Ketamine may modify intestinal motility by acting at GABAA-receptor complex; An in vitro study on the guinea pig intestine

In the present study the effect of ketamine, a dissociative anaesthetic, on the GABA- and on the specific GABA_A-agonist muscimol-induced responses of the isolated guinea pig ileum was investigated. GABA as well as muscimol produce a concentration-dependent contractile effect on the duodenum, jejunum and ileum. The sensitivity of the intestinal parts to both the above substances increases from the duodenum to the ileum. Ketamine produces a non-competitive inhibition of the GABA- and muscimol-induced contractions of the ileum, while it does not influence the ileal cholinergic contractions induced by exogenous acetylcholine. These results suggest that ketamine may modify intestinal motility through its antagonistic action at the GABA_A-receptor complex.     

Different contractile effects of substance P on the intestine of mammals

Summary The contractile effect of substance P was examined on the longitudinal muscle of isolated sections of the gut of cat, guinea-pig, pig, rabbit, and rat. Substance P caused contraction of all intestinal regions investigated, but there were marked qualitative and quantitative differences in the contractile responses to substance P. Low concentrations of substance P that did not cause tonic contraction (0.22–2.2 nM), increased the phasic longitudinal contractions observed in the ileum of cat, pig, and rabbit. Higher concentrations induced a tonic longitudinal contraction of the ileum, which in the cat, pig and rat was accompanied by facilitation and in the rabbit by inhibition of the phasic contractions. While in the ileum of guinea-pig and rabbit the maximal longitudinal contraction induced by substance P was equal to the maximal effect of acetylcholine, the maximal response to substance P was only about 50% of that to acetylcholine in the ileum of cat, pig, and rat. The jejunum, ilcum and colon of the rabbit responded to substance P and acetylcholine with similar maximal contractions, but the jejunum appeared to be most and the ileum least sensitive to substance P. The results suggest qualitatively and quantitatively different roles of substance P in the intestinal motility of different mammals.     

The antispasmodic activity of Buddleja scordioides and Buddleja perfoliata on isolated intestinal preparations

The antispasmodic activity of extracts from the aerial parts of Buddleja scordioides and Buddleja perfoliata (family: Scrophulariaceae) was studied on isolated tissue preparations from rabbit and guinea pig intestine. The chloroformic extract from the plants exhibited a significant relaxation on the spontaneous contraction of isolated rabbit jejunum at concentrations ranging from 1 to 400 mug/ml, and also caused an inhibitory effect on both K(+) and Ca(2+) induced contractions in the same tissue. The extracts at moderate doses (50 mug/ml) reduced 5-hydroxytryptamine (5-HT), acetylcholine and histamine induced contractions on isolated guinea pig ileum. Therefore, B. scordioides and B. perfoliata possess similar relaxant mechanism of action, in view of the fact that both inhibit K(+) induce contraction and act through serotoninic, muscarinic and histaminic receptors. So, these data support the idea that the extracts may interfere either with calcium mobilization from intracellular stores, or with calcium interaction with regulatory proteins (e.g., calmodulin), or in other steps in the calcium signaling pathway. This leads us to suggest that the spasmolytic effect of both Buddleja species on smooth muscular contractility are due to the same or similar compounds occurring in these two species, which might be present in similar quantities.     

Comparison of the Intestinal Secretory Response to 5-Hydroxytryptamine in the Rat Jejunum and Ileum In-vitro

A secretory response to 5-hydroxytryptamine (5-HT) is observed throughout the intestinal tract; this investigation has compared the nature of this response in the jejunum and ileum of the rat in-vitro. Different basal electrical activity was observed for jejunal and ileal sheets of rat small intestine. In both intact and stripped preparations the basal short-circuit current (SCC) was greater and the tissue resistance lower in the jejunum than in the ileum. 5-HT caused concentration-dependent increases in SCC in intact and stripped preparations of both regions. EC50 values were similar in the jejunum and ileum, stripped sheets from both regions showing greater sensitivity. In the ileum the maximum increase in SCC induced by 5-HT was similar in intact and stripped sheets, but in the jejunum the response was greater in intact preparations. The jejunal response to 5-HT was reduced in the absence of bicarbonate but unaffected by lack of chloride, whereas the ileal response was inhibited by removal of chloride but unaltered in bicarbonate-free conditions. In intact sheets the tetrodotoxin-sensitive neural component was greater in the jejunum. In stripped sheets a neural component could still be detected in the ileum, but not in the jejunum. There are, therefore, fundamental differences in the way in which the jejunum and ileum respond to 5-HT stimulation—the jejunal response is primarily a result of stimulation of bicarbonate secretion whereas chloride secretion predominates in the ileum. The myenteric plexus appears to play a more prominent role in the jejunum; in the ileum other neural elements also contribute to the response.     

