Effects of actinomycin D on airway constriction induced by tachykinins and capsaicin in guinea-pigs.

The effects of actinomycin D on airway constriction induced by tachykinins was studied in guinea-pigs in vitro and in vivo. Actinomycin D significantly inhibited the constriction of isolated guinea-pig trachea induced by neurokinin A (NKA) and eledoisin. Conversely, substance P (SP)- and physalaemine-induced constrictions were not affected by actinomycin D. The same selectivity in the inhibitory action of actinomycin D against tachykinins was also observed in in vivo. Actinomycin D given i.v. specifically inhibited the increase in airway resistance induced by NKA. I.v. injection of NKA caused not only airway constriction but also transient systemic hypotension. Interestingly, actinomycin D injected i.v. inhibited only airway constriction and the systemic hypotension induced by NKA was not affected. These results clearly suggest that actinomycin D specifically inhibits NKA-induced airway constriction in guinea-pigs. Actinomycin D also had an inhibitory action on the airway constriction induced by capsaicin. In the case of capsaicin-induced constriction, actinomycin D was more effective on the later phase of constriction than on the acute phase. The airway constriction induced by capsaicin is thought to be mediated by the release of SP and NKA from sensory nerve endings, and the persistent increase in airway resistance induced by capsaicin is thought to be due mainly to NKA.     

Involvement of endogenous tachykinins and CGRP in the motor responses produced by capsaicin in the guinea-pig common bile duct

In functional experiments, we have investigated the effect exerted by neurotransmitters released from capsaicin-sensitive primary afferent nerve terminals in the isolated guinea-pig common bile duct. In resting preparations, capsaicin (0.1 microM) produced a quick contraction (45.1+/-4% of KCl 80mM) which was abolished by either atropine (1 microM) or tetrodotoxin (0.5 microM). The tachykinin receptor-selective antagonists GR 82334 (NK1 receptor-selective; 3 microM), MEN 11420 (NK2 receptor-selective; 1 microM) and SR 142801 (NK3 receptor-selective; 0.1 microM) administered separately failed to reduce the capsaicin-evoked contraction, whereas any combination of the three antagonists was effective: GR 82334 plus MEN 11420, 36+/-7% reduction; GR 82334 plus SR 142801, 48+/-4% reduction; MEN 11420 plus SR 142801, 55+/-3% reduction; GR 82334 plus MEN 11420 plus SR 142801, 57+/-5% reduction. Neither the CGRP1 receptor antagonist h-CGRP (8-37) (1.5 microM) nor the P2X purinoceptor antagonist PPADS (50 microM) affected the contractile response to capsaicin. The effect of capsaicin (0.1 microM) was abolished by pretreatment with capsaicin itself (10 microM for 15 min). Human calcitonin gene-related peptide (h-CGRP; 0.1 microM) mimicked the effect of capsaicin on resting preparations (contractile response =28% of KCl 80 mM). In preparations precontracted with a submaximal concentration of KCl (24 mM), and in the presence of atropine (1 microM), GR 82334 (3 microM) and MEN 11420 (3 microM), capsaicin (1 microM) produced a tetrodotoxin-insensitive long-lasting relaxation (45+/-3% reduction of tone, at 4min from administration), which was unaffected by the nitric oxide (NO) synthase inhibitor, L-NOARG (100 microM). h-CGRP (10-50 nM) produced a similar sustained relaxation of precontracted preparations (59+/-4% reduction of tone). h-CGRP (8-37) (1.5 microM) almost completely reversed the relaxations produced by both capsaicin and h-CGRP. Application of electrical field stimulation (EFS: trains of stimuli of 10Hz; 0.25ms pulse width; supramaximal voltage; for 60s) to precontracted preparations produced a sustained, tetrodotoxin (1 microM)-sensitive relaxation (32+/-4% reduction of tone). L-NOARG (100 microM) greatly reduced (69+/-5% inhibition) the EFS-elicited relaxation. A complete reversal of the relaxant response to EFS into a contraction was obtained by administering L-NOARG to preparations in which a functional blockade of capsaicin-sensitive primary afferent neurons had been achieved by incubating the tissue with capsaicin (10 microM) for 15 min. At immunohistochemistry, tachykinin- and CGRP-immunoreactivities (TK-IR/CGRP-IR) were detected in varicose nerve fibers throughout the common bile duct, while TK-IR cell bodies were observed in the terminal portion (ampulla) only. In vivo pretreatment with capsaicin (50 mg/kg; 6-7 days before) decreased the number of CGRP-IR nerves, whereas the TK-IR neural network was apparently unchanged. In conclusion, our data provide functional evidence for the presence of capsaicin-sensitive primary afferent nerve endings in the guinea-pig terminal biliary tract, whose stimulation by capsaicin or EFS produces the release of tachykinins and CGRP. In addition, morphological evidence is provided that the bulk of TK-IR material in the biliary tract is contained in intrinsic neuronal elements, while CGRP in this tissue is of extrinsic origin only. Tachykinins, probably released in small amounts by capsaicin, act by activating receptors of the NK1, NK2 and NK3 type, most probably located on intrinsic cholinergic neurons, which in turn release ACh to produce the final excitatory motor response. The contractile response to capsaicin obtained in the presence of the three tachykinin receptor antagonists could be due to the co-released CGRP and/or to other unknown neurotransmitters. CGRP produces either indirect excitatory or direct inhibitory responses by stimulation of CGRP2 and CGRP1 receptors, respectively.     

