Evidence for a role of tachykinins as sensory transmitters in the activation of micturition reflex

The possible involvement of tachykinin neurokinin-1 and neurokinin-2 receptors in the activation of various micturition-related reflexes was assessed by the intrathecal administration of selective neurokinin-1 or neurokinin-2 receptor antagonists at lumbosacral spinal cord level in urethane-anaesthetized rats. The effect of the glutamate N-methyl-D-aspartate receptor antagonist, 2-amino-5-phosphonovaleric acid, was also investigated for comparison. The effect of antagonists was investigated on: (i) the chemonociceptive vesicovesical reflex activated by topical application of capsaicin onto the urinary bladder; (ii) the distension-induced micturition reflex produced by transvesical filling with saline; (iii) distension-induced rhythmic bladder contractions in isovolumetric conditions (urethra-ligated rats); and (iv) the somatovesical excitatory reflex caused by noxious perineal pinching. The neurokinin-2 receptor selective antagonists MEN 10,376 and SR 48,968 were ineffective in the three models in all doses tested. Selective neurokinin-1 receptor antagonists blocked the chemonociceptive reflex produced by topical application of capsaicin with the rank order of potency (lowest effective dose in brackets): GR 82,334 (1 nmol/rat) > RP 67,580 (10 nmol/rat) > (+/-)CP 96,345 (100 nmol/rat). Unlike GR 82,334, RP 67,580 (10 nmol/rat) and (+/-)CP 96,345 (100 nmol/rat) were also effective on the distension-induced micturition reflex elicited by transvesical filling. Similarly, distension-induced rhythmic contractions were inhibited by RP 67,580 (10 nmol/rat) and (+/-)CP 96,345 (100 nmol/rat) whereas the effect of GR 82,334 was not significant. RP 68,651, the enantiomer of RP 67,580 devoid of neurokinin-1 receptor blocking activity, was inactive in both models. 2-Amino-5-phosphonovateric acid (250 nmol/rat) blocked the three types of vesicoexcitatory reflexes. Intravenous administration of (+/-)CP 96,345, RP 67,580 or 2-amino-5-phosphonovateric acid at the same doses proven effective after the intrathecal route, had no effect on distension-induced rhythmic contractions. To ascertain whether the effect of neurokinin-1 receptor antagonists or 2-amino-5-phosphonovaleric acid may be related to a blockade of tachykinins released from capsaicin-sensitive primary afferent neurons, the effect of RP 67,580 was investigated on the distension-evoked micturition reflex in capsaicin-pretreated rats. Capsaicin pretreatment (50 mg/kg, subcutaneously, four days before) increased bladder capacity. RP 67,580 was no longer effective in capsaicin-pretreated rats. In contrast, 2-amino-5-phosphonovateric acid produced a further increase in bladder capacity in capsaicin-pretreated rats. We conclude that tachykinin neurokinin-1 but not neurokinin-2 receptors are involved in the activation of vesicoexcitatory micturition-related reflexes in the rat spinal cord.(ABSTRACT TRUNCATED AT 400 WORDS)

A non-peptide NK1-receptor antagonist, RP 67580, inhibits neurogenic inflammation postsynaptically

