Determination of dietary essential fatty acids in a deep-sea fish, the splendid alfonsino Beryx splendens: functional characterization of enzymes involved in long-chain polyunsaturated fatty acid biosynthesis

The splendid alfonsino Beryx splendens is a commercially important deep-sea fish in East Asian countries. Because the wild stock of this species has been declining, there is an urgent need to develop aquaculture systems. In the present study, we investigated the long-chain polyunsaturated fatty acid (LC-PUFA) requirements of B. splendens, which are known as essential dietary components in many carnivorous marine fish species. The fatty acid profiles of the muscles, liver, and stomach contents of B. splendens suggested that it acquires substantial levels of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) from its natural diet. The functional characterization of a fatty acid desaturase (Fads2) and three elongases (Elovl5, Elovl4a, and Elovl4b) from B. splendens confirmed their enzymatic capabilities in LC-PUFA biosynthesis. Fads2 showed Δ6 and Δ8 bifunctional desaturase activities. Elovl5 showed preferential elongase activities toward C₁₈ and C₂₀ PUFA substrates, whereas Elovl4a and Elovl4b showed activities toward various C_18-22 substrates. Given that Fads2 showed no Δ5 desaturase activity and no other fads-like sequence was found in the B. splendens genome, EPA and arachidonic acid cannot be synthesized from C₁₈ precursors; hence, they can be categorized as dietary essential fatty acids in B. splendens. EPA can be converted into DHA in B. splendens via the so-called Sprecher pathway. However, given that fads2 is only expressed in the brain, it is unlikely that the capacity of B. splendens to biosynthesize DHA from EPA can fulfill its physiological requirements. These results will be useful to researchers developing B. splendens aquaculture methods.

The Molting Biomarker Molecule Exists as 2-Acetamido-2-deoxy-gluconic Acid in Urine of Blue Crabs and Helmet Crabs

N-Acetyl-d-glucosamino-1,5-lactone 1 has been reported as a candidate component of the sex pheromone mixture of female blue crabs, Callinectes sapidus, since it is present in the urine of reproductive females and males detect it. Theoretically, 1 can convert to a 1,4-lactone isomer 2 or to the corresponding carboxylic acid, 2-acetamido-2-deoxygluconic acid 3 by hydrolysis in aqueous solution. In this study, we examined the biologically relevant state of equilibrium mixture of 1, 2, and 3 in crab urine using ESI-MS and NMR analyses. The ESI-MS analysis showed that the dominant form of solubilized synthetic 1 is lactone 1 and/or 2, immediately after solubilization in deuterated water, seawater, and phosphate buffer and gradually changing to carboxylic acid 3 which becomes most predominant in phosphate buffer. The NMR analysis showed that synthetic 1 converts to other forms in deuterated water and seawater, and reaches an equilibrium mixture of at least three forms within 24 h. In contrast, 1 converts to a single state of another form in deuterated water with 35 mm phosphate buffer pH 7.6 within 24 h, which is identical to the state in urine with or without phosphate buffer. Thus, we conclude that the molting biomarker sensed by male crabs is 3.

Long-term analgesic effect of a single dose of anti-NGF antibody on pain during motion without notable suppression of joint edema and lesion in a rat model of osteoarthritis

OBJECTIVE

Osteoarthritis (OA) patients experience exaggerated pain during movements such as walking. Anti-nerve growth factor (NGF) antibodies have recently shown analgesic effects in OA patients. We examined the effect of a single dose of anti-NGF antibody on pain during motion, joint edema and lesion in a rat model of OA to determine whether the analgesic effect demonstrated in clinical studies can be translated to a preclinical model.

METHODS

Sodium monoiodoacetate (MIA)-induced arthritic rats that develop a right-left gait imbalance when walking as an index of pain during motion. This imbalance was assessed using a gait analysis system called "CatWalk". Edema size and lesion score in the relevant knee joint were also measured. The effect of a single intravenous injection of an anti-NGF monoclonal antibody AS2886401-00 on these parameters was assessed.

RESULTS

AS2886401-00 administered at 0.3 or 1 mg/kg on Day 3 post-MIA injection resulted in a statistically significant improvement in gait imbalance even on Day 35. When gait measurement was set on Week 3 post-MIA administration, administration of the antibody at a timing close to the gait measurement, i.e., 1 or 24 h prior to the measurement, was less effective. AS2886401-00 did not suppress either edema or lesion.

CONCLUSIONS

A single dose of anti-NGF antibody exerts a long-lasting analgesic effect on pain during motion in a rat model of OA. This finding could be associated with the analgesic efficacies that anti-NGF antibodies have exhibited in clinical studies. It appears unlikely that analgesia is secondary to inhibition of joint edema and lesion.