Regulation by phosphodiesterase isoenzymes of non-adrenergic non-cholinergic contraction in guinea-pig isolated main bronchus.

1. We have investigated the role of phosphodiesterase isoenzymes in modulating electric field stimulation (EFS), substance P and capsaicin-induced contraction of the guinea-pig isolated main bronchus. 2. Non-adrenergic non-cholinergic contractile responses were elicited by EFS (3 Hz, 20 s) in the guinea-pig isolated main bronchus in the presence of the non-selective muscarinic antagonist, atropine (0.1 microM), the non-selective beta-adrenoceptor antagonist, propranolol (1 microM), the neutral endopeptidase inhibitor, thiorphan (10 microM) and the cyclo-oxygenase inhibitor, indomethacin (5 microM). The type III, type III/IV, type IV and type V phosphodiesterase isoenzyme inhibitor, SKF 94836, benzafentrine, Ro-20-1724 and zaprinast respectively, significantly attenuated the contractile response to EFS. The IC50 (95% confidence limits) value for SKF 94836, benzafentrine, Ro-20-1724 and zaprinast was 8.3 microM (0.89-78); 0.7 microM (0.1-4.5); 0.5 microM (0.2-1.2) and 13 microM (2-87) respectively. 3. The phosphodiesterase isoenzyme inhibitors, SKF 94836, Ro-20-1724 and zaprinast, partially attenuated the contractile response to substance P (10 nM). Benzafentrine significantly inhibited the contractile response to substance P, yielding an IC50 value of 1.9 microM (0.9-3.8). 4. The phosphodiesterase isoenzyme inhibitor, Ro-20-1724 (0.1-100 microM) failed to reduce significantly the contractile potency of capsaicin (P > 0.05). In contrast, SKF 94836 (1 microM), benzafentrine (10 microM) and zaprinast (100 microM) significantly reduced the contractile potency of capsaicin (P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of capsaicin,tachykinins, calcitonin gene-related peptide and bradykinin in the pig iris sphincter muscle