1. The non-peptide neurokinin NK1-receptor antagonist, RP 67580 (3aR, 7aR), a perhydroisoindolone derivative, powerfully reduced plasma extravasation in rat hind paw skin induced by local application of xylene (ID50 = 0.03 mg kg-1, i.v.) or capsaicin (ID50 = 0.06 mg kg-1, i.v.), or by i.v. injection of exogenous substance P (SP) or septide ([pGlu6,Pro9]SP(6-11)) (ID50 = 0.04-0.05 mg kg-1, i.v.). RP 67580 (1 mg kg-1, i.v.) also abolished capsaicin-induced nasal fluid hypersecretion (by 82 +/- 5%). These effects were found to be stereospecific, the enantiomer, RP 68651 (3aS, 7aS), being inactive at 1 mg kg-1, i.v. 2. In rats neonatally treated with capsaicin (50 mg kg-1, s.c.), plasma extravasation induced by SP was significantly increased (by 43 +/- 7%). RP 67580 (1 mg kg-1, i.v.) completely inhibited the SP-induced plasma extravasation in capsaicin neonatally treated-animals, as it did in control animals. This result suggests that RP 67580 acts at the postsynaptic level for the inhibition of plasma extravasation. 3. Opioid receptor agonists, mu-(morphine) and kappa-(PD-117302) at 10 mg kg-1, s.c., in contrast to NK1-receptor antagonists, did not inhibit plasma extravasation induced by exogenous SP. They were, however, partially effective against plasma extravasation induced by electrical nerve stimulation (74 +/- 4% and 48 +/- 9% inhibition at 10 mg kg-1, s.c. of morphine and PD-117302, respectively, compared to 90 +/- 3% inhibition obtained with RP 67580, 3 mg kg-1, s.c.). These results indicate the presynaptic action of opioid receptor agonists, in contrast to the postsynaptic action of NK1-receptor antagonists for the inhibition of plasma extravasation.4. Ligature of the saphenous nerve distal to the point of electrical stimulation, local application of lignocaine to the saphenous nerve, neonatal capsaicin pretreatment, and colchicine at very low doses(120 microg kg-1 day-1 given for 3 days) were found to prevent plasma extravasation elicited by electrical nerve stimulation.5. The foregoing results demonstrate that the non-peptide NK1-receptor antagonist, RP67580, is a potent inhibitor of plasma extravasation induced in skin by NK1-receptor agonists, by local application of chemical irritants (capsaicin or xylene) or by electrical nerve stimulation. Moreover, opioid receptor agonists and colchicine inhibit plasma extravasation induced by electrical nerve stimulation but not that elicited by exogenous SP. Therefore, it is possible to inhibit neurogenic inflammation either at the presynaptic level with opioid receptor agonists and colchicine, or at the postsynaptic level withNK1-receptor antagonists, and that the new non-peptide NK1-receptor antagonists may have a great potential for alleviation of inflammation in various pathological syndromes in man.

Interaction of the substance P receptor antagonist RP 67580 with the rat brain NK1 receptor expressed in transfected CHO cells

In the present study, we describe the effects of RP 67580, a substance P non-peptide antagonist, in binding and second messenger experiments performed using transfected Chinese hamster ovary cells expressing the rat NK1 receptor. The cDNA sequence encoding the rat brain substance P receptor was transfected in Chinese hamster ovary cells, and cellular clones which stably express the corresponding protein were isolated. [3H]Substance P binding was performed in homogenates of these transfected cells and revealed the presence of NK1 receptors in displacement experiments, using peptide analogs of three mammalian tachykinins (substance P, neurokinin A, neurokinin B). Scatchard analysis indicated a KD value of 0.33 +/- 0.13 nM and a Bmax value of 5.83 +/- 1.16 pmol/mg of protein. RP 67580, a selective NK1-receptor antagonist was found to displace the specific binding of [3H]substance P. When [3H]RP 67580 was used as a ligand, it displayed a high affinity (KD value: 1.22 +/- 0.27 nM) in transfected cell homogenates and only competed with NK1 receptor ligands. Substance P stimulated the hydrolysis of phosphoinositide in a time- and concentration-dependent manner and this effect was mimicked by selective agonists of the NK1 receptor ([Pro9]SP and septide). RP 67580 did not induce any accumulation of inositol phosphates, but was found to inhibit the inositol phosphate increase mediated by substance P, without affecting the maximal response. From these results, one may conclude that the receptor expressed by the transfected Chinese hamster ovary cells revealed similar binding characteristics as the NK1 receptor present in the rat brain and also confirmed the high affinity and the antagonist properties of RP 67580.

Characterization of a human NK1 tachykinin receptor in the astrocytoma cell line U 373 MG

The human NK1 tachykinin receptor in the astrocytoma cell line U 373 MG was characterized using selective agonists and antagonists described for this receptor in the rat. Specific [3H]substance P binding sites were present on cell homogenates, whereas [3H]neurokinin A or [3H]-senktide binding sites were absent. The binding was saturable and reversible. The binding of [3H]substance P was inhibited by very low concentrations of [L-Pro9]substance P and [Sar9,Met(O2)11]substance P; septide was approximately 1,000-fold less potent. The most potent peptide antagonist was trans-4-hydroxy-1-(1H-indol-3-ylcarbonyl)-L-prolyl-N-methyl-N-(phe nylmethyl)-L- tyrosineamide. The rank order of potency for the nonpeptide antagonists was (S,S)-CP 96,345 > (+/-)-CP 96,345 > (+/-)-2-chlorobenzylquinuclidinone > (R,R)-CP 96,345 > RP 67580 > RP 68651. In [3H]-inositol-labeled cells, substance P stimulated phosphatidylinositol turnover. A good correlation was found when the abilities of NK1 receptor agonists for stimulating inositol phosphate production and for inhibiting [3H]substance P binding were compared. Similarly, the binding and functional assays were well correlated for the antagonists. As a result of its high sensitivity and selectivity, the U 373 MG cell line thus appears an excellent tool for investigating the pharmacology of the human NK1 receptor.

