Protection by ipratropium bromide and metaproterenol against methacholine and histamine bronchoconstriction

To establish relative protection against methacholine and histamine, 40 μg of ipratropium bromide, an anticholinergic compound, 1.3 mg of metaproterenol or placebo aerosols were administered by metered-dose inhaler prior lo inhalation challenge with methacholine or histamine in nine asthmatic subjects. Double-blind, randomized challenges were performed. Subjects required a mean methacholine dose of l.72 ± 0.73 and 2.46 ± 0.72 (Ln inhalation units), and mean histamine dose of 2.l6 ± 0.65 and 2.68 ± 0.49, to cause a drop of 20% and 35% respectively in the FEV₁ following the placebo. In the methacholine challenges, both ipratropium bromide and metaproterenol had significant protection as compared to placebo (P<0.001). There was no statistical difference in the degree of protection against methacholine between ipratropium bromide and metaproterenol. In histamine challenges, metaproterenol had significant protection as compared to the placebo, while ipratropium bromide did not protect against histamine.     

Double-blind study of ipratropium bromide, a new anticholinergic bronchodilator.

The efficacy and acceptability of ipratropium given by metered-dose inhaler were evaluated in two double-blind crossover tests against placebo, one preceding and one following a 2-wk period of continual open-label ipratropium treatment. Ten patients with chronic bronchitis and 10 with bronchial asthma participated. Ipratropium produced increase in FEV 1 of more than 15% within 5 min of inhalation, and this effect was maintained for 4 to 5 hr. Statistically significant mean increases over the FEV 1 baseline values were recorded after ipratropium treatment in both the initial and the final crossover tests. There were no adverse reactions to any of the placebo or ipratropium test doses or to the ipratropium treatment. Serial electrocardiograms, laboratory tests, blood pressure, and pulse rate showed no change from lthe baseline. Sputum volume and dry-weight determinations in the patients with bronchitis before and after the 14-day treatment revealed no changes.     

Bronchoconstriction by nebulized metabisulfite solutions (SO2) and its modification by ipratropium bromide

A nebulized solution of sodium metabisulfite (MBS) induced bronchoconstriction in nine subjects with asthma. An anticholinergic drug, ipratropium bromide (IPRA), in doses (500 to 700 micrograms) which were found to inhibit methacholine-induced bronchoconstriction, protected three of the nine subjects against nebulized MBS. These results suggest that both cholinergic and non-cholinergic reflex mechanisms are involved in MBS-induced bronchoconstriction.     

The effect of inhaled ipratropium bromide alone and in combination with oral terfenadine on bronchoconstriction provoked by adenosine 5'-monophosphate and histamine in asthma.

The aim of this study was to investigate the effect of terfenadine, an antihistamine, 180 mg orally, the anticholinergic drug, ipratropium bromide (IB), 0.5 mg nebulized aerosol, the combination of these two drugs, and placebo tablets and aerosol on histamine- and adenosine 5'-monophosphate (AMP)-induced bronchoconstriction in a randomized, double-blind fashion. Airway response was evaluated as FEV1. After placebo, the geometric mean (GM) provocative concentration causing a 20% in FEV1 from the postsaline baseline value (PC20) for histamine and AMP was 0.63 and 5 mg/ml, respectively. Terfenadine displaced the FEV1 concentration-response curves obtained with both histamine (GM PC20 values increasing to 26.92 mg/ml) and AMP (GM PC20 values increasing to 26.7 mg/ml) to the right. IB had a small, but significant, protective effect against the fall in FEV1 produced by histamine and AMP, the GM PC20 values increasing to 1.69 and to 12.6 mg/ml, respectively. Terfenadine and IB in combination produced protection against histamine and AMP that was more than the production produced by either drug alone, the GM PC20 values increasing to 54.76 and 47.7 mg/ml, respectively. There was no correlation between degree of bronchodilatation induced by active treatments and concentration ratios for AMP or histamine. These data suggest that histamine release and vagal reflexes both contribute to AMP-induced bronchoconstriction in clinical asthma in man.     

