal adaptation to the repeated treatment with neuroleptics.

Immunohistochemical and chromatographic studies of peptides with tachykinin-like immunoreactivity in the central nervous system of the lamprey

The distribution and chemical properties of compounds with tachykinin-like immunoreactivity (TK-LI) in the spinal cord and brain of lampreys (Lampetra fluviatilis and Ichthyomyzon unicuspis) were investigated by means of immunohistochemistry and various chromatographic methods combined with radioimmunoassay. The distribution of TK immunoreactive fibers in the lamprey spinal cord was investigated with 13 different TK antisera which gave positive staining in pilot experiments. The antisera were raised against substance P (SP) (n = 6), physalaemin (PHY) (n = 1), neurokinin A (NKA) (n = 2), kassinin (KAS) (n = 2) or eledoisin (ELE) (n = 2). Pre-incubation of these antisera with their corresponding TKs abolished or reduced the immunostaining. Four different patterns of distribution were found with the 13 antisera, and they did not seem to be related to the TKs against which the antisera were raised. The different patterns could be explained by assuming the presence of the three different TKs. Six different antisera, raised against SP (n = 2), KAS (n = 2) or ELE (n = 2), were used for radioimmunoassay. The TK-LI material eluted as several separate components in various chromatographic systems. The central nervous system (CNS) of the lamprey did not contain measurable amounts of SP, NKA, neurokinin B (NKB), KAS or ELE. The present data imply that the lamprey CNS contains at least three different TKs probably different from SP, PHY, NKA, NKB, KAS or ELE; these are possibly new, not earlier described TKs. The three hypothetical TKs differ in their distribution.

Tachykinin multiplicity in rat central nervous system as studied using antisera raised against substance P and neurokinin A

Antisera were raised in rabbits against the tachykinins neurokinin A (NKA) and substance P (SP). All NKA-antisera tested cross-reacted markedly with NKB, kassinin and eledoisin in radioimmunoassay (RIA), but virtually not with SP and physalaemin. Also when used for immunohistochemistry, one of the NKA-antisera was found to be virtually without cross-reactivity with SP. The most specific SP-antiserum did not cross-react with NKA but to some extent with NKB at the immunohistochemical level. Using these two antisera, the same distribution pattern of immunoreactivity was seen in both the rat substantia nigra and dorsal spinal cord. In neutral extracts of the substantia nigra, all NKA-antisera used for RIA detected a major component which eluted at the position of NKA in reverse phase high performance liquid chromatography, while no or only little immunoreactivity was detected at the position of NKB. A major component of substance P-like immunoreactivity (SPLI) co-eluting with SP and one or two minor SPLI-components were also detected in these extracts. An SP-antiserum, which cross-reacted markedly with physalaemin, detected an additional rather prominent component. In neutral water extracts of dorsal spinal cord the component detected with the NKA-antisera at the position of NKB, as well as one of the SPLI-components not eluting in the position of SP, were much more prominent than in the corresponding extracts of substantia nigra. In acetic acid extracts of both tissues, only one major SPLI-component co-eluting with SP could be detected, while only very small amounts of immunoreactivity eluting at the position of NKA and NKB (dorsal spinal cord only) could be detected using the NKA-antisera. The present results illustrate the importance of the extraction method used in immunochemical studies and demonstrate that the relative proportions of various tachykinins are markedly different in the rat substantia nigra and dorsal spinal cord.

The contractile activities of neurokinin A, B and related peptides on smooth muscles

The contractile activities of neurokinin A (NKA), neurokinin B (NKB) and related peptides on the guinea-pig ileum, rat vas deferens and rat duodenum were compared to the activity of substance P (SP). The potencies of NKA and NKB on the guinea-pig ileum (SP-P tissue) were nearly the same as that of SP. NKA was approximately 250-400 times more potent than SP on the rat vas deferens (EC50 = 59.5 nM; SP, EC50 = 1500 nM) and rat duodenum (EC50 = 1.8 nM; SP, EC50 = 674 nM) (SP-E tissues). NKB also showed high contracting activity on the rat duodenum (EC50 = 3.1 nM) but was 10 fold less active than NKA on the rat vas deferens. These results suggest that neurokinin peptides are possible endogenous agonists for the SP-E tissues. The contractile potency of NKA and NKB remained nearly complete after removal of N-terminal tripeptide portions, i.e., His-Lys-Thr and Asp-Met-His from the native peptides, respectively. However, the removal of the Asp residue from both NKA7 and NKB7 decreased activity until it was similar to that of SP.