Polyclonal antibodies against the rat NK1 receptor: characterization and localization in the spinal cord

We have developed antibodies against the NK1 receptor and have investigated its cellular distribution. Rabbit polyclonal antibodies were generated against peptide (19-32) of the rat brain NK1 receptor. They were very specific to the NK1 site as shown by ELISA against various epitopes of NK1, NK2 and NK3 receptors and by immunoblotting of proteins from bacteria transfected with rat brain NK1 receptor cDNA and from rat cortex. Determining how immunostained NK1 receptors are distributed in the rat spinal cord made it possible to identify the cellular structures on which NK1 receptors are located and where they form synapses with SP terminals. In the superficial layers of the dorsal horn, the NK1 receptors appeared mainly of dendritic nature and were, like SP, abundant. In the deep layers of the dorsal horn and in the ventral horn, they were associated mostly with cell bodies.

Comparison in different tissue preparations of the in vitro pharmacological profile of RP 67580, a new non-peptide substance P antagonist

We describe the effects of RP 67580, a new non-peptide substance P (SP) antagonist, on tachykinin-induced contractions of guinea-pig ileum, trachea and urinary bladder, rabbit pulmonary artery and rat portal vein. All NK1 agonists tested (SP, Septide, SPOMe and [Pro9]SP) contracted guinea-pig ileum, trachea and urinary bladder (pD2 = 7.5 to 9.1), but they had no effect on rabbit pulmonary artery or rat portal vein (pD2 < 6). RP 67580 inhibited these effects: guinea-pig ileum, pA2 = 7.1 to 7.6; guinea-pig trachea and urinary bladder, pKB = 6.3 to 6.8. The difference in RP 67580 activity in these tissues might be due to the existence of subtypes of NK1 receptors. RP 67580 (1 microns) did not affect the contractions induced by the two NK2 agonists, NKA and [Lys5, MeLeu9, Nle10]NKA(4-10) (pA2 < 6), except in guinea-pig ileum (pA2 = 7.3-7.5) where these two NK2 agonists interact apparently with NK1 receptors. In the tissue preparations used, RP 67580 (1 micron) was without effect on contractions induced by the NK3 agonists: NKB and senktide. These results indicate the high selectivity for NK1 receptors of RP 67580. In all cases, similar results were obtained with another non-peptide SP antagonist, (+/-) CP-96,345. The present work provides further evidence that RP 67580 and (+/-) CP-96,345 exert in vitro a potent, selective and competitive antagonistic action on NK1 receptors and suggests the existence of at least two distinct NK1 receptor subtypes in some guinea-pig peripheral organs.

[Pro9]SP and [pGlu6, Pro9]SP(6-11) interact with two different receptors in the guinea-pig ileum as demonstrated with new SP antagonists

Structural considerations led us to postulate that the introduction of the dipeptides DPro9-Pro10 and DPro9-MeLeu10 should lock the C-terminal tetrapeptide of SP in a type II' beta-turn structure, a prerequisite for antagonist activity. Indeed, as the GR 71251, [DPro9, Pro10, Trp11]SP was more potent in inhibiting the septide, (pA2 = 6.5), than the [Pro9]SP, (pA2 < or = 5), spasmogenic activity in the guinea-pig ileum bioassay. This result confirms that septide, [pGlu6, Pro9]SP(6-11), a peptide active in the guinea-pig ileum bioassay and practically devoid of binding potencies for the three specific NK-1, NK-2 and NK-3 tachykinin binding sites interacts with a tachykinin receptor different from the NK-1 receptor sensitive to [Pro9]SP. Interestingly enough, the reintroduction of the leucine side-chain in position 10 yielded [DPro9, MeLeu10, Trp11]SP, an antagonist, equipotent in inhibiting both the septide- and the [Pro9]SP-evoked contractile response in the guinea-pig ileum bioassay, (pA2 = 6.6).

