Further investigations on the antipropulsive effect of centrally administered histamine and its relation with morphine

The effect of intracerebroventricularly (i.c.v.) administered histamine (100 μg/rat) on intestinal myoelectrical activity was investigated in the jejunum of fasted rats. Histamine caused the disappearance of phase III and a partial reduction of phase II of migrating myoelectric complexes. This effect was antagonized by i.c.v. pretreatment with mepyramine (10 μg/rat), an H₁ receptor antagonist. Lesions of central noradrenergic neurons by i.c.v. injection of the neurotoxin 6-hydroxydopamine strongly reduced both the inhibition of intestinal propulsion and the migrating myoelectric complexes profile induced by i.c.v. histamine, whereas pretreatment with p-chlorophenylalanine, a selective depletor of serotonin stores, had no effect. It thus appears that aminergic pathways are involved in the visceral effects of central histamine. Mepyramine (200 μg/rat i.c.v.) partially reduced the slowing of intestinal transit induced by high doses of morphine. Pretreatment with compound 48/80 (10 μg/rat i.c.v.), a mast cell degranulator, but not with -fluoromethylhistidine, an irreversible inhibitor of histidine decarboxylase, reduced the antipropulsive action of i.c.v. morphine to the same extent as mepyramine, suggesting that histamine released from cerebral mast cells by high doses of morphine could contribute to the intestinal inhibition by morphine.     

A pharmacological analysis of the rat mast cell 5-HT gastric lesion test and the effects of ketanserin

Pronounced lesions of the gastric mucosa were induced by Compound 48/80 (1.0 mg/kg, i.v.) in rats protected from lethal shock of released histamine by the experimental histamine H₁-antagonist R 37 617. The intensity score of the lesions correlated with serum pepsinogen levels. Generally the stomachs were greatly distended and contained blood and regurgitated food residues. Compounds from many different pharmacological classes were tested in this procedure. Complete protection was obtained with serotonin antagonists. Also isoproterenol and salbutamol fully protected, apparently by counteracting the serotonin-induced circulatory stasis. No obvious effect was obtained with antagonists of acetylcholine, dopamine, and histamine, with α- and β-adrenergic blocking agents, with narcotic analgesics, and with various other agents unless doses were administered that by far exceeded the range of their primary activity. The lowest ED50 of ketanserin for protection was 0.15 mg/kg (time—2 hr, both s.c. and p.o.), indicating its high oral effectiveness against venoconstriction induced by endogenous serotonin. These doses also abolished cyanosis and reduced stomach distension, abnormal gastric contents, and serum pepsinogen levels. In view of the recently elucidated differences between serotonin antagonists, the mast cell 5-HT gastric lesion test appears appropriate to measure the peripheral serotonin S₂-antagonism of compounds.     

Effects of prolonged treatment with compound 48/80 on the gastric mucosa and mast cells in the rat

Effects of prolonged administration of compound 48/80 (48/80) on the gastric mucosa, serotonin and histamine levels in serum, and mast cells of rats were studied. Daily administration of 48/80 (0.75 mg/kg, i.p.) for 2 or 4 days produced widespread gastric lesions. Further administration of the agent for up to 12 days did not aggravate the lesions which had developed in the early period of administration of the drug. There were only a few visible lesions and numerous healed ones. Almost the same phenomenon was observed with the daily administration of serotonin plus histamine (10 mg/kg each, i.p.) for 2 to 12 days. While 48/80 given for 2 or 4 days increased serotonin and histamine levels in serum, it induced no appreciable increase of these amines after 8 or 12 days of treatment. Serotonin and histamine levels in peritoneal mast cells significantly decreased after the treatment with 48/80 over a 4 day period. The decrease in gastric lesions after prolonged treatment with 48/80 is due to both the depletion of serotonin and histamine from mast cells and an increased resistance of the gastric mucosa with healed lesions.     

Compound 48/80 and substance P induced release of histamine and serotonin from rat peritoneal mast cells

The effect of substance P and compound 48/80 on histamine and serotonin release from not isolated and isolated mast cells have been compared in experiments in vitro. The response of not isolated and isolated mast cells were virtually identical. The release of both amines, in response to 48/80 and substance P, was dose-dependent. The percentage of histamine released by 48/80 was significantly higher than the percentage of serotonin, the difference being higher at lower concentrations of compound 48/80 after 15 min of incubation. Substance P also showed a tendency to higher efficiency for histamine than for serotonin release. In contrast to 48/80, the dose-response curves for histamine and serotonin release were parallel. These results support the view that the ratio between histamine and serotonin release depends on the liberator used. They also showed that this ratio can depend on the concentration of the agent inducing secretion. The results indicate that substance P as well as 48/80 act rather selectively as histamine liberators and that there is some difference in releasing properties of 48/80 and substance P.     

