Possible involvement of 5-HT4 receptors, in addition to 5-HT3 receptors, in the emesis induced by high-dose cisplatin in Suncus murinus.

To clarify the mechanism for the severe emesis concomitant with intensive chemotherapy, we investigated the effects of 5-HT3- and 5-HT4-receptor antagonists on the emesis induced by the high-dose of cisplatin in Suncus murinus. The emesis induced by 50 mg/kg of cisplatin was reduced by the oral pretreatment with tropisetron, which is known as a 5-HT3- and 5-HT4-receptor dual antagonist in vitro, with the ID50 value of 0.52 mg/kg. On the contrary, granisetron, a selective 5-HT3-receptor antagonist, did not markedly inhibit the emesis at up to 30 mg/kg. Moreover, GR125487, a selective 5-HT4-receptor antagonist, did not inhibit the emesis. However, co-administration of GR125487 and granisetron significantly reduced the number of emetic episodes. The study of the co-administration of GR125487 with tropisetron showed that GR125487 did not further enhance the inhibitory effect of tropisetron alone, suggesting that the anti-emetic effect of tropisetron is mediated via the blockade of both 5-HT3 and 5-HT4 receptors. These results suggest that both the 5-HT3 and 5-HT4 receptors are involved in the emesis induced by the high-dose of cisplatin in Suncus murinus.

The effect of zaldaride maleate, an antidiarrheal compound, on acetylcholine-induced intestinal electrolyte secretion.

The effect of zaldaride on acetylcholine-induced colonic electrolyte secretion was examined. The short-circuit current response to acetylcholine was partially reduced by tetrodotoxin, a neuronal blocker, and was completely inhibited by atropine, an acetylcholine M receptor antagonist, in the rat colonic preparations. The tetrodotoxin sensitive effect was significantly inhibited by zaldaride, whereas the tetrodotoxin insensitive effect was not affected. Acetylcholine release from synaptosomes of submucosal nerves of guinea-pig colon was significantly reduced by zaldaride. Zaldaride may reduce colonic electrolyte secretion by acetylcholine due to the inhibition of acetylcholine release from synaptosomes of colonic submucosal nerves.

Acceleration by KW-5092 of intestinal motility associated with acetylcholine release in vivo.

Effect of KW-5092 ([1-[2-[[[5-(piperidinomethyl)-2-furanyl]methyl]amino]ethyl]-2- imidazolidinylidene]propanedinitrile fumarate) on intestinal motility and release of endogenous acetylcholine (ACh) were measured simultaneously in the small intestine of anesthetized dog using the in vivo microdialysis method. Intraarterial and intravenous administrations of KW-5092 accelerated the intestinal motility and increased dialysate ACh concentrations. These KW-5092-induced responses paralleled the increase in blood concentration of KW-5092. Thus, the acceleration of intestinal motility by KW-5092 was found in vivo to be associated with an increase in ACh release from the intestinal cholinergic neurons.

Synthesis of tricyclic compounds as steroid 5alpha-reductase inhibitors.

A series of 4-phenoxybutyric acid derivatives attached to a tricyclic skeleton were prepared and evaluated as 5alpha-reductase inhibitors. Structure activity relationships for these compounds in terms of rat epididymis (type 2) 5alpha-reductase inhibitory activities reveal that 1) the substitution pattern at the 11-position of dibenz[b,e]oxepin influenced potency, 2) higher lipophilicity of the tricyclic skeleton improved potency, whereas the existence of a basic nitrogen atom in this skeleton was detrimental to potency, and 3) isobutyl substitution at the 8 positon of the azepine skeleton was tolerated. Among the tricyclic compounds studied, 4-[3-[5-benzyl-8-(2-methyl)propyl-10,11-dihydrodibenz[b,f]azepine- 2-carboxamido]phenoxy]butyric acid (26) was the most potent inhibitor of rat type 2 5alpha-reductase at 0.1 microM.