Distribution of neurokinin B in rat spinal cord and peripheral tissues: comparison with neurokinin A and substance P and effects of neonatal capsaicin treatment

In the present study, highly specific radioimmunoassays were developed and used to measure neurokinin B, neurokinin A and substance P in the rat spinal cord and various peripheral tissues. The results are as follows. (1) Neurokinin B and neurokinin A were distributed all along the rostrocaudal axis of the spinal cord, as is substance P, and were more concentrated in the dorsal than in the ventral region. (2) Substance P was more abundant in the central and peripheral nervous tissues than neurokinin A, while in certain peripheral organs, neurokinin A was more abundant than substance P. In the spinal cord, neurokinin B concentrations were lower than those of the other two tachykinins. (3) In contrast to neurokinin A and substance P, neurokinin B was not detected in any of the peripheral tissues examined. (4) Capsaicin treatment reduced by half neurokinin A and substance P concentrations in the dorsal region of the spinal cord, the dorsal root ganglia and the sciatic nerve, but was without effect on neurokinin B concentrations in the spinal cord. Neurokinin A, like substance P, may therefore have an important function in the transmission of sensory information, particularly in nociceptive transmission from the periphery to the spinal cord and in peripheral neurogenic inflammation. In contrast, since neurokinin B was not found in the sensory neurons, it is not likely to have these functions, but may perhaps control them.

Pharmacological properties of a potent and selective nonpeptide substance P antagonist

We describe here the pharmacological properties of RP 67580 [(3aR,7aR)-7,7-diphenyl-2-[1-imino-2-(2-methoxyphenyl)ethyl] perhydroisoindol-4-one], a nonpeptide antagonist of substance P (SP). In vitro, the compound was found to inhibit in a competitive manner (Ki = 4.16 +/- 0.59 nM) [3H]SP binding to neurokinin receptors type 1 (NK1 receptors) in rat brain membranes. Contractions induced by SP and septide (a selective NK1 agonist) in guinea pig ileum were competitively inhibited by RP 67580 (pA2 = 7.16 and 7.59, respectively). Moreover, RP 67580 displayed the profile of a specific antagonist of NK1 receptors: it was not active on NK2 and NK3 receptors as seen in binding assays and in isolated preparations of rabbit pulmonary artery and rat portal vein. In the rat, low intravenous doses of RP 67580 totally inhibited the plasma extravasation induced by SP in the urinary bladder (ED50 = 0.04 mg/kg i.v.) and by antidromic electrical stimulation of the saphenous nerve in the hind paw skin (ED50 = 0.15 mg/kg i.v.). This compound was also active in two classical analgesic tests in mice: phenylbenzoquinone-induced writhing (ED50 = 0.07 mg/kg s.c.) and the formalin test (ED50 = 3.7 mg/kg s.c.). Its potency was of the same order as that of morphine. Thus we conclude that RP 67580, a SP antagonist, belongs to a class of drugs that may be useful in the management of various clinical pathologies where pain and neurogenic inflammation are involved.

Species differences between [3H] substance P binding in rat and guinea-pig shown by the use of peptide agonists and antagonists

The affinities of various substance P agonists and antagonists for NK1 receptors in rat and guinea-pig tissues were compared. Striking species differences were observed. Both septide and [D-Pro4,D-Trp7,9]SP-(4-11) possessed much higher affinity for sites in the guinea-pig (brain and ileum) than for sites in the rat brain. These results could be explained by differences in the structure of the NK1 receptor according to the species, although the existence of various subtypes of NK1 binding sites in the two species cannot be excluded.

Selective agonists of NK-2 binding sites highly active on rat portal vein (NK-3 bioassay)

All the synthetized NKA and NKA (4-10) agonists have been found active in the rat portal vein bioassay. Even [Lys5, MeLeu9, Nle10] NKA(4-10), a highly potent competitor of NK-2 binding sites with very low binding potencies for NK-1 and NK-3 sites (IC50 greater than microM) is still active in contracting the rat portal vein. These results suggest that this tissue contains not only a fairly large population of NK-3 receptors but also a minor population of NK-2 receptors. Comparison of the activities of NKA C-terminal analogues on the guinea-pig ileum suggests that 1) only a small population of NK-2 receptors are present in this tissue and 2) beside NK-1, NK-2 and NK-3 receptors, another type of receptor sensitive to C-terminal sequences might be present in the guinea-pig tissue.

Further demonstration that [Pro9]-substance P is a potent and selective ligand of NK-1 tachykinin receptors

