Gastrointestinal motor activity in conscious ferrets

Gastrointestinal motility was measured with force transducers in conscious ferrets. The gastrointestinal motility pattern in both the interdigestive and digestive states was similar to that reported for humans. The activity front, phase III contractions of the migrating motor complex, occurred cyclically in the antrum and migrated to the duodenum and ileum in the interdigestive state, and relatively low-amplitude contractions were sustained in the antrum, duodenum and ileum in the digestive state. Colonic motility was characterized by basal relatively low-amplitude contractions and a single high-amplitude contraction preceding defecation. Cisapride (0.3-3 mg/kg s.c.) enhanced antral and colonic motility. This ferret model will help the investigation and evaluation of drug effects on gastrointestinal motility in humans.

Effect of ramosetron on short-circuit current response in rat colonic mucosa

We investigated the effects of ramosetron (YM060, (-)-(R)-5-[(1-methyl-1H-indol-3-yl)carbonyl]-4,5,6,7-tetrahydro-1 H-benzimidazole monohydrochloride) on the short-circuit current (Isc) responses to 5-HT receptor agonists in the rat distal colon, and compared its potency to that of other 5-HT3 receptor antagonists. 5-Hydroxytryptamine (5-HT) concentration-dependently increased Isc. The Isc response to 5-HT was partially reduced by tetrodotoxin and ramosetron, and strongly inhibited by GR113808 ([[1-[(2-methyl-sulphonyl) amino]ethyl]-4-piperidin-yl]methyl 1-methyl-1 H-indole-3-carboxylate). 2-Methyl-5-HT and 5-methoxytryptamine also increased Isc. The former response was inhibited by ramosetron, and the latter was abolished by GR113808. Ramosetron, YM114 (KAE-393, (-)-(R)-5-[(1-indolinyl)carbonyl]-4,5,6,7-tetrahydro-1 H-benzimidazole monohydrochloride) and granisetron concentration-dependently antagonized the Isc responses to 2-methyl-5-HT with reduction in the maximal response at higher concentrations. Apparent pA2 values for these antagonists were 10.40, 10.37 and 8.99, respectively. Ondansetron produced clear rightward shifts of the concentration-response curves to 2-methyl-5-HT, with a pA2 value of 8.53. These results suggest that 5-HT increases Isc through the 5-HT3 and 5-HT4 receptors, and that ramosetron is a potent and selective 5-HT3 receptor antagonist in rat colonic mucosa.

YF476 is a new potent and selective gastrin/cholecystokinin-B receptor antagonist in vitro and in vivo

BACKGROUND

We newly synthesized YF476 ((R)-1-[2,3-dihydro-2-oxo-1-pivaloylmethyl-5-(2'-pyridyl)-1H-1, 4benzodiazepin-3-yl]-3-(3-methylamino-phenyl)urea) as a gastrin/cholecystokinin-B (CCK-B) receptor antagonist. We investigated the pharmacological profile of YF476 in vitro and in vivo.

METHODS

We examined the binding properties of YF476 to the rat brain, cloned canine and cloned human gastrin/CCK-B receptors, and the effect of YF476 on secretagogue-induced gastric acid secretion in rats and Heidenhain pouch dogs.

RESULTS

YF476 replaced the specific binding of [125I]CCK-8 to the rat brain, cloned canine and cloned human gastrin/CCK-B receptors, with Ki values of 0.068, 0.62 and 0.19 nM, respectively. The affinity of YF476 for rat brain gastrin/CCK-B receptor was 4100-fold higher than that for rat pancreatic CCK-A receptor. In anaesthetized rats, intravenous YF476 inhibited pentagastrin-induced acid secretion with an ED50 value of 0.0086 micromol/kg, but did not affect histamine- and bethanechol-induced acid secretion at a dose of 10 micromol/kg. In Heidenhain pouch dogs, intravenous and oral YF476 inhibited pentagastrin-stimulated gastric acid secretion in a dose-dependent manner with ED50 values of 0.018 and 0.020 micromol/kg, respectively, but did not affect histamine-induced acid secretion.

CONCLUSION

These results suggest that YF476 is an extremely potent and highly selective gastrin/CCK-B receptor antagonist, and that the gastrin/CCK-B receptor is not involved in histamine- or bethanechol-induced gastric acid secretion in dogs or rats.