Measurement and partial characterization of the multiple forms of neurokinin A-like immunoreactivity in carcinoid tumours

An antiserum raised against neurokinin A has been used to demonstrate storage and release of neurokinin A-like immunoreactivity by carcinoid tumours. The antiserum showed reactivity towards members of the tachykinin family of polypeptides in the order: neurokinin A greater than eledoisin greater than neurokinin B greater than kassinin greater than substance P greater than physalaemin but the magnitude of the cross-reactivity with substance P and physalaemin was less than 1% of that of neurokinin A. A sensitive (IC50 238 fmol/ml; minimum detectable concentration, 9 fmol/ml) radioimmunoassay was set up using this antiserum. Extracts of metastatic tumour tissue from four patients with a primary carcinoid tumour in the midgut contained both neurokinin A-like immunoreactivity (NKA-LI) and substance P-like immunoreactivity (SP-LI). The concentrations (pmol/g wet weight) of NKA-LI and SP-LI in the tumours were: patient A 210, 201; patient B 2276, 6849; patient C 1198, 834 and patient D 424, 379. Analysis of the tumour extracts by reverse phase HPLC indicated that the NKA-LI was heterogeneous. Under two different conditions of chromatography, one component was eluted with the same retention time as neurokinin A. Two further components were more hydrophobic than neurokinin A but were not eluted with the retention time of neurokinin B. Analysis of these components by gel filtration indicated a molecular weight in the 3000-4000 range suggesting that they may be related to neuropeptide K, an N-terminally extended form of neurokinin A. NKA-LI and SP-LI were undetectable in the plasma of patients A and D but were elevated in patient B (NKA-LI 1005 +/- 114; SP-LI 345 +/- 85 fmol/ml) and patient C (NKA-LI 80 +/- 31; SP-LI 21 +/- 13 fmol/ml).

Regional distribution of substance P, neurokinin alpha and neurokinin beta in rat spinal cord, nerve roots and dorsal root ganglia, and the effects of dorsal root section or spinal transection

The regional distribution of 3 mammalian tachykinins (substance P, neurokinin alpha and neurokinin beta) in the rat spinal cord and related structures was investigated using a method of radioimmunoassay combined with high performance liquid chromatography. Substance P and neurokinin alpha were found to be distributed in a very similar manner with fairly constant molar ratios i.e. ratios of substance P to neurokinin alpha were 3.69 in the dorsal root ganglia, 3.49 in the dorsal root and 3.09 in the dorsal horn of the cervical spinal cord. On the other hand, the distribution of neurokinin beta was different from other tachykinins; although concentrated in the dorsal horn, neurokinin beta in the dorsal root ganglia or in the dorsal roots was negligibly small in amount. When the cervical dorsal roots were sectioned unilaterally, substance P and neurokinin alpha were decreased in a parallel fashion in the dorsal horn, whereas neurokinin beta was not. In addition neurokinin alpha was selectively and significantly decreased in the dorsal horn of the intact side when compared to that in the unoperated control rat. Since the magnitude of a decrease of neurokinin alpha in molar basis was approximately the same as a decrease of substance P, these findings suggest that the neurokinin alpha and substance P-containing primary afferent fibres could project partly to the contralateral dorsal horn as well. When the thoracic spinal cord was transected, substance P (and neurokinin alpha) was decreased in the ventral part of the lumbar spinal cord, suggesting the presence of tachykinin(s)-containing descending fibres.(ABSTRACT TRUNCATED AT 250 WORDS)

Multiple tachykinins (neurokinin A, neuropeptide K and substance P) in capsaicin-sensitive sensory neurons in the guinea-pig

