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S Giuliani

Publications and source records attributed to S Giuliani.

At least 91 records · Page 5Linked to original sources
PubMed1994

A thiorphan-sensitive mechanism regulates the action of both exogenous and endogenous calcitonin gene-related peptide (CGRP) in the guinea-pig ureter.

The aim of this study was to assess the existence of mechanisms regulating the intensity and duration of action of calcitonin gene-related peptide (CGRP), the main candidate inhibitory transmitter released from capsaicin-sensitive afferents in the guinea-pig ureter. In a first series of experiments, performed in capsaicin-pretreated ureters, exogenously administered human alpha CGRP (h alpha CGRP) produced inhibition of contractions of the guinea-pig isolated ureter evoked by direct electrical stimulation of smooth muscle. The intensity and duration of the inhibitory effect of h alpha CGRP were potentiated by the inhibitor of neutral endopeptidase, thiorphan, while captopril and bestatin were without effect. In a second series of experiments, background motility of the guinea-pig ureter was evoked by administration of endothelin-1 (ET-1): electrical stimulation of intramural nerves produced a transient suppression of the ET-1-evoked contractions, ascribable to release of endogenous CGRP. Thiorphan enhanced the inhibitory effect produced by endogenous CGRP, while bestatin and captopril were without effect. These findings demonstrate that a thiorphan-sensitive mechanism, presumably neutral endopeptidase, regulates the intensity and duration of the inhibitory activity of both exogenous and endogenous CGRP in the guinea-pig ureter. The existence of a mechanisms for inactivation of the released peptide is consistent with the proposed role of CGRP as inhibitory neurotransmitter in this preparation.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1994

Effect of Bay K 8644 and ryanodine on the refractory period, action potential and mechanical response of the guinea-pig ureter to electrical stimulation.

We have investigated the effect of the dihydropyridine calcium channel agonist, Bay K 8644, and of the plant alkaloid blocker of calcium-induced calcium release (CICR) from the sarcoplasmic reticulum, ryanodine, on the refractory period, action potential and mechanical response of the guinea-pig isolated ureter to electrical stimulation. All experiments were performed in ureters pre-exposed to 10 microM capsaicin to eliminate the inhibitory influence exerted by local release of sensory neuropeptides on ureteral excitability and contraction. In organ bath experiments, electrical field stimulation with parameters which produce direct excitation of ureteral smooth muscle (train of pulses at 10 Hz, 5 ms pulse width, 60 V for 1 s) produced tetrodotoxin- (1 microM) resistant phasic contractions. The response to EFS was abolished by nifedipine (1 nM-3 microM) and was enhanced by Bay K 8644 (1 nM-3 microM). In the presence of Bay K 8644 (1 microM), nifedipine (30 microM) abolished the evoked contractions. Ryanodine (10-100 microM) had no significant effect on the amplitude of evoked contraction. The response of the guinea-pig ureter to direct electrical stimulation of smooth muscle is characterized by a refractory period: at least 40 s interstimulus interval was required to produce a second response in all preparations tested. Bay K 8644 (1 microM) markedly reduced the refractory period of the ureter and a similar effect was observed with ryanodine (100 microM). To further analyze the effect of Bay K 8644 and ryanodine on the refractory period, the response of the ureter was investigated over a 10 s period of stimulation (other parameters as above). In control ureters, continuous stimulation for 10 s produced only one phasic contraction just after the beginning of the train of stimuli. In the presence of Bay K 8644 or ryanodine, more than one phasic contraction developed during a 10 s stimulation, i.e. the refractory period became shorter than the train duration. When both Bay K 8644 and ryanodine were tested on the same preparations, an additive excitatory effect was observed on the mechanical response to electrical stimulation. A slight elevation of KCl concentration (5-10 mM) reduced the refractory period of the ureter as observed with ryanodine or Bay K 8644. Application of KCl (80 mM) produced a biphasic contractile response of the ureter: a series of phasic contractions occurred first, which were then replaced by a slowly developing tonic response. Bay K 8644 (1 microM) enhanced both components of the response to KCl. Ryanodine (10 and 100 microM) markedly prolonged the duration of phasic contractions evoked by KCl and, at 100 microM, slightly (about 25%) reduced the amplitude of tonic contraction.(ABSTRACT TRUNCATED AT 400 WORDS)

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1994

Effect of omega-conotoxin on cholinergic and tachykininergic excitatory neurotransmission to the circular muscle of the guinea-pig colon.