[Effects of topical corticosteroids on subepithelial haze after excimer laser corneal surgery--objective and quantitative method for evaluating haze]

To examine the effectiveness of topical corticosteroids in decreasing subepithelial haze induced by excimer laser keratectomy, we performed excimer laser keratectomy on 24 eyes of 12 albino rabbits using a scanning excimer laser system (EC-5000, NIDEK, Japan). Topical dexamethasone 0.1% was applied topically to 8 corneas after surgery (steroid group), but not to the others (control group). Slit-lamp biomicroscopic examination and objective measurement of scattered light from subepithelial haze were performed before and 2, 4, 8 and 12 weeks after surgery, the rabbits were killed after 2 or 12 weeks and the eyes were examined histologically. In both groups, densitometric values of scattered light intensity increased up to 4 weeks after surgery, and then decreased gradually. However, the values of the steroid group were larger than those of the control group at all stages, and the values of the steroid group at 12 weeks after surgery were similar to preoperative values. There was statistically significant difference in scattered light intensity between the two groups (p < 0.005). Two weeks after surgery, the corneas of the control group showed epithelial hyperplasia and a remarkable increase in activated keratocytes and subepithelial fibrous tissues. However, in the steroid group these light microscopic findings could not be observed. At 12 weeks after surgery, the corneas of the control group retained a small amount of activated keratocytes and fibrous tissues, and those of the steroid group were normal. This study suggests that a short course of topical corticosteroids may be very effective in decreasing subepithelial haze after excimer laser corneal surgery.

(3R)-N-(1-(tert-butylcarbonylmethyl)-2,3-dihydro-2-oxo-5-(2-pyridyl)-1H-1,4-benzodiazepin-3-yl)-N'-(3-(methylamino)phenyl)urea (YF476): a potent and orally active gastrin/CCK-B antagonist

A number of new 1,4-benzodiazepin-2-one-based gastrin/CCK-B receptor antagonists related to the archetypal analogue L-365,260, and more closely to the recently reported compound YM022, have been synthesized and evaluated for biological activity. The compounds were screened for their ability to inhibit the binding of [125I]CCK-8 to gastrin/CCK-B receptors prepared from rat brains and that of [3H]L-364,718 to CCK-A receptors from rat pancreas, and were shown to be potent and selective ligands for the gastrin/CCK-B receptor. Functional studies in vivo demonstrated the compounds to be antagonists of the receptor as evidenced by their ability to inhibit pentagastrin-induced gastric acid secretion in anesthetized rats. More extensive evaluation in vivo included determination of ED50 values in the rat acid secretion model for selected compounds and an examination of the effect of these compounds on pentagastrin-induced gastric acid secretion in Heidenhain pouch dogs following oral and intravenous administration. Two compounds, i.e. (3R)-N-[1-[(tert-butylcarbonyl)methyl]-2,3-dihydro-2-oxo-5-(2-pyri dyl) -1H-1,4-benzodiazepin-3-yl]-N'-[3-(methylamino)phenyl]urea, 15c (YF476), and (3R)-N-[1-[(tert-Butylcarbonyl)methyl]-2,3-dihydro-2-oxo-5- (2-pyridyl)-1H-1,4-benzodiazepin-3-yl]-N'-[3-(dimethylamino)phenyl ]urea hydrochloride, 15d, showed potent dose-dependent effects in both models with the former showing excellent oral bioavailability and an ED50 of 21nmol/kg po in dogs. 15c is currently under clinical investigation for the treatment of gastro-oesophagal reflux disease (GORD).

Boron diffusion across the dialysis membrane during hemodialysis

To investigate the movement of boron across the dialysis membrane, serum and dialysate boron levels of long-term hemodialysis (HD) patients (n = 17) were determined using inductively coupled plasma emission spectrometry in both the inlet and the outlet side of the dialyzer. Results revealed that 77.8% of the serum boron in the inlet side of the dialyzer was filterable and 94.4% of filterable boron was actually filtered during HD. Boron dialysance was found to be 138.6 +/- 16.1 ml/min, and this value was higher than the clearance value of blood urea nitrogen (not significant), phosphorus and creatinine (p < 0.001). It is concluded that HD is effective in eliminating serum boron even at low concentrations, and boron can be classified as an element that is easily diffusible across the dialysis membrane. There seems to be relatively little relation of boron to serum constituents of macromolecules that are reported to have a major impact on the diffusion of trace elements across the HD membrane.

