Biomedical subjects

C A Maggi

Publications and source records attributed to C A Maggi.

At least 271 records · Page 15Linked to original sources

PubMed1992

NK-1, but not NK-2, tachykinin receptors mediate plasma extravasation induced by antidromic C-fiber stimulation in rat hindpaw: demonstrated with the NK-1 antagonist CP-96,345 and the NK-2 antagonist Men 10207.

The effects of intradermal injection of CP-96,345 and Men 10207, selective antagonists for NK-1 and NK-2 tachykinin receptors, respectively, on the extravasation of plasma protein induced by antidromic stimulation of unmyelinated sensory fibers in the sciatic nerve was studied in rat hindpaw. Activation of unmyelinated fibers by antidromic sciatic nerve stimulation (1 Hz, 5 min) consistently evoked a localized plasma extravasation of Evans blue on the skin area of the hindpaw innervated by the sciatic nerve, which was not inhibited by intradermal injection of saline or Men 10207 (9 and 35 nmol). In contrast, CP-96,345 (3 and 9 nmol, but not 1 nmol), injected intradermally 15 min prior to nerve stimulation dose-dependently inhibited this response. Plasma extravasation induced by intravenously injected substance P was also inhibited by CP-96,345. Since CP-96,345 is a highly selective antagonist for NK-1 tachykinin receptors, it is suggested that the plasma extravasation induced by antidromic C-fiber stimulation and by systemically applied tachykinins is mediated by NK-1 tachykinin receptors.

Animals↗

PubMed1992

Cyclophosphamide cystitis in rats: involvement of capsaicin-sensitive primary afferents.

The involvement of capsaicin-sensitive primary afferent neurons in cyclophosphamide (CYP)-induced cystitis has been investigated in rats. CYP (150 mg/kg) was administered 48 h before testing in both vehicle- and capsaicin- (50 mg/kg s.c., 4 days before) treated rats. Some experiments were also performed 96 h after bilateral removal of pelvic ganglia to produce bladder denervation. CYP administration produced a marked detrusor hyperreflexia which was abolished by capsaicin pretreatment, demonstrating that it is mediated through stimulation of capsaicin-sensitive afferent neurons. CYP administration was followed by a marked increase in bladder weight and plasma protein extravasation (measured by the Evans blue leakage technique). The latter effect was largely prevented by ganglionectomy but was aggravated by capsaicin pretreatment. The effect of capsaicin was suppressed by ganglionectomy. Isolated strips of detrusor muscle from CYP-treated animals developed less tension in response to various stimuli as compared to strips from vehicle-treated animals; however, when contractile responses were expressed as percentage of an internal standard (carbachol-induced contraction) no difference was evident between the two groups. The bladder content of calcitonin gene-related peptide, used as a marker of the bladder afferent fibres that are capsaicin-sensitive in adult rats, was slightly reduced as compared to controls, but the difference can be accounted for by the increased bladder weight. We conclude that CYP-induced cystitis is not accompanied by a toxic effect on bladder nerves and that the decrease in bladder capacity is entirely mediated through stimulation of capsaicin-sensitive afferent fibres, presumably linked to the formation of the irritant metabolite of CYP, acrolein.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

Activity of peptide and non-peptide antagonists at peripheral NK1 receptors.

We investigated the affinity of several tachykinin antagonists reportedly selective for NK1 receptors at various tachykinin receptors and NK2 receptors subtypes. The four antagonists tested were: L 668,169, Spantide II, Ac-Thr-DTrp(for)-Phe-NMeBzl (FR 113680) and the novel nonpeptide antagonist (+/-)-CP-96,345. The four antagonists were found to be effective against NK1 receptor-mediated responses in the guinea-pig ileum with the following rank order of potency (pKB values in parentheses): (+/-)-CP-96,345 (8.11) greater than Spantide II (7.08) greater than FR 113680 (6.61) greater than or equal to L 558,169 (6.44). (+/-)-CP-96,345, Spantide II and FR 113680 were distinctly more potent at NK1 receptors than at NK2 receptors (NK2A in the rabbit pulmonary artery, NK2B in the hamster trachea). L 668,169 antagonized neurokinin A-induced contractions in the hamster trachea with an affinity similar (pKB value 6.16) to that found in the guinea-pig ileum for NK1 receptors (pKB value 6.44). All antagonists were inactive at NK3 receptors of the rat portal vein. In a second series of experiments, the affinities of test antagonists for NK1 receptors in the guinea-pig ileum were compared to those for NK1 receptors in the guinea-pig vas deferens, the rabbit jugular vein and the rat urinary bladder. For each antagonist, the affinity measured in the guinea-pig vas deferens and the rabbit jugular vein was comparable to that found in the guinea-pig ileum. In the rat urinary bladder, (+/-)-CP-96,345 was about 100 times less potent in blocking NK1 receptor-mediated contractions than in the guinea-pig ileum.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗

PubMed1992

Cysteamine induced-duodenal ulcers are associated with a selective depletion in gastric and duodenal calcitonin gene-related peptide-like immunoreactivity in rats.