Evidence for histamine and 5-hydroxytryptamine like effects of MK-212 on guinea pig ileum, taenia coli and rat fundus strip

MK-212 (1 x 10(-7)M -- 1 x 10(-5)M) produced dose-dependent contractions of guinea pig ileum, taenia coil and rat fundus strip. The responses to MK-212 in all three preparations were blocked competitively by cyproheptadine (1 x 10(-8)M) a 5-HT receptor antagonist. Mepyramine (1 x 10(-8)M)-H1 receptor antagonist also inhibited competitively the responses of guinea pig ileum and taenia coli to MK-212. However, it failed to block significantly the responses of rat fundus strip to MK-212. Metiamide (1 x 10(-6)M), propranolol (1 x 10(-6)M) or atropine (1 x 10(-6)M) did not produce any significant effects on MK-212 induced contractile responses of guinea pig ileum, taenia coli and rat fundus strip. Our findings suggest that MK-212 produces both 5-HT as well as histamine like effects on the guinea-pig ileum, taenia coli and rat fundus strip.     

Spasmolytic constituents of Cedrus deodara (Roxb.) Loud: pharmacological evaluation of himachalol.

Himachalol has been identified as the major antispasmodic constituent in the wood of Cedrus deodara. The pharmacological studies of himachalol on various isolated smooth muscles (guinea pig ileum, rabbit jejunum, rat uterus, and guinea pig seminal vesicle) and against different agonists (acetylcholine, histamine, serotonin, nicotine, and barium chloride) indicated spasmolytic activity similar to that of papaverine. It was a more potent antagonist of barium chloride-induced spasm of guinea pig ileum than papaverine but less effective in reverting a similar spasm of rabbit jejunum and had no relaxing effect alone. In the conscious immobilized cat, intragastric administration of himachalol or papaverine (100 mg/kg) produced equal inhibition of carbachol-induced spasm of the intestine, lasting about 2 hr, but himachalol had a faster onset of action. Himachalol was devoid of spasmolytic effect on the bronchial musculature of guinea pig but was 3.3 times more potent than papaverine in antagonizing epinephrine-induced contraction of the guinea pig seminal vesicle. Intravenous injection of himachalol (3-10 mg/kg) in the cat produced a dose-dependent fall in blood pressure and an increased femoral blood flow.     

Effect of oxybutynin hydrochloride on isolated smooth muscles (ileum, urinary bladder and urethra)

Effects of oxybutynin hydrochloride on isolated smooth muscle were investigated in preparations of isolated rabbit bladder body, bladder base, collum vesicae and urethra. ACh produced a marked contraction of the preparation from the bladder body and produced no response in the collum vesicae and the urethra; however, NE caused a marked contraction of the preparations from the collum vesicae and the urethra and relaxation in the bladder body. Oxybutynin and papaverine hardly had any effect on these preparations. Effects of oxybutynin on the contractile response of the isolated ileum or urinary bladder of rabbit, guinea pig and rat in comparison with atropine, papaverine, flavoxate and other drugs were investigated. The responsibility of these preparations to ACh were approximately 100 times higher in the ileum than in the urinary bladder. Oxybutynin showed a competitive inhibition to contractile response induced by ACh in the ileum and urinary bladder, whose potency was about 1/7-1/10 that of atropine. In the ileum of rats which were treated with oxybutynin orally at a dose of 1, 10 or 100 mg/kg for 60 days, the response to ACh in the preparations of the animals treated by 100 mg/kg were decreased, but the anticholinergic action in the groups treated with oxybutynin were not significantly different compared with the nontreated or saline treated group. On the other hand, oxybutynin showed a non-competitive inhibition to contractile response induced by Ba2+, Ca2+ and histamine in the guinea pig ileum and Ba2+, high-K+, Ca2+ and ATP in the rabbit urinary bladder. These potencies of oxybutynin were equal or slightly stronger than that of papaverine or flavoxate. However, oxybutynin had no effect on the contraction induced by NE in the rabbit urethra. The above results suggest that oxybutynin has atropine-like anticholinergic action and direct muscle relaxant action evidenced by non-competitive inhibition to contractile response induced by several agonists.     

