Nitric oxide synthase inhibition reverts muscarinic receptor down-regulation induced by pilocarpine- and kainic acid-evoked seizures in rat fronto-parietal cortex.

We investigated how nitric oxide (NO) synthase inhibitor modulates muscarinic receptor expression in epileptic rats. We found that subchronic treatment (4 days) with Nω-nitro-l-arginine reduced the down-regulation of muscarinic receptors induced by pilocarpine and kainic acid in rat fronto-parietal cortex, notwithstanding the dramatic potentiation of seizures induced by both convulsants. Furthermore, functional experiments in fronto-parietal cortex slices, showed that Nω-nitro-l-arginine reduces the down-regulating effect of pilocarpine on carbachol-induced phosphoinositol hydrolysis. Finally, Nω-nitro-l-arginine greatly potentiated the induction of basic fibroblast growth factor (FGF2) by pilocarpine. These data suggest a potential role of NO in a regulatory feedback loop to control muscarinic receptor signal during seizures. The dramatic potentiation of convulsions by NO synthase inhibitors in some animal models of seizures could derive from preventing this feedback loop.

Oral tremor induced by the muscarinic agonist pilocarpine is suppressed by the adenosine A2A antagonists MSX-3 and SCH58261, but not the adenosine A1 antagonist DPCPX.

Tremulous jaw movements in rats, which can be induced by dopamine (DA) antagonists, DA depletion, and cholinomimetics, have served as a useful model for studies of tremor. Although adenosine A(2A) antagonists can reduce the tremulous jaw movements induced by DA antagonists and DA depletion, there are conflicting reports about the interaction between adenosine antagonists and cholinomimetic drugs. The present studies investigated the ability of adenosine antagonists to reverse the tremorogenic effect of the muscarinic agonist pilocarpine. While the adenosine A(2A) antagonist MSX-3 was incapable of reversing the tremulous jaw movements induced by the 4.0mg/kg dose of pilocarpine, both MSX-3 and the adenosine A(2A) antagonist SCH58261 reversed the tremulous jaw movements elicited by 0.5mg/kg pilocarpine. Systemic administration of the adenosine A(1) antagonist DPCPX failed to reverse the tremulous jaw movements induced by either an acute 0.5mg/kg dose of the cholinomimetic pilocarpine or the DA D2 antagonist pimozide, indicating that the tremorolytic effects of adenosine antagonists may be receptor subtype specific. Behaviorally active doses of MSX-3 and SCH 58261 showed substantial in vivo occupancy of A(2A) receptors, but DPCPX did not. The results of these studies support the use of adenosine A(2A) antagonists for the treatment of tremor.

Lipoic acid alters delta-aminolevulinic dehydratase, glutathione peroxidase and Na+,K+-ATPase activities and glutathione-reduced levels in rat hippocampus after pilocarpine-induced seizures.

In the present study, we investigated the effects of lipoic acid (LA) in the brain oxidative stress caused by pilocarpine-induced seizures in adult rats. Wistar rats were treated with 0.9% saline (i.p., control group), lipoic acid (10 mg/kg, i.p., LA group), pilocarpine (400 mg/kg, i.p., pilocarpine group), and the association of LA (10 mg/kg, i.p.) plus pilocarpine (400 mg/kg, i.p.), 30 min before the administration of LA (LA plus pilocarpine group). After the treatments, all groups were observed for 1 h. The enzyme activities [delta-aminolevulinic dehydratase (delta-ALA-D), glutathione peroxidase (GPx), glutathione reductase (GR), and Na+,K+-ATPase] as well as the glutathione-reduced (GSH) and ascorbic acid (AA) concentrations were measured using spectrophotometric methods, and the results were compared to values obtained from saline and pilocarpine-treated animals. Protective effects of LA were also evaluated on the same parameters. In pilocarpine group, no changes were observed in GPx and GR activities and AA content. Moreover, in the same group, decrease in GSH levels as well as a reduction in delta-ALA-D and Na+,K+-ATPase activities after seizures was observed. In turn, in LA plus pilocarpine group, the appearance of seizures was abolished, and the decreases in delta-ALA-D and Na+,K+-ATPase activities produced by seizures as well as increases in GSH levels and GPx activity were reversed, when compared to the pilocarpine seizing group. The results of the present study demonstrated that preadministration of LA abolished seizure episodes induced by pilocarpine in rat, probably by reducing oxidative stress in rat hippocampus caused by seizures.