Anxiolytic-like effect of saiboku-to, an oriental herbal medicine, on histaminergics-induced anxiety in mice

Effect of saiboku-to, an oriental herbal medicine, on anxiety in mice was investigated using a light/dark test. Anxiogenic- and anxiolytic-like effects were evaluated on the basis of shortened and prolonged time spent in the light zone of the test. Subacute administration (once a day for 7 days) of saiboku-to (0.5-2.0 g/kg, p.o.) induced anxiolytic-like effect. To assess the effect of saiboku-to on brain histaminergic system in a state of anxiety, Compound 48/80 (1.0 microg/2 microl, i.c.v.), a non-neuronal mast cell histamine releaser, or thioperamide (10.0 mg/kg, i.p.), a neuronal histamine releaser possessing the inhibitory effect of histamine H(3) autoreceptors, induced decrease in the time spent in the light zone by co-injection with cimetidine (10.0 microg/2 microl, i.c.v.), a H(2) inhibitor, suggesting anxiety-like effect. These histaminergics-induced experimental anxieties were inhibited by pre-treatment with subacute administration of saiboku-to, as well as single treatment with diazepam. The results suggest that saiboku-to exhibits anxiolytic-like effect closely related to histaminergic system in the brain.     

Inflammatory response induced by intrapleural injection of antiserum to IgE in rat. An evaluation of the role of histamine

Intrapleural injection of antiserum to rat IgE (anti-IgE) into rats resulted in release of histamine from mast cells and rapid effusion of fluid and plasma proteins into the pleural cavity. By 4 hr this was followed by infiltration of neutrophils. These responses were dependent on the amount of anti-IgE injected, and maximal responses were greater than those obtained with compound 48/80. The effusion of fluid and protein, but not the infiltration of cells, was partially suppressed by prior treatment with the H1 histamine receptor antagonist mepyramine (5 mg/kg, s.c.) or the H2 antagonist metiamide (100 mg/kg, s.c.) and was almost totally suppressed (85-88%) when both drugs were administered simultaneously. Neither methysergide (1 and 4 mg/kg, s.c.) nor indomethacin (5 and 10 mg/kg, i.v.) had an effect on the responses to anti-IgE. Although it seemed likely that histamine was a primary mediator of increased vascular permeability, the intrapleural injection of histamine agonists or histamine in large amounts (50 micrograms) provoked a much less intense response than did anti-IgE. The effects of injected histamine may not, therefore, mimic those induced by histamine released from mast cells in situ. The intrapleural injection of histamine releasers such as anti-IgE may serve as a useful model to test the therapeutic efficacy of antihistamine drugs. The present results also confirm previous reports that localized neutrophil infiltration occurs after mast cell degranulation.     

The effect of compound 48/80, substance P and pentagastrin on the isolated guinea pig atrium

It has been shown that histamine is present in guinea pig hearts. In the present work, the effect of some substances, known to liberate mast cell histamine, on the isolated guinea pig atria was studied. Compound 48/80 (100 micrograms/ml), pentagastrin (10(-6) M) and substance P (10(-5) M) were added 2-3 times to the isolated organs and the frequency of contractions was measured. At the end of experiments, the atria were examined histologically for mast cell degranulation. Compound 48/80 and pentagastrin increased the frequency of contractions of isolated atria. Substance P provoked a dose-dependent decrease of contraction frequency; this effect was diminished by atropine (10(-5) M). All three substances provoked pronounced degranulation of mast cells present in the atrium, the effect of substance P being significantly greater than the effects of the other two substances. It can be concluded that mast cells, present in guinea pig atrium, are sensitive to the histamine liberators used; histamine is released in quantities high enough to produce an effect.     