Reserpine causes biphasic nociceptive sensitivity alteration in conjunction with brain biogenic amine tones in rats

The present study investigated the precise relationship between brain biogenic amine (dopamine, noradrenaline, and serotonin) tones and nociception. Nociceptive sensitivities to multimodal (muscle pressure, tactile, cold, and heat) stimuli were assessed in acute phase (up to 24 h after reserpine or tetrabenazine injection) and chronic phase (on day 2 or later) in rats. A single injection of reserpine (3 mg/kg s.c.) significantly decreased biogenic amines in the spinal cord (SC), thalamus (THA), and prefrontal cortex (PFC) in both acute and chronic phases, but significantly increased a dopamine metabolite 3,4-dihydroxyphenylacetic acid (DOPAC) in the SC and a serotonin metabolite 5-hydroxyindoleacetic acid (5-HIAA) in the SC and THA in acute phase. The content of all biogenic amine metabolites was at low level in chronic phase. Animals exhibited hypersensitivities to tactile and heat stimuli and hyposensitivity to muscle pressure stimulus in acute phase. In chronic phase, they manifested hypersensitivities to all modes of stimuli. Tetrabenazine (20 mg/kg i.p.) significantly decreased brain biogenic amines for a short time, although it did not significantly affect the nociceptive sensitivities. In conclusion, a single injection of reserpine causes a biphasic alteration of nociceptive sensitivities, which is in conjunction with the dynamic change of brain biogenic amine tones, in rats. Cold and heat hypersensitivities in addition to mechanical ones are induced by the reserpine treatment. Sustained modification of brain biogenic amine tones would be critical to induce a robust change in nociceptive sensitivities based on the different effects between reserpine and tetrabenazine.

Purinergic P2X receptor activation induces emetic responses in ferrets and Suncus murinus (house musk shrews)

BACKGROUND AND PURPOSE

Despite the rapid progress made in understanding the significant role played by signalling via extracellular ATP in physiology and pathology, there has been no clear information generated on its involvement in the emetic response.

EXPERIMENTAL APPROACH

In the present study, the emetogenic potential of extracellular ATP signalling in mammalian species was examined using ferrets and Suncus murinus (house musk shrews). A slowly degradable ATP analogue, alpha,beta-methyleneATP (alpha,beta-meATP), was used to activate the P2X receptors, and either the non-selective P2 receptor antagonist, pyridoxal phosphate-6-azophenyl-2',4'-disulphonic acid (PPADS), or the specific P2X(3) homomer and P2X(2/3) heteromer antagonist, A-317491, were tested against the agonist-induced response.

KEY RESULTS

Intraperitoneal injection of alpha,beta-meATP produced significant emetic responses in ferrets (1 - 30 mg kg(-1)) and in Suncus murinus (5 - 50 mg kg(-1)). The responses occurred frequently within the first 10 min after administration, much less frequently from 11 to 60 min and no responses occurred later than 60 min. The emetic responses were completely inhibited by intraperitoneal pre-treatment with PPADS (100 mg kg(-1)) or A-317491 (100 mg kg(-1)). Abdominal surgical vagotomy did not reduce the emetic response in Suncus murinus significantly.

CONCLUSIONS AND IMPLICATIONS

These results for the first time indicate that the activation of P2X receptors evokes emetic responses in mammalian species. The P2X(3) homomer and.or P2X(2/3) heteromer in the area postrema could be responsible for the emetic response. This finding contributes to the elucidation of the roles played by extracellular ATP signalling in various emetic symptoms.

Energy expenditure during walking in amputees after disarticulation of the hip

We have compared the energy expenditure during walking in three patients, aged between 51 and 55 years, with unilateral disarticulation of the hip when using the mechanical-controlled stance-phase control knee (Otto Bock 3R15) and the microprocessor-controlled pneumatic swing-phase control knee (Intelligent Prosthesis, IP). All had an endoskeletal hip disarticulation prosthesis with an Otto Bock 7E7 hip and a single-axis foot. The energy expenditure was measured when walking at speeds of 30, 50, and 70 m/min.

Two patients showed a decreased uptake of oxygen (energy expenditure per unit time, ml/kg/min) of between 10.3% and 39.6% when using the IP compared with the Otto Bock 3R15 at the same speeds. One did not show any significant difference in the uptake of oxygen at 30 m/min, but at 50 and 70 m/min, a decrease in uptake of between 10.5% and 11.6% was found when using the IP. The use of the IP decreased the energy expenditure of walking in these patients.

Energy expenditure during walking in amputees after disarticulation of the hip. A microprocessor-controlled swing-phase control knee versus a mechanical-controlled stance-phase control knee

We have compared the energy expenditure during walking in three patients, aged between 51 and 55 years, with unilateral disarticulation of the hip when using the mechanical-controlled stance-phase control knee (Otto Bock 3R15) and the microprocessor-controlled pneumatic swing-phase control knee (Intelligent Prosthesis, IP). All had an endoskeletal hip disarticulation prosthesis with an Otto Bock 7E7 hip and a single-axis foot. The energy expenditure was measured when walking at speeds of 30, 50, and 70 m/min. Two patients showed a decreased uptake of oxygen (energy expenditure per unit time, ml/kg/min) of between 10.3% and 39.6% when using the IP compared with the Otto Bock 3R15 at the same speeds. One did not show any significant difference in the uptake of oxygen at 30 m/min, but at 50 and 70 m/min, a decrease in uptake of between 10.5% and 11.6% was found when using the IP. The use of the IP decreased the energy expenditure of walking in these patients.