New derivatives of benzylamide with anticonvulsant activity.

Previously obtained picolinic acid benzylamide is a potent anticonvulsant with low neurotoxicity. In search for new effective anticonvulsants twelve new benzylamides (1-12) were synthesized and preliminary evaluated in the Anticonvulsant Screening Program (ASP) of Antiepileptic Drug Development Program (ADDP) of NIH. Two of them appeared the most promising: 1-cyclopentenecarboxylic acid benzylamide (1-Cpc-BZA) (9) showed MES ED50 = 85,36 mg/kg (PI = 2,49), scPTZ ED50 = 1,37 mg/kg (PI = 1,37), 6Hz-EST ED50 = 50,29 mg/kg and cyclopentanecarboxylic acid benzylamide (Cpc-BZA) (11) showed pilocarpine ED50 = 154.75 mg/kg and pilocarpine ED97 = 270.95 mg/kg.

Neuroprotective effects of erythropoietin in the rat hippocampus after pilocarpine-induced status epilepticus.

Neuroprotective functions of erythropoietin (Epo) are thought to involve a heteroreceptor composed of both Epo receptor (Epo-R) and common beta chain (betac). Here, we measured the response of hippocampal Epo system components (Epo, Epo-R and betac) during neurodegenerative processes following pilocarpine-induced status epilepticus (SE), and examined whether recombinant human Epo (rHuEpo) could support neuronal survival. We evidence that Epo is induced in astroglia following SE, in particular within areas displaying delayed neuronal death. In addition, we demonstrate for the first time that rHuEpo reduces considerably hippocampal neurodegeneration following SE. rHuEpo may thus supplement astroglial induction of Epo to promote enhanced hippocampal neuronal survival following SE. We also show that Epo-R is expressed by neurons and astrocytes mainly, while betac is barely detectable in basal conditions and induced in reactive microglia exclusively following SE. Altogether, our results suggest that Epo/rHuEpo exerts neuroprotection, through Epo-R signaling and independently of betac, and, therefore, may be anti-epileptogenic.

Effects of Salvia officinalis L. (sage) leaves on memory retention and its interaction with the cholinergic system in rats.

OBJECTIVE: The leaves of sage (Salvia officinalis L., Lamiaceae) are reported to have a wide range of biological activities, such as anti-bacterial, fungistatic, virustatic, astringent, eupeptic and anti-hydrotic effects. To determine the mnemogenic effect of sage leaves, we investigated the effects of ethanolic extract of sage leaves and its interaction with cholinergic system on memory retention of passive avoidance learning in rats. METHODS: Post-training intracerebroventricular (i.c.v.) injections were carried out in all the experiments except ethanolic extract (i.p. intraperitoneally). RESULTS: Administration of ethanolic extract (50 mg/kg), pilocarpine (0.5 and 1 mg/rat), the muscarinic cholinoceptor agonist, and nicotine (0.1 and 1 microg/rat) increased, while mecamylamine (1, 5 microg/rat), the muscarinic cholinoceptor antagonist, and mecamylamine (0.01 and 0.1 microg/rat), the nicotine cholinoceptor antagonist decreased memory retention in rats. Activation of muscarinic cholinoceptors by pilocarpine potentiated the response of ethanolic extract. Also, pharmacological blockade of scopolamine attenuated potentiating effect of ethanolic extract. Activation of nicotinic cholinoceptor by nicotine potentiated the response of ethanolic extract. Blockade of nicotinic cholinoceptor by mecamylamine attenuated the response of ethanolic extract. CONCLUSION: It is concluded that the ethanolic extract of salvia officinalis potentiated memory retention and also it has an interaction with muscarinic and nicotinic cholinergic systems that is involved in the memory retention process.

The GABA uptake inhibitor beta-alanine reduces pilocarpine-induced tremor and increases extracellular GABA in substantia nigra pars reticulata as measured by microdialysis.