Previous studies have indicated that [Pro9]-substance P ([Pro9]-SP) possesses very good affinity for NK-1 binding sites and that, in contrast to substance P, it interacts selectively with these sites. Therefore, [3H][Pro9]-SP (75 Ci/mmol) was synthesized in order to study its binding to membranes of the rat brain. Specific binding of [3H][Pro9]-SP (75% of total binding) was temperature-dependent, saturable, and reversible. Scatchard analysis and Hill plots revealed the existence of a single population of noninteracting binding sites (KD and Bmax values: 1.48 nM and 29.7 fmol/mg of protein, respectively). Competition studies with several tachykinins and analogues indicated that the pharmacological profile of [3H][Pro9]-SP binding sites is identical to that of NK-1 binding sites. Rat brain sections labeled with either [3H][Pro9]-SP or [3H]SP, revealed a close similarity in the topographical distribution of [3H][Pro9]-SP and [3H]SP binding sites. Biochemical, pharmacological, and autoradiographic data obtained with [3H][Pro9]-SP did not provide any evidence for the existence of subtypes of NK-1 binding sites. [Pro9]-SP had neither agonist nor antagonist properties on NK-2 and NK-3 receptors. Indeed, it did not stimulate phosphoinositide turnover on the hamster urinary bladder (NK-2 assay) and was devoid of activity on the contraction of the rabbit pulmonary artery (NK-2 assay) and of the rat portal vein (NK-3 assay). As a result of its high selectivity, [Pro9]-SP thus appears an excellent tool for investigating the functional properties of NK-1 receptors.

Evidence for a Ca2+-independent association between calpain II and phospholipid vesicles

Possible interactions between calpain II and phospholipids such as phosphatidylinositol, phosphatidylserine and phosphatidylcholine were studied using fluorescence and gel filtration techniques. Changes in fluorescence intensity of purified calpain II show that the enzyme strongly interacts with phosphatidylinositol and phosphatidylserine and to a lesser extent with phosphatidylcholine. These results are corroborated by the gel filtration technique which permits the isolation of the enzyme phospholipid complex. Association between calpain II and various phospholipid vesicles can occur in the absence of calcium. Such binding occurs without any observable change of the molecular mass of the two subunits on SDS-polyacrylamide gel electrophoresis.

[The biochemical effects of a new antidepressive, metapramine (RP 19560) on activity of the dopaminergic and cholinergic systems of the rat striatum]

The effects of metapramine (R.P. 19,560) on dopaminergic and cholinergic activities were mainly studied in the rat striatum. Metapramine, contrarily to apomorphine, is devoid of in vitro affinity for dopamine receptors and does not modify in vivo, the utilisation of dopamine in the striatum. Moreover, metapramine does not modify the increase of dopamine utilisation induced by thioproperazine, a neuroleptic of the phenothiazine family. Consequently metapramine is devoid of direct or indirect effect on nigrostriatal dopaminergic system. Metapramine, like dopaminergic agonists, increases acetylcholine levels in the striatum. Moreover metapramine is inactive in cerebral cortex and hippocampus. Metapramine partly or completely antagonises the decrease of acetylcholine levels induced by two neuroleptics of the phenothiazine family (thioproperazine and prochlorperazine), by reserpine or an association of reserpine and alpha-methyl-p-tyrosine. Metapramine which possesses a clinical antidepressant efficacy could be indicated for correction of extra-pyramidal side effects induced by neuroleptics or observed in parkinsonism.

Suriclone, a new anxiolytic of the cyclopyrrolone family: evidence for possible interference with GABAergic systems

The action of suriclone (R.P. 31,264), a new non-benzodiazepine compound of the cyclopyrrolone family with clinical anxiolytic activity was examined using biochemical and electrophysiological models supposed to be capable of revealing central GABAergic activity. Suriclone, which does not act directly on the gamma-aminobutyric acid (GABA) receptor (muscimol binding assay), markedly reduced the increase of striatal HVA level induced in the rat by a neuroleptic and decreased the cerebellar vermis cGMP content. Moreover, in the cat, suriclone was able to enhance dorsal root potential amplitude which reflects an increase of the presynaptic inhibition. In view of these results, a central GABAergic mechanism of action may be proposed for suriclone.

Pharmacological studies on zopiclone

Zopiclone (RP 27 267) is an hypnotic with a chemical structure different from that of the benzodiazepines (BZD) or barbiturates. Studies of zopiclone in classical psychopharmacological tests, in comparison with BZD and barbiturates, have shown that it exhibits the five main types of activity considered as characteristic of the pharmacological profile of BZD and partly of that of barbiturates (anticonvulsant, myorelaxant, antiaggressive, sedative-hypnotic and 'anticonflict'). However, like BZD, zopiclone differs from barbiturates by a high safety margin. Electrophysiological studies performed in cats have shown that zopiclone induces modifications in sleep-wakefulness pattern which are close to those observed with BZD, specially with nitrazepam. Moreover, zopiclone increases the threshold for arousal by reticular formation stimulation, rather more than nitrazepam, but with a shorter duration of action. The short duration of action of zopiclone has been demonstrated in other species using different tests.