%VO2max as an indicator of prosthetic rehabilitation outcome after dysvascular amputation

In this study, independent ambulation of at least 100 metres with/without a cane was regarded as successful prosthetic rehabilitation. The subjects were classified into two groups according to this criterion at the time of discharge. The successful group attained this performance, the other group failed to reach this level. The successful group included 8 unilateral trans-femoral amputees aged 72.2 +/- 2.1 years who underwent amputation at more than 70 years, and succeeded in walking with a prosthesis. The group which failed included 9 unilateral trans-femoral amputees aged 63.2 +/- 2.1 years who underwent amputation between the ages of 60-65 years, and had great difficulty in walking with a prosthesis. The purpose of this research was to investigate whether or not %VO2max as an indicator of physical fitness is useful in predicting prosthetic rehabilitation outcome after dysvascular amputation by comparing these two groups. Evaluation of physical fitness was conducted before the subjects began prosthetic rehabilitation. Information about each subject before fitting with a prosthesis was collected retrospectively from clinical charts made during admission. The successful group were capable of strenuous exercise, reaching the intensity of 50% VO2max or more. In the group which failed only one reached the intensity of 50% VO2max. The working capacity of 50% VO2max or greater would appear to be a valid initial guideline level of physical fitness at which an amputee can expect to succeed in walking with a prosthesis. Apart from physical fitness, a lesser number of comorbidity, good ability to stand on the remaining leg, and a strong will to walk were found to be important factors contributing to successful prosthetic rehabilitation. This study also showed that age alone was not an important factor.

Neurometer measurement of current stimulus threshold in rats

We examined the current stimulus threshold in rats with the Neurometer, a device used clinically for measuring perception and pain thresholds. Although many studies have indicated the usefulness of this device in the quantification of nerve dysfunction in patients, we have found no published reports on the use of the Neurometer in animals. Transcutaneous nerve stimuli of the three sine-wave pulses produced by the Neurometer (at 2000, 250, and 5 Hz) were applied to plantar surface of rats. The intensity of each stimulation at which rats vocalized or were hardly startled was defined as the current stimulus threshold. With repeated stimulation, the thresholds were almost constant. Repeated topical application to the area around the stimulating electrode of a high concentration of capsaicin, which acts on small-diameter fibers, increased the thresholds at 250 and 5 Hz, but did not affect the 2000-Hz threshold. Intravenous morphine (2-5 mg/kg) increased all three thresholds, whereas intrathecal morphine (20 or 80 microg) increased only the 5-Hz threshold. Intravenous injection of a minor tranquilizer, diazepam, at 1 mg/kg raised the thresholds at 2000 and 250 Hz, but did not affect the 5-Hz threshold. Higher dose of diazepam increased all three thresholds. These results suggest that the Neurometer makes possible selective examination of subsets of nerve fibers that differ in diameter not only in humans but also in animals. The present study in rats, in which we established a method of measurement, may provide helpful suggestions for the interpretation of data in humans.

Effect of endurance training program based on anaerobic threshold (AT) for lower limb amputees

We have already reported that the one-leg cycling test driven by the subject's sound leg as the exercise load test is effective in measuring the anaerobic threshold (AT) of unilateral lower limb amputees. The aim of this research is to investigate whether or not endurance training based on each subject's AT gained from the one-leg cycling test is useful in improving the physical fitness of lower limb amputees. The test subjects were all unilateral transfemoral amputees comprising a group of 14 undertaking endurance training and a control group of 10. The form of endurance training is driving an ergometer with the sound limb only in the same way as the load test. The training program was designed so that the subjects would exercise at a target heart rate corresponding to AT point for 30 minutes per day, 3-5 days each week for 6 weeks. After the training periods, in the training subjects the AT and maximum oxygen uptake (__O2max) increased significantly. The rate of increase averaged 36.5%, 26.0%, respectively, compared to their levels before the training. On the contrary, no changes occurred in the control subjects. These results suggest that our chosen training program based on each subject's AT is effective in improving the physical fitness of lower limb amputees.