The occurrence of tachykinins in sensory neurons of the guinea-pig was studied by means of radioimmunoassay combined with ion-exchange and high-performance liquid chromatography as well as by immunohistochemistry. Antisera raised against kassinin (antiserum K12), neurokinin A (NKA) (antiserum NKA2) and substance P (SP) (antisera SP25 and SP2) were used. Antiserum K12 detected NKA, neuropeptide K (NPK) and a component eluting in the position of eledoisin (ELE) in extracts of the lung and ureter. Neurokinin B (NKB) was, however, not found. Neutral water extraction favored recovery of NKA and of the ELE-like component, while NPK was found only in acid extracts. The SP antisera detected two immunoreactive components of which the major form coeluted with synthetic SP. Capsaicin pretreatment depleted all these various forms of immunoreactivity in several peripheral organs including the ureter and lung. The immunoreactivity detected by antisera K12 or SP25 in radioimmunoassay had a similar regional distribution pattern in peripheral tissues. Immunohistochemical examination revealed that antiserum NKA2 stained the same spinal ganglion cells as the SP2 antiserum. The distribution of capsaicin-sensitive nerve fibers stained by these two antisera was also identical in peripheral organs such as the ureter, inferior mesenteric ganglion, heart and lung. It is concluded that multiple tachykinins, including SP, NKA, NPK and an ELE-like peptide, are present in capsaicin-sensitive sensory nerves in the guinea-pig. This finding can most likely be related to the origin of SP, NKA and NPK from the same precursor molecule, subsequent posttranslational tissue processing and axonal transport to terminal regions.

Tachykinin receptors in smooth muscles: a study with agonists (substance P, neurokinin A) and antagonists

Four preparations, sensitive to tachykinins, the guinea-pig urinary bladder, the rat duodenum, the hamster and dog urinary bladders have been investigated and compared with four other preparations described before: the guinea-pig ileum and trachea, the dog carotid artery and the rabbit mesenteric vein. On the basis of the order of potency of agonists, evaluated with substance P, physalaemin, eledoisin, kassinin and neurokinin A, the preparations can be separated into three groups, the guinea-pig urinary bladder and the dog carotid artery, in which substance P is the most potent and neurokinin A the weakest tachykinin, the rabbit mesenteric vein, the guinea-pig trachea and the rat duodenum, in which the opposite order is observed and the hamster and dog urinary bladders, in which kassinin is the most potent agonist. The guinea-pig ileum shows similar sensitivity to the five tachykinins. C-terminal partial sequences appear to be weaker than SP-(1-11) in three of the four new preparations, SP-(6-11) being first in the rat duodenum and slightly weaker than SP-(1-11) in the hamster and dog urinary bladders. Studies performed with antagonists or inhibitors of endogenous agents suggest that substance P and neurokinin A act directly on specific receptors. The effects of the two peptides are reduced by antagonists analogues of the sequence SP-(4-11). One of the antagonists, [D-Pro4,Lys6,D-Trp7,9,10, Phe11]SP-(4-11) has been shown to be competitive against substance P and neurokinin A in the guinea-pig ileum, the guinea-pig urinary bladder and the rat duodenum. This compound, shows definitely higher activity against neurokinin A and kassinin, compared to substance P in various preparations. [D-Tyr4,D-Trp7,9,Nle11]SP-(4-11) is the most potent tachykinin antagonist in the hamster and dog urinary bladders. In these preparations, the antagonists act also against substance P, but with lower affinity. These findings with antagonists support the indication, emerged from the order of potency of agonists, that tachykinins may act on two and possibly three different receptor types.

The metabolism of neuropeptides. Neurokinin A (substance K) is a substrate for endopeptidase-24.11 but not for peptidyl dipeptidase A (angiotensin-converting enzyme)

Both endopeptidase-24.11 and peptidyl dipeptidase A have previously been shown to hydrolyse the neuropeptide substance P. The structurally related peptide neurokinin A is also shown to be hydrolysed by pig kidney endopeptidase-24.11. The identified products indicated hydrolysis at two sites, Ser5-Phe6 and Gly8-Leu9, consistent with the known specificity of the enzyme. The pattern of hydrolysis of neurokinin A by synaptic membranes prepared from pig striatum was similar to that observed with purified endopeptidase-24.11, and hydrolysis was substantially abolished by the selective inhibitor phosphoramidon. Peptidyl dipeptidase A purified from pig kidney was shown to hydrolyse substance P but not neurokinin A. It is concluded that endopeptidase-24.11 has the general capacity to hydrolyse and inactivate the family of tachykinin peptides, including substance P and neurokinin A.

Current contributions of peptide synthesis to studies on brain-gut-skin triangle peptides

The usefulness of a strong acid, such as MSA or TFMSA/TFA, as a deprotecting reagent in peptide synthesis was examined. By synthesizing several structurally related brain-gut-skin triangle peptides, a number of advantageous features of the thioanisole-mediated deprotecting procedure were demonstrated. New amino acid derivatives, Arg(Mts), Trp(Mts) and Asp(OChp), were introduced to improve the synthetic methodology of complex peptides and the superior properties of Cys(Ad) were evaluated.