Neurokinin A-induced guinea pig gallbladder contraction: Potential mechanism of action

The present study was performed to examine the mechanism of action of neurokinin A (NKA) on guinea pig gallbaldder smooth muscle. Muscle strips were prepared and mounted in 10 mL tissue bath containing Krebs' solution under 1 g tension. NKA induced a concentration-dependent increase in gallbladder muscle tension and reached a maximal response at 1 μM. The EC₅₀ value was approximately 30nM. Preincubation of the muscle strips with neurotoxins, tetrodotoxin (1 μM), or omega-conotoxin (0.1 μM) had no effect on the NKA contractile response. NKA-induced gallbladder contractions were insensitive to cyclooxygenase inhibitors (5 μM) piroxicam and indomethacin. In contrast, the calcium channel blockers verapamil and diltiazem (0.1–1 μM) significantly blocked the contractile response to NKA. The intracellular calcium chelator BAPTA/AM had no significant effect on NKA activity. The removal of extracellular calcium, however, completely abolished the contractile response of NKA. These data suggest that NKA has a direct contractile effect on guinea pig gallbladder smooth muscle, which is independent of prostaglandin release. The primary source of calcium involved in mediating the NKA contractile response is the extracellular pool, suggesting that NKA might act via activation of L-type voltage-operated calcium channels to mediate its action. © 1992 Wiley-Liss, Inc.     

The presynaptic activity of huwentoxin-I, a neurotoxin from the venom of the chinese bird spider Selenocosmia huwena.

Three different types of isolated nerve-synapse preparations, guinea pig ileum, rat vas deferens and toad heart, were used to investigate the physiological activity of Huwentoxin-I, a neurotoxin from the venom of the spider Selenocosmia huwena. The twitch response of isolated guinea pig ileum induced by electrical stimulus can be inhibited by HWTX-I. After blockage, contraction of the ileum can be induced by exogenously applied acetylcholine. HWTX-I caused the inhibition of the twitch response to electrical nerve stimulation in the rat vas deferens. After the twitch was completely inhibited, noradrenaline triggered rhythmic contraction of the vas deferens. The inhibitory effect on heart of toad induced by stimulating sympathetic-vagus nerve can be reversed by HWTX-I, although exogenously applied acetylcholine still acts as an effective inhibitor. All of these results support the conclusion that HWTX-I has the presynaptic activity that effects the release of neurotransmitter from the nerve endings of both the cholinergic synapse and the adrenergic synapse.     

The Alkaloids of Datura quercifolia H.B.K

Abstract

In vitro methods were used to determine the effects of petroleum ether extract of Croton penduliflorus seed oil (PEE-CP) on the guinea pig ileum and rat uterus. Increasing the dose of PEE-CP produced increasing contractile responses in both the guinea pig ileum and rat uterus. Atropine and adrenaline blocked the action of PEE-CP in a dose-dependent manner. Mepyra-mine and hexamethonium partially blocked the responses of the guinea pig ileum and rat uterus to PEE-CP. Some contractions induced by PEE-CP in the guinea pig ileum, which survived te-trodotoxin treatment, were enhanced by neostigmine. PEE-CP appears to produce its effect through cholinergic, histaminergic and β-adrenergic mechanisms.     

Calcium-dependent smooth muscle excitatory effect elicited by the venom of the hydrocoral Millepora complanata.

In the present paper, we describe the results obtained from a preliminary pharmacological and biochemical study of the fire coral Millepora complanata, a regular component of coral reefs in the Mexican Caribbean. The protein-containing crude extract obtained from M. complanata (tested from 0.001 to 1000 microg protein/ml) caused a concentration-dependent stimulation of spontaneous contractions of the guinea pig ileum. The extract (EC(50)=11.55+/-2.36 microg/ml) was approximately 12-fold less potent than ionomycin (EC(50)=0.876+/-0.25 microg/ml) and its maximum induced contraction (1mg protein/ml) was equivalent to 68% of the response to 60mM KCl. FPLC size exclusion chromatography of the M. complanta extract afforded 12 primary fractions, of which only FV (containing proteins with molecular weights ranging from 17 to 44 kDa) and FVIII (consisting of peptides with molecular weights lesser than 1.8k Da) elicited an excitatory effect when tested at the EC(50) of the original extract. After incubation in Ca(2+)-free medium, the ileal response to FV and FVIII was significantly reduced. Blockage of L-type Ca(2+) channels with nifedipine (1 microM) inhibited FV and FVIII-evoked contractions. Cd(2+) (10 microM), an unspecific blocker of voltage-activated calcium channels, also antagonized FV and FVIII-induced effects, whereas the Na(+) channel blocker tetrodotoxin (10nM) did not significantly affect FV and FVIII responses. These results suggest that the contractions induced by the bioactive fractions obtained from the crude extract of M. complanata are caused mainly by a direct action on smooth muscle cells, via an increase in Ca(2+) permeability that occurs, at least partly, through L-type voltage-dependent Ca(2+) channels found in the cell membrane of smooth muscle.     