The aim of this study was to compare the stimulus-response characteristics of the cholinergic and tachykininergic excitatory transmission to the circular muscle of the guinea-pig proximal colon and their susceptibility to inhibition by the N-type calcium channel blocker omega-conotoxin (CTX). All experiments were performed in the presence of guanethidine (3 microM), indomethacin (10 microM), L-nitroarginine (L-NOARG, 30 microM) and apamin (0.1 microM). In the presence of the tachykinin receptor antagonists, FK 888 (10 microM0 and GR 94,800 (3 microM), to block NK1 and NK2 receptors, respectively, electrical field stimulation (EFS) produced frequency-dependent atropine- (1 microM) sensitive contractions. In the presence of atropine (1 microM), EFS produced tachykininergic contractions which were abolished by the combined administration of FK 888 (10 microM) and GR 94,800 (3 microM). The maximal responses produced by cholinergic and tachykininergic neurotransmission ranged between 80 and 100% of the maximal contractile response to 80 mM KCl. The frequency of stimulation, pulse width and voltage required to produce 50% of the maximal cholinergic and tachykininergic contraction were not different from each other, although cholinergic transmission appeared more efficient in producing twitch contractions in response to single pulse EFS. Furthermore, cholinergic transmission was more efficient than tachykininergic transmission in producing contraction in response to short periods of EFS. CTX (0.1 microM for 30 min) produced a large and comparable rightward shift of the cholinergic and tachykininergic frequency-response curve (19 and 17 fold increase in the frequency of stimulation producing 50% of the maximal response, respectively) and markedly depressed (51 and 43% inhibition, respectively) the maximal concentrations response.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗
PubMed1994

Multiple mechanisms in the smooth muscle relaxant action of calcitonin gene-related peptide (CGRP) in the guinea-pig ureter.

We have investigated the ability of human alpha CGRP (CGRP) to inhibit the electrically-evoked myogenic contractions of the guinea-pig ureter, in comparison with the K channel opener, cromakalim, and the adenylate cyclase activator, forskolin. CGRP (0.1 nM-0.1 microM) produced a concentration-dependent inhibition of the evoked contractions; its action was prevented by the CGRP receptor antagonist, CGRP(8-37) (1 microM), while it was unaffected by the nitric oxide (NO) synthase inhibitor, L-nitroarginine (30 microM). The effect of CGRP was antagonized in a noncompetitive manner (depression of Emax, no change in EC50) by glibenclamide (1-10 microM), a blocker of ATP-sensitive potassium channels (KATP). A substantial fraction of the inhibitory effect of CGRP was glibenclamide-resistant, however. Glibenclamide also blocked the inhibitory action of cromakalim (0.1-10 microM) without affecting the inhibition produced by forskolin (0.1-30 microM). When tested in a low-K medium (extracellular K reduced from 5.9 to 1.2 mM), the inhibitory effects of CGRP, cromakalim and forskolin were enhanced. The inhibitory effect of forskolin was partly antagonized by glibenclamide when tested in a low-K medium. CGRP (0.1 microM), cromakalim (3 microM) and forskolin (10 microM) inhibited the contractile response to KCl (80 mM), which is characterized by a distinct phasic and tonic component: cromakalim selectively inhibited the phasic response to KCl with CGRP and forskolin inhibited both components. The inhibitory effect of CGRP on the phasic contraction to KCl was partly glibenclamide-(1 microM) sensitive, while that on the tonic contraction was glibenclamide-resistant. The inhibitory action of forskolin on both components of the response to KCl was unchanged by glibenclamide.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗
PubMed1994

The behavioral response induced by intravesical instillation of capsaicin rats is mediated by pudendal urethral sensory fibers.