We have measured the endogenous levels of gastric and duodenal calcitonin gene-related peptide (CGRP)-, neurokinin A (NKA)-, galanin-vasoactive intestinal polypeptide (VIP)- and neuropeptide Y (NPY)-like immunoreactivity (li) in relation to cysteamine-induced gastric lesions and duodenal ulcers in rats. CGRP-li but not NKA-, galanin-, VIP- or NPY-li was decreased in gastric and duodenal samples following a single ulcerogenic dose of cysteamine (900 mg/kg p.o.). Temporal relationships of this phenomenon showed that CGRP-li was selectively decreased (stomach 45%, duodenum 68% as compared to controls, respectively after 24 h) concomitantly to the formation of acute gastric lesions and duodenal ulcers. Animals bearing healed ulcers 12 days after cysteamine, had gastroduodenal CGRP-li similar to control values. Pretreatment with the selective sensory neurotoxin capsaicin decreased gastroduodenal CGRP-li but not NKA-, galanin-, VIP- or NPY-li, showing that CGRP might be considered a marker of the afferent innervation of the gastroduodenal tract. The residual gastroduodenal CGRP-li levels in capsaicin-pretreated animals were not decreased by cysteamine administration, indicating that the effect of cysteamine is restricted to a peptide pool of primary afferent origin. Duodenal CGRP-li is selectively decreased by the duodenal ulcerogen cysteamine during the acute phase of ulcers formation and might be among the local mediators which afford protection against the ulcerogenic stimuli.

Animals↗

PubMed1992

Effects of selective tachykinin receptor antagonists on capsaicin- and tachykinin-induced bronchospasm in anaesthetized guinea-pigs.

Bronchospasm induced by i.v. injection of equieffective doses of acetylcholine, capsaicin or selective tachykinin receptor agonists ([Sar9]SP sulfone or [beta-Ala8]neurokinin A (NKA-4-10)) (for NK1 and NK2 receptors, respectively) was studied in anaesthetized guinea-pigs. The NK1 and NK2 receptor antagonists, (+/-)-CP96,345 (3 mumol/kg i.v.) and MEN 10,376 (3 mumol/kg i.v.), selectively abolished the bronchoconstriction induced by the respective agonist, showing that both NK1 and NK2 receptors mediate bronchoconstriction in guinea-pig airways and that they are activated independently. Capsaicin-induced bronchospasm was inhibited by atropine (1.5 mumol/kg i.v.) and MEN 10,376 (3 mumol/kg i.v.), but unaffected by (+/-)-CP96,345 (3 mumol/kg i.v.). Hexamethonium (79 mumol/kg i.v.), propranolol (17 mumol/kg i.v.) and physostigmine (0.9 mumol/kg i.v.) enhanced the airway constriction induced by acetylcholine, capsaicin, [Sar9]SP sulfone or [beta-Ala8]NKA-(4-10) while guanethidine (67 mumol/kg s.c. for two days) increased only bronchoconstriction induced by capsaicin or the selective NK2 receptor agonist. In hexamethonium-treated animals, MEN 10,376 still abolished the increase in insufflation pressure induced by [beta-Ala8]NKA-(4-10) and reduced the increase elicited by capsaicin. In summary, in anaesthetized guinea pig i.v. capsaicin-induced bronchospasm through activation of postjunctional NK2 (but not NK1) receptors along with activation of cholinergic pathways. This motor response is moderated by the simultaneous stimulation of a sympathetic bronchodilating mechanism(s), possibly through activation of NK2 receptors localized in sympathetic ganglia.

Anesthesia↗

PubMed1992

Veratridine evokes release of calcitonin gene-related peptide from capsaicin-sensitive nerves of rat urinary bladder.