Effects of KW-5092 on antroduodenal coordination and gastric emptying in guinea-pigs.

KW-5092 (2-[1-[2-[[5-(piperidinomethyl)-2-furanyl] methylamino]ethyl]imidazonylidin-2-ylidenene]malononitrile fumarate) is a novel gastroprokinetic agent with both acetylcholine release facilitatory and acetylcholinesterase inhibitory activity. We have investigated the effects of KW-5092 on antroduodenal coordination and gastric emptying in guinea-pigs. In the guinea-pig isolated gastroduodenal preparation, KW-5092 at 3 x 10(-7) to 3 x 10(-6) M significantly increased antroduodenal coordination. The effect of KW-5092 was almost completely inhibited by atropine or tetrodotoxin. Cisapride, a gastroprokinetic agent with acetylcholine release facilitatory activity, also increased coordination whereas neither acetylcholine nor the acetylcholinesterase inhibitor neostigmine affected it. In-vivo, KW-5092 and cisapride enhanced gastric emptying whereas neostigmine delayed it. These results suggest that acetylcholine release facilitation, but not acetylcholinesterase inhibition, is involved in the enhancement by KW-5092 of antroduodenal coordination and gastric emptying.

Indole and benzimidazole derivatives as steroid 5alpha-reductase inhibitors in the rat prostate.

A novel series of indole and benzimidazole derivatives were synthesized and evaluated for their inhibitory activity of rat prostatic 5alpha-reductase. Among these compounds, 4-¿2-[1-(4,4'-dipropylbenzhydryl)indole-5-carboxamido]phenoxy¿buty ric acid (15) and its benzimidazole analogue 25 showed potent inhibitory activities for rat prostatic 5alpha-reductase (IC50 values of 9.6+/-1.0 and 13+/-1.5 nM, respectively), with the potency very close to that of finasteride. Compound 30, in which the moiety between the benzene ring and amide bond was replaced by quinolin-4-one ring, showed almost equipotent activity (IC50= 19+/-6.2nM) with the correspondent amide derivative 13. This result was consistent with the previous observation that the coplanarity of this moiety might contribute to the potent inhibitory activity.

Effect of KW-5092, novel gastroprokinetic agent, on the peristalsis in the isolated guinea pig ileum.

We examined the effect of KW-5092, a gastroprokinetic agent with acetylcholinesterase inhibitory and acetylcholine release facilitatory activities, on the peristalsis of isolated guinea pig ileum. KW-5092 (10(-9)-3 x 10(-6)M) increased the frequency of the peristaltic wave without changing its amplitude. Neostigmine increased the frequency at 10(-7) M, but domperidone (10(-8)-3 x 10(-6)M) had no effect on the peristalsis. The present results suggest that KW-5092 enhances the peristalsis via the inhibition of acetylcholinesterase, resulting in the intestinal propulsion.

Indole derivatives as a new class of steroid 5 alpha-reductase inhibitors.

A series of indole derivatives with varied substituents on the alpha, beta-unsaturated double bond were synthesized and evaluated for their ability to inhibit rat prostatic 5 alpha-reductase. Compounds possessing an ethyl substituent at the beta-position of the double bond showed potent inhibitory activity. Among them, (Z)-4-{2-[[3-[1-(4,4'-difluorobenzhydryl)indol-5-yl]-2-pentenoy l]- amino]phenoxy}butyric acid (16, KF20405) showed the maximum potency with an IC50 value of 0.48 +/- 0.086 nM, which was 20-fold higher potency than 1 (MK-906). Compound 16 effectively inhibited DHT production 4 h after a 3 mg/kg oral administration. Several potent indole derivatives, 1 and 2 ((+/-)-ONO-3805), were tested versus rat and human isozymes. Nonsteroidal inhibitors such as indole derivatives and 2 were 2-3 orders of magnitude less potent for human type 2 isozyme than steroidal inhibitor 1 and expressed a significant species deference for these isozymes.