Novel 5-hydroxytryptamine (5-HT3) receptor antagonists. Synthesis and structure-activity relationships of 9-methyl-2,3,4,9-tetrahydrothiopyrano[2,3-b]indol-4-one derivatives

Novel 9-methyl-4,9-dihydrothiopyrano[2,3-b]indol-4-one derivatives 2b-e, 3-methylene-9-methyl-2,3,4,9-tetrahydrothiopyrano[2,3-b]indol-4-on e derivatives 3b-e and 9-methyl-2,3,4,9-tetrahydrothiopyrano[2,3-b]indol-4-one derivatives 4a-e were prepared. The 5-hydroxytryptamine (5-HT3) receptor-antagonistic activities of these compounds were evaluated by using the von Bezold-Jarisch reflex test (B. J. reflex, rats) and the contractile response to 5-HT in the isolated distal colon (guinea pig). The 5-ethyl-4-imidazolyl derivative 4d was found to be 79 times more potent than ondansetron 1 in the B. J. reflex test (ID50 = 0.048 microgram/kg, i.v.), and the 5-methyl-4-imidazolyl derivative 4c was found to be 126 times more potent than 1 in the colonic contraction (IC50 = 0.0062 microM) assay.

B cell epitope mapping of the bacterial superantigen staphylococcal enterotoxin B: the dominant epitope region recognized by intravenous IgG

We showed that i.v. IgG contains Abs against a major group of bacterial superantigens, and that they can inhibit superantigen-elicited T cell activation. The B cell epitope region of the superantigen and the inhibitory mechanism have remained unknown. To analyze the dominant B cell epitopes on the bacterial superantigen SEB (staphylococcal enterotoxin B), we constructed fusion proteins of SEB deletion mutants, and the reactivities of these recombinant proteins to i.v. IgG and healthy human sera were evaluated by means of immunoblotting. Intravenous IgG and healthy human sera mostly recognized the C-terminal fragment (amino acid (aa) 133-239). The C-terminally truncated protein (aa 1-228) and the truncated mutant delta 225-234 lost reactivity, while the truncated protein (aa 1-234) did not, suggesting that the region (aa 225-234) is the dominant B cell epitope. The mutant, in which residues 226-229 of SEB were exchanged for residues 209-212 of streptococcal pyrogenic exotoxin A, reduced the reactivity with the C-terminal region-specific IgG purified by affinity chromatography. The C-terminal region-specific IgG inhibited SEB-elicited T cell activation, suggesting that this Ab that recognizes the epitope functions as the humoral defensive factor against SEB in humans. Furthermore, the assumed epitope region was homology to the residues (aa 32-41) of human thymopoietin, containing the biologic active site.

B cell epitope mapping of the bacterial superantigen staphylococcal enterotoxin B: the dominant epitope region recognized by intravenous IgG

We showed that i.v. IgG contains Abs against a major group of bacterial superantigens, and that they can inhibit superantigen-elicited T cell activation. The B cell epitope region of the superantigen and the inhibitory mechanism have remained unknown. To analyze the dominant B cell epitopes on the bacterial superantigen SEB (staphylococcal enterotoxin B), we constructed fusion proteins of SEB deletion mutants, and the reactivities of these recombinant proteins to i.v. IgG and healthy human sera were evaluated by means of immunoblotting. Intravenous IgG and healthy human sera mostly recognized the C-terminal fragment (amino acid (aa) 133-239). The C-terminally truncated protein (aa 1-228) and the truncated mutant delta 225-234 lost reactivity, while the truncated protein (aa 1-234) did not, suggesting that the region (aa 225-234) is the dominant B cell epitope. The mutant, in which residues 226-229 of SEB were exchanged for residues 209-212 of streptococcal pyrogenic exotoxin A, reduced the reactivity with the C-terminal region-specific IgG purified by affinity chromatography. The C-terminal region-specific IgG inhibited SEB-elicited T cell activation, suggesting that this Ab that recognizes the epitope functions as the humoral defensive factor against SEB in humans. Furthermore, the assumed epitope region was homology to the residues (aa 32-41) of human thymopoietin, containing the biologic active site.