Summary Capsaicin-sensitive sensory neurons of the rabbit iris, by releasing tachykinins, exert a major role in the control of pupil motility in response to various noxious stimuli. However, the contribution of sensory innervation to the regulation of iris smooth muscle tone in other mammals species is not known. We have studied the effects produced by electrical field stimulation, capsaicin, substance P, neurokinin A, calcitonin gene-related peptide (CGRP), and bradykinin in the isolated iris sphincter muscle of the pig.Capsaicin (10 M): a) contracted the isolated sphincter muscle and; b) released immunoreactivity for substance P (SP-LI) and CGRP (CGRP-LI) from this preparation. These two effects were no longer observed at the second exposure to the drug. Electrical field stimulation (10 Hz, 60 V, 0.5 ms for 5 s) produced a biphasic contractile response. The rapid component was inhibited by atropine (1 M), while the delayed response was blocked by previous exposure to capsaicin (10 M).Substance P and neurokinin A consistently produced contraction of the pig iris sphincter muscle, substance P being more potent than neurokinin A. CGRP induced a contractile response in more than 50% of the preparations. The tachykinin antagonist [D-Argl, D-Trp^7,9, Leu¹¹-substance P (3 M) blocked: a) the effect of substance P (1 nM); b) the delayed response to electrical field stimulation and; c) reduced by more than 50% response to capsaicin. Bradykinin (10 M) failed to release either SP-LI or CGRP-LI. The contractile response evoked by bradykinin was unaffected by in vitro pretreatment with capsaicin (10 M).The existence in the pig iris of capsaicin-sensitive sensory fibres releasing neuropeptides and thus regulating sphincter muscle tone is proposed. Send offprint requests to Dr. P. Geppetti at the above address     

Respiratory actions of tachykinins in the nucleus of the solitary tract: effect of neonatal capsaicin pretreatment

1. The respiratory response to microinjection of capsaicin and tachykinin receptor agonists into the commissural nucleus of the solitary tract (cNTS) was investigated in adult, urethane-anaesthetized rats which had been pretreated with capsaicin (50 mg kg(-1) s.c.) or vehicle (10% Tween 80, 10% ethanol in saline) as day 2 neonates. 2. Microinjection of capsaicin (1 nmol) into the cNTS of vehicle-pretreated rats, significantly reduced respiratory frequency (59 breaths min(-1), preinjection control, 106 breaths min(-1)) without affecting tidal volume (VT). In capsaicin-pretreated rats, the capsaicin-induced bradypnoea was markedly attenuated (minimum frequency, 88 breaths min(-1); control, 106 breaths min(-1)). 3. In vehicle-pretreated rats, microinjection of substance P (SP, 33 pmol), neurokinin A (NKA, 33 pmol) and NKB (330 pmol), and the selective NK(1) tachykinin receptor agonists, [Sar(9), Met(O(2))(11)]-SP (33 pmol) and septide (10 pmol), increased VT (maxima, 3.60 - 3.93 ml kg(-1)) compared with preinjection control (2.82 ml kg(-1)), without affecting frequency. The selective NK(3) agonist senktide (10 pmol) also increased VT (3.93 ml kg(-1)) which was accompanied by a bradypnoea (-25 breaths min(-1)). The selective NK(2) agonist, [Nle(10)]-NKA(4-10) (330 pmol) increased VT slightly but significantly decreased frequency (-12 breaths min(-1)). In capsaicin-pretreated rats, VT responses to SP and [Sar(9), Met(O(2))(11)]-SP were increased whereas the response to septide was abolished. Both the VT and bradypnoeic responses to senktide and [Nle(10)]-NKA(4-10) were significantly enhanced. 4. These results show that neonatal capsaicin administration markedly reduces the respiratory response to microinjection of capsaicin into the cNTS. The destruction of capsaicin-sensitive afferents appears to sensitize the NTS to SP, NKB, [Sar(9),Met(O(2))(11)]-SP, senktide and [Nle(10)]-NKA(4-10). Moreover, the loss of septide responsiveness in capsaicin-pretreated rats, suggests that 'septide-sensitive' NK(1) receptors may be located on the central terminals of afferent neurons.     

Contractile effects of substance P and other tachykinins on the mouse isolated distal colon.

1. Substance P (SP), physalaemin, eledoisin and kassinin induced concentration-related contractions of the longitudinal muscle of the mouse distal colon. The responses were not antagonized by atropine (1.5 x 10(-7) M), mepyramine (2.5 x 10(-7) M), methysergide (5 x 10(-7) M), timolol (10(-6) M), phentolamine (10(-6) M) or naloxone (4 x 10(-7) M). They were enhanced by tetrodotoxin (TTX, 1.5 x 10(-7) M). These observations indicate that the contractile responses to the tachykinins result from a direct activation of smooth muscle cells. 2. The contractile activity provoked by SP and physalaemin was inhibited by nifedipine (a Ca2+-entry blocker) and was abolished in Ca2+-free EGTA solution. Such data suggest that the myogenic effects of SP and physalaemin are mainly dependent on their ability to promote Ca2+ influx. 3. Eledoisin and kassinin evoked a contractile response in the absence of external Ca2+ and their myogenic activity was, to some extent, resistant to the inhibitory effect of nifedipine. This may indicate that an additional process, probably the release of an intracellularly bound Ca2+ store, participates in the mechanism by which eledoisin and kassinin contract the mouse distal colon. 4. After desensitization of the mouse distal colon to SP, the contractile activity provoked by SP or physalaemin was totally abolished whilst the responses evoked by eledoisin and kassinin were barely affected. These observations and other experimental findings indirectly support the assumption that the mouse distal colon could possess different tachykinin-binding sites.     