Adenosine A1 receptor blockade reverses dysmotility induced by ischemia-reperfusion in rat colon

This study was designed to assess whether adenosine A1 receptor antagonists [(R)-1-[(E)-3-(2-phenylpyrazolo[1,5-a]pyridin-3-yl) acryloyl]-piperidin-2-yl acetic acid (FK352) and 8-cyclopentyl-1,3-dipropylxanthine (DPCPX)] reverse dysmotility induced by ischemia-reperfusion in the rat colon. The gene of adenosine A1 receptor was expressed in the colon. Clamping (30 min) of the colonic marginal vessels was followed by reperfusion, and the propulsive colonic motility was evaluated. Propulsion was significantly slowed by ischemia-reperfusion, while FK352 and DPCPX abolished this delay. In contrast, the non-selective adenosine receptor antagonist, 8-phenyltheophylline, failed to affect the dysmotility. Thus, adenosine A1 receptor antagonists have potent therapeutic potential against ischemia-reperfusion-induced dysmotility in the colon.

Pharmacological profile of YM-31636, a novel 5-HT3 receptor agonist, in vitro

We investigated the in vitro pharmacological profile of YM-31636 (2-(1H-imidazol-4-ylmethyl)-8H-indeno[1,2-d]thiazole monofumarate). In cloned human 5-HT3A receptors, YM-31636 had a pKi value of 9.67 vs. ramosetron and pKi values for other 5-HT3 receptor agonists were less than 7. YM-31636 showed very low affinities for other receptors. YM-31636 induced contraction of isolated guinea pig distal colon. The intrinsic activity was approximately 0.90 compared with 5-hydroxytryptamine's (5-HT) 1.0, and the potency was 26 times greater than that of 5-HT. YM-31636 increased short-circuit current (Isc) in the isolated guinea pig distal colon. In this case, the relative intrinsic activity was approximately 0.19. In isolated guinea pig right atrium, YM-31636 induced tachycardia with the relative intrinsic activity of approximately 0.23. All these effects of YM-31636 were antagonized by ramosetron, a selective 5-HT3 receptor antagonist. These results suggest that YM-31636 is a potent and selective 5-HT3 receptor agonist, preferentially acting on the contraction of the colon.

The role of 5-hydroxytryptamine3 and 5-hydroxytryptamine4 receptors in the regulation of gut motility in the ferret

The role of 5-hydroxytryptamine (5-HT)3 and 5-HT4 receptors in the regulation of gut motility in the ferret was investigated. The selective 5-HT3 receptor antagonist ramosetron (1 - 10 microg/kg s.c.) prolonged the interval of gastric antral migrating motor complex, but had only slight effect on small intestinal and colonic motility in unfed animals. The selective 5-HT4 receptor antagonist SB 204070 did not affect motility throughout gut in unfed animals. Neither ramosetron nor SB 204070 affected the motility throughout gut in fed animals. In conclusion, neither 5-HT3 nor 5-HT4 receptors tonically regulate ferret gut motility except that 5-HT3 receptors have a key role in the occurrence of migrating motor complex specifically in the stomach. The role of 5-HT3 and 5-HT4 receptor system in the regulation of gut motility in ferrets is similar to that in other mammalian species studied, including humans. This similarity suggests that the ferret is a suitable model animal to study gut motor functions in humans.

Stimulation of gastric acid secretion by progesterone metabolites as neuroactive steroids in anesthetized rats

The effect of neuroactive progesterone metabolites, 5alpha- and 5beta-pregnan-3alpha-ol-20-one, and their stereoisomers at the 3 C site, 5alpha- and 5beta-pregnan-3beta-ol-20-one, on gastric acid secretion was investigated in urethane-anesthetized rats. Both 5alpha- and 5beta-pregnan-3alpha-ol-20-one dose-dependently (0.3-3 mg x kg(-1), i.v.) stimulated gastric acid secretion with an early onset of action. Their potency and efficacy were almost the equivalent of one another. In contrast, their stereoisomers did not have a significant effect even at 10 mg x kg(-1) (i.v.). The 5beta-pregnan-3alpha-ol-20-one (3 mg x kg(-1), i.v.)-stimulated gastric acid secretion was remarkably inhibited by bilateral vagotomy or pretreatment with atropine (1 mg x kg(-1), i.v.). An antagonist of the GABA(A) receptor, picrotoxin, at 3 and 6 mg x kg(-1) (i.v.), significantly inhibited the 5beta-pregnan-3alpha-ol-20-one (3 mg x kg(-1), i.v.)-stimulated gastric acid secretion. These results indicate that naturally occurring neuroactive steroids, 5alpha- and 5beta-pregnan-3alpha-ol-20-one, stimulate gastric acid secretion in a stereoselective and dose-dependent manner in urethane-anesthetized rats. It is likely that the action of these neuroactive steroids is of central origin and that interaction with GABA(A) receptors and stimulation of vagal pathway are involved in its mechanism of action.