S-8921, an ileal Na+/bile acid cotransporter inhibitor decreases serum cholesterol in hamsters

The ileal Na+/bile acid cotransporter (IBAT) maintains the reabsorption of bile acids from the intestine in the enterohepatic circulation of bile acids. In the present study, we showed that S-8921 could dose-dependently inhibit the uptake of [3H] taurocholate in the COS7 cell line which constitutively expresses hamster IBAT. The IC50 value of S-8921 against 60 microM of [3H] taurocholate uptake was 66 +/- 8 microM and kinetic analysis revealed that the inhibition by 100 microM of S-8921 was a mixture of competitive and non-competitive types. In vivo administration of S-8921 by its incorporation into diet (0.001-0.1%) caused dose-dependent decrease of serum cholesterol concentrations accompanied by increased fecal excretion of bile acids in hamsters which were not loaded with cholesterol and bile acid. These data suggest that the inhibition of IBAT could decrease serum cholesterol in the non-cholesterol and -bile acid loaded normal condition.

Investigation of 5-HT3 receptor-mediated contraction in guinea-pig distal colon

We investigated the participation of cholinergic and tachykininergic mechanisms in 5-hydroxytryptamine (5-HT)-induced contraction via 5-HT3 receptors in longitudinal and circular muscle of guinea-pig isolated distal colon. 5-HT produced concentration-dependent contractile responses in longitudinal and circular muscle. The 5-HT3 receptor antagonists ramosetron (YM060) ((R)-5-[(1-methyl-3-indolyl) carbonyl]-4,5,6,7-tetrahydro-1H-benzimidazole hydrochloride), YM114 (KAE-393) ((R)-5-[(2,3-dihydro-1-indolyl)carbonyl]-4,5,6,7-tetrahydro-1 H-benzimidazole hydrochloride), ondansetron and granisetron produced a concentration-dependent shift to the right of the 5-HT concentration-response curves in both muscle. However, methysergide and GR113808 had no effect on 5-HT-induced contraction. In the longitudinal muscle, atropine concentration-dependently inhibited 5-HT-induced contraction, and tetrodotoxin abolished it. (+/-)-CP96,345 attenuated the contractile response to 5-HT, but (+/-)-SR48,968 had no effect on it. In the presence of atropine, (+/-)-CP96,345 completely blocked 5-HT-induced contraction. In the circular muscle, atropine had no effect on the contractile response to 5-HT, whereas tetrodotoxin completely suppressed it. The contractile response elicited by 5-HT in the circular muscle was not inhibited by either (+/-)-CP96,345, (+/-)-SR48,968, devazepide, L-365,260 or indomethacin. It is suggested that 5-HT acts via 5-HT3 receptors to release acetylcholine and substance P, which in turn are responsible for contraction of the longitudinal muscle. In the circular muscle, as in the longitudinal muscle, 5-HT-induced contraction is mediated by the 5-HT3 receptor. Unlike the case in longitudinal muscle, however, this contraction involves neither cholinergic nor tachykininergic transmission. It is also suggested that neither cholecystokinin (CCK) nor prostaglandins participate in 5-HT3 receptor-mediated contraction in circular muscle.

Hemodialysis effect on serum boron level in the patients with long term hemodialysis

Serum and dialysate boron levels in 17 patients with long term hemodialysis (HD) were determined by inductively coupled plasma emission spectrometry (ICPES). Serum boron level was compared with the value of age matched 467 healthy controls and the relationship between serum and dialysate boron level was analyzed. The results showed that serum boron level was significantly higher at the beginning of HD, and lower at the completion of HD in comparison with controls. Although the dialysate was contaminated with trace boron, HD resulted in an excessive decrease of serum boron, rather than boron exposure from the dialysate. Boron hemodialyzability was almost proportional to the gradient of the boron level at the beginning of HD and it could be controlled by the adjustment of the gradient. In conclusion, the serum boron level was very much disturbed in long term HD patients. If boron excess in serum at the beginning of HD, or deficiency at the completion of HD may contribute to the complications of HD patients, fine adjustment and close surveillance of the gradient should be taken into account.

Levels of human hepatocyte growth factor (hHGF) in peritoneal fluid after partial hepatectomy

BACKGROUND/AIMS

Human hepatocyte growth factor (hHGF), now known to be identical with scatter factor and tumor cytotoxic factor, is thought to be involved in the regeneration of the liver in humans.

MATERIAL AND METHODS

We measured the levels of immunoreactive hHGF levels in peritoneal fluid before and after partial hepatectomy in 37 patients, 10 with and 27 without cirrhosis. The presence of hHGF was confirmed in human peritoneal fluid with rat hepatocytes in primary culture and Western blot.