Regional differences in the effects of capsaicin and tachykinins on motor activity and vascular permeability of the rat lower urinary tract

Summary 1. The effects of capsaicin, substance P (SP) and neurokinin A (NKA) on motor activity and vascular permeability was investigated in the rat lower urinary tract (bladder dome and neck, proximal urethra and ureters). 2. Capsaicin produced contractions of the rat bladder dome and neck and of the proximal urethra in vitro, which were unaffected by tetrodotoxin and abolished by ganglionectomy. SP and NKA were almost equipotent in producing a contraction of the rat isolated bladder dome or neck and urethra. However, the maximal response to NKA was about twice that of SP on the urethra and bladder neck. 3. Capsaicin did not affect motility of the unstimulated rat isolated ureter, while NKA or SP activated rhythmic contractions, NKA being about 850 times more potent than SP. Either capsaicin or field stimulation produced a transient inhibition of the NKA-activated rhythmic contractions of the rat isolated ureter which was prevented by capsaicin-desensitization. 4. The capsaicin-(1 M) or field stimulation-induced inhibition of NKA-activated rhythmic contractions of the rat isolated ureter were unaffected by removal of pelvic ganglia but abolished by cold storage (72 h at 4°C). 5. Intravenous capsaicin induced an inflammatory response (Evans blue leakage) in the bladder, proximal urethra and ureters in vivo. Plasma extravasation was greater in the ureters, urethra and bladder neck than in the dome. SP, NKA and histamine produced a dose-dependent dye leakage in all segments of the rat urinary tract, the response being slightly greater in the bladder neck than in the dome. 6. The capsaicin-induced inflammatory response was abolished by systemic capsaicin-desensitization and reduced, to a variable extent, by pelvic ganglionectomy, in the various tissues examined. Topical application of tetrodotoxin on the bladder dome failed to affect the capsaicin-induced plasma extravasation in the urinary bladder. 7. These findings indicate that chemoceptive, capsaicin-sensitive nerves are present throughout the whole rat lower urinary tract and their activation determines a variety of visceromotor responses and an increase of vascular permeability. In various instances the response to capsaicin may be explained by the action of tachykinins but some effects may involve other sensory neuropeptides. Send offprint requests to C. A. Maggi at the above address     

Development and inhibition of mouse ear oedema induced with capsaicin.

Oedema was induced in one ear of male mice of the CFLP strain with capsaicin solution (10 microliters/40 micrograms/ear). The development in time and the extent of the oedema were determined by the oedema-disk gravimetric technique. The maximum oedema was attained in less than 1 h, and there was, subsequently, a gradual decrease. The extent of the mouse ear oedema induced in this way and measured after 60 min was inhibited to a statistically significant degree and in a dose-dependent manner by the antihistamine chloropyramine, the antihistamine-antiserotonin cyproheptadine, the non-steroidal anti-inflammatory agent piroxicam, the prostaglandin antagonist di-4-phloretin phosphate, and the lipoxygenase inhibitor nordihydroguairetic acid. The method proved suitable for the detection of oedema and for the biologically quantitative determination of the state of desensitization induced with capsaicin.     