Pharmacological properties of a novel gastrointestinal prokinetic benzamide selective for human 5-HT4 receptor versus human 5-HT3 receptor

Binding properties of gastrointestinal prokinetic benzamides for both cloned human 5-hydroxytryptamine (5-HT)3 receptors and cloned human 5-HT4 receptors were examined and pharmacological properties of YM-53389{(+)-(S)-2-chloro-5-methoxy-4-[5-(2-piperidylmethyl)-1,2, 4-oxadiazol-3-yl]aniline monohydrochloride} were characterised in animals. Cisapride, renzapride and zacopride inhibited specific binding of [3H]ramosetron to cloned human 5-HT3 receptors, with Ki values of 684, 7.64 and 0.38 n m, respectively. YM-53389, however, slightly replaced that (Ki>10,000 n m). YM-53389, cisapride, renzapride and zacopride replaced specific binding of [3H]GR 113808 to cloned human 5-HT4 receptors, with Ki values of 54.6, 41.5, 115 and 373 n m, respectively. The potency for inhibitory effect of YM-53389 on 5-HT3 receptor-mediated contraction in the guinea-pig isolated colon was very low with pIC50 of 4.7. YM-53389 exerted 5-HT4 receptor-mediated relaxation in the carbachol-precontracted rat isolated oesophagus with pEC50 of 6.3. In mice, YM-53389 at 10 and 30 mg kg-1, s.c. significantly shortened whole gut transit time, in contrast to cisapride, renzapride and zacopride which were reported to delay that. YM-53389 had no significant effect on upper gastrointestinal propulsion at doses up to 30 mg kg-1, s.c. Based on these results, YM-53389 may surpass existing benzamides in facilitating lower intestinal propulsion and benefit patients with gastrointestinal disorders associated with impair of intestinal propulsion, such as constipation, based on the selective interaction with human 5-HT4 receptors vs human 5-HT3 receptors.

The efficacy of physiological cost index (PCI) measurement of a subject walking with an Intelligent Prosthesis

The Intelligent Prosthesis may enable lower limb amputees to walk faster than with conventionally damped prostheses and as a result the physical burden involved in walking could be expected to be considerably higher. The aim of this study was to investigate whether or not physiological cost index (PCI) is applicable as an indicator for monitoring the amount of exercise load involved in walking with an Intelligent Prosthesis. The method used a treadmill and monitored gas exchange, ventilation and heart rate (HR) in 6 unilateral trans-femoral amputees, ages were between 17 and 34 with an average age of 23.1. The exercise protocol was as follows: for each person speeds at 0.8 times the subject's free level walking speed, 1.0 times, 1.2 times, 1.4 times and for some 1.6 times were applied. In each case the index of correlation between PCI and oxygen uptake in response to walking speed was calculated. A significant correlation was observed between PCI and oxygen uptake in each case, which indicated a close relationship between cardiopulmonary factor and energy consumption while walking. These results suggest that PCI is of use as an indicator for ascertaining the amount of exercise load in walking with an Intelligent Prosthesis.

Synthesis of the selective 5-hydroxytryptamine 4 (5-HT4) receptor agonist (+)-(S)-2-chloro-5-methoxy-4-[5-(2-piperidylmethyl)-1,2,4-oxadiazol-3-y l]aniline

In a search for novel 5-hydroxytryptamine 4 (5-HT4) agonists focusing on the linker group of benzamide derivatives, 2-chloro-5-methoxy-4-[5-(2-piperidylmethyl)-1,2,4-oxadiazol-3-yl]a niline (2) was prepared and its optical isomers were separated. The S isomer 2(S) showed high affinity for the human 5-HT4 receptor without affinity for the human 5-HT3 receptor, and potent 5-HT4 agonistic activity in longitudinal muscle myenteric plexus (LMMP) preparations of guinea pig ileum. The R isomer 2(R) showed opposite selectivity. As a result of other receptor binding studies, 2(S) (YM-53389) was shown to be a highly selective 5-HT4 agonist.

The efficacy of the one-leg cycling test for determining the anaerobic threshold (AT) of lower limb amputees

The aim of this study was to investigate whether or not the one-leg cycling test driven by the subject's sound leg as the exercise load method is an applicable method for determining the anaerobic threshold (AT) of lower limb amputees. To evaluate physical fitness, a graded exercise test that monitored gas exchange, ventilation and heart rate (HR) was performed in 51 unilateral lower limb amputees. AT was successfully measured for 42 out of 51 subjects, an 82.3% success rate. The average AT was 12.7 +/- 2.2 ml/kg/min, and the average HR at AT points was 117.7 +/- 16.2 beats/min. The average peak oxygen uptake was 20.1 +/- 5.6 ml/kg/min, and the average peak HR was 145.1 +/- 22.4 beats/min. The peak HR exceeded the HR at AT by an average 27.4 beats/min, which indicates that a comparatively intense exercise load above the AT level is possible. The average AT was 40.9% of the predicted maximum oxygen uptake, which seems reasonable when compared to the reports of other researchers. These results suggested that the one-leg cycling test driven by the sound limb is of use as a method for determining the AT of lower limb amputees.