Roles of brain phosphatidylinositol-specific phospholipase C and diacylglycerol lipase in centrally administered histamine-induced adrenomedullary outflow in rats

Recently, we reported that intracerebroventricularly (i.c.v.) administered histamine evokes the secretion of noradrenaline and adrenaline from adrenal medulla by brain cyclooxygenase-1- and thromboxane A2-mediated mechanisms in rats. These results suggest the involvement of brain arachidonic acid cascade in the histamine-induced activation of the central adrenomedullary outflow. Arachidonic acid is released mainly by phospholipase A2 (PLA2)-dependent pathway or phospholipase C (PLC)/diacylglycerol lipase-dependent pathway. In the present study, histamine (27 nmol/animal, i.c.v.) -induced elevation of plasma noradrenaline and adrenaline was dose-dependently reduced by U-73122 (PLC inhibitor) (10 and 100 nmol/animal, i.c.v.), ET-18-OCH3 (phosphatidylinositol-specific PLC inhibitor) (10 and 30 nmol/animal, i.c.v.) and RHC-80267 (diacylglycerol lipase inhibitor) (1.3 and 2.6 micromol/animal, i.c.v.). However, mepacrine (PLA2 inhibitor) (1.1 and 2.2 micromol/animal, i.c.v.) and D609 (phosphatidylcholine-specific PLC inhibitor) (30, 100 and 300 nmol/animal, i.c.v.) had no effect. These results suggest the involvement of brain phosphatidylinositol-specific PLC and diacylglycerol lipase in the centrally administered histamine-induced activation of the adrenomedullary outflow in rats.     

CHANGES IN HISTAMINE CONTENT FOLLOWING PHARMACOLOGICALLY-INDUCED MAST CELL DEGRANULATION IN THE RAT CONJUNCTIVA

Compound 48/80 was applied into one eye of male Wistar rats and a drop of vehicle into the contralateral eye. Another group of rats received sodium cromoglycate in both eyes every 6 h for a period of 48 h. One eye was challenged with compound 48/80 30 min after the end of treatment with sodium cromoglycate. The eyes were monitored clinically and the histamine content of the conjunctiva was determined fluorometrically. The basal histamine levels in rat conjunctival homogenates were quantified. Pharmacologically-induced mast cell degranulation by a single application of 0.1 g ml(-1)of compound 48/80 resulted in significant decreases of conjunctival histamine levels 1, 12 and 24 h after challenge. Sodium cromoglycate prevented the effect of compound 48/80 when administered into the eye prior to the challenge with the non-immunogenic histamine releaser. Upon termination of the application, the membrane stabilizer was unable to reverse the reduced histamine levels in the conjunctival homogenates.     

Role of endogenous serotonin and histamine in the pathogenesis of gastric mucosal lesions in unanaesthetised rats with a single treatment of compound 48/80, a mast cell degranulator.

In unanaethetised rats with a single injection of compound 48/80, a mast cell degranulator (0.75 mg kg-1, i.p.), gastric lesions occurred with increased serum serotonin and histamine levels and reduced gastric mucosal blood flow at 0.5 h after the injection and developed at 3 h. Pretreatment with either cyproheptadine (a serotonin and histamine antagonist) or methysergide (a serotonin antagonist) prevented the formation of gastric mucosal lesions with attenuation of reduced gastric mucosal blood flow at 0.5 h after compound 48/80 injection, while pretreatment with either amitriptyline (a selective inhibitor of histamine release from mast cells), tripelennamine (a histamine H1-receptor antagonist), famotidine (a histamine H2-receptor antagonist) or cimetidine (a histamine H2-receptor antagonist) had no effect. Pretreatment with either cyproheptadine, methysergide, amitriptyline or tripelennamine prevented the development of gastric mucosal lesions at 3 h after compound 48/80 injection, while pretreatment with either famotidine or cimetidine had no effect. These results indicate that in unanaesthetised rats with a single compound 48/80 treatment, acutely released endogenous serotonin causes gastric mucosal lesions, while released endogenous histamine mainly contributes to the lesion development and that gastric acid plays little role in the pathogenesis of the compound 48/80-induced acute gastric lesions.     

Alterations in histamine levels in the rat induced by compound 48/80

Histamine release in the rat was induced in vivo either by a single dose of compound 48/80 injected i.v. or by four repeated, daily doses of the same compound injected i.p. After i.v. injection the levels of blood histamine were determined and after i.p. injections the changes in both tele-methylhistamine and histamine levels in different tissues were investigated. I.v. injection of 48/80 induced a very rapid and marked increase of blood histamine by 7.4 to 11-fold over the control levels within the first two minutes. After repeated i.p. injections of compound 48/80 most tissues showed higher than normal tele-methylhistamine/histamine ratios. The results suggest that agents known to induce release of histamine from mast cells may exert significant changes in blood and tissue histamine levels and that liberated histamine is thereafter extensively catabolized.     