Evidence that tachykinins are the main NANC excitatory neurotransmitters in the guinea-pig common bile duct

1. Application of electrical field stimulation (EFS; trains of 10 Hz, 0.25 ms pulse width, supramaximal voltage for 60 s) to the guinea-pig isolated common bile duct pretreated with atropine (1 μM), produced a slowly-developing contraction (`on'' response) followed by a quick phasic `off '' contraction (`off peak'' response) and a tonic response (`off late'' response), averaging 16±2, 73±3 and 20±4% of the maximal contraction to KCl (80 mM), n=20 each, respectively. Tetrodotoxin (1 μM; 15 min before) abolished the overall response to EFS (n=8).
2. Neither in vitro capsaicin pretreatment (10 μM for 15 min), nor guanethidine (3 μM, 60 min before) affected the excitatory response to EFS (n=5 each), showing that neither primary sensory neurons, nor sympathetic nerves were involved. N^ω-nitro-L-arginine (L-NOARG, 100 μM, 60 min before) or naloxone (10 μM, 30 min before) significantly enhanced the `on'' response (294±56 and 205±25% increase, respectively; n=6–8, P<0.01) to EFS. The combined administration of L-NOARG and naloxone produced additive enhancing effects (655±90% increase of the `on'' component, n=6, P<0.05).
3. The tachykinin NK₂ receptor-selective antagonist MEN 11420 (1 μM) almost abolished both the `on'' and `off late'' responses (P<0.01; n=5 each) to EFS, and reduced the `off-peak'' contraction by 55±8% (n=5, P<0.01). The subsequent administration of the tachykinin NK<sub>1</sub> receptor-selective antagonist GR 82334 (1 μM) and of the tachykinin NK<sub>3</sub> receptor-selective antagonist SR 142801 (30 nM), in the presence of MEN 11420 (1 μM), did not produce any further inhibition of the response to EFS (P>0.05; n=5 each). At 3 μM, GR 82334 significantly reduced (by 68±9%, P<0.05, n=6) the `on'' response to EFS.
4. The contractile `off peak'' response to EFS observed in the presence of both MEN 11420 and GR 82334 (3 μM each) was abolished (P<0.01; n=6) by the administration of the P₂ purinoceptor antagonist pyridoxalphosphate-6-azophenyl-2′,4′-disulphonic acid (PPADS, 30 μM). PPADS (30 μM) selectively blocked (75±9 and 50±7% inhibition, n=4 each) the contractile responses produced by 100 and 300 μM ATP.
5. Tachykinin-containing nerve fibres were detected by using immunohistochemical techniques in all parts of the bile duct, being distributed to the muscle layer and lamina propria of mucosa. In the terminal part of the duct (ampulla) some labelled ganglion cells were observed.
6. In conclusion, this study shows that in the guinea-pig terminal biliary tract tachykinins, released from intrinsic neuronal elements, are the main NANC excitatory neurotransmitters, which act by stimulating tachykinin NK₂ (and possibly NK₁) receptors. ATP is also involved as excitatory neurotransmitter. Nitric oxide and opioids act as inhibitory mediators/modulators in this preparation.

     

Actions of calcitonin gene-related peptide and tachykinins in relation to the contractile effects of capsaicin in the guinea-pig and rat heart in vitro

Summary 1. The effects of calcitonin gene-related peptide (CGRP), neurokinin A (NKA), neuropeptide K (NPK) and substance P (SP) on contractility of the guinea-pig and rat heart were studied in vitro in relation to the response to capsaicin. 2. Human (h) CGRP alpha (a) and beta () were equipotent in stimulating the contractile force and rate of the spontaneously beating guinea-pig right atrium. 3. Both NKA and NPK inhibited contractile force and rate in the guinea-pig atrium whilst a mainly negative chronotropic effect was observed in the whole heart. SP did not influence cardiac contractility. 4. Human CGRP and mimicked the contractile effects of capsaicin in the guinea-pig atrium. In the whole heart preparation, hCGRP and capsaicin increased heart rate whereas capsaicin also evoked an atropine-resistant inhibition of contractile force. The stimulatory effect of capsaicin on heart rate was absent after systemic capsaicin pretreatment, while the inhibition of ventricular contractile tension remained unchanged. 5. Extended incubation with hCGRP or was associated with development of cross-tachyphylaxis between these two agents in the guinea-pig atrium. However, CGRP tachyphylaxis did not change the atrial response to noradrenaline, forskolin or NKA. The stimulatory effects of capsaicin on atrial contractility were absent after tachyphylaxis to hCGRP or . 6. There was no detectable supersensitivity to the stimulatory effects of rat (r) CGRP on the spontaneously beating atrium after capsaicin pretreatment of adult or neonatal rats. In conclusion the present data provide further evidence that the capsaicin-induced stimulation of atrial contractility is due to local release of CGRP. CGRP tachyphylaxis seems to be a specific, receptor-mediated event and is not related to down-regulation of the adenylate cyclase system. The inhibition of the contractile force in whole heart preparations by capsaicin is most likely due to a non-cholinergic effect independent of tachykinin release. Send offprint requests to A. Franco-Cereceda at the above address     