Effects of gastroprokinetic agents on gastroparesis in streptozotocin-induced diabetic rats

The influence of diabetic hyperglycemia on solid gastric emptying in rats was examined. Diabetes was produced by streptozotocin (STZ, 40 mg/kg i.v.), and diabetic hyperglycemia was observed from 1 day after the STZ injection. The gastric emptying of glass beads in the diabetic rats was significantly delayed compared with that in age-matched control rats at 1, 3 and 7 days after diabetes induction. A slight decrease in gastric emptying was observed in the diabetic rats from 2 to 52 weeks after the diabetes induction. We also investigated the influence of gastroprokinetic agents on STZ-induced diabetic gastroparesis and subdiaphragmatic vagotomy-induced gastroparesis in rats. The selective 5-HT3 receptor antagonists ramosetron (YM060), YM114 (KAE-393), granisetron and ondansetron, and the substituted benzamides (5-HT4 receptor agonist/5-HT3 receptor antagonists) cisapride mosapride and SC-53116 dose-dependently enhanced gastric emptying in normal rats. These compounds also reversed the impairment of diabetic gastroparesis rats at 7 days after the STZ injection, but higher doses were required. The solid gastric emptying in subdiaphragmatic vagotomized rats was also delayed. Ramosetron and the substituted benzamides cisapride and zacopride partially reversed the gastroparesis in the vagotomized rats. These results suggest that acute hyperglycemia is important mechanism for the delay of solid gastric emptying in diabetic rats. It is also suggested that selective 5-HT3 receptor antagonists and substituted benzamides enhance gastric emptying not only in normal rats but also in diabetic and vagotomized rats.

The selective 5-hydroxytryptamine (5-HT)4-receptor agonist RS67506 enhances lower intestinal propulsion in mice

Interactions of gastrointestinal prokinetic benzamides with 5-hydroxytryptamine (5-HT)3 and 5-HT4 receptors and the relation to their effects on gastrointestinal propulsion were investigated. Renzapride and zacopride potently inhibited 5-HT3-receptor-mediated contractions in the guinea pig colon, whereas RS67506 (1-(4-amino-5-chloro-2-methoxyphenyl)-3-[1-(2-methyl sulphonylamino)ethyl-4-piperidinyl]-1-propanone hydrochloride), a selective 5-HT4-receptor agonist, showed no inhibition. RS67506, renzapride and zacopride all exerted 5-HT4 receptor-mediated relaxation in the carbachol-precontracted rat oesophagus. In mice, RS67506 shortened the whole gut transit time, whereas renzapride and zacopride were reported to prolong it. Gastrointestinal prokinetic benzamides, which are selective for 5-HT4-receptor agonistic over 5-HT3-receptor antagonistic action, may be useful in treating gastrointestinal disorders associated with impaired lower intestinal propulsion such as constipation.

Effect of a selective 5-HT3 receptor agonist on gastric motility in fasted and fed dogs

The effect of m-chlorophenylbiguanide, a selective 5-HT3 receptor agonist, on gastric antral motility was investigated in conscious dogs with a force transducer implanted chronically. m-Chlorophenylbiguanide (0.1-1 mg/kg i.v.) dose dependently enhanced antral motility in the fasted state, and the amplitude of m-chlorophenylbiguanide (1 mg/kg i.v.)-induced antral contractions reached the level of natural phase III contractions. In contrast, m-chlorophenylbiguanide reduced the amplitude of antral contractions in the fed state. A selective 5-HT3 receptor antagonist, ramosetron (0.0003-0.03 mg/kg i.v.), inhibited both effects of m-chlorophenylbiguanide. m-Chlorophenylbiguanide (1 mg/kg i.v.)-induced contractions were inhibited by atropine (0.03 or 0.1 mg/kg i.v.). These results indicate that pharmacological activation of 5-HT3 receptors has opposite effects on canine gastric antral motility in the fasted and in the fed state, being stimulatory and inhibitory, respectively. The stimulatory effect seems to be mediated mainly via the release of acetylcholine.

Combined blockade of 5-HT3- and 5-HT4-serotonin receptors inhibits colonic functions in conscious rats and mice

We have already reported that 5-hydroxytryptamine3 (5-HT3) receptor antagonists failed to modify 5-HT-accelerated colonic transit in conscious rats, but the 5-HT3 and 5-HT4 receptor dual antagonist FK1052 prevented the enhancement. In this study, the inhibitory effect on the stimulated colonic transit was not also observed with 5-HT4 receptor antagonists (SDZ205-557 and SB204070) in freely moving rats with chronic cannulas implanted into the proximal colon. In contrast, combined antagonism by simultaneous administration of ondansetron and the 5-HT4 receptor antagonist exerted a drastic inhibitory effect on the propulsive motility. Furthermore, we examined the effect of 5-HT receptor antagonists on 5-HT-induced fluid secretion in mice. Although none of these selective 5-HT receptor antagonists (YM060 and ondansetron as 5-HT3 receptor antagonist, SB204070 as 5-HT4 receptor antagonist) by itself produced a great inhibition of the 5-HT-induced diarrhea, the combination of a 5-HT3 receptor antagonist and a 5-HT4 receptor antagonist markedly reduced the diarrhea. These data suggest that 5-HT-accelerated colonic motility and 5-HT-evoked fluid secretion are mediated by both 5-HT3 and 5-HT4 receptors and that the pathways activated by these receptors may collaborate.