Calcium-dependent potassium-stimulated release of neurokinin A and neurokinin B from rat brain regions in vitro

The release of the tachykinins neurokinin A (NKA) and neurokinin B (NKB) from superfused slices of rat brain was studied. For radioimmunoassay of superfusates and tissue extracts an antiserum which reacts with both NKA and NKB but not with substance P was used. The released immunoreactive material, as well as the immunoreactive material in extracts of the tissue slices, was characterized by cation exchange chromatography and reversed phase high performance liquid chromatography (reversed phase-HPLC). Potassium (50 mM) evoked a calcium-dependent release of tachykinin-like immunoreactivity from slices of frontal cortex and striatum. Reversed phase-HPLC accumbens, striatum and the ventral part of the mesencephalon revealed two major immunoreactive components which co-eluted with synthetic NKA and NKB. Furthermore, the superfusates also contained three minor unidentified immunoreactive components.

Neuromedin U-8 and U-25: novel uterus stimulating and hypertensive peptides identified in porcine spinal cord

Two novel peptides eliciting a potent stimulant effect on the rat uterus smooth muscle have been purified and identified in porcine spinal cord. These peptides were designated as neuromedin U-8 (8 amino acids long) and U-25 (25 amino acids long) referring to their uterus stimulating activity. Sequence analyses and syntheses revealed that neuromedin U-8 is a novel octapeptide with a C-terminal amide structure, while U-25 contains the U-8 sequence at its C-terminus, preceded by paired Arg residues, implicating their biosynthetic relationship. Their potent uterus stimulating activity and hypertensive effect, as well as their unique C-terminal amide structure are indicative of their specialized physiological function.

Potentiation of tachykinin-induced plasma protein extravasation by calcitonin gene-related peptide

The effect of neuropeptides on plasma protein extravasation was investigated in the abdominal skin of rats. Substance P (SP), neurokinin A (NKA), and neurokinin B (NKB) induced extravasation with a threshold dose of about 1 pmol. Calcitonin gene-related peptide (CGRP) was ineffective up to 6 pmol. However, when CGRP was injected together with either of the tachykinins extravasation was potentiated. A dose of 6 pmol CGRP shifted the dose-response curve of SP to the left by a factor of about 100. The vasoconstrictor neuropeptide Y (NPY, 12 pmol) reduced the extravasation caused by SP or SP plus 6 pmol CGRP. These results indicate that all 3 tachykinins currently known to be present in sensory neurons induce plasma protein extravasation, i.e. mimic one sign of neurogenic inflammation. This activity is potentiated in the presence of CGRP which coexists with SP and NKA indicating that neurogenic inflammation may be augmented by these interactions.

In vivo and in vitro actions of mammalian tachykinins

Recently, two kassinin-like tachykinins have been isolated from mammalian nervous tissue. The potencies of these peptides, substance K (neurokinin alpha) and neuromedin K (neurokinin beta) were compared with those of substance P, eledoisin, and kassinin in various pharmacological systems in vivo and in vitro. In contracting the isolated guinea-pig ileum and rabbit jejunum the potencies of eledoisin, kassinin, substance K, and neuromedin K were 13-80% that of substance P. In the rat vas deferens substance K and neuromedin K potentiated the electrically induced contractions with potencies similar to those of eledoisin and kassinin; they were 46-236 times as potent as substance P. In stimulating salivation in the rat after intravenous injection, eledoisin, kassinin, and substance K were respectively 2.3, 1.3 and 0.33 times as potent as substance P. In contrast, neuromedin K exhibited negligible activity. Each peptide tested led to a short fall in blood pressure after intravenous injection in the rabbit, substance P being 12-250 times as potent as the other peptides. Substance P was 20 times as potent as substance K or neuromedin K in inducing vasodilatation in the rat hind paw in vivo. Of the peptides tested, only substance P (10 nmol/min) significantly increased the release of histamine from the rat isolated hindquarter preparation. The results are discussed with respect to several theories of tachykinin receptor heterogeneity.