Antagonism by (D-Pro2, D-Trp7,9)-substance P of the cerebrovascular dilatation induced by substance P

The effects of (D-Pro2, D-Trp7,9)-substance P, a structural analogue of substance P, were examined in two models on cerebrovascular responses to substance P(SP) in cats; in vitro using segments of the middle cerebral artery and in situ by microapplication of the peptides close to pial arterioles. (D-Pro2, D-Trp7,9)-SP in concentrations up to 6.6 x 10(-6) M was without significant effect upon isolated middle cerebral arteries under normal conditions and in arteries contracted with prostaglandin F2 alpha. SP caused concentration-dependent relaxations of middle cerebral arteries contracted by prostaglandin F2 alpha (mean +/- SE; EC50: 2.0 +/- 1.6 x 10(-9) M). The presence of (D-Pro2, D-Trp7,9)-SP shifted the concentration-response curve of SP towards higher concentrations without significantly effecting the maximum response of the arteries to SP. A relaxation by 24.2 +/- 4.0% (n = 6) was obtained in prostaglandin F2 alpha contracted arteries by increasing the potassium concentration with 2 mM in the buffer solution. This response to potassium was unaltered in the presence of 6.6 x 10(-6)M of (D-Pro2, D-Trp7,9)-SP (25.0 +/- 7.1%, n = 5). Perivascular microapplication of SP around individual pial arterioles in situ effected dose-dependent increases in vascular calibre (mean response 14.5 +/- 2% with SP, 10(-7)M). The concomitant perivascular administration of (D-Pro2, D-Trp7,9)-SP (6.6 x 10(-6)M), which alone did not alter the arteriolar calibre, attenuated significantly the cerebrovascular response to SP (mean response 1.5 +/- 3.2%). On the basis of the agonist-antagonist relation found, these observations point to the possibility of a specific SP receptor site in cerebral arteries and arterioles.     

Thyrotropin-releasing hormone (TRH) counteracts neuronal damage induced by a substance P antagonist

Summary Intrathecal administration of the substance P antagonist Spantide caused marked necrotic changes of the gray matter of the spinal cord extending several segments from the injection site. Intravenous treatment with several doses of thyrotropin releasing hormone before and after Spantide injection completely prevented the necrotic lesion.     

Involvement of substance P in hyperalgesia induced by intrathecal galanin.

Previously we have demonstrated that an intrathecal injection of galanin (GAL) decreases the nociceptive threshold for mechanical stimulation without effect on thermal nociceptive responses. The present experiments were conducted to determine whether substance P (SP) would be involved in such a decrease in the nociceptive threshold produced by GAL. An intrathecal injection of anti-SP monoclonal antibody inhibited the nociceptive threshold-decreasing effect of intrathecal GAL (0.1 nmol/rat). This antibody significantly suppressed the contractile action of SP (3 nM) on the longitudinal muscle and that of neurokinin A (3 nM) to a lesser degree. Binding of [125I]Tyr8-SP to this antibody was inhibited by SP in a concentration-dependent manner in the range 0.1-33 nM without suppression by GAL at a concentration of 3300 nM. In addition, an intrathecal injection of the anti-SP monoclonal antibody increased the nociceptive threshold for mechanical stimulation in carrageenin-inflamed rats without effect on thermal nociceptive behaviors. The capsaicin (0.5 microM)-evoked release of immunoreactive SP from dorsal-half slices of the spinal cord was increased by galanin (1 microM, but not 0.1 microM) without effects on basal release. An intrathecal injection of GAL did not produce aversive responses (biting, licking and scratching) at doses of 0.1 and 1 nmol/rat. GAL (0.1 nmol/rat) did not affect biting/licking behaviors evoked by SP (1 nmol/rat), but inhibited SP-evoked scratching behavior. These results suggest that the nociceptive threshold-decreasing action of intrathecal GAL is at least in part mediated by SP, and that GAL may act on primary afferent terminals to increase the release of SP evoked by stimulation.     

Thermal analgesia and substance P depletion induced by capsaicin in guinea-pigs

Treatment of adult guinea-pigs with subcutaneous doses of capsaicin of 1, 5, 50, 200, 200, 500, 500 mg/kg in daily succession increased skin flinch latency and depleted substance P from dorsal root ganglia. Similar treatment of animals with doses of 50, 100, 100, 100, 100 mg/kg significantly increased skin flinch latency and hot-plate escape latency and depleted substance P from dorsal root ganglia and dorsal spinal cord. Capsaicin had no effect on levels of substance P in other CNS regions or in any region of the gastrointestinal tract. Responses to mechanical pressure were not altered by capsaicin treatment.Depletion of primary afferent substance P in guinea-pigs appears to result in substantial thermal antinociception without producing comparable pressure antinociception.     