The behavioral response induced by the intravesical instillation of capsaicin has been investigated in catheter-implanted, freely moving, conscious male and female rats. Intravesical instillation of capsaicin (25 nmol/rat in 0.5 ml) evoked an intense licking directed toward the lower abdominal and perineal skin which lasted for 15 min. Capsaicin-induced licking was reduced by systemic capsaicin pretreatment at a dose of 150 mg/kg but not at 50 mg/kg, administered 4 days before the intravesical instillation. Both doses of capsaicin effectively abolished the eye-wiping response to local capsaicin application. The capsaicin-induced licking was preserved (and prolonged) in both male and female animals subjected to bilateral ablation of the pelvic ganglia, 48 h before the intravesical instillation of the irritant. The capsaicin-induced licking was almost abolished by placing a ligature around the proximal urethra (24 h before), in order to avoid the contact of the irritant with the urethra or by previous section of the pudendal nerves (48 h before). One hour intravesical infusion with tetrodotoxin (1 and 10 microM) reduced the amplitude of micturition contractions but did not prevent the licking response evoked by capsaicin. On the contrary, the intravesical infusion of lidocaine (100 mM) abolished both micturition contractions and the capsaicin-induced licking. We conclude that the behavioral response induced by the intravesical instillation of capsaicin is mainly due to the stimulation of urethral afferents travelling within pudendal nerves.

Animals↗
PubMed1994

In vivo effects of neurokinin B on rat urinary bladder motility: involvement of tachykinin NK1 and NK2 receptors.

The ability of the selective tachykinin NK1 and NK2 receptor agonists, [Sar9] substance P (SP) sulfone and [beta Ala8] neurokinin A (NKA), respectively, and neurokinin B (NKB) to stimulate urinary bladder contractions was determined in urethane-anaesthetized rats with intact bladder innervation and in animals with acute, bilateral ablation of pelvic ganglia. In addition, tachykinin receptors mediating the response to the agonists were characterized by means of the non-peptide NK1 and NK2 receptor selective antagonists, RP 67,580 and SR 48,968 respectively. In both experimental conditions (normal and ganglionectomized), the three tachykinin agonists induced a dose-dependent increase in intravesical pressure, however reflex bladder contractions were produced by the agonists only in animals with intact bladder innervation. RP 67,580 (10 mumol/kg, i.v.) reduced the response to [Sar9]SP sulfone (50 pmol/rat) in both preparations without modifying the effects induced by the NK2 receptor agonist. On the other hand, SR 48,968 (1 mumol/kg, i.v.) antagonized responses induced by [beta Ala8] NKA (50 pmol/rat) but not those evoked by [Sar9] SP sulfone. In animals with intact urinary bladder innervation, the effect of NKB (50 pmol/rat) was inhibited by SR 48,968 (1 mumol/kg, i.v.) but not by RP 67,580; on the contrary, in rats with ablation of pelvic ganglia, the direct bladder contraction induced by NKB was reduced by RP 67,580 (10 mumol/kg, i.v.) but not by SR 48,968. We conclude that NKB induces reflex and direct bladder muscle contractions by stimulating NK2 and NK1 receptors, respectively.

Animals↗
PubMed1994

Specialization of tachykinin NK1 and NK2 receptors in producing fast and slow atropine-resistant neurotransmission to the circular muscle of the guinea-pig colon.

We studied the relative contribution of tachykinin NK1 and NK2 receptors in producing nonadrenergic noncholinergic excitation of the circular muscle of the guinea-pig proximal colon in response to electrical field stimulation. All experiments were performed in the presence of atropine, guanethidine, indomethacin, apamin and L-nitroarginine. In organ bath experiments, electrical stimulation produced a tetrodotoxin-sensitive frequency-dependent contraction. The NK1 receptor antagonists, FK 888 (1-10 microM) and GR 82,334 (0.3-3 microM) markedly reduced but did not abolish the nonadrenergic noncholinergic response. The NK2 receptor antagonist, GR 94,800 (0.3-3 microM) was partly effective at 3 microM. The combined administration of FK 888 (10 microM) and GR 94,800 (3 microM) or GR 82,334 and GR 94,800 abolished the nonadrenergic noncholinergic contraction. The response to a prolonged period of stimulation (3 Hz for 5 min) was evenly depressed by FK 888 or GR 82,334, while GR 94,800 was more effective in inhibiting the late (87% inhibition) than the peak response (25% inhibition). In the presence of nifedipine (1 microM) a marked inhibition of the nonadrenergic noncholinergic contraction was observed and a time lag was evident between stimulus application and onset of contraction, which showed slow onset and offset kinetics. The nifedipine-resistant nonadrenergic noncholinergic contraction was unaffected by FK 888 or GR 82,334 but was suppressed by GR 94,800. Submaximally effective (1-3 nM) concentrations of substance P and neurokinin A produced distinct patterns of contraction: the response to substance P was fast and declined rapidly toward baseline; the response to neurokinin A was slow and sustained. In the presence of nifedipine, the response to substance P was greatly depressed and became slower in onset; nifedipine did not affect the contraction to neurokinin A but slowed its time-course. In sucrose gap experiments, either a short (10 Hz for 1 s) or a prolonged period of electrical stimulation (3 Hz for 3 min) evoked membrane depolarization, action potentials and contraction: in response to the "prolonged" stimulation, distinct phasic and tonic component of contraction were observed. Nifedipine abolished action potentials and the phasic contraction produced by a short period of stimulation, reduced by about 50% the maximal contraction developed during the prolonged stimulation without affecting the amplitude of the tonic response. In the presence of nifedipine, GR 82,334 (3 microM) blocked the membrane depolarization but did not affect contraction; GR 94,800 (0.1 microM) did not affect depolarization but abolished contraction.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1994