Vascular permeability and vasodilation induced by the Loxosceles intermedia venom in rats: involvement of mast cell degranulation, histamine and 5-HT receptors.

The mechanisms involved in both local and systemic effects of Loxosceles intermedia (brown spider) venom (LIV) are still poorly understood. We show using rats treated with Evans blue dye (50 mg/kg, i.v.) that small doses of the LIV (0.1, 0.3, 1 and 3 microg/site) dose-dependently increase the vascular permeability in rats, an effect unchanged by indomethacin (5mg/kg, i.p.), atropine (1mg/kg, i.p.), HOE-140 (2mg/kg, s.c.) or SR140333 (0.3mg/kg, i.p.), but fully avoided by promethazine (15 mg/kg, i.p.), methysergide (2mg/kg, i.p.) and compound 48/80 (3mg/kg/day for 3 days). Addition of cumulative concentrations of LIV (0.1-5 microg) in phenylephrine-contracted aortic rings resulted in a partial ( approximately 40%) and endothelium-dependent relaxation, inhibited by the nitric oxide synthase inhibitors L-NAME (10 microM) and L-NMMA (1mM), and the guanylate cyclase inhibitors methylene blue (100 microM) and ODQ (10 microM). LIV-induced relaxation was abolished by compound 48/80 (10 microM) and pyrilamine (a selective histamine H1 receptor antagonist; 100 microM), but not by atropine (1 microM) and indomethacin (10 microM). Our results disclose that LIV increases vascular permeability and induces vascular relaxation. These effects occur due to its ability to degranulate mast cells and release mediators such as histamine and serotonin.     

Effects of central and peripheral depletion of serotonergic system on carrageenan-induced paw oedema

The role of serotonergic system was investigated on peripheral inflammation induced by intraplantary injection of carrageenan. Para-chlorophenylalanine (PCPA) was administered intracerebroventriculary (50, 100 microg/rat) or intraperitoneally (150 mg/kg, 3 days) and 2 or 24 h later, respectively, inflammation was induced by injection of carrageenan. Paw oedema was decreased significantly in PCPA-treated (100 microg/rat, i.c.v.) rats compared to control groups. Injection of exogenous serotonin (i.c.v.) by dose of 0.70 nmol/10 microl/rat, but not the dose of 0.35 nmol/10 microl/rat, 15 min after induction of inflammation completely reversed the anti-inflammatory effects of PCPA. Myeloperoxidase activity in inflamed paws was reduced significantly in groups received PCPA (either i.c.v. or i.p.) compared to controls. Exogenous serotonin (0.70 nmol/10 microl/rat) reduced inflammatory response when injected (i.c.v.) 30 min before or 30 min after the induction of inflammation. Injection of serotonin at the time of induction of inflammation had no inflammatory/anti-inflammatory effect. These results suggest that serotonin, as a neurotransmitter in central nervous system, may be involved in modulating peripheral inflammation.     

Attenuation of the antinociceptive action of the selective kappa-opioid receptor agonist, U-50,488H by ICS-205-930

The antinociceptive action of s.c. administered U-50,488H was antagonized by s.c. administered ICS-205-930, a selective 5-HT3 receptor antagonist. To characterize the site of interaction, U-50,488H and ICS-205-930 were administered either intracerebroventricularly (i.c.v.) or intrathecally (i.t.). When U-50,488H was administered i.c.v., its antinociception action was antagonized by ICS-205-930 given either i.c.v. or i.t., increasing the ED50 values of U-50,488H by approximately twofold from 48 to 98 and 90 nmol/mouse, respectively. However, when U-50,488H was administered i.t., its antinociception action was not antagonized by ICS-205-930 given either i.c.v. or i.t. These findings suggest that i.c.v., but not i.t. administered U-50,488H may release serotonin both supraspinally and spinally to interact with 5-HT3 receptors to produce antinociception.     