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.

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.

Characterization of 5-hydroxytryptamine (5-HT) receptor subtypes influencing colonic motility in conscious dogs

We examined the effects of exogenous 5-hydroxytryptamine (5-HT) and selective 5-HT receptor agonists and antagonists on proximal, middle and distal colonic motility in conscious fasted dogs with extraluminal force transducers implanted chronically. 5-HT (0.003-0.1 mg/kg i.v.) dose-dependently enhanced motility along the entire length of the colon. The 5-HT (0.03 mg/kg i.v.)-induced response was inhibited by 0.1-1.0 mg/kg i.v. methysergide, a 5-HT1/2 antagonist, at all recording sites and by 0.1-1.0 mg/kg i.v. ketanserin, a 5-HT2A antagonist, at the middle and distal sites only. At 1 mg/kg i.v., YM060, a 5-HT3 antagonist, reduced the amplitude of the initial transient high-amplitude contractions induced by 5-HT, but did not affect the tonic contraction induced by 5-HT. At doses up to 3 mg/kg i.v., 2-methoxy-4-amino-5-chlorobenzoic acid 2-(diethylamino) ethyl ester (SDZ205-557), a 5-HT4 antagonist, and hexamethonium (up to 10 mg/kg i.v.) did not affect 5-HT-induced responses at any recording site. Renzapride, a 5-HT4 agonist, also stimulated motility along the entire length of the colon at 0.3 mg/kg i.v.. The renzapride-induced response was inhibited by 1 mg/kg i.v. SDZ205-557 or 3 mg/kg i.v. hexamethonium. m-Chlorophenylbiguanide (m-CPBG), a 5-HT3 agonist, (1 mg/kg i.v.) produced a transient high-amplitude contraction at all recording sites and this contraction was eliminated by pretreatment with 0.03 mg/kg i.v. YM060. The contraction produced by m-CPBG declined rapidly, so the increase in the motility index by m-CPBG was not significant at any recording site. Of the antagonists tested, 0.1-1 mg/kg i.v. methysergide produced a delayed and prolonged contractile response at the middle and distal sites. The onset of the response was delayed about 20 min after application and the response was maintained over the subsequent 60-min observation period. The methysergide (1 mg/kg i.v.)-induced response was inhibited by 3 mg/kg i.v. hexamethonium. The other antagonists, ketanserin, YM060 and SDZ205-557, had no contractile effect at any recording site. These results indicate that exogenous 5-HT stimulates motility along the entire length of the fasted canine colon and that 5-HT-induced responses in the proximal colon are mediated mainly by 5-HT1, whereas those in the middle and distal colon are mediated by both 5-HT1 and 5-HT2 receptors. Renzapride and methysergide also stimulate colonic motility via additional mechanisms. The activation of 5-HT4 receptors and the blockade of endogenous 5-HT inhibitory regulation via 5-HT1 receptors may be involved in the action of renzapride and methysergide respectively.

Gastrin receptor antagonist YM022 prevents hypersecretion after long-term acid suppression

Female rats were treated orally for 13 wk with YM022 (300 mumol.kg-1.day-1) and with omeprazole (400 mumol.kg-1.day-1) or famotidine (900 mumol.kg-1.day-1) with or without YM022. At 2 h after the last dose, YM022 and omeprazole markedly inhibited basal and pentagastrin-induced acid secretion. Famotidine was less potent than YM022 and omeprazole against both secretions. The degree of increase in plasma gastrin level in the three groups was parallel to the antisecretory potencies of the drugs. At 14 days after the cessation of omeprazole treatment, the secretory response to pentagastrin increased above that of the control. This hyperresponse lasted for > or = 56 days. In the famotidine-treated group, a small increase in secretory response to pentagastrin was observed but was not statistically significant. The increase in secretory response to pentagastrin was paralleled by an increase in mucosal cell mass. In contrast, YM022 not only exhibited a long-lasting inhibition of pentagastrin-induced acid secretion but also prevented the hyperresponse to pentagastrin caused by omeprazole. These results indicate that the hypergastrinemia caused by long-term administration of antisecretory drugs increases mucosal secretory response to pentagastrin through a gastrin/cholecystokinin B receptor-mediated pathway in rats.