Further studies on the effects of disodium cromoglycate on guinea pig ileum

Transmural electrical stimulation was carried out on innervated strips of the longitudinal muscle of guinea pig ileum. Disodium cromoglycate (DSCG) inhibited the electrically induced contractions. Five minutes later, prostaglandin E2 (2.5 ng/ml) was added to the bath and it reversed the action of DSCG. Furthermore, DSCG inhibits significantly the guinea pig ileum contractions induced by nicotine and also those induced by histamine and acetylcholine on ileum denervated by cooling. These results suggest that DSCG effects on guinea pig ileum contraction are mediated by membrane-stabilizing properties of this drug on smooth muscle fibres as well as on myenteric plexus.     

Effects of the novel 5-HT3 agonist MKC-733 on the rat, mouse and guinea pig digestive tract

The contractile activity of the novel 5-HT(3) receptor agonist MKC-733 was determined in intestinal tissues of rats, guinea pigs and mice. The potential influence of non-5-HT(3) receptors was removed by the inclusion of methysergide and GR125487. MKC-733 had a lower efficacy than 5-HT in the rat jejunum, ileum and distal colon; however, it had similar efficacy and potency to 5-HT in the rat proximal colon. The activity profile of MKC-733 was different in the guinea pig intestine where it exhibited greater potency and efficacy than 5-HT in all regions. MKC-733 showed little to no response in the regions of the mouse intestine. Responses to MKC-733 in the rat and guinea pig tissues were inhibited by ondansetron, confirming its action on 5-HT(3) receptors. These in vitro studies indicate that MKC-733 displays both regional and species specificities.     

Anticholinergic action of disopyramide in intestinal smooth muscle of the guinea pig: inhibition of muscarinic receptors (M1 and M2).

Antimuscarinic actions of disopyramide were investigated by measuring the contractile responses of intestinal smooth muscles and ligand binding in cardiac and intestinal membrane preparations. Disopyramide caused a parallel shift of the dose-response curves for acetylcholine, McN-A-343, and carbachol to the right in the guinea pig taenia caeci; pA2 values were 5.4 for acetylcholine, 5.5 for McN-A-343 and 5.9 for carbachol. In the guinea pig ileum, disopyramide competitively antagonized acetylcholine in the contractile responses, having the pA2 value of 6.1. In microsomal fractions of the guinea pig taenia caecum and heart, disopyramide was capable of replacing 3H-QNB; K1 values were 7 x 10(-6) M for the taenia and 2 x 10(-6) M for the heart. These results suggest that disopyramide exerts antimuscarinic action through M1 and M2 receptors with a potency approximately 3 times greater for M2 than M1.     

葛缕酮的气道扩张作用和呼吸道抗过敏作用

目的观察留兰香油中葛缕酮的气道扩张作用和对呼吸道介质的影响。方法用豚鼠药物引喘法、豚鼠离体气管片法、致敏豚鼠肺组织ＳＲＳ Ａ释放和拮抗ＳＲＳ Ａ、致敏豚鼠离体气管Ｓｃｈｕｌｔｚ Ｄａｌｅ反应法检测。结果葛缕酮对豚鼠药物性哮喘具有保护作用,灌胃给药延长５０％剂量为７６ｍｇ·ｋｇ－１,气雾给药为６３ｇ·Ｌ－１;对豚鼠离体气管有直接松弛作用,ｐＤ２值为４２７±００８,并有抗氨甲酰胆碱作用;能抑制致敏豚鼠肺组织ＳＲＳ Ａ的释放,ＩＣ５０为１８ｍｇ·Ｌ－１,拮抗ＳＲＳ Ａ收缩回肠的ＩＣ５０为２７ｍｇ·Ｌ－１,并能抑制致敏豚鼠离体气管的Ｓｃｈｕｌｔｚ Ｄａｌｅ反应。结论葛缕酮具有气道扩张作用和呼吸道抗过敏作用。     

Effects of dapiprazole on contractile responses of guinea pig isolated ileum

The effects of dapiprazole, a relatively new alpha 1-adrenolytic agent, on contractile responses and on spontaneous mechanical activity were studied in guinea pig isolated ileum. Dapiprazole (10(-10) to 10(-4) M) produced a concentration-dependent inhibition of high K+ (80 mM) -induced contractions. These inhibitory effects were observed with dapiprazole added either before or after the induced contractions. The Ca2+-induced contractions of K+-depolarized ileum were also inhibited by dapiprazole. Dapiprazole inhibited in a non competitive manner the responses of the ileum to: carbachol, histamine, 5-hydroxytryptamine, pentagastrin, angiotensin II and cholecystokinin. In order to analize whether dapiprazole exerts an intracellular effect on Ca2+-store, skinned preparations were used. The results suggest that dapiprazole might inhibit Ca2+ entry through both voltage-and receptor-operated channels of the smooth muscle membrane.     