RESULTS

Levels of hHGF increased significantly in peritoneal fluid after surgery, with its total concentration being correlated with the weight of resected liver 168 hours postoperatively.

CONCLUSION

Findings suggest that the hHGF levels in peritoneal fluid may indicate the extent of hepatic damage following partial hepatectomy and other liver diseases.

Weight of resected liver is positively correlated with serum hHGF level

BACKGROUND/AIMS

Human hepatocyte growth factor (hHGF) is involved in the control of liver regeneration.

MATERIAL AND METHODS

We measured serum hHGF levels before and after partial hepatectomy in 43 patients and recorded the weight of the resected liver.

RESULTS

Serum hHGF levels increased soon after operation and decreased thereafter. In the noncirrhotic group, the maximum hHGF concentration and the area under the curve of hHGF seven days postoperatively correlated with the weight of the resected liver.

CONCLUSION

The amount of injured liver tissue can be approximated by the serum hHGF levels. This calculation can be useful in evaluating cases of hepatectomy, general hepatic injury, liver transplantation, and other types of hepatic damage.

Serum levels of hyaluronic acid indicate the severity of joint symptoms in patients with systemic and polyarticular juvenile rheumatoid arthritis

OBJECTIVE

Elevated serum levels of hyaluronic acid (HA) correlate with joint inflammation in adult rheumatoid arthritis (RA). There are no laboratory indices for specifically assessing joint inflammation. Therefore, serial measurements of HA were assessed as a possible tool for measuring the severity of arthritic symptoms in children with juvenile rheumatoid arthritis (JRA).

METHODS

Serum levels of HA, measured by a sandwich assay method using HA binding protein, were correlated with the severity of joint symptoms and with laboratory test values in 71 patients with JRA, 30 children with other rheumatic diseases, and 138 children without rheumatic disease.

RESULTS

Serum levels of HA showed significant correlation with the severity of joint symptoms, but not with systemic symptoms, in patients with systemic and polyarticular JRA. No other laboratory tests, including C-reactive protein and erythrocyte sedimentation rate, reflected the severity of joint symptoms. This correlation of serum levels of HA with joint symptoms was observed in patients with systemic and polyarticular JRA, but not in pauciarticular JRA, other rheumatic diseases, or nonrheumatic diseases, even when signs of arthritis were present in the latter 3 groups.

CONCLUSION

Serum levels of HA are useful in objectively evaluating arthritic symptoms in patients with systemic and polyarticular JRA, and may have diagnostic value in this disease.

Compounds possessing 5-HT3 receptor antagonistic activity inhibit intestinal propulsion in mice

The role of 5-HT3 receptors in the control of intestinal propulsive activity was investigated in mice by a simple method in which the time taken for excretion of the head of an orally administered non-absorbable marker (whole gut transit time) was measured. Selective 5-HT3 receptor antagonists ramosetron (YM060) at 0.01-0.3 mg/kg s. c. and ondansetron at 0.1-1 mg/kg s.c. dose-dependently prolonged the whole gut transit time. Prokinetic benzamides, such as renzapride (0.3-10 mg/kg s.c.), zacopride (0.01-0.3 mg/kg s.c.) and cisapride (0.1-3 mg/kg s.c.), which have been reported to possess 5-HT3 receptor blocking properties, also dose-dependently prolonged it. These results indicate that activation of 5-HT3 receptors seems to be one factor that underlies the physiological control of intestinal propulsive activity in mice. In contrast to their beneficial therapeutic effects on gastroduodenal dysmotility, prokinetic benzamides, at least those which have 5-HT3 receptor antagonistic activity, may be unsuitable in the treatment of impaired lower intestinal propulsive activity.

Novel 5-hydroxytryptamine (5-HT3) receptor antagonists. IV. Synthesis and pharmacological evaluation of the oxidation products of (-)-(R)-5-[(1-methyl-1H-indol-3-yl)carbonyl] -4,5,6,7-tetrahydro-1H-benzimidazole hydrochloride (YM060: ramosetron)