Excitation and inhibition via adenosine receptors of the twitch response to electrical stimulation in isolated guinea pig ileum.

The effects of adenosine and its related compounds on the cholinergic twitch response were examined in electrically stimulated guinea pig ileum. Adenosine (3 x 10(-7)-10(-5) M) and an adenosine A1-receptor agonist N6-cyclohexyladenosine (CHA, 10(-8)-10(-6) M) suppressed the twitch. Conversely, the A2a-receptor agonist 2-[p-(2-carboxyethyl)phenethylamino]-5'-N- ethylcarboxamidoadenosine (CGS 21680, 10(-9)-10(-7) M) potentiated the twitch in half the preparations examined. The A1-antagonist 1,3-dipropyl-8-cyclopentylxanthine (DPCPX), which per se did not affect the twitch, recovered the attenuated twitch caused by CHA (10(-7) M) or adenosine (10(-6) M) and converted it into a potentiated twitch. These results suggest the presence of adenosine A1- and A2a-receptors coupled negatively and positively, respectively, to acetylcholine release in the preparation.

Effects of KW-5092, a novel gastroprokinetic agent, on intestinal water and electrolyte transport in rats.

KW-5092 ([1-[2-[[[5-(piperidinomethyl)- 2-furanyl]methyl]amino]ethyl]-2-imidazolidinylidene]propanedini trile fumarate) enhances acetylcholine release from enteric neurons and inhibits acetylcholinesterase (AChE), resulting in the enhancement of a wide range of gastrointestinal motilities. The present study examined the effects of KW-5092 on intestinal water and electrolyte transport in rats. In the jejunum, oral or intrajejunal administration of the laxative bisacodyl (30 mg/kg) significantly inhibited absorption of water, Na+ and Cl-, and significantly enhanced K+ secretion. In contrast, neither KW-5092 (1-30 mg/kg) nor the AChE inhibitor neostigmine (0.3-10 mg/kg), orally or intrajejunally administered, affected water or electrolyte transport in the jejunum. Similar results were obtained in the colon when the drugs were applied orally or intracolonically. Moreover, neither KW-5092 (1-30 mg/kg, p.o.) nor neostigmine (0.3-10 mg/kg, p.o.) induced diarrhea, while bisacodyl (30 mg/kg, p.o.) induced diarrhea in all the rats examined. These results demonstrate that KW-5092 or neostigmine at the gastroprokinetic doses does not affect intestinal water or electrolyte transport in rats, suggesting that cholinergic activation enhances gastrointestinal motility rather than intestinal secretion of water and electrolytes.

KW-5092, a novel gastroprokinetic agent, reverses the norepinephrine-induced decline of the gastric mucosal blood flow in rats.

We examined the effects of KW-5092 ((1-[2-[[[5-(piperidinomethyl)-2-furanyl]methyl]-amino]ethyl]- 2-imidazolidinylidene) propanedinitrile fumarate), a novel gastroprokinetic agent, on gastric mucosal blood flow (GMBF) in anesthetized rats. Intravenous infusion of KW-5092 (0.1 mg/kg/min for 30 min), which did not affect the basal GMBF, reversed the norepinephrine (1 microgram/kg/min, i.v. infusion for 30 min)-induced decline of GMBF in the corpus and the antrum. The improvement by KW-5092 of the GMBF was abolished by atropine (0.1 mg/kg/min, i.v. infusion for 30 min). These results suggest that KW-5092, via cholinergic activation, could counteract the decline of GMBF induced by adrenergic activation.

A novel pyridobenzazepinone derivative with long lasting thromboxane synthase inhibition.