The protective effect of ipratropium bromide aerosol against bronchospasm induced by hyperventilation and the inhalation of allergen, methacholine and histamine

The ability of the anticholinergic agent, ipratropium bromide, Atrovent, (40 mcg from a metered dose inhaler) to prevent bronchoconstriction produced by four different provocation tests was compared with placebo in 12 asthmatic patients. The provocation tests used were hyperventilation and inhalations of histamine, methacholine and an allergen to which the subject was known to be sensitive. The order in which each patient received the tests was determined according to a Latin-square design and remained the same on both test days. Pretreatment with ipratropium bromide and placebo was allocated randomly and administered in double-blind fashion. Ipratropium bromide provided significant protection at the 5% level against all four types of challenge. The average number of breaths required to produce a fall of at least 20% in FEV1 (forced expiratory volume in one second) was doubled for both histamine and allergen and increased by a factor of six for methacholine. The fall in FEV1 induced by hyperventilation was approximately halved. No side effects were noted with ipratropium bromide.     

Protection of nedocromil sodium on bronchoconstriction induced by inhaled neurokinin A (NKA) in asthmatic patients

Neurokinin A (NKA) has been shown to exert a potent contractile action on bronchial smooth muscles both in vitro and in vivo. Although this effect seems to be due either to a direct action of this peptide on specific muscular receptors or to an indirect effect on mast cells and/or nerves, its mechanism of action in bronchial asthma is still unknown. In the present study we have investigated the airway response to inhaled NKA in 10 asthmatic subjects and the activity of the novel pyranoquinoline dicarboxylic acid drug, nedocromil sodium, on this response. Ten asthmatic patients with stable asthma took part in the study consisting of four separate visits. On the first two occasions we derived histamine and NKA PD15 values in absence of any drug treatment. On the following two visits the inhalation challenge with NKA was performed after administration of either nedocromil sodium or matched placebo administered as pressurized aerosols via metered dose inhalers in a randomized double-blind order. Inhaled NKA produced a dose-related fall in FEV1 in all the subjects studied. Inhaled nedocromil sodium had a significant effect on the FEV1 response to NKA inhalation, the geometric mean PD15 value increasing from 16.6 to 32.2 x 10(-9) mol. We conclude that nedocromil sodium attenuates subsequent responsiveness to inhaled NKA in asthmatic subjects.     

Feeding suppression induced by a fecal anorexigenic substance (FS-T)

Intraperitoneal (IP) injection of a fecal anorexigenic substance (FS-T) induced significant suppression of feeding and this suppression recovered on the second day. At 2 hr after IP injection, at the time of maximum feeding suppression, plasma glucose, insulin and free fatty acid (FFA) levels did not change but amino acid level decreased. Intra-third cerebral ventricle (ICV) infusion of FS-T induced parallel but more potent feeding suppression. Analysis of meal patterns demonstrated that suppression of feeding after ICV treatment continued into the second day. FS-T was applied electrophoretically to glucose-sensitive and non glucose-sensitive neurons in the lateral hypothalamic area (LHA) and to glucoreceptor and non glucoreceptor neurons in the ventromedial hypothalamic nucleus (VMH). It significantly inhibited glucose-sensitive neurons but not non glucose-sensitive neurons, and excited both neuron types in the VMH. FS-T might thus work directly through the hypothalamic feeding control centers to suppress feeding. Even after pronase treatment of FS-T, a non-dialysable fraction of large molecular weight, consisting of protein and carbohydrate, maintained the original anorexigenic activity.     

Synaptically evoked membrane potential oscillations induced by substance P in lamprey motor neurons.