Modulation of cardiac activity by tachykinins in the rat substantia nigra.

1. The effects of tachykinin NK(1), NK(2) and NK(3) receptor agonists and antagonists were measured on blood pressure (MAP) and heart rate (HR) after bilateral microinjection into the substantia nigra (SN) of awake, unrestrained rats. 2. Increasing doses (25 pmol - 1 nmol) of selective agonists at NK(1) ([Sar(9),Met(O(2))(11)]SP), NK(2) ([beta-Ala(8)]NKA(4 - 10)) and NK(3) (senktide) receptors into the SN produced tachycardia which was selectively and reversibly blocked by the prior injection of tachykinin antagonists at NK(1) (RP67580, 250 pmol), NK(2) (SR48968, 250 pmol) and NK(3) (R-820, 500 pmol) receptor. A rapid fall in MAP followed by a pressor response was seen with 1 nmol of [Sar(9),Met(O(2))(11)]SP. Behavioural activity was elicited by 1 nmol of [Sar(9),Met(O(2)(11)]SP (sniffing > face washing = grooming) and senktide (sniffing > wet dog shake > rearing = locomotion). Tachykinin antagonists had no direct cardiovascular or behavioural effects. 3. The tachycardia produced by 100 pmol of [beta-Ala(8)]NKA(4 - 10) or senktide was abolished by an i.v. treatment with atenolol (beta(1)-adrenoceptor antagonist, 5 mg kg(-1)) while that evoked by [Sar(9),Met(O(2))(11)]SP was reduced. A combination of atenolol (5 mg kg(-1)) and atropine (muscarinic antagonist, 1 mg kg(-1)) blocked the response evoked by [Sar(9),Met(O(2))(11)]SP. 4. These data suggest that the SN is a potential site of modulation of cardiac activity by tachykinins. In addition to the withdrawal of the cardiovagal activity by NK(1) receptor, the three tachykinin receptors appear to increase the sympatho/adrenal drive to the heart. This occurs independently of changes in MAP and behaviour. Hence, this study highlights a new central regulatory mechanism of cardiac autonomic activity.     

Role of kinins in anaphylactic-induced bronchoconstriction mediated by tachykinins in guinea-pigs.

1. In the present study, we have investigated the role of kinins in allergen-induced bronchoconstriction. 2. Anaesthetized guinea-pigs were sensitized to ovalbumin, ventilated artificially, pretreated with atropine (1.4 mumol kg-1, i.v.) and total pulmonary resistance (RL) measured. In preliminary studies in the presence of the neutral endopeptidase inhibitor, phosphoramidon (4.5 mumol kg-1, i.v.), the bradykinin B2 receptor antagonist Hoe 140 (0.1 mumol kg-1, i.v.) completely abolished the increase in RL following aerosolized bradykinin (1 mM, 40 breaths), but had no effect on the increase in RL following aerosolized neurokinin A (NKA, 10 microM, 40 breaths). On the other hand, a combination of the NK1 (CP-96,345, 2 mumol kg-1, i.v.) and NK2 (SR 48968, 0.3 mumol kg-1, i.v.) tachykinin receptor antagonists abolished completely the increase in RL produced by NKA and partially inhibited the increase in RL produced by bradykinin. These results confirm previous studies that suggest that bradykinin induces the release of tachykinins from sensory nerves in guinea-pig airways. 3. Aerosolized ovalbumin (0.5%, 5 breaths) increased RL in sensitized guinea-pigs pretreated with atropine (1.4 mmol kg-1, i.v.), an effect that began within 2 min and reached a maximum within 5 min; RL remained above baseline at 20 min. Pretreatment with the bradykinin B2 receptor antagonist, Hoe 140, decreased the bronchoconstrictor effect of ovalbumin markedly at 10 to 20 min. In the presence of phosphoramidon (4.5 mumol kg-1, i.v.) the inhibition induced by Hoe 140 was apparent earlier and remained over the 20 min period of study.(ABSTRACT TRUNCATED AT 250 WORDS)     