A novel pyridobenzazepinone derivative (Z)-11-(5-carboxypentylidene)-6-methyl-5, 11-dihydropyrido +ad4,3-C] [1] benzazepin-5 (6H)-one (CAS 127654-03-9, KF 13218), inhibited human and bovine platelet thromboxane synthase with IC50 values of 27 +/- 5.8 nmol/l (mean +/- S.E.M.) and 36 +/- 6.9 nmol/l, respectively. The compound did not inhibit cyclooxygenase or 5-lipoxygenase up to a dose of 100 mumol/l and did not antagonize thromboxane A2/prostaglandin H2 receptors. KF13218 inhibited arachidonic acid-induced thromboxane B2 production by human intact platelets with an IC50 value of 5.3 +/- 1.3 nmol/l. The IC50 value of KF13218 for the intact platelets was about 5 times lower than that for the microsomal enzyme. The inhibition of thromboxane synthase in platelets by KF13218 was sustained after removal of the extracellular compound. After oral dosing in rat from 0.03 mg/kg to 3 mg/kg, KF13218 dose-dependently inhibited the thromboxane B2 production in serum, and the inhibition was retained for 72 h. KF13218, at a dose of 0.1 mg/kg p.o. prevented mortality induced by sodium arachidonate in rabbit. It is concluded that KF13218 is a potent, selective and long lasting thromboxane synthase inhibitor.

(E)-4-(2-[[3-(indol-5-yl)-1-oxo-2-butenyl]amino]phenoxy)butyric acid derivatives: a new class of steroid 5 alpha-reductase inhibitors in the rat prostate. 1.

A series of (E)-4-(2-[[3-(indol-5-yl)-1-oxo-2-butenyl]amino]phenoxy)butyric acid derivatives was prepared, and the derivatives were demonstrated to be potent inhibitors of steroid 5 alpha-reductase in the rat prostate. The structure-activity relationships were as follows. An alpha-branched alkyl or benzyl substituent of proper size at position 1 of the indole is crucial for optimal enzyme inhibitory activity. N-Methylation of the amide NH resulted in complete loss of activity. Thus, coplanarity of the benzene ring and amide moiety is essential for such activity. Among the compounds prepared, (E)-4-(2-[[3-[1-[bis(4-fluorophenyl)methyl]indol-5-yl]-1-oxo-2- butenyl]-amino]phenoxy)butyric acid (57, KF18678) was one of the most potent compounds (rat prostate 5 alpha-reductase IC50 = 3.3 nM).

Effects of the adenosine A1-receptor antagonist on defecation, small intestinal propulsion and gastric emptying in rats.

We examined the effects of 1,3-dipropyl-8-cyclopentylxanthine (DPCPX) and (R)-7,8-dihydro-8-ethyl-2-(3-noradamantyl)-4-propyl-1H-imidazo[2,1 -i]purin- 5(4H)-one (KF20274), selective adenosine A1-receptor antagonists, on the gastrointestinal propulsion in rats, as compared with those of the laxative bisacodyl. DPCPX and KF20274 (p.o.) dose-dependently increased the fecal pellet output, whereas these drugs at the dose that increased defecation did not affect small intestinal propulsion or gastric emptying. Bisacodyl increased defecation and slowed gastric emptying without any influence on small intestinal propulsion. Bisacodyl, but not DPCPX or KF20274, induced diarrhea at the dose inducing defecation. The present results suggest that the adenosine A1-receptor antagonist selectively enhances the lower gastrointestinal propulsion, resulting in defecation without diarrhea.

Enhancement of defecation and distal colonic motor activity by KW-5092, a novel gastroprokinetic agent, in rats.