Naftopidil, a new alpha-adrenoceptor blocking agent with calcium antagonistic properties: characterization of Ca2+ antagonistic effects.

The newly developed antihypertensive agent naftopidil blocks alpha 1-adrenoceptors and inhibits Ca2+ entry via potential-dependent channels in vascular muscle. The aim of our study was to detect possible Ca2+ channel blocking activity in various isolated preparations of the guinea pig heart. Prazosin and verapamil were used for reference. In papillary muscles, 10 microM of all drugs reduced the force of contraction Fc. The action potential duration and the refractory period were hardly affected by naftopidil, decreased by verapamil, and slightly increased by prazosin. In constant-flow Langendorff hearts, the drugs reduced the perfusion pressure, decreased the Fc, and slowed the spontaneous heart rate (order of potency: verapamil much greater than naftopidil greater than prazosin). In voltage-clamped ventricular cardiomyocytes, the calcium current ICa was completely inhibited by verapamil (pD2 value of 6.9) and to 53.5% by naftopidil (pD2 value of 6.4). Prazosin (10 microM) decreased ICa by little more than 10%. There were no differences in the steady-state inhibition of ICa by the two enantiomers of naftopidil. The block of ICa was clearly use dependent. Radioligand binding studies with (+)-[3H]PN 200-110. (-)-[3H]desmethoxy-verapamil, and (+)-cis-[3H]diltiazem in guinea pig skeletal muscle T-tubulus membranes demonstrated that racemic naftopidil exhibited some affinity for the three distinct drug receptor domains of the L-type Ca2+ channel. In conclusion, the present data are consistent with the hypothesis that naftopidil is a weak ligand for L-type calcium channels. It partially blocks ICa and shows no stereoselectivity.     

Some pharmacological characteristics of the guinea pig ileum opioid system activated by cholecystokinin.

Naloxone, added after contractions induced by CCK-8 on the guinea pig ileum preparation, elicited a contraction attributed to the release of endogenous opioid which could inhibit the excitatory action of the peptide. With large concentrations of CCK-8, the preparation gave reproducible responses with time. Naloxone, added before the peptide, protracted the excitatory response to CCK-8, but not its height. Morphine decreased the response to CCK-8 but simultaneously raised the response to naloxone. The latter effect appeared very similar to the withdrawal contraction observed after brief exposure of the opioid in the guinea pig ileum to opioids. Clonidine, and alpha-2 adrenoceptor agonist, and nifedipine, a calcium channel antagonist, both known to interfere with tolerance and physical dependence, affected the excitatory response to CCK-8 and the subsequent response to naloxone in a different way.     

Effect of shakuyaku-extract on electrical stimulation induced contraction of guinea pig ileum

It was reported that Paeoniae Radix extracts (S) depressed the contraction induced by electrical stimulation on the isolated guinea pig ileum. In the present study, the mechanisms of the inhibitory action of S on the contraction of guinea pig ileum were investigated. Theophylline and phentolamine are respective antagonists of adenosine and norepinephrine, decreased the inhibitory action by S on the contraction of guinea pig ileum about 50%. Thus these data suggest that some unknown substances with adrenergic and adenosine like actions may be contained in S. Furthermore the possibility of other inhibitors in S was suggested.     

异型南五味子丁素和戈米辛J对豚鼠心室肌细胞L—型钙离子通道的阻断作用

目的：研究异型南五味子丁素（HD）和戈米辛J（GJ）对豚鼠心肌L－型钙离子通道的作用。方法：全细胞膜片箝记录。结果：异型南五子丁素1,10μmol／L及戈米辛J10μmol／L可抑制L－型Ca^2 电流。HD和GJ对钙电流稳态激活都无影响,但它们可改变钙电流的稳态失活,提示两种药物作用于L－型钙通道的失活态.结论：HD和GJ对豚鼠心室肌细胞L－型钙离子通道有阻断作用。