Involvement of unique mechanisms in the induction of scratching behavior in BALB/c mice by compound 48/80

Compound 48/80 induced scratching behavior in BALB/c mice, and the role of mast cell mediators in this behavior was examined. Mouse scratching behavior was detected and evaluated using a new apparatus, MicroAct. Compound 48/80 increased the incidence of scratching behavior and scratching time in a dose-dependent manner, accompanied by a potent activation of mast cells and a potent increase in vascular permeability. Dibucaine and mu-opioid receptor antagonists inhibited the scratching behavior. Although histamine H(1) receptor antagonists potently inhibited the vascular permeability increase, they did not affect the scratching behavior. Methysergide inhibited the scratching behavior slightly without affecting the vascular permeability increase, whereas cyproheptadine inhibited both. A cyclooxygenase inhibitor, a 5-lipoxygenase-activating protein inhibitor and a PAF receptor antagonist did not affect the scratching behavior. High doses of serotonin induced scratching behavior less frequently than did compound 48/80. Furthermore, mast cell-deficient WBB6F1-W/W(v) mice exhibited frequent scratching behavior after injection of compound 48/80. These results clearly indicate that compound 48/80 can induce scratching behavior in mice independent of mast cell mediators.     

Cyclic AMP independent inhibition by papaverine of histamine release induced by compound 48/80.

Compound 48/80-induced histamine release from isolated rat peritoneal mast cells was inhibited in a dose-dependent manner by papaverine (ic₅₀ approx 20 μM). This effect of papaverine was not influenced by PGE₁ (14–140 μM), even though PGE₁ markedly increased must cell cAMP levels. Papaverine (0.5 mM) completely inhibited histamine release without causing any change in cAMP levels. Theophylline (0.1 and 0.5 mM) potentiated histamine release induced by submaximal concentrations of compound 48/80, while cAMP levels were increased. IBM X was as potent as papaverine in causing inhibition of mast cell phosphodiesterase. IBM X (0.14–0.7 mM) had no effect on histamine release but caused a 6–20 fold increase in mast cell cyclic AMP. Papaverine inhibition of histamine release was gradual at the onset and was parallelled by a depletion of mast cell ATP content. The inhibition of 48/80-induced histamine release and depletion of mast cell ATP levels was reversed by glucose. It is concluded that papaverine induced inhibition of 48/80-induced histamine release is independent of cAMP, is unrelated to phosphodiesterase inhibition but is dependent upon inhibition of energy production.     

A method for determining whether hypotension caused by novel compounds in preclinical development results from histamine release

INTRODUCTION: Many therapeutic agents stimulate histamine release from mast cells, which results in a decrease in blood pressure. The purpose of this study is to establish a method to determine if the mechanism of action, or one of the mechanisms, of hypotensive compounds is related to the release of histamine. The method was developed using a novel hypotensive compound, SC-372. METHODS: In Inactin anesthetized rats, after intravenous administration of SC-372 (0.3-7 mg/kg), the 2 and 7 mg/kg resulted in a dose-dependent decrease in blood pressure. Histamine (0.1 and 1 mg/kg) was injected intravenously to establish whether histamine release was the mechanism of action for the hypotension induced by SC-372. Compound 48/80 (0.1 mg/kg, promotes histamine release) and Cromolyn (1 mg/kg/min, [5 min], prevents histamine release from mast cells) were characterized and used intravenously in combination with/or compared to SC-372. RESULTS: Histamine resulted in a decrease in blood pressure that was unaffected by Cromolyn (1 mg/kg). Administration of Compound 48/80 resulted in a rapid reduction of systemic blood pressure. Intravenous infusion of Cromolyn prior to the injection of Compound 48/80 significantly attentuated the hypotensive response and the increase in histamine levels in the plasma. Intravenous administration of SC-372 resulted in a rapid reduction in blood pressure with a profile similar to that of Compound 48/80. When the rats were treated with Cromolyn prior to the administration of SC-372, both the blood pressure and plasma histamine levels were maintained at their pretreatment control levels. DISCUSSION: These data indicate that Compound 48/80 and Cromolyn can be used in rats to screen for histamine release-dependent drug-induced hypotension and suggest that the rapid decrease in blood pressure caused by SC-372 may result from histamine release from mast cells.     