KW-5092 ([1-[2-[[[5-(piperidinomethyl)-2-furanyl]- methyl]amino]ethyl]-2-imidazolidinylidene]propanedinitrile fumarate) is a novel gastroprokinetic agent with acetylcholinesterase inhibitory and acetylcholine release facilitatory activity. The present study examined the effects of KW-5092 on the defecation and colonic motor activity in rats. KW-5092, at 1 to 30 mg/kg, p.o., dose-dependently increased the fecal pellet output. In the in vitro study, KW-5092, at 10(-6) M to 10(-5) M, evoked contraction of the isolated distal colonic preparation. In the in vivo study, KW-5092, at 1 to 10 mg/kg, p.o., induced an increase in the distal colonic motor index, which was dose-dependently inhibited by atropine (0.1 to 1 mg/kg, i.v.). The present results suggest that KW-5092 induces the defecation in rats by enhancing the distal colonic motor activity via its acetylcholinesterase inhibitory activity and/or acetylcholine release facilitatory activity. KW-5092 may be a useful drug in the treatment of constipation.

Stimulating effects of KW-5092, a novel gastroprokinetic agent, on the gastric emptying, small intestinal propulsion and colonic propulsion in rats.

KW-5092 ((1-[2-[[[5-(piperidinomethyl)-2-furanyl]methyl]amino]ethyl]- 2-imidazolidinylidene) propanedinitrile fumarate) is a novel gastroprokinetic agent with acetylcholinesterase (AChE) inhibitory activity and acetylcholine (ACh) release facilitatory activity. The present study examined the effects of KW-5092 on gastrointestinal (GI) propulsion in rats. KW-5092 at 1 to 30 mg/kg, p.o. dose-dependently enhanced the gastric emptying, small intestinal propulsion and the proximal and distal colonic propulsion. Metoclopramide, a dopamine D2-receptor antagonist with ACh release facilitatory activity, dose-dependently enhanced the gastric emptying at 0.03 to 1 mg/kg, p.o., whereas this drug did not affect the small intestinal propulsion, or the proximal and distal colonic propulsion. Neostigmine, an AChE inhibitor, dose-dependently enhanced the small intestinal propulsion and the proximal and the distal colonic propulsion at 0.3 to 10 mg/kg, p.o., whereas it delayed the gastric emptying at 10 mg/kg, p.o. The present results demonstrate that KW-5092 enhances the GI propulsion from the stomach to the colon and that metoclopramide or neostigmine enhances only the upper or the lower GI propulsion, respectively. Thus, KW-5092 may be a gastroprokinetic drug of a novel type for the treatment of GI motility dysfunctions in a wide range from the stomach to the colon.

Inhibitory effects of KW-5092, a novel gastroprokinetic agent, on the activity of acetylcholinesterase in guinea pig ileum.

KW-5092 ([1-[2-[[[5-(piperidinomethyl)-2- furanyl]methyl]amino]ethyl]-2-imidazolidinylidene] propanedinitrile fumarate) is a novel gastroprokinetic agent with acetylcholinesterase (AChE) inhibitory activity and acetylcholine release facilitatory activity. The present study used guinea pig ileal homogenates to examine the inhibitory effects of KW-5092 on the activities of AChE and butyrylcholinesterase (BuChE). KW-5092 inhibited AChE and BuChE with the IC50 values of 6.8 x 10(-8) M and 2.4 x 10(-5) M, respectively. The IC50 values of neostigmine for AChE and BuChE were 3.6 x 10(-8) M and 1.9 x 10(-7) M, respectively. HSR-803 (N-[4-[2-(dimethylamino)ethoxy]benzyl]-3,4-dimethoxybenzamide hydrochloride), a gastroprokinetic agent, inhibited AChE and BuChE with the IC50 values of 8.6 x 10(-6) M and 6.0 x 10(-4) M, respectively. The AChE inhibition by KW-5092 was reversible and noncompetitive, whereas that by HSR-803 was reversible and uncompetitive. On the other hand, the AChE inhibition by neostigmine was non-competitive when the enzyme was preincubated with this inhibitor for 2 min prior to the addition of the substrate, and it was nearly competitive when the enzyme, the inhibitor and the substrate were incubated simultaneously. The present results demonstrate that KW-5092 is a selective, reversible and noncompetitive inhibitor of AChE with different characteristics from those of neostigmine and HSR-803. The AChE inhibitory action may contribute to its gastroprokinetic effect.