Tachykinin receptors in the guinea-pig renal pelvis: activation by exogenous and endogenous tachykinins.

1. The contractile response to substance P, neurokinin A, selective agonists for the NK1, NK2 and NK3 tachykinin receptors and the activity of receptor-selective antagonists has been investigated in circular muscle strips of the guinea-pig isolated renal pelvis in the presence of indomethacin (3 microM). 2. Neurokinin A was the most potent agonist tested, being about 32 times more potent than substance P. The action of both substance P and neurokinin A was enhanced by peptidase inhibitors (bestatin, captopril and thiorphan, 1 microM each). The selective NK2 receptor agonist [beta Ala8] neurokinin A (4-10), was slightly less potent and effective than neurokinin A itself. The selective NK1 receptor agonist [Sar9] substance P sulphone was effective at low (nM) concentrations but its maximal effect did not exceed 30% of maximal response to substance P or neurokinin A. The NK3-selective agonist [MePhe7] neurokinin B was effective only at high (microM) concentrations. 3. The pseudopeptide derivative of neurokinin A(4-10), MDL 28,564, displayed a clear-cut agonist character, although it was less potent than neurokinin A. 4. The responses to roughly equieffective (25-35% of maximal response) concentrations of [beta Ala8] neurokinin A (4-10), MDL 28,564 and [MePhe7] neurokinin B were antagonized to a similar extent by MEN 10,376 (3 microM), a selective NK2 tachykinin receptor antagonist, while the response to [Sar9] substance P sulphone was unchanged. 5. The response to [Sar9] substance P sulphone was inhibited by the NK1 receptor-selective antagonist, GR 82,334 (3 microM) while the response to [beta Ala8] neurokinin A (4-10) was unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)     

Inflammatory and motor responses by tachykinins in the guinea-pig oesophageal sphincter

1 The aim of this study was to characterize the tachykinin receptors involved in producing plasma protein extravasation and contractile responses of the guinea-pig oesophageal sphincter. 2 In anaesthetized guinea-pigs, the selective tachykinin NK-1 receptor agonist [Sar⁹,Met(O₂)¹¹]substance P produced plasma protein extravasation (PPE) which was not affected by the treatment with the tachykinin NK-2 receptor antagonist MEN 10627 (1 μmol kg^??1 i.v.) or the histamine H₁-receptor antagonist, diphenhydramine (34.5 μmol kg^??1 i.v.). However, the [Sar⁹,Met(O₂)¹¹]substance P-induced PPE was blocked by the previous administration of the peptide tachykinin NK-1 receptor antagonist FK 888 or by the non-peptide antagonist SR 140333, yielding ED₅₀ values of 1.1 ± 0.2 and 0.01 ± 0.004 μmol kg^??1 i.v., respectively. 3 The tachykinin NK-2 or NK-3 receptor agonists [β-Ala⁸]neurokinin A (4–10) or [MePhe⁷]neurokinin B, respectively, produced a weak PPE at high doses. The effect of [MePhe⁷]neurokinin B-induced PPE was inhibited by SR 140333. 4 In the guinea-pig isolated oesophageal sphincter, [Sar⁹,Met(O₂)¹¹]substance P did not exert any contractile effect up to 10 μm . The selective tachykinin NK-2 receptor agonist ([β-Ala⁸]neurokinin A (4–10), produced concentration-dependent contractions (pD₂ = 7.6 ± 0.03) which were inhibited by the selective tachykinin NK-2 receptor antagonist, MEN 10627 (pA₂ = 8.6 ± 0.1). Also, the tachykinin NK-3 receptor selective agonist [MePhe⁷]neurokinin B induced concentration-dependent contractile responses, but these responses were inhibited by MEN 10627. 5 Altogether, these data indicate that the stimulation of tachykinin NK-1 receptor produces a vascular inflammatory response, while activation of tachykinin NK-2 receptors mediate the contraction of the guinea-pig oesophageal sphincter.     