The spinal cord contains multiple factors causing plasma protein extravasation in the skin

Nervous tissue was analyzed for possible mediators of neurogenic inflammation. Acid extracts of spinal cord or spinal roots contained activity causing plasma protein extravasation when injected into the rat abdominal skin. The activity was more than 1000-fold higher than could be attributed to the content of substance P (SP). It was not depleted from spinal cord after destruction of afferent C fibers by capsaicin and was resistant to proteolytic enzymes. The activity was clearly separated from SP or neurokinins by HPLC or gel filtration and was due to compounds of high polarity and low molecular weight. Further HPLC separated at least 6 peaks, two of which were found to contain adenosine and AMP, respectively, as active substances. The activity of these compounds and of the peaks was reduced by antihistaminics. A further compound identified was 5-HT. Thus, while several active non-peptidergic compounds were found, no clear evidence for a new mediator of neurogenic inflammation was obtained.

Identification of substance P precursor forms in human brain tissue

Substance P prohormones were identified in the caudate nucleus, hypothalamus, and substantia nigra of human brain. A polypeptide fraction of acidic brain extracts was fractionated on Sephadex G-50. The lyophilized fractions were sequentially treated with trypsin and a substance P-degrading enzyme with strong preference toward the Phe7-Phe8 and Phe8-Gly9 bonds. The released substance P(1-7) fragment was isolated by ion-exchange chromatography and quantitated by a specific radioimmunoassay. Confirmation of the structure of the isolated radioimmunoassay-active fragment was achieved by electrophoresis and HPLC. By using this enzymatic/radioimmunoassay procedure, two polypeptide fractions of apparent Mr 5000 and 15,000, respectively, were identified. The latter component was the major one of the two but was estimated to account for only about 5% of total substance P radioimmunoassay activity. Because it is of the size predicted from the nucleotide sequences of cDNA for substance P prohormones in bovine brain, the Mr 15,000 component may represent the full-length prohormone.

Chemical and immunochemical characterisation of substance P-like immunoreactivity and physalaemin-like immunoreactivity in a carcinoid tumour

Extracts of a carcinoid tumour, resected from the mid-portion of the ileum of a patient with no symptoms of endocrine disorder, were associated with a high concentration of substance P-like immunoreactivity. Using reverse-phase high performance liquid chromatography and antisera specifically directed against the C-terminal and N-terminal regions of substance P and against the N-terminal region of physalaemin, the following components were isolated and identified: substance P and its oxidised form, [pGlu5]substance P-(5-11) peptide and its oxidised form, and the oxidised form of physalaemin. The identity of tumour substance P with the undecapeptide was confirmed by amino acid analysis and high performance ion-exchange chromatography. In vitro incubation of tumour tissue from a lymph node metastasis from the same patient with [3H]leucine resulted in incorporation of radioactivity into newly synthesised substance P.

Stimulation of connective tissue cell growth by substance P and substance K

Connective tissue cells proliferate actively when cultured in the presence of serum. Platelet-derived growth factor (PDGF), a basic protein of relative molecular mass approximately 30,000, has been identified as the major serum mitogen for these cells; its main physiological/pathophysiological role may be to initiate wound healing in connection with tissue injury. However, growth of cultured cells is also influenced by several other factors, including epidermal growth factor, fibroblast growth factor, insulin and somatomedins. Furthermore, Rozengurt and Sinnett-Smith recently showed that bombesin, a neuroendocrine peptide isolated from frog skin, stimulates DNA synthesis and cell division in cultures of a specific subtype of 3T3 cells. Substance P and substance K (also known as neurokinin A or neuromedin L) are mammalian peptides belonging to the tachykinin family. Substance P has been studied extensively; it is distributed widely throughout the central and peripheral nervous system, including primary sensory neurones, and can be released in the periphery from axon collaterals of stimulated pain fibres and contribute to the inflammatory response. Substance K is a member of the tachykinin family isolated from mammalian spinal cord; Nawa et al. determined the primary structure of two types of substance P precursors, one of which contained a sequence homologous to substance K, as well as the sequence of substance P. We report here that substance P and substance K stimulate DNA synthesis in cultured arterial smooth muscle cells and human skin fibroblasts, and that this stimulation is inhibited by the substance P-antagonist spantide.

Neuropeptide K: isolation, structure and biological activities of a novel brain tachykinin

A 36 amino acid residue peptide, which contains a substance K sequence at its C-terminus has been isolated from porcine brain extracts. The primary structure of the peptide, designated neuropeptide K (NPK), was found to be: (sequence; see text) This N-terminally extended form of substance K is present in a high concentration in the brain. The peptide is highly biologically active with regard to gallbladder contraction, protein extravasation, hypotension and bronchial smooth muscle spasm and may act as an additional tachykinin neuromessenger.