The effect of superfusion with veratridine on the release of calcitonin gene-related peptide-like immunoreactivity (CGRP-LI) was studied in slices of rat urinary bladder. Exposure to veratridine (1-200 microM) produced a concentration-related release of CGRP-LI. Veratridine (50 microM)-evoked CGRP-LI release was abolished in slices pre-exposed to capsaicin (10 microM for 40 min) or superfused in a Ca(2+)-free medium containing 1 mM EDTA. After exposure to veratridine (50 microM for 40 min), capsaicin (10 microM) was still able to release CGRP-LI. CGRP-LI release evoked by veratridine (50 microM) was inhibited by about 60% by tetrodotoxin (0.3 microM), attenuated (30%) by nifedipine (1 microM), and not affected by omega-conotoxin (0.1 microM). The capsaicin antagonist ruthenium red (10 microM) did not affect veratridine (50 microM)-evoked CGRP-LI release. The present results indicate that depolarization by veratridine induces CGRP-LI release from capsaicin-sensitive nerve fibres, an effect that is entirely dependent on extracellular Ca2+. The Ca2+ influx that promotes CGRP-LI release is mediated mostly by nifedipine-, omega-conotoxin- and ruthenium red-insensitive channels.

Animals↗

PubMed1992

Release of calcitonin gene-related peptide like-immunoreactivity induced by electrical field stimulation from rat spinal afferents is mediated by conotoxin-sensitive calcium channels.

Electrical field stimulation (EFS, 10 V, 50 mA/cm2, 5-50 Hz, 1 ms pulse duration, 10 s train every 20 s for 5 min) produced a rapid and reproducible outflow of calcitonin gene-related peptide like-immunoreactivity (CGRP-LI) from superfused slices from the dorsal half of the rat spinal cord which is abolished by tetrodotoxin (TTX, 0.3 microM), in vitro capsaicin desensitization (10 microM for 30 min) and in Ca-free medium. The response was unaffected by ruthenium red (10 microM), indomethacin (10 microM) and nifedipine (1 microM) while it was abolished by omega-conotoxin (omega-CTX, 0.1 microM) and, in a naloxone-sensitive manner, by morphine (3 microM). Since CGRP release from capsaicin-sensitive afferents evoked by EFS in rat peripheral tissues is conotoxin-resistant, these findings provide direct evidence for a qualitative difference between central and peripheral endings of capsaicin-sensitive primary afferents in the mechanisms regulating transmitter release in the same species.

Animals↗

PubMed1992

Demonstration of a neurokinin A receptor subtype in transfected fibroblasts.

In competitive radioligand binding assays, the NK2 receptor antagonists [Tyr5,D-Trp6,8,9,Arg10]NKA(4-10) (MEN 10207) and [Tyr5,D-Trp6,8,9,Arg10]NKA(3-10) (MEN 10208) had high and low affinity, respectively, in bovine stomach membranes and SKLKB82#3 cells, a murine fibroblast cell line transfected with a cDNA encoding for the bovine NK2 receptor. These antagonists also had different affinities when inhibiting neurokinin A-induced polyphosphoinositide hydrolysis in SKLKB82#3 murine fibroblasts. Thus, the de novo protein expressed by the SKLKB82#3 murine fibroblasts may represent a distinct NK2 receptor subtype.

Animals↗

PubMed1992

Heterogeneity of NK-2 tachykinin receptors in hamster and rabbit smooth muscles.

The possible existence of NK-2 receptor subtypes in peripheral smooth muscle preparations from rabbit and hamster was investigated by studying the effect of neurokinin A, the selective NK-2 receptor agonist [beta Ala8] neurokinin A (4-10), the selective NK-2 tachykinin receptor antagonists, MEN 10,376, L 659,877 and R 396, and the pseudopeptide derivative of neurokinin A (4-10), MDL 28,564. All experiments were performed in the presence of peptidase inhibitors (captopril, bestatin and thiorphan, 1 microM each). Both neurokinin A and [beta Ala8] neurokinin A (4-10) produced concentration-dependent contractions of the rabbit isolated bronchus and hamster isolated stomach and colon, as well as enhancement of the nerve-mediated twitches of rabbit isolated vas deferens (pars prostatica). MEN 10,376, L 659,877 and R 396 antagonized the effect of the NK-2 receptor selective agonist in all four tissues under study, although marked differences in antagonist potency were evident for the three antagonists. Thus MEN 10,376 was distinctly more potent (about 100 times) in rabbit than in hamster preparations while L 659,877 and R 396 were more potent in hamster than rabbit preparations. MDL 28,564 showed a distinct agonist character in rabbit preparations while it was virtually inactive in hamster preparations, where it antagonized the effect of the NK-2 receptor selective agonist.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗

PubMed1992

Tachykinin antagonists inhibit nerve-mediated contractions in the circular muscle of the human ileum. Involvement of neurokinin-2 receptors.