In physicochemical and pharmacokinetic evaluations of (--)-(R)-5-[(1-methyl-1H-indol-3-yl)carbonyl] -4,5,6,7-tetrahydro-1H-benzimidazole hydrochloride 1 (YM060: ramosetron), which is a highly potent 5-hydroxytryptamine(-HT3) receptor antagonist, 4-hydroxy-6-[(1-methyl-1H-indol-3-yl) carbonyl]4,5,6,7-tetrahydro-1H-benzimidazole 2 was identified as a degradation product and metabolite of 1. The (--)-(4R,6S)-isomer 2 was synthesized from the diketone derivative 3, via the stereoselective reduction of 3 followed by the stereocontrolled epimerization of the (--)-(4S,6S)-isomer 10, the epimer of 2. The stereochemistry of 2 and 10 was determined by NMR and HPLC studies. Compounds 2 and 10 were found to be potent 5-HT3 receptor antagonists, like 1. Among the other oxidation products, the diketone derivatives 3 and 7 and the dihydroxylated derivative 4 retained antagonistic activity similar to that of ondansetron. This is of interest, because they do not possess the amine group which is known to be necessary for high affinity to the 5-HT3 receptor.

Novel 5-hydroxytryptamine (5-HT3) receptor antagonists. III. Pharmacological evaluations and molecular modeling studies of optically active 4,5,6,7-tetrahydro-1H-benzimidazole derivatives

The R- and S-enantiomers of the 4,5,6,7-tetrahydro-1H-benzimidazole derivatives 3-8 were prepared by optical resolution. Each R-isomer, except for 3, was almost two orders of magnitude more potent than its S-isomer as a 5-hydroxytrptamine (5-HT3) receptor antagonist, as judged from they effect on the von Bezold-Jarisch reflex (B. J. reflex) in rats, the contraction of isolated guinea-pig colon and the receptor-binding affinity. The (--)-(R)-5-[(1-methyl-1H-indol-3-yl)carbonyl] derivative 6R.HCl (ramosetron = YM060) and (--)-(R)-5-[(1-indolinyl)carbonyl] derivative 4R.HCl (YM114 = KAE-393) given p.o. were hundreds of times more potent than 1 (ondansetron) and 2 (granisetron) in their inhibitory effects on cisplatin-induced emesis in ferrets and restraint stress-induced increases in fecal pellet output in rats. Three-dimensional molecular modeling studies suggested that the 'chiral selection' of the enantiomers might be influenced by the steric repulsion between the aromatic ring part and the conformationally restricted 4,5,6,7-tetrahydro-1H-benzimidazole ring in "equatorial-twist" conformation. In our pharmacophore model for the 5-HT3 receptor antagonist, a basic center exists at the left side of the aromatic-carbonyl plane when viewing from the aromatic part with the carbonyl oxygen atom upwards, whereas the "handedness" is ambiguous in the previously proposed model.

Comparative evaluation of the role of endogenous gastrin in basal acid secretion in conscious rats provided with chronic fistula and pylorus ligation

We determined the relative contributions of endogenous gastrin, histamine and cholinergic tone to basal acid secretion in chronic fistula rats. Results were compared with those for acid secretion in pylorus-ligated rats. In chronic fistula rats, YM022 ¿(R)-1-[2,3-dihydro-1-(2'-methylphenacyl)-2-oxo-5-phenyl-1 H-1,4-benzodiazepin-3-yl]-3-(3-methylphenyl)urea¿ dose-dependently inhibited pentagastrin-stimulated acid secretion and abolished this secretion at 1 mumol/kg, s.c., but did not affect histamine- and carbachol-induced acid secretion even at 10 mumol/kg. In contrast, famotidine at 1 mumol/kg completely inhibited not only the acid secretion induced by histamine but also those by pentagastrin and carbachol. Furthermore, atropine abolished carbachol- and pentagastrin-stimulated acid secretion and significantly suppressed histamine-stimulated acid secretion at 0.1 mumol/kg. YM022 dose-dependently inhibited basal acid secretion. The YM022 dosage required to inhibit basal acid secretion is consistent with that required to suppress pentagastrin-induced acid secretion. Famotidine (1 mumol/kg) and atropine (0.1 mumol/kg) also abolished basal acid secretion. In pylorus-ligated rats, YM022 inhibited acid secretion in a dose-dependent manner; the inhibition at 1 mumol/kg, i.v. was 65%. No additional effect was observed when rats were dosed at 30 mumol/kg. Famotidine partially inhibited acid secretion in these rats, whereas atropine abolished this secretion. These results indicate that the major part of basal acid secretion in rats is attributable to endogenous gastrin via histamine- and cholinergic tone-dependent pathways. Moreover, pylorus ligation reduces the relative contribution of gastrin to acid secretion due to the activation of cholinergic tone.