Regional distribution and in vivo release of tachykinin-like immunoreactivities in rat brain: evidence for regional differences in relative proportions of tachykinins

The regional distribution of various forms of tachykinin-like immunoreactivity (TKLI) was studied in rat brain using radioimmunoassay. TKLI was measured with two different tachykinin-antisera (K12 and E7), which react with neurokinin A (NKA) and neurokinin B (NKB) but not with substance P (SP) and with a specific SP-antiserum. TKLI-K12 and TKLI-E7 were found to have similar regional distributions which were, however, significantly different from that of the substance P-like immunoreactivity (SPLI). Thus, the ratio of the tissue concentrations of TKLI-K12 or TKLI-E7 to that of SPLI was higher in frontal cortex and hippocampus and lower in pons/medulla oblongata than in the other regions studied. Cation-exchange chromatography of neutral water extracts of brain tissue revealed two major immunoreactive components of TKLI-K12 and TKLI-E7, one of which co-eluted with synthetic NKB while the other appeared in the same region as synthetic NKA. The relative quantities of these components varied depending on the brain region studied. No TKLI-K12 or TKLI-E7 co-eluted with synthetic SP. Almost all of the SPLI in acetic acid or water extracts of brain tissue eluted as a single chromatographic component in the same position as synthetic SP. Potassium-stimulated in vivo release of TKLI-K12, TKLI-E7 and SPLI in striatum of rat brain could be demonstrated using intracerebral dialysis. The present results imply that tachykinins, which may serve as neurotransmitters or neuromodulators, are present in different proportions in different regions of rat brain.

Substance P antagonists showing some selectivity for different receptor types

Five antagonists have been used against substance P (SP) and neurokinin A (NA) in isolated smooth muscle preparations containing either SP-P (the guinea pig ileum (G.P.I.), the dog carotid artery (D.C.A.) or SP-E receptors (the rat duodenum (R.D.), the dog (D.U.B.) and hamster urinary bladders (H.U.B.]. [D-Pro4,D-Trp7,9,10, Phe11]SP-(4-11) was found to be selective for SP-P receptors, since it showed high affinity both against SP and NA, on the G.P.I. and D.C.A., while it was found to be inactive on some SP-E receptor systems (D.U.B., H.U.B.) and very weak in others (R.D.). Two octapeptide antagonists, modified in position 6, [D-Pro4,Ala6,D-Trp7,9,10,Phe11]SP-(4-11) and [D-Pro4,Lys6,D-Trp7,9,10,Phe11]SP-(4-11) showed some selectivity for SP-E receptors since they acted as full agonists on one SP-P preparation (the D.C.A.) and the first compound contracted also the G.P.I. In addition to being pure antagonists on the D.U.B., H.U.B. and on the R.D., the two octapeptides showed a higher potency against the SP-E stimulant NA, compared to SP, in the R.D. Two undecapeptide antagonists were active against SP and NA on both SP-P and SP-E receptor preparations and therefore were less discriminative than the octapeptides. They were however more active against NA on the R.D., similar to the octapeptides modified in position 6. It is concluded that: (a) both agonists and antagonists appear to be useful for the characterization of tachykinins receptors; (b) either the whole N-terminal portion of SP or a shorter sequence, modified in position 6, increase the antagonist affinity against NA in the SP-E receptor system of the rat duodenum.

Characterization of substance P-like immunoreactivity in submammalian species by high performance liquid chromatography