The effects of some newly developed tachykinin antagonists that are selective for the neurokinin (NK)-1 (L 668,169) or the NK-2 (MEN 10,207, L 659,877 and R 396) tachykinin receptor on the cholinergic and noncholinergic contraction and on the nonadrenergic noncholinergic relaxation produced by electrical field stimulation (50 Hz) were investigated in mucosa-free circular strips of the human ileum. The strips were contracted by substance P and neurokinin A as well as by selective NK-2-receptor ligands, [beta Ala8]neurokinin A(4-10), and MDL 28,564, the latter peptide being capable of discriminating between NK-2-receptor subtypes. The selectivity of the antagonists for NK-1 or NK-2 receptors was confirmed in pharmacological experiments using substance P, neurokinin A, and [beta Ala8]neurokinin A(4-10) as stimulants. Among the NK-2-selective antagonists, MEN 10,207 displayed the highest affinity, followed by L 659,877 and R 396. The antagonists MEN 10,207 and L 659,877 inhibited the noncholinergic contraction to electrical stimulation in a concentration-dependent manner; L 668,169 and R 396 were poorly effective. Thus the potency of antagonists toward the noncholinergic response closely paralleled their rank order of potency at NK-2 receptors. The cholinergic contraction and nonadrenergic noncholinergic relaxation were not inhibited by the antagonists. Both substance P- and neurokinin A-like immunoreactivities were detected in extracts of the human ileum, and the identity of the corresponding peptides was confirmed by reverse-phase high-performance liquid chromatography. It was concluded that in addition to NK-1 receptors, the circular muscle of the human ileum also contains NK-2 receptors. Activation of the latter is chiefly responsible for the noncholinergic contraction to nerve stimulation.

Aged↗

PubMed1992

Therapeutic potential of capsaicin-like molecules: studies in animals and humans.

Capsaicin-sensitive primary afferent neurons in the peripheral nervous system are widely distributed to both the somatic and visceral territories: their inactivation following capsaicin "desensitization" is expected to produce analgesia and to be useful for a number of human diseases such as asthma, urinary incontinence, inflammatory diseases of the gut, arthritis and psoriasis. The present communication reviews the therapeutic potential of capsaicin-like drugs in the pathophysiology of the mammalian urinary bladder.

Analgesia↗

PubMed1992

N-terminal truncated analogs of men 10376 as tachykinin NK-2 receptor antagonists.

Three N-terminal fragments of the selective tachykinin NK-2 receptor antagonist MEN 10376 (H-Asp-Tyr-DTrp-Val-DTrp-DTrp-Lys-NH2) have been synthesized and tested in several mammalian tissues in order to establish the minimum length of the peptide chain for maintenance of the antagonist activity. Biological activity has been determined on the rabbit pulmonary artery (RPA) and hamster trachea (HT) preparations, chosen as representative of the NK-2A and NK-2B receptor subtypes, respectively, and on the rabbit bronchus (RB), guinea-pig bronchus (GPB), human urinary bladder (HuUB), human ileum (HuI) and human colon (HuC) preparations to verify the previously described NK-2A character of these tissues. The N-terminal tetrapeptide was inactive in the RPA and HT, while the N-terminal hexa- and penta- peptides maintained antagonist activity in all preparation investigated. The selectivity of the latter two peptides confirms that the receptor expressed in RB, GPB, HuUB, HuC and HuI tissues is of the NK-2A type.

Amino Acid Sequence↗

PubMed1992

Effect of the NK-1 receptor antagonist GR 82,334 on reflexly-induced bladder contractions.

The effect of intrathecal administration of the novel tachykinin NK-1 receptor antagonist GR 82,334 has been tested in three reflexes which excite urinary bladder motility. GR 82,334 at 1 but not at 0.1 nmol/rat blocked the chemonociceptive micturition reflex induced by the topical application of capsaicin (4 micrograms/50 microliters) onto the urinary bladder. At the same dose proven effective in the chemonociceptive reflex, GR 82,334 did not affect either micturition reflex induced by bladder filling or the urinary bladder contraction induced by perineal pinching. These results suggest that, in urethane-anesthetized rats, specific stimuli applied in the periphery activate NK-1 receptors at spinal cord level facilitating urinary bladder reflex contractions.

Animals↗

PubMed1992

Pharmacological evidence for the involvement of multiple calcitonin gene-related peptide (CGRP) receptors in the antisecretory and antiulcer effect of CGRP in rat stomach.