Calcitonin gene-related peptide (CGRP) regulates excitability and refractory period of the guinea pig ureter.

Previous studies have indicated that calcitonin gene-related peptide (CGRP), released from the peripheral endings of capsaicin-sensitive primary afferent neurons, may play a role as an inhibitory transmitter in the guinea pig ureter. The aim of this study was to compare the effect of capsaicin desensitization and administration of a CGRP receptor antagonist on the excitability and refractory period of the guinea pig ureter to electrical field stimulation. Electrical field stimulation using a long (5 msec.) pulse width produced phasic contractions of the ureter which were unaffected by tetrodotoxin, that is, were produced through direct excitation of ureteral smooth muscle. Human alpha CGRP (1 to 10 nM.) produced a concentration-dependent transient suppression of the evoked contractions, and its effect was prevented by the CGRP receptor antagonist human alpha CGRP(8-37) (1 microM.). In vitro capsaicin pretreatment (10 microM. for 15 minutes) to block neuropeptide release from peripheral endings of sensory nerves or administration of the CGRP receptor antagonist enhanced the responsiveness of the guinea pig ureter to electrical stimulation. In control ureters, the application of two trains of electrical stimuli failed to produce a second contraction at intertrain intervals greater than 20 seconds. The intertrain interval required to obtain a second contraction averaging 50% of the amplitude of the first response (ITI50) of control ureters was about 50 seconds. In vitro capsaicin pretreatment or administration of the CGRP receptor antagonist reduced the refractory period of the ureter to electrical field stimulation: ITI50 averaged 8.8 and 9.1 seconds after capsaicin or CGRP antagonist pretreatment, respectively. These findings demonstrate that capsaicin pretreatment or blockade of CGRP receptors produced qualitatively and quantitatively similar excitatory effects on ureteral excitability and refractory period and are in general agreement with the idea that CGRP is a primary inhibitory transmitter in guinea pig ureter. Inhibition of motility by CGRP could be important for setting the frequency of ureteral peristalsis and suppression of latent pacemakers to prevent the occurrence of antiperistaltic waves.

Animals↗
PubMed1994

Effect of longitudinal muscle-myenteric plexus removal and indomethacin on the response to tachykinin NK-2 and NK-3 receptor agonists in the circular muscle of the guinea-pig ileum.