Substance P-like immunoreactivity (SP-LI) as measured by RIA was found to be present in a variety of submammalian species and invertebrates. We analyzed this SP-LI in extracts from submammalian species by high performance liquid chromatography. The following species were investigated for the presence of SP-LI (RIA) which was further characterized by subsequent HPLC (investigated areas in parentheses): Hagfish (brain plus spinal cord), (brain, intestine, skin), frog (brain, intestine), turtle (brain, intestine), lizard (brain, intestine, skin) and mouse (spinal cord). RIA alone was performed in extracts from branchiostoma and cricket. The concentrations of SP-LI in brain, spinal cord and intestine of different submammalian species except branchiostoma brain and intestine and turtle brain, were in a similar range (2.1-5.3 fmol/mg in the brain, 0.2-2.0 fmol/mg in the spinal cord, 0.3-4.2 fmol/mg in the intestine). In the turtle brain, extremely high SP-LI concentrations (210 fmol/mg) were found, whereas brain and intestine of branchiostoma contained very little SP-LI (0.1 fmol/mg). In the skin of different species, SP-LI concentrations varied from 0.04 fmol/mg (trout) to 2.0 fmol/mg (lizard). In the cricket, high SP-LI concentrations were found in the cerebral ganglion (15 fmol/mg protein) and in the subesophageal ganglion (27 fmol/mg protein). HPLC analysis of extracts showed that all tissues investigated contained a substance which co-eluted with synthetic SP, and in most tissues a peak was present which co-eluted with SP sulfoxide. Only in mouse spinal cord, trout brain and hagfish brain were these the only peaks.(ABSTRACT TRUNCATED AT 250 WORDS)

Evolutionary relationship between nonmammalian and mammalian peptides

An hypothesis has been developed to rationalize the evolution of regulatory peptides. In order to account for critical relationships involving peptide regulators, their receptors, and peptide processing enzymes, the following generalizations will be supported: (1) peptides arose from protein precursors as proteolytic digestion by-products and acquired hormonal status during the course of natural selection; (2) initially, peptides served primarily nutritional roles, thereby permitting increased growth rates and reproductive advantages for recipient cells; (3) specific peptide sequences were conserved during evolution and were associated with biological activities which were essential for survival of species as divergent as unicellular organisms, amphibians, and mammals; and (4) regulatory peptides probably arose simultaneously with their membrane-oriented, macromolecular receptor sites. In support of the conservation of sequence information or function, or both, during evolutionary development, evidence has been obtained to indicate that peptide sequences which occur in two classes of amphibian peptides appear to be extensively conserved in mammals. Studies with an antiserum directed against the N-terminal sequence of amphibian physalaemin have permitted the recognition of a mammalian octapeptide which exhibits 80% homology with residues 1-5 in that region. Another study with an antiserum directed against the midregion (sequence 5-8) of amphibian bombesin has indicated the existence of milk peptides which mimic bombesin in several pharmacological bioassays. These studies indicate that radioimmunoassays can be powerful tools in facilitating recognition of peptide sequences conserved throughout evolution.

Substance K and substance P differentially modulate mesolimbic and mesocortical systems

The newly discovered peptide substance K (SK) is an aliphatic tachykinin structurally related to the aromatic tachykinin substance P (SP). Immunohistochemical examination showed a close association between SK afferents and dopamine (DA) cell bodies. Examination of the possible role of SK in modulating midbrain DA systems revealed that SP, but not SK, is associated with the stress response of the mesocortical system. Ventral tegmental area injections of SK effected locomotor hyperactivity, a mesolimbic-mediated behavior. Ventral tegmental injections of SP, but not SK, activated DA metabolism in the prefrontal cortex, while SK injections altered DA metabolism in the nucleus accumbens, but not the cortical site. These data suggest that SK and SP may differentially modulate the mesolimbic and mesocortical systems.

Neuromedins: novel smooth-muscle stimulating peptides identified in porcine spinal cord

Two novel peptides, neuromedin U-8 and U-25, eliciting a potent uterus stimulating activity, have been purified and identified in porcine spinal cord. Sequence analyses and syntheses revealed that neuromedin U-8 is a novel octapeptide with a C-terminal amide structure, while U-25 contains the U-8 sequence at its C-terminus, preceded by paired Arg residues, implicating their biosynthetic relationship. Their potent uterus stimulating activity and hypertensive effect, as well as their unique C-terminal amide structure are indicative of their specialized physiological function. In addition, by utilizing a specific radioimmunoassay for neuromedin B that is a bombesin-like peptide identified in porcine spinal cord, we have isolated two novel "big" neuromedin B, designated neuromedin B-32 and B-30, from pig brain and spinal cord, indicative of their biosynthetic relationship. Nine neuromedins (B, B-30, B-32, C, K, L, N, U-8 and U-25) thus far identified in porcine spinal cord as the smooth-muscle stimulating peptides, are classified into four families; B-(bombesin-like), K-(kassinine-like), N-(neurotensin-like) and U-groups.