Possible physiological role of endogenous adenosine in defecation in rats.

Evacuated feces after intraperitoneal administration of selective adenosine receptor antagonists were evaluated in rats. The selective adenosine A1 receptor antagonists, 1,3-dipropyl-8-cyclopentylxanthine (DPCPX) (100-300 micrograms/kg i.p.) and (R)-7,8-dihydro-8-ethyl-2-(3-noradamantyl)-4-propyl-1H-imidazo[2,1 -i]purin- 5(4H)-one (KF20274) (30-300 micrograms/kg i.p.), significantly increased defecation, whereas the selective adenosine A2 receptor antagonist 4-amino-8-chloro-1-phenyl[1,2,4]triazolo[4,3-a]quinoxaline (CP-66,713) failed to cause a significant increase at up to 10 mg/kg i.p. The defecation caused by DPCPX (100 micrograms/kg) was markedly alleviated by (2S)-N6-(2-endo-norbornyl)adenosine ((S)-ENBA) (30-300 micrograms/kg s.c.), a selective adenosine A1 receptor agonist, but not influenced by 2-[p-(2-carboxyethyl)phenethylamino]-5'-N-ethylcarboxamidoadenosin e (CGS 21680) (30-1000 micrograms/kg s.c.), a selective adenosine A2 receptor agonist. These results suggest that endogenous adenosine plays a physiological role in sustained inhibition of defecation via adenosine A1 receptors.

Synthesis of 2-imidazolidinylidene propanedinitrile derivatives as stimulators of gastrointestinal motility--II.

In a previous paper, we reported that a novel ranitidine derivative 2 (fumarate: KW-5092), which had a 2-imidazolidinylidene propanedinitrile moiety (A), showed potent gastrointestinal motility enhancing activity. In order to obtain more potent gastrointestinal motility enhancing agents than compound 2 and to examine the effects of various substituents both at a nitrogen atom (B) in the 2-imidazolidinylidene propanedinitrile moiety and a basic nitrogen atom (C), compounds 5-29 were synthesized and evaluated for acetylcholinesterase (AChE) inhibitory activity and potentiating action on electrically stimulated contractions of guinea pig ileum. Introduction of alkyl, benzyl, aryl or acyl groups to the nitrogen (B) or (C), remarkably influenced both activities. Among these, compounds 14 and 15 showed more potent AChE inhibitory activity (IC50 = 6.7, 6.8 nM, respectively) than compound 2 and were active in potentiating action on the ileal contraction (EC30 = 9.5, 11 nM, respectively) together with a negligible histamine H2-receptor blocking property. Furthermore, these compounds were found to be more effective in the enhancement of gastrointestinal motility in anesthetized rabbits than compound 2.

Susceptibility to adenosine agonists of giant migrating contraction induced by glycerol enema in anesthetized rats.

The present study examined whether adenosine agonists influence the occurrence of giant migrating contractions (GMCs) induced by glycerol enema (65%, 2 ml/kg) in rats. Catheter pressure transducers were used to measure the colonic luminal manometric alterations. The adenosine A1 agonists (2S)-N6-(2-endo-norbornyl)adenosine ((S)-ENBA) (10 micrograms/kg, i.v.) and N6-cyclohexyladenosine (30 micrograms/kg, i.v.) abolished the GMCs, whereas the adenosine A2 agonist 2-[p-(2-carboxyethyl)phenethylamino]-5'-N-ethylcarboxamidoadenosin e (CGS 21680) (30-300 micrograms/kg, i.v.) failed to influence the GMCs. The suppressive action of (S)-ENBA on the GMCs was entirely counteracted by the peripheral adenosine antagonist 8-(p-sulfophenyl)theophylline (10 mg/kg, i.v.). The present observations suggest that the adenosine A1 agonist suppresses the GMCs via peripheral adenosine receptors.