Facilitation by tachykinins of neurotransmission in guinea-pig pulmonary parasympathetic nerves.

1. The effect of tachykinins on cholinergic neurotransmission was studied in an innervated tracheal tube preparation isolated from guinea-pigs anaesthetized with urethane. The tracheal tube was bathed in Krebs-Henseleit solution containing 5 microM indomethacin. 2. Neurokinin A (NKA), eledoisin (El) and substance P (SP) caused concentration-dependent increases in intraluminal pressure (ILP), with an order of potency NKA greater than El much greater than SP. 3. Low concentrations of tachykinins, that had little effect on ILP, caused an increase in the contractions elicited by stimulation of the preganglionic vagal nerve fibres and by postganglionic (transmural) stimulation. The order of potency was NKA greater than or equal to El greater than SP. Contractions induced by exogenous acetylcholine (ACh) were not increased by the tachykinins. 4. The magnitude of the tachykinin-induced augmentation of responses to nerve stimulation was inversely related to stimulation voltage and frequency. 5. These results suggest that tachykinins act on NK2 receptors, both on the trachealis muscle and on postganglionic pulmonary parasympathetic nerve terminals. Activation of the neuronal receptors may increase the probability of transmitter release from the nerve terminals.     

Modulation of gastric contractions in response to tachykinins and bethanechol by extrinsic nerves.

1. Extrinsic reflexes elicited by changes in gastric wall tension play an important role in regulating gastric tone. The present study investigated whether such reflexes modulate gastric contractions induced by close arterially administered neurokinin A (NKA), substance P (SP), SP-methylester and bethancehol in anaesthetized rats. 2. Reflex pathways were acutely interrupted by either subdiaphragmatic vagotomy or prevertebral ganglionectomy. C-fibre afferent nerve activity was abolished by pretreating rats with capsaicin 10 to 16 days before the experiments. 3. The order of potency in inducing gastric contractions was NKA greater than SP greater than bethanechol. SP-methylester was markedly less effective than SP and its effects did not fit sigmoid dose-response curves (DRCs). The maximal responses to NKA, SP, and bethanechol were similar, whilst the DRC for SP was significantly flatter than those for NKA or bethanechol. Pretreatment of the rats with the peptidase inhibitors phosphoramidon or captopril did not increase the contractile response to SP. 4. Prevertebral ganglionectomy had no significant effect on the DRCs for SP and NKA, whereas vagotomy shifted the DRCs for all three test substances to the left. 5. Capsaicin pretreatment did not change the DRC for NKA in rats with intact vagus but shifted that for bethanechol to the left. The leftward of the DRC for NKA caused by vagotomy was prevented in capsaicin-pretreated rats whereas the vagotomy-induced shift of the DRC for bethanechol remained unaltered. The shift of the DRC for SP seen in response to vagotomy was only slightly reduced by capsaicin pretreatment. 6. These data may be interpreted as demonstrating two neuronal mechanisms for modulating drug-induced gastric contractions.(ABSTRACT TRUNCATED AT 250 WORDS)     

一测多评法测定天然辣椒碱中2种主要成分

目的建立以1种对照品同时测定天然辣椒碱中2种成分的质量评价方法。方法以辣椒辣素为对照,采用一测多评法,同时测定辣椒辣素和二氢辣椒辣素的含量。结果测得辣椒辣素与二氢辣椒辣素的相对校正因子为1.12,同时采用外标法和一测多评法测定样品中二氢辣椒辣素含量,采用t检验对二者测定值进行比较,二者之间无显著差异(P>0.05);以辣椒辣素的保留时间为1.00,计算得二氢辣椒辣素的相对保留时间为1.355,相对保留时间及保留时间差的RSD均小于5%。结论采用一测多评法,以辣椒辣素为对照,利用相对校正因子可实现同时测定辣椒辣素和二氢辣椒辣素的含量。