The role of the renin-angiotensin system in compound 48/80-induced thirst in rats

The role of the renin-angiotensin system in compound 48/80 (3 mg/kg s.c.)-induced thirst in rats was investigated. Bilateral nephrectomy attenuated drinking induced by compound 48/80 but notpolyethylene glycol (PEG) (30%, 5 ml s.c.). Pretreatment with tripelennamine (histamine H1-receptor antagonist, 40 mg/kg i.p.) prior to the administration of compound 48/80 reduced the effect of compound 48/80 on drinking, but pretreatment with cimetidine (histamine H2-receptor antagonist, 40 mg/kg i.p.) or propranolol (β-adrenoceptor antagonist, 10 mg/kg i.p.) had no effect. The effect of SQ 14,225 (angiotensin converting enzyme inhibitor) in various concentrations (0.5–100 mg/kg s.c.) was investigated on the drinking response caused by compound 48/80 (3mg/kg s.c.), PEG (30%, 5 ml s.c.), isoprenaline (0.5 mg/kg s.c.) and hypertonic saline (5.8%, 2 ml s.c.). SQ 14,225 at a dose of 50 mg/kg significantly attenuated the compound 48/80-induced water intake when administered within 30 min prior to the injection of compound 48/80. Pretreatment with a high dose of SQ 14,255 (50 or 100 mg/kg s.c.) 15 min prior to the injection of dipsogens caused inhibition of the drinking response to compound 48/80 or isoprenaline, but not to PEG or hypertonic saline. Pretreatment with lower doses of SQ 14,225 (0.5 or 5 mg/kg, s.c.) had no inhibitory effect on compound 48/80- or isoprenaline-induced water intake. The inhibition of water intake by SQ 14,225 seems to be dependent on the dose and time between administration of SQ 14,225 and compound 48/80 or isoprenaline. Compound 48/80 and hypertonic saline were additively effective in producing the drinking response. The present results suggest that a decrease of plasma volume following plasma extravasation caused by s.c. administration of compound 48/80 may stimulate the juxtaglomerular cells of the kidney to release renin and that the consequent increase of angiotensin in turn stimulates water intake.It is concluded that the renin-angiotensin system makes a contribution to compound 48/80-induced thirst.     

The intracerebroventricularly administered mast cells degranulator compound 48/80 increases the pituitary-adrenocortical activity in rats

The effect of brain mast cells degranulation by compound 48/80 on the pituitary-adrenocortical activity, measured indirectly through corticosterone secretion, and the involvement of a histaminergic mechanism in that stimulation was investigated in conscious rats. All the drugs were given intracerebroventricularly (icv), histamine antagonists 15 min prior to compound 48/80. Compound 48/80 induced a significant dose- and time-related increase in the serum corticosterone levels. That increase, measured 1 h after administration of compound 48/80, was moderately diminished by icv pretreatment of rats with mepyramine and cimetidine, histamine H1- and H2-receptor antagonists. Three hours after administration of compound 48/80 mast cells of the thalamus and the hypothalamus were completely degranulated. At the same time the thalamus and the whole brain histamine levels were substantially higher than in the saline-treated control rats. The above results suggest that histamine liberated from the brain mast cells and central histamine receptors play a moderate role in increasing the pituitary-adrenocortical activity by compound 48/80.     

Antiallergic effects of 4-[2-oxo-3-(1H-tetrazol-5-yl)-2H-chromen-8-yloxy]-bu tyric acid

Antiallergic effects of 4-[2-oxo-3-(1H-tetrazol-5-yl)-2H-chromen-8-yloxy]-buty ric acid (C4C) were studied. C4C is an active principal metabolite of an orally effective antiallergic agent, KP-136. C4C (0.2-1 mg/kg, i.v.) markedly inhibited the mast cell-mediated homologous PCA of rats and the experimental allergic asthma of rats and guinea pigs, although it had almost no effects on heterologous PCA and compound 48/80-induced cutaneous response in rats. C4C (0.2 mg/kg, i.v.) was scarcely effective on cutaneous responses induced by intradermal injection of histamine and serotonin which are principal chemical mediators of rat homologous PCA, and it blocked the decrease of skin histamine content after the PCA. In addition, C4C (0.01-0.5 micrograms/ml) inhibited the increase of 45Ca uptake of mast cells, the histamine release and the degranulation induced by the antigen-antibody interaction. These effects of C4C were much the same as those of KP-136. From the above findings, C4C is considered to be an antiallergic agent that inhibits the mast cell activation by blocking the calcium influx, and it shares similar pharmacological properties with KP-136.