Substantia nigra pars reticulata (SNr) is a major output nucleus of the basal ganglia that receives GABAergic projections from neostriatum and globus pallidus. Previous research has shown that local pharmacological manipulations of GABA in SNr can influence tremulous jaw movements in rats. Tremulous jaw movements are defined as rapid vertical deflections of the lower jaw that resemble chewing but are not directed at a particular stimulus, and evidence indicates that these movements share many characteristics with parkinsonian tremor in humans. In order to investigate the role of GABA in motor functions related to tremor, the present study tested the GABA uptake blocker beta-alanine for its ability to reduce pilocarpine-induced tremulous jaw movements. In a parallel experiment, the effect of an active dose of beta-alanine on dialysate levels of GABA in SNr was assessed using microdialysis methods. GABA levels in dialysis samples were measured using high performance liquid chromatography with electrochemical detection. beta-Alanine (250-500 mg/kg) significantly reduced tremulous jaw movements induced by pilocarpine (4.0 mg/kg). Moreover, systemic administration of beta-alanine at a dose that reduced tremulous jaw movements (500 mg/kg) resulted in a substantial increase in extracellular levels of GABA in SNr compared to the pre-injection baseline. Thus, the present results are consistent with the hypothesis that GABAergic tone in SNr plays a role in the regulation of tremulous jaw movements. This research may lead to a better understanding of how parkinsonian symptoms are modulated by SNr GABA mechanisms.

Chronic lithium treatment inhibits pilocarpine-induced mossy fiber sprouting in rat hippocampus.

Lithium remains the gold standard in the treatment of bipolar disorder. Long-term treatment with lithium may lead to specific adaptational changes in gene expression that contribute to a neuroprotective effect. In this study, the pilocarpine model of spontaneous limbic epilepsy was used to induce mossy fiber sprouting (axonal growth of the dentate granule cells that synapse on the pyramidal cells of the CA3 region) to examine the prophylactic neuroprotective effects of lithium in vivo. There were four groups of animals: pilocarpine treated (Pil+/Li-); pilocarpine treated followed by lithium (Pil+/Li+); lithium alone (Pil-/Li+); control (Pil-/Li-). Timm staining was used to obtain density measurements in the stratum oriens and the inner molecular layer of the hippocampus. Mossy fiber density was higher in the pilocarpine-treated animals compared to controls. Chronic lithium following pilocarpine treatment attenuated the density of mossy fibers but lithium alone had no effect. No changes in hilar volume or neuronal number were detected using stereological procedures. The ability of lithium to attenuate activation-induced reorganization in the hippocampus provides evidence for its role as a neuroprotective agent in an in vivo model that may be relevant to its clinical effects in bipolar disorder.

Inhibition of pilocarpine-induced salivation in rats by central noradrenaline.

Peripheral treatment with cholinergic or adrenergic agonists results in salivation and the possibility of synergy between cholinergic and adrenergic efferent mechanisms in the control of salivation has been proposed. Central injections of the cholinergic agonist pilocarpine also induce salivation, while the effects of central injections of noradrenaline (norepinephrine) are not known. Here (a) the effects of intracerebroventricular (i.c.v.) injection of noradrenaline on the salivation induced by i.c.v. or intraperitoneal (i.p.) injection of pilocarpine and (b) the receptors involved in the effects of central noradrenaline on pilocarpine-induced salivation were investigated. Male Holtzman rats with a stainless-steel guide cannula implanted into the lateral ventricle were used. Rats were anaesthetized with tribromoethanol (200mg/kg body weight) and saliva was collected on small, preweighed cotton balls inserted into the animal's mouth. Noradrenaline (40, 80 and 160 nmol/1 microl) injected i.c.v. reduced the salivary secretion induced by pilocarpine (0.5 micro mol/1 microl) injected i.c.v.. Noradrenaline (80 and 160 nmol/1 microl) injected i.c.v. also reduced the salivation induced by pilocarpine (4 micromol/kg) injected i.p. Previous treatment with the alpha(2)-adrenergic receptor antagonists RX 821002 (40, 80 and 160 nmol/1 microl) or yohimbine (160 and 320 nmol/1 microl) abolished the inhibitory effect produced by i.c.v. injection of noradrenaline on pilocarpine-induced salivation in rats. Prazosin (alpha(1)-adrenergic receptor antagonist) injected icv did not change the effect of noradrenaline on pilocarpine-induced salivation. Prior icv injection of only RX 821002 (80 or 160 nmol/1 microl) or yohimbine (320 nmol/1 microl) increased pilocarpine-induced salivation. The results show that (1) contrary to its peripheral effects, noradrenaline acting centrally inhibits cholinergic-induced salivation in rats; (2) central mechanisms involving alpha(2)-adrenergic receptors inhibit pilocarpine-induced salivation.

Short-term effects of pilocarpine on rat hippocampal neurons in culture.