Short-lasting application (10 min) of tachykinin neuropeptides evokes long-lasting (>24 h) modulation of N-methyl-D-aspartate (NMDA)-evoked locomotor network activity in the lamprey spinal cord. In this study, the net effects of the tachykinin substance P on the isolated spinal cord have been examined by recording from motor neurons in the absence of NMDA and ongoing network activity. Brief bath application of substance P (30 s to 2 min) induced irregular membrane potential oscillations in motor neurons. These oscillations consisted of depolarizing and hyperpolarizing phases and were associated with phasic ventral-root activity. The oscillations were blocked by the tachykinin antagonist spantide II. They were also blocked by tetrodotoxin (TTX), suggesting that they were not dependent on intrinsic membrane properties of the motor neurons but were synaptically mediated. Substance P could also have a direct effect, however, because a membrane potential depolarization persisted in the presence of TTX. Protein kinase agonists and antagonists were used to investigate the intracellular pathways through which substance P acted. The oscillations were blocked by the selective protein kinase C (PKC) antagonist chelerythrine. However, the TTX-resistant membrane potential depolarization was not significantly affected by blocking PKC. The protein kinase A and G antagonist H8 did not affect either the oscillations or the direct TTX-resistant membrane potential depolarization. The glutamate receptor antagonist kynurenic acid abolished the substance-P-evoked oscillations, suggesting that they were dependent on glutamate release. The oscillations were abolished or reduced by the AMPA/kainate receptor antagonist 6-cyano-7-nitroquinoxalene-2,3-dione but were only reduced by the NMDA receptor antagonist D-AP5. The oscillations were thus mediated by glutamatergic inputs with a greater dependence on non-NMDA receptors. Blocking glycinergic inputs with strychnine resulted in large depolarizing plateaus and bursts of spikes. The glutamatergic and glycinergic inputs underlying the oscillations are apparently evoked through direct and indirect excitatory effects on inhibitory and excitatory premotor interneurons. Substance P thus has a distributed excitatory effect in the spinal cord. While it can activate premotor networks, this activation alone is not able to evoke a coordinated behaviorally relevant motor output.     

Effect of nedocromil on bronchospasm induced by inhalation of substance P in asthmatic subjects

Several studies have demonstrated that neuropeptides are present in peptidergic fibres of bronchial tissue. The aim of the present study was to evaluate in vivo the effect of nedocromil sodium (2 × 2 mg) on bronchospasm induced by inhalation of substance P. Six moderate asthmatic patients, mean age 25.17 years, were studied. Airway response was measured as FEV₁ and the dose of substance P (using a dose range of 23–736 nmol) producing a 20% decrease in FEV₁ (PD₂₀) was calculated from the individual semilogarithmic dose-response curves. Patients were studied on 3 separate days in a randomized, double-blind manner. On the first day a baseline PD₂₀ value was determined. On subsequent days substance P challenge was performed after pretreatment (20 min before challenge) with either placebo or nedocromil sodium. Student's paired t -test and Wilcoxon's test were used for statistical analysis. The results of this study demonstrated that inhalation of substance P causes a dose-dependent bronchoconstriction and that the bronchoconstriction induced by substance P can be prevented by pre-treatment with nedocromil sodium.     

Effects of verapamil and sodium cromoglycate on bronchoconstriction induced by isocapnic hyperventilation

Twenty-four patients who were known to develop bronchoconstriction in response to isocapnic hyperventilation (IH) took part in a double-blind, placebo-controlled trial to assess the effects of verapamil (5 mg) and sodium cromoglycate (SCG) 20 mg in the prevention of IH-induced bronchoconstriction. Both drug and placebo were inhaled in dry powder form and responses were assessed by serial measurements of forced expiratory volume in 1 sec (FEV₁). Sodium cromoglycate was shown to offer significant protection whereas verapamil powder provoked bronchoconstriction in over 40% of patients and these patients appeared to be those with more marked degrees of bronchial reactivity.     

Onset and duration of inhibition of ipratropium bromide nasal spray on methacholine-induced nasal secretions

We performed a randomized, double-blind, placebo-controlled cross-over study with two different concentrations of ipratropium bromide (Atrovent®) nasal spray to evaluate its onset and duration of inhibition. Twenty-four subjects with perennial rhinitis participated in the trial. Fifteen minutes to 12 hours after administration of ipratropium bromide (42 or 168 μg/nostril) or placebo nasal spray, methacholine challenges were performed and nasal secretion weights measured. After placebo administration the effect of methacholine remained unchanged over the 12-h-period. Both the 42 and 168 μg/nostril doses significantly inhibited the nasal hypersecretions induced by methacholine challenge within 15 min of treatment (P < 0.05). The 168 μg dose of ipratropium bromide continued to significantly reduce secretion weights through 6 hours, but the effectiveness of the 42 μg dose disappeared within 3 h. In addition to having a longer duration, the 168 μg/nostril dose produced approximately twice the inhibitory effect of the 42 μg dose.