1. The effect of removal of the longitudinal muscle-myenteric plexus (LM-MP) and/or indomethacin (10 microM) on the response to the tachykinin NK-2 receptor selective agonist, [beta Ala8]NKA(4-10), or to the NK-3 receptor selective agonist, senktide, was investigated by measuring mechanical activity (isotonic recording) of circular muscle (ring preparation) of the guinea-pig ileum. 2. Indomethacin (10 microM) increased the percentage of ileal rings displaying spontaneous activity, either intact or LM-MP-free. The response to senktide (10 nM and 1 microM) was lower in LM-MP-free than in intact ileal rings, either in the absence or presence of indomethacin. The response to a low concentration (10 nM) of [beta Ala8] NKA (4-10) was enhanced in LM-MP-free rings and by indomethacin. 3. In intact ileal rings, the response to senktide was unaffected by atropine (3 microM) alone or by the tachykinin NK-2 receptor antagonist MEN 10,376 (10 microM) alone while it was reduced by the combined administration of the two antagonists. The response to senktide was greatly reduced by tetrodotoxin (TTX, 1 microM). Senktide-induced contractions (10 nM) were also reduced by the blocker of N-type voltage-sensitive calcium channels, omega-contoxin (CTX, 0.1 microM). 4. In about 30% of preparations tested, an inhibitory response (decrease in spontaneous activity) to 10 nM senktide, was disclosed in CTX-treated intact ileal rings. This inhibitory effect was TTX-sensitive. 5. In LM-MP-free ileal rings, the response to senktide was abolished or reduced by atropine and MEN 10,376, alone or in combination, and was also reduced or abolished by TTX and CTX. 6. The response to [beta Ala8]NKA (4-10) was inhibited by MEN 10,376, in both intact and LM-MP-free ileal rings while it was unaffected by atropine, TTX or CTX. 7. These results indicate that indomethacin pretreatment induces a regular background activity for studying the motor response to tachykinins in the circular muscle of the ileum, probably by blocking the formation of relaxant prostanoids. A further increase in sensitivity to direct smooth muscle stimulation (NK-2 receptor agonist) can be obtained by removal of the LM-MP. The response to NK-3 receptor stimulation is diminished but not abolished by removal of the LM-MP, suggesting that NK-3 receptors are located on neuronal bodies of myenteric neurons, but possibly also at other sites (possibly, nerve terminals).(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1994

Comparison of tachykinin NK1 and NK2 receptors in the circular muscle of the guinea-pig ileum and proximal colon.

1. The aim of this study was the pharmacological characterization of tachykinin NK1 and NK2 receptors mediating contraction in the circular muscle of the guinea-pig ileum and proximal colon. The action of substance P (SP), neurokinin A (NKA) and of the synthetic agonists [Sar9]SP sulphone, [Glp6,Pro9]SP(6-11) (septide) and [beta Ala8]NKA(4-10) was investigated. The affinities of various peptide and nonpeptide antagonists for the NK1 and NK2 receptor was estimated by use of receptor selective agonists. 2. The natural agonists, SP and NKA, produced concentration-dependent contraction in both preparations. EC50 values were 100 pM and 5 nM for SP, 1.2 nM and 19 nM for NKA in the ileum and colon, respectively. The action of SP and NKA was not significantly modified by peptidase inhibitors (bestatin, captopril and thiorphan, 1 microM each). 3. Synthetic NK1 and NK2 receptor agonists produced concentration-dependent contraction of the circular muscle of the ileum and proximal colon. EC50 values were 83 pM, 36 pM and 10 nM in the ileum, 8 nM, 0.7 nM and 12 nM in the colon for [Sar9]SP sulphone, septide and [beta Ala8]NKA-(4-10), respectively. The pseudopeptide derivative of NKA(4-10), MDL 28,564 behaved as a full or near-to-full agonist in both preparations, its EC50s being 474 nM and 55 nM in the ileum and colon, respectively. 4. Nifedipine (1 microM) abolished the response to septide and [Sar9]SP sulphone in the ileum and produced a rightward shift and large depression of the response in the colon. The response to [beta Ala8]NKA(4-10) was abolished in the ileum and largely unaffected in the colon. 5. The NK1 receptor antagonists, (+/-)-CP 96,34, FK 888 and GR 82,334 competitively antagonized the response to septide and [Sar9]SP sulphone in both preparations without affecting that to [beta Ala8]NKA(4-10). In general, the NK1 receptor antagonists were significantly more potent toward septide than [Sar9]SP sulphone in both preparations. 6. The NK2 receptor antagonists, GR 94,800 and SR 48,968 selectively antagonized the response to [beta Ala8]NKA(4-10) without affecting that to [Sar9]SP sulphone or septide in the ileum and colon. SR 48,968 produced noncompetitive antagonism of the response to the NK2 receptor agonist in the ileum and competitive antagonism in the colon. 7. MEN 10,376 and the cyclic pseudopeptide MEN 10,573 antagonized in a competitive manner the response to [beta Ala8]NKA(4-10) in the ileum and colon. While MEN 10,573 was equipotent in both preparations, MEN 10,376 was significantly more potent in the colon than in the ileum. MEN 10,376was also effective against septide in both preparations, without affecting the response to [Sar9] SP sulphone. MEN 10,573 antagonized the response to [Sar9]SP sulphone and septide in both preparations,pKB values against septide being intermediate, and significantly different from, those measured against[Beta Ala 8]NKA(4-10) and [Sa9]lSP sulphone.8. These findings show that tachykinin NK1 and NK2 receptors mediate contraction of the circular muscle of the guinea-pig ileum and colon. In both preparations NK1 receptor antagonists display higher apparent affinity when tested against septide than [Sar9]SP sulphone. These findings are compatible with the proposed existence of NK1 receptor subtypes in guinea-pig, although alternative explanations (e.g.agonist binding to different epitopes of the same receptor protein) cannot be excluded at present.Furthermore, an intraspecies heterogeneity of the NK2 receptor in the circular muscle of the guinea-pig ileum and colon is suggested.