PURPOSE: Status epilepticus (SE) has been considered an epileptogenic factor in humans. In the pilocarpine (PILO) model, after a brief period marked by SE, the rats exhibit recurrent spontaneous seizures, mimicking the clinical features of temporal lobe epilepsy. The aim of our study was to identify the molecular actions of PILO that could account for its ability to induce SE. METHODS: Whole-cell mode of the patch-clamp technique was applied to cultured hippocampal neurons (2-3 weeks old) in the absence and in the presence of PILO (1-10 microM), to study the spontaneous activity, the evoked, and the miniature postsynaptic currents. The postsynaptic currents were isolated pharmacologically. RESULTS: PILO (1 and 10 microM) caused an initial increase followed by a decrease in the frequency of spontaneous activity. The increase in the frequency of excitatory postsynaptic currents (EPSCs) and inhibitory PSCs (IPSCs) was blocked by atropine (1 microM), indicating that this effect is mediated through muscarinic receptors. PILO also promoted a brief increase of the amplitude of IPSCs indirectly evoked by stimulation of a neuron synaptically connected to the neuron under study. Conversely, PILO promoted a sustained increase on the amplitude of electrically evoked EPSCs. In presence of tetrodotoxin (TTX; 300 nM), PILO (1 microM) increased the frequency of miniature EPSCs and IPSCs without changing their amplitude during the first 3 min of application. CONCLUSIONS: These results indicate that PILO acting through muscarinic receptor causes an imbalance between excitatory and inhibitory transmission that can result in the generation of SE observed in animals acutely treated with PILO.

Anticonvulsive activity of Butea monosperma flowers in laboratory animals.

The bioassay-guided fractionation of dried flowers of Butea monosperma (BM) was carried out to isolate the active principle responsible for its anticonvulsant activity. The petroleum ether extract was fractionated by column chromatography using solvents of varying polarity such as n-hexane, n-hexane:ethyl acetate, ethyl acetate, and methanol. The anticonvulsive principle of B. monosperma was found to be a triterpene (TBM) present in the n-hexane:ethyl acetate (1:1) fraction of the petroleum ether extract. TBM exhibited anticonvulsant activity against seizures induced by maximum electroshock (MES) and its PD(50) was found to be 34.2+/-18.1 mg/kg. TBM also inhibited seizures induced by pentylenetetrazol (PTZ), electrical kindling, and the combination of lithium sulfate and pilocarpine nitrate (Li-Pilo). However, TBM was not effective against seizures induced by strychnine and picrotoxin. TBM exhibited depressant effect on the central nervous system. After repeated use for 7 days, the PD(50) (MES) of TBM increased to 51.5+/-12.1 mg/kg. Similarly, after repeated use of TBM, the duration of sleep induced by pentobarbital was not reduced significantly. Further studies are required to investigate its usefulness in the treatment of epilepsy.

Evidence for the involvement of the muscarinic cholinergic system in the central actions of pentoxifylline.

This study shows that pentoxifylline (ptx), a xanthine derivative, significantly attenuates scopolamine-induced memory impairment in rats, as demonstrated in a passive avoidance task (50 mg/kg intraperitoneally [i.p.]) and in an elevated T-maze (10 and 50 mg/kg i.p.). Ptx (25, 50 and 100 mg/kg i.p.) also potentiates oxotremorine-induced tremors in mice, in a dose-dependent manner, and this effect was completely prevented by atropine. In addition, ptx (50 and 100 mg/kg i.p.) increased the number of animals developing pilocarpine-induced seizures, and potentiated the latency to the first pilocarpine-induced convulsion. Hippocampus homogenates from rats treated with ptx (100 mg/kg) for 1 week and sacrificed 15 min after the last injection showed a significant decrease in the muscarinic receptor numbers, indicative of a downregulation phenomenon. Similar effects were observed when assays were performed 24 h after the last ptx injection (10 and 50 mg/kg i.p.), but not after 72 h. Additionally, in vitro assays showed that ptx inhibits acetylcholinesterase activity in a dose-dependent manner when incubated with homogenates from rat hippocampus. Our data suggest that the muscarinic agonist effect of ptx could possibly depend on factors such as endogenous cholinergic activity.

Effect of duration of pilocarpine-induced status epilepticus on subsequent cognitive function in rats.