We have investigated the effect of the C-terminal fragment of human calcitonin gene-related peptide (human-CGRP8-37), a CGRP antagonist, on alpha-CGRP and salmon Calcitonin (sCT)-induced inhibition of gastric acid secretion stimulated by pentagastrin (24 nmol kg-1 h-1 i.v.) and gastric lesions induced by acetylsalycilic acid (ASA; 25 mM) in rats anaesthetized with urethane. Close intra arterial infusion of alpha-CGRP (2-5 nmol kg-1) and sCT (5 nmol kg-1) produced a reduction in gastric acid hypersecretion induced by pentagastrin. The concomitant infusion with human-CGRP8-37 (10 nmol kg-1) reversed the effect of both agonists. ASA-ulcers were reduced in a dose-dependent manner by infusion of alpha-CGRP (1-2 nmol kg-1 i.a.), but not by sCT (10 nmol kg-1 i.a.). Human-CGRP8-37 at a dose of 10 nmol kg-1 i.a. was unable to reverse the alpha-CGRP antiulcer effect. An higher dose of human-CGRP8-37 (50 nmol kg-1 i.a.) showed agonistic properties reducing ASA ulcers. These results suggest that the inhibitory effects of alpha-CGRP on stimulated acid secretion and aspirin ulcers are mediated by different mechanisms and/or different receptors.

Animals↗

PubMed1992

Evidence for tachykinin NK-2B-like receptors in guinea-pig alveolar macrophages.

Mammalian tachykinins dose-dependently activate guinea-pig alveolar macrophages, by interacting with tachykinin NK-2 receptors, mainly. By evaluating the effects of different NK-2 tachykinin receptor antagonists, we now provide evidence that tachykinin NK-2 receptors in guinea-pig alveolar macrophages meet the pharmacological criteria used to define the NK-2B subtype.

Amino Acid Sequence↗

PubMed1992

Affinity of R 396, an NK-2 tachykinin receptor antagonist, for NK-2 receptors in preparations from different species.

We have assessed the affinity of R 396 (Ac. Leu-Asp-Gln-Trp-Phe-Gly NH2) in a number of NK-2 tachykinin receptor bearing-tissues from several species. The cyclic analog of R 396, (MEN 10354) was less potent and selective than the linear hexapeptide at NK-2 tachykinin receptors subtypes in the rabbit pulmonary artery and hamster trachea. The affinity of R 396, as measured by a smooth muscle contraction assay and a radioligand binding assay, was higher (about 10 fold) for NK-2 receptors expressed in hamster tissues (urinary bladder, stomach and trachea) than in rat tissues (urinary bladder, vas deferens, colon and stomach) and a further drop in affinity was observed in bovine tissues (urinary bladder and stomach) or rabbit bronchus. The results are discussed in relation to the proposed existence of NK-2 receptor subtypes and raise the question of the existence of species-related differences as compared to the existence of true receptor subtypes.

Amino Acid Sequence↗

PubMed1992

Interaction of amyloid beta protein (25-35) with tachykinin receptors.

Amyloid beta protein (25-35) failed to significantly interact with tachykinin NK1 (rat forebrain, guinea-pig ileum) NK2 (rabbit pulmonary artery, hamster trachea) or NK-3 (guinea-pig cortex) receptors, as determined by radioligand binding and functional assays. A weak interaction (Ki 14.8 microM) was detected with NK2 receptors in rat small intestine. It appears unlikely that direct interaction with tachykinin receptors may account for the reported ability of amyloid beta protein (25-35) to affect neuronal survival.

Amino Acid Sequence↗

PubMed1992

Structure-activity relationship study of R396, an NK2 tachykinin antagonist selective for the NK2B receptor subtype.

We report on a structure-activity study of R396 (Ac-Leu-Asp-Gln-Trp-Phe-Gly-NH2), a linear hexapeptide tachykinin antagonist selective for the putative NK2B receptor subtype. Asp2, Trp4 and the C-terminal glycinamide have been challenged by classical amino acid substitutions with the aim of elucidating the structural requirements responsible for NK2 subtype selectivity. The biological activities indicate that Asp2 has a crucial role for the high affinity of R396 at the NK2B subtype: none of the analogues substituted in position 2 display higher affinity as compared to R396, regardless of the nature of the residue introduced. Trp4 has been replaced by other aromatic residues, again yielding weak antagonist or inactive compounds. Finally, the C-terminal amide appears to be crucial for affinity, the free acid analogue being devoid of biological activity. On the other hand, antagonistic activity is maintained both by the desGly pentapeptide and by the analogue bearing beta Ala in place of Gly in position 6. In conclusion, since the NK2B selectivity pattern was maintained throughout the whole series of R396 replacement analogues, we speculate that the overall conformational features of this family of linear hexapeptides favour the interaction with the NK2B receptor subtype.

Amino Acid Sequence↗