Neurokinin A-like immunoreactivity in rat primary sensory neurons; coexistence with substance P

Rat spinal cord, dorsal root ganglia and skin were investigated employing immunohistochemical technique with specific antisera to neurokinin A and substance P. Neurokinin A-like immunoreactivity was detected in the spinal dorsal horn and skin with a similar distribution pattern as that of substance P-like immunoreactivity. After dorsal root transection a parallel decrease of neurokinin A and substance P-like immunoreactivity was observed in the dorsal horn. Using colchicine pretreatment a population of neurokinin A positive cell bodies was seen in the dorsal root ganglia, and by comparison of consecutive sections of the same cells stained for substance P it was revealed that these neurons also display substance P-like immunoreactivity. However, substance P-, but not neurokinin A-, immunoreactive cells were also observed. It is concluded that neurokinin A- and substance P-like immunoreactivity coexist in a population of rat primary sensory neurons.

Distribution and localization of regulatory peptides

A new group of modulatory substances present in both endocrine cells and central and peripheral nerves has been described in the past few years. These substances are biochemically recognized as peptides and their actions affect many bodily functions. They are now widely known as regulatory peptides. The development of new immunocytochemical techniques, closely allied to radioimmunoassay, has disclosed that the regulatory peptides are present either in cells or in nerves, in almost every tissue of the body. The presence of peptides (the classical hormones) in endocrine cells was already known at the beginning of the century, but the presence of similar substances in nerve fibers, where they probably act as neurotransmitters, is a recent and revolutionary discovery. More than 30 peptides (neuropeptides) have been found to be present in nerves, to which the term "peptidergic" has been applied, although it is now known that in certain cases a neuropeptide can be present in the same nerves as a classical neurotransmitter, for example acetylcholine with VIP, or noradrenaline with NPY. Little is known about the physiological role of these neuropeptides. It is not yet fully accepted that they act as neurotransmitters although there is strong evidence for this, particularly in the case of substance P and VIP. The investigation of the regulatory peptides is now in an initial phase. The involvement of new disciplines, such as molecular biology, in this field is producing new and very exciting discoveries, including the isolation of novel peptides and precursors, the study of which will further contribute to the understanding of the basic control mechanisms.

Regional distribution of neuromedin K and neuromedin L in rat brain and spinal cord

Neuromedin K and neuromedin L are novel mammalian tachykinins isolated from porcine spinal cord. We have developed a highly sensitive radioimmunoassay for neuromedin K. Since the radioimmunoassay for neuromedin K has significant crossreactivity with neuromedin L and substance P, we can simultaneously determine the tissue concentrations of neuromedin K, neuromedin L and substance P after separation of the tissue extracts by reverse phase high performance liquid chromatography. Substance P is found to be the most abundant mammalian tachykinin in every brain region. The ratio of the concentration of substance P to neuromedin K is small in cerebral cortex and large in medulla-pons, while that of substance P to neuromedin L is rather constant in a range of 2.0-2.5. In spinal cord, dorsal half contains more neuromedin K and L than ventral half as is the case with substance P. These results indicate that both neuromedin K and L are endogenous mammalian tachykinins with specific physiological functions.

Rat sensory ganglia incorporate radiolabelled amino acids into substance K (neurokinin alpha) in vitro

Isolated rat dorsal root ganglia incorporated [3H]valine, [3H]serine, [3H]phenylalanine and [3H]histidine into a peptide which co-eluted with authentic substance K (neurokinin alpha) on reverse-phase HPLC. Confirmation of the identity of this peptide with substance K was obtained by demonstrating that the sulphoxide derivative of the peptide co-eluted with substance K sulphoxide. Substance P and substance K were synthesised in the ratio 2.6:1. The implications of these results for the co-synthesis of substance P and substance K in sensory neurones are discussed.

Neuromedin N: A novel neurotensin-like peptide identified in porcine spinal cord

A novel neurotensin-like peptide, designated neuromedin N, has been isolated from porcine spinal cord by using a bioassay for a stimulant effect on guinea pig ileum. By microsequencing, the amino acid sequence of the peptide has been determined to be Lys-Ile-Pro-Tyr-Ile-Leu, which is found to be quite homologous to the COOH-terminal sequence of neurotensin. This structure has been confirmed by synthesis. Neuromedin N exhibits a contractile activity on guinea pig ileum and induces a hypotensive response in the rat similar to that with neurotensin. These findings suggest that neuromedin N may be a new neuromediator or hormone with a specific spectrum of biological activity.