The aim of this study was to determine the effect of the duration of pilocarpine-induced status epilepticus (SE) on subsequent cognitive function in rats. SE was induced by pilocarpine (320 mg/kg i.p.) and was terminated by injection of 1 mg/kg diazepam at 30, 60 and 90 min in 3 groups of 10 rats each. Cognitive function was tested by a passive avoidance task and was assessed at the baseline and on days 1, 7, 14 and 21 (post SE). It was found that cognitive function was disrupted on days 7, 14 and 21 post SE in rats who had SE for 60 and 90 min, whereas it was not affected in rats that had 30 min of SE. Hence, the duration of SE may affect future cognitive performance and mandates emergency treatment.

Effect of MK-801 on pilocarpine-evoked seizures in mice exposed to transient incomplete brain ischemia.

The aim of the study was to examine the role of NMDA receptors in the modulation of brain tolerance after transient cerebral ischemia. Adult mice were exposed for 30 min to bilateral clamping of common carotid arteries (BCCA) under anaesthesia. The non-competitive NMDA antagonist, MK-801 was administered intraperitoneally (ip) in two experimental paradigms: a) acute: twice at 1.0 mg/kg; 1 h before the clamping of the vessels and 6 h after re-circulation; b) chronic at a dose of 0.1 mg/kg, started 24 h after recirculation and continued once daily for 13 days with the last injection 24 h before the induction of convulsions. Seizures were evoked with pilocarpine (400 mg/kg, ip) 14 days after BCCA. It was found that transient incomplete brain ischemia induced protection against pilocarpine toxicity. The acute treatment with MK-801 did not diminish the anticonvulsant action of the procedure. In contrast, the chronic treatment with the drug led to a marked potentiation of the effect. In conclusion, it can be suggested that studied NMDA receptor antagonist used at relatively low dose may enhance the brain tolerance activated after a transient ischemic episode.

[Effects of propiverine hydrochloride (propiverine) on the muscarinic receptor binding affinity in guinea pig tissues and on salivation in conscious dogs].

Propiverine is a drug for the treatment of incontinence and pollakiuria. Such micturitional disorders are principally caused by a hyperactive bladder. The effects of propiverine, its active metabolite, 1-methyl-4-piperidyl benzilate N-oxide (DPr-P-4 (N-->O)), oxybutynin and terodiline on muscarinic receptors in guinea pig urinary bladder, salivary glands, cerebral cortex, ileal longitudinal muscle and heart were compared. Both propiverine and DPr-P-4 (N-->O) competitively inhibited specific binding of 3H-quinuclidinyl benzilate (3H-QNB) to membrane fractions of these tissues. Oxybutynin, terodiline, pirenzepine and atropine also competitively inhibited the binding of 3H-QNB. The order of these drugs in terms of their affinity for muscarinic receptors was as follows: atropine > oxybutynin > pirenzepine, DPr-P-4 (N-->O), terodiline > propiverine. Propiverine and DPr-P-4 (N-->O) had no selectivity for muscarinic receptors in these tissues, the same as atropine. In contrast, pirenzepine, a M1-selective drug, had 10.1 times greater affinity for muscarinic receptors in the cerebral cortex than in urinary bladder, and the affinity of oxybutynin for muscarinic receptors in salivary glands and in cerebral cortex was 10.9 times and 13.9 times higher, respectively, than in urinary bladder. The affinity of terodiline for muscarinic receptors in the cerebral cortex was 4.4 times higher than in urinary bladder. In this study, the effect of propiverine and oxybutynin on pilocarpine (1 mg/kg, s.c.)-induced salivation in conscious dogs was also compared. Propiverine (5 mg/kg, i.v.) had no effect on pilocarpine-induced salivation, whereas oxybutynin (0.1 mg-0.5 mg/kg, i.v.) inhibited it significantly and dose-dependently. The ID50 values (95% confidence limits) for propiverine and oxybutynin during the 20 min after intravenous administration were 6.88 mg/kg (4.71-15.67) and 0.154 mg/kg (0.115-0.205), respectively. These findings suggest that although propiverine, its active metabolite DPr-P-4 (N-->O), oxybutynin and terodiline competitively inhibit the binding of 3H-QNB to muscarinic receptors, the affinity of these drugs for the muscarinic receptors of these tissues is very different and that propiverine has less effect on salivation than oxybutynin.

Treatment with dexamethasone alters yawning behavior induced by cholinergic but not dopaminergic agonist.