Animals↗
PubMed1994

Effect of cromakalim and glibenclamide on spontaneous and evoked motility of the guinea-pig isolated renal pelvis and ureter.

1. We have investigated the effect of the potassium (K) channel opener, cromakalim, on the spontaneous myogenic activity of the guinea-pig isolated renal pelvis and on myogenic contractions evoked by direct electrical stimulation of the guinea-pig isolated ureter. 2. In the presence of Bay K 8644 (1 microM), electrical stimulation of the guinea-pig ureter (10 Hz for 1 s, pulse width 5 ms, 60 V) produced regular tetrodotoxin-(1 microM) resistant phasic contractions which were suppressed by 3 microM cromakalim. Glibenclamide (0.1-3 microM), 4-aminopyridine (4-AP, 0.1-2 mM) and tetraethylammonium (TEA, 1-10 mM) produced a concentration-dependent inhibition of the effect of cromakalim with the rank order of potency (EC50 in parentheses): glibenclamide (0.64 microM) >> 4-AP (1.11 mM) > TEA (6.6 mM). Apamin (0.1-0.3 microM) was without effect. 3. Cromakalim (0.1-10 microM) produced concentration-dependent inhibition and suppression of spontaneous contractions of the guinea-pig isolated renal pelvis and of evoked contractions of the ureter with EC50 values of 0.71 and 0.47 microM, respectively. 4. Glibenclamide (1 microM) produced a rightward shift of the concentration-response curve to cromakalim in both the renal pelvis and ureter, without producing depression of the maximal inhibitory effect. Glibenclamide did not affect the spontaneous activity of the renal pelvis while it produced a slight enhancement (10-15% increase) of evoked contractions of the ureter. Glibenclamide did not affect the inhibitory action of the adenylate cyclase activator, forskolin, in the renal pelvis or ureter. 5. In electrophysiological experiments (sucrose gap), cromakalim (0.3 and 1 microM) produced hyperpolarization of ureter smooth muscle. Cromakalim also produced a transient suppression of action potentials and accompanying phasic contractions evoked by electrical stimulation. Before suppression of evoked contractions, a shortening of action potential duration was observed concomitant with the developing hyperpolarization produced by cromakalim. A lower concentration (0.1 MicroM) of cromakalim did not affect membrane potential but shortened action potential duration and reduced the evoked contraction.6. Glibenclamide (1 MicroM) inhibited the hyperpolarizing action of cromakalim and prevented its inhibitory action on evoked action potentials and contractions of the ureter. Glibenclamide also produced a slight prolongation of action potential duration and increased the amplitude and duration of the accompanying mechanical response.7. These findings demonstrate that activation of cromakalim- and glibenclamide-sensitive K channels produces a powerful mechanism for regulation of pyeloureteral motility and suppression of latent pacemakers of the ureter in guinea-pig. Glibenclamide-sensitive K channels take part in determining action potential shape and duration in the guinea-pig ureter.

Action Potentials↗
PubMed1994

Characterization of the capsaicin-sensitive component of cyclophosphamide-induced inflammation in the rat urinary bladder.