Because stressful manipulations have been reported to modify drug-induced yawning, the present study investigated the effects of single and repeated treatment with a synthetic glucocorticoid, dexamethasone (DEXA) on apomorphine- and pilocarpine-induced yawning in male rats. Neither single nor repeated treatment with DEXA altered apomorphine-induced yawning. Single administration of DEXA, however, resulted in an increased number of yawns induced by pilocarpine. Conversely, repeated administration of DEXA led to a decreased number of yawns induced by pilocarpine. In conclusion, the present findings show that dopaminergic and cholinergic are distinctly altered by DEXA, in terms of yawning behavior when animals received DEXA.

Inhibition of pilocarpine-induced aqueous humor flare, hypotony, and miosis by topical administration of anti-inflammatory and anesthetic drugs to dogs.

OBJECTIVE: To investigate the mechanism by which pilocarpine causes increased aqueous humor (AH) flare, hypotony, and miosis in dogs. ANIMALS: 6 dogs with normal eyes. PROCEDURE: Both eyes of each dog were treated topically with a 2% solution of pilocarpine, and 1 eye of each dog was additionally treated with commercially available ophthamic solutions. Breakdown of the blood-aqueous barrier (BAB) was quantitated in each eye, using laser flaremetry to measure AH flare. Intraocular pressure and pupil size were also measured. RESULTS: Pilocarpine caused increased flare from BAB breakdown that was inhibited by the drugs tested. Inhibition (most to least) of BAB breakdown was flurbiprofen more than diclofenac, proparacaine, or suprofen, which were more than 0.125 or 1.0% prednisolone. Inhibition appeared dose-dependent and caused consensual inhibition in the contralateral eye. Intraocular pressure was decreased only in proparacaine-treated eyes and increased in eyes treated with nonsteroidal anti-inflammatory drugs (NSAID). Flurbiprofen and proparacaine were the most effective at blocking miosis. CONCLUSIONS: Pilocarpine produced a predictable, reproducible BAB breakdown in dogs. Miosis and increased AH flare were inhibited equally by proparacaine or NSAID, suggesting that these signs were caused by neuropeptide release into the AH from antidromic stimulation, which subsequently triggers prostaglandin production. Hypotony was inhibited only by anti-inflammatory drugs. CLINICAL RELEVANCE: Proparacaine in combination with pilocarpine would be the best choice for treating dogs with acute glaucoma. Topical administration of NSAID should not be used to treat dogs with acute glaucoma, because they increase intraocular pressure and negate the effects of pilocarpine.

Blockade of pilocarpine- or kainate-induced mossy fiber sprouting by cycloheximide does not prevent subsequent epileptogenesis in rats.

Post-injury sprouting of hippocampal mossy fibers has been suggested to be a causal mechanism underlying the development of temporal lobe epilepsy. However, this hypothesis rests entirely on indirect correlational evidence. Here we demonstrate that cycloheximide, a protein synthesis inhibitor, blocked pilocarpine- and kainate-induced mossy fiber sprouting in rats, but did not prevent the subsequent development of spontaneous seizures or affect their frequency. These results provide direct evidence against a causal role for mossy fiber sprouting in temporal lobe epileptogenesis.

[Antisecretory effect of dl-(15R)-15 methyl-PGE2 methyl ester (PG6E) on perfusing rats in vivo].

The antisecretion effect of dl-(15R)-15 methyl-PGE2 methyl ester (PG6E) was studied in perfusing rats in vivo. The results showed that PG6E at the dose 0.1 mg.kg-1 decreased markedly the acid secretion and antagonized the gastric acid secretion induced by histamine, pilocarpin and pentagastrin in rats. This action of PG6E appeared to be similar to that of cimetidine (40 mg.kg-1).

Further pharmacological study on Sho-seiryu-to as an antiallergic.

Examination was made of the pharmacological characteristics of Sho-seiryu-to, an antiallergic kampo medicine. Sho-seiryu-to suppressed histamine release from rat peritoneal mast cells, but failed to inhibit the binding of [3H]-mepyramine to histamine H1 receptors in guinea pig cerebral cortex and lung. Sho-seiryu-to had no effect on cutaneous reactions induced by serotonin, platelet-activating factor (PAF), leukotriene (LT) C4 or LTD4. Ketotifen prolonged electrically induced convulsions, while Sho-seiryu-to did not. Sho-seiryu-to did not affect salivation induced by pilocarpine. Sho-seiryu-to thus does not appear to inhibit histamine H1 receptors or inflammation induced by serotonin, PAF, LTC4 and LTD4, but suppresses mast cell activity. Sho-seiryu-to would thus have only a few side effects such as dry mouth and convulsions due mainly to the blockage of the action of muscarinic in salivary glands and histamine in the brain.