1. Cyclophosphamide (CYP) (150 mg kg-1, i.p. 0.5-48 h before) caused a time-dependent plasma protein extravasation in the rat urinary bladder with the maximal extravasation occurring at between 2 and 4 h after administration of the drug. 2. Prior capsaicin desensitization of capsaicin-sensitive primary afferent neurones (CSPANs) (50 mg kg-1, s.c., 4 days before) resulted in approximately 50% inhibition of the magnitude of the extravasation response at the 2 h time-point. 3. Intraperitoneal (i.p.) pretreatment with the tachykinin NK1 receptor antagonist, RP 67,580 (0.44 mg kg-1) or the bradykinin B2 receptor antagonist, Hoe 140 (0.13 mg kg-1) had significant inhibitory effects, giving responses of 56 +/- 6% and 39 +/- 4% of the control extravasation response to CYP treatment after 2 h. Pretreatment with the tachykinin NK2 receptor antagonist, SR 48,968 (0.3 mg kg-1, i.p.), the histamine H1 receptor blocker, chlorpheniramine (10 mg kg-1, i.p.), the 5-HT receptor blocker, methysergide (6 mg kg-1, i.p.) or the cyclo-oxygenase inhibitor indomethacin (5 mg kg-1, i.p.) had no significant effect upon the development of the extravasation response at this same time-point. 4. In rat isolated urinary bladder strips, the active metabolite of CYP, acrolein (1-300 microM) produced a concentration-dependent contraction that was significantly reduced by in vitro capsaicin desensitization (10 microM for 15 min) indicating direct stimulation of CSPANs. CYP was without appreciable effect. 5. The effect of acrolein in vitro was significantly reduced by pretreatment of the bladder with a combination of tachykinin NK1 and NK2 receptor antagonists, RP 67,580 (3 microM) and SR 48,968 (1 microM). The dose-response curve to acrolein was also significantly inhibited by treatment with indomethacin (10 microM) and slightly affected by Hoe 140 (1 microM). 6. These findings demonstrate the contribution of CSPANs to the development of CYP-induced cystitis.Plasma protein extravasation involves activation of tachykinin NKI and bradykinin B2 receptors.Activation of CSPANs in the urinary bladder is likely to be due to the conversion of CYP into its active metabolite, acrolein, and not to a direct effect of CYP upon these nerve-endings.

Acrolein↗
PubMed1994

Arylsulphatase A (ASA) activity in parkinsonism and symptomatic essential tremor.

Arylsulphatase A (ASA) activity was evaluated in 47 patients with a diagnosis of parkinsonism or essential tremor. Mean ASA activity was significantly reduced compared with both a healthy control group of 71 individuals (p < 0.01) and with a group of 44 neurological patients without movement disorders (p < 0.02). Using definite clinical criteria the patients were classified as typical or atypical with respect to Parkinson's disease (PD) or essential tremor (ET). A normal ASA level was found in all the cases showing typical clinical features (PD and ET), while ASA activity was significantly lowered (p < 0.01) in 55.6% of the atypical cases (Parkinsonian syndrome or symptomatic ET). Our data support the hypothesis of a non-casual association between low ASA level and the clinical features of parkinsonism or symptomatic ET.

Aged↗
PubMed1994

MEN 10,627, a novel polycyclic peptide antagonist of tachykinin NK2 receptors.

We describe the in vitro and in vivo pharmacological properties of MEN 10,627 or cyclo(Met-Asp-Trp-Phe-Dap-Leu)cyclo(2 beta-5 beta), the first example of a polycyclic peptide tachykinin NK2 receptor antagonist. MEN 10,627 is endowed with high affinity for NK2 receptor expressed in various species with pKB values ranging between 10.1 (hamster trachea) and 8.1 (rabbit pulmonary artery). The antagonism is of competitive type in both functional and radioligand binding assays. A 100- to 10,000-fold selectivity was found vs. NK1 or NK3 receptors expressed in various species. As an NK2 receptor antagonist, MEN 10,627 is 10- to 100-fold more potent than the monocyclic peptide antagonist L 659,877 or cyclo(Met-Gln-Trp-Phe-Gly-Leu). At the hamster NK2 receptor, MEN 10,627 is about 30-fold more potent than the nonpeptide NK2 receptor antagonist SR 48,968 [(S)-N-methyl-N[4-acetylamino-4-phenylpiperidino)-2-(3,4-dichlorophenyl) butyl]benzamide], whereas the converse is true for the rabbit NK2 receptor. Furthermore, MEN 10,627 is, up to micromolar concentrations, devoid of antagonist properties toward a wide range of transmitters of both peptide and nonpeptide nature. In urethane-anesthetized rats in vivo, MEN 10,627 (10-100 nmol/kg i.v.) produced long-lasting inhibition of contraction of the urinary bladder and duodenum produced by i.v. administration of the NK2 receptor agonist [beta Ala8]NKA(4-10), without affecting the responses produced by i.v. administration of the NK1 receptor agonist [Sar9]SP sulfone or acetylcholine. In anesthetized rats, both MEN 10,627 and SR 48,968 blocked urinary bladder contraction induced by the NK2 receptor agonist after intravenous, intranasal or intraduodenal administration. Equieffective doses of MEN 10,627 producing about 50% inhibition of the response to [beta Ala8]NKA(4-10) in the rat urinary bladder in vivo, were 0.01, 0.03 and 3 mumol/kg after intravenous, intranasal and intraduodenal administration, respectively. The corresponding doses of SR 48,968 were 0.03, 0.1 and 1 mumol/kg, after intravenous, intranasal and intraduodenal administration, respectively. In conclusion, MEN 10,627 is a potent and selective NK2 receptor antagonist, endowed with high potency and long duration of action in vivo, which is not restricted to parenteral administration.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Sequence↗
PubMed1993

MEN 10,573 and MEN 10,612, novel cyclic pseudopeptides which are potent tachykinin NK-2 receptor antagonists.

The activity and selectivity of MEN 10,573 and MEN 10,612, novel cyclic pseudopeptides which are selective tachykinin NK-2 receptor antagonists is described, as compared to that of previously characterized linear and cyclic compounds. For the NK-2 receptor, the activity of test compounds was investigated in the hamster isolated trachea (HT) and the endothelium-deprived rabbit isolated pulmonary artery (RPA), two preparations which are endowed with pharmacologically distinct forms of the NK-2 receptor. The novel cyclic pseudopeptides, MEN 10,573 and MEN 10,612 displayed very high affinity for the NK-2 receptor in the HT (pA2 8.66 and 9.06, respectively) which is higher than that observed in the RPA (pA2 7.31 and 7.41 for MEN 10,573 and MEN 10,612, respectively). The antagonism exerted by MEN 10,573 and MEN 10,612 was of competitive nature in both preparations. MEN 10,573 and MEN 10,612 also displayed competitive antagonism for NK-2 receptor-mediated responses in the rabbit bronchus (RB), rat vas deferens (RVD), circular muscle of the human colon (HUC) and ileum (HUI). In the RB, HUC and HUI, the potency of the novel cyclic pseudopeptides was comparable to that of MDL 29,913 and about 10-fold greater than that of L659,877. In the RVD however, the potency of MEN 10,573 MEN 10,612 or MDL 29,913 was similar to that of L659,877. In anaesthetized rats, i.v. injection of MEN 10,612 produced a selective and long-lasting blockade of the urinary bladder contraction produced by the i.v. injection of the NK-2 receptor selective agonist [beta Ala8]neurokinin A(4-10), without affecting the response to the NK-1 receptor selective agonist [Sar9]substance P sulfone.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1993

Nitric oxide is the mediator of tachykinin NK3 receptor-induced relaxation in the circular muscle of the guinea-pig ileum.

The tachykinin NK3 receptor agonist, senktide, produces concentration-dependent contraction of the circular muscle of the guinea-pig ileum (EC50 2.59 nM). In the presence of the blocker of neuronal type of voltage-sensitive calcium channels, omega-conotoxin (0.1 microM), the contractile response to a low concentration of senktide was converted to an inhibitory effect on spontaneous activity of the ileum. This inhibitory effect was further enhanced in the presence of atropine (1 microM) and was abolished by tetrodotoxin (1 microM), indicating its neural origin. In the presence of atropine and omega-conotoxin, the inhibitory response to senktide (1 nM) was greatly inhibited or even abolished by L-nitroarginine (30 microM), its effect being prevented by L-arginine but not by D-arginine (300 microM in each case). Apamin (0.1 microM) failed to significantly affect the inhibitory response to senktide. Apamin enhanced spontaneous activity of the preparation while L-nitroarginine had no effect. Neither apamin nor L-nitroarginine affected the inhibitory response to isoprenaline. These findings indicate that inhibition of circular muscle activity produced through NK3 receptor stimulation in the guinea-pig ileum is mediated through a neuronal pathway involving nitric oxide or a nitric oxide-like substance(s) generation.

Animals↗