YM022 [(R)-1-[2,3-dihydro-1-(2'-methylphenacyl)-2-oxo-5-phenyl- 1H-1,4-benzodiazepin-3-yl]-3-(3-methylphenyl)urea], a potent and selective gastrin/cholecystokinin-B receptor antagonist, prevents gastric and duodenal lesions in rats

We evaluated the effect of YM022 [(R)-1-[2,3-dihydro-1-(2'- methylphenacyl)-2-oxo-5-phenyl-1H-1,4-benzodiazepin-3-yl]-3- (3-methylphenyl)urea], a potent and selective gastrin/cholecystokinin-B receptor antagonist, on gastric acid secretion and gastric and duodenal lesions in rats. Oral YM022 (0.1-10 mumol/kg), famotidine (0.3-30 mumol/kg) and omeprazole (3-100 mumol/kg) dose-dependently suppressed acid secretion in pylorusligated rats with ED50 values of 0.83, 1.63 and 10.9 mumol/kg, respectively. YM022 (1-10 mumol/kg p.o.), famotidine (1-10 mumol/kg p.o.) and omeprazole (10-100 mumol/kg p.o.) prevented indomethacin-induced gastric lesions in a dose-related manner. The potency of YM022 was comparable to that of famotidine and was 8 times greater than that of omeprazole. YM022 and famotidine partially inhibited gastric damage induced by water-immersion and restraint stress, whereas omeprazole abolished these lesions. In an acidified ethanol-induced gastric injury model, all three drugs inhibited the formation of erosions. The YM022 dosage required in this model was much greater than that required in the inhibition of gastric acid. The inhibitory effect of YM022 was partially reversed by indomethacin, indicating the involvement of a prostaglandin-mediated pathway. YM022 (3-100 mumol/kg p.o.), famotidine (1-30 mumol/kg p.o.) and omeprazole (3-100 mumol/kg p.o.) inhibited mepirizole-induced duodenal ulcers. On the basis of ED50 values, YM022 was 5 times less potent than famotidine and as potent as omeprazole against mepirizole-induced duodenal ulcers. These results suggest that YM022 possesses antisecretory and antiulcer activities that are as potent as those of famotidine in rats and that YM022 represents a useful therapeutic agent in the treatment of peptic ulcer disease.

Mechanisms of cisplatin- and m-chlorophenylbiguanide-induced emesis in ferrets

We investigated the involvement of peripheral and central serotonin (5-HT)3 receptors in cisplatin- and 5-HT3 receptor agonist-induced emesis in ferrets. Cisplatin (10 mg/kg i.v.)-induced emesis was inhibited by intravenous YM060 (0.003-0.1 microgram/kg). A highly selective and potent 5-HT3 receptor agonist, m-chlorophenylbiguanide (1-10 mg/kg i.p.), dose dependently elicited emesis an effect which was inhibited by YM060 (0.003-0.3 microgram/kg i.v.). Vagotomy markedly reduced this emesis, and the combination of abdominal vagotomy and greater splanchnicectomy abolished emesis. Lesion of greater splanchnic nerves alone did not markedly inhibit emesis. Intracerebroventricularly (4th ventricle) administered YM060 inhibited cisplatin- and m-chlorophenylbiguanide-induced emesis only at higher doses (0.01-0.1 and 0.01-0.03 microgram, respectively). Intracerebroventricularly (4th ventricle) administered m-chlorophenylbiguanide (30-100 micrograms) produced only a weak retching response. These results indicate that stimulation of abdominal vagal afferent nerves via peripheral 5-HT3 receptors is important for triggering cisplatin- and m-chlorophenylbiguanide-induced emesis in ferrets.

Effect of FK1052, a potent 5-hydroxytryptamine3 and 5-hydroxytryptamine4 receptor dual antagonist, on colonic function in vivo

5-Hydroxytryptamine (5-HT) is an important neurotransmitter and hormone/paracrine agent mediating various enteric functions. Its precise physiological and pathophysiological role remains unclear. This study investigated the effects of 5-HT on colonic function and the effects of the newly developed 5-HT3 and 5-HT4 receptor antagonist, FK1052, on colonic responses to 5-HT or stress stimulus in vivo. In conscious rats, both 5-HT and 5-methoxytryptamine significantly increased fecal pellet output and accelerated colonic transit. In contrast, the effect of 2-methyl-5-HT was slight. Although ondansetron and granisetron slightly reduced 5-HT (1 mg/kg s.c.) stimulated colonic transit, FK1052 [(+)-8,9-dihydro-10-methyl-7-[(5-methyl-4-imidazolyl)methyl]pyrido- [1,2-a]-indole-6(7H)-one hydrochloride], at 0.1 mg/kg p.o., inhibited completely the increases in the colonic transit. Furthermore, FK1052, ondansetron and granisetron significantly depressed the increase in fecal pellet output caused by wrap-restraint stress, with ED50 values of 0.21, 3.0 and 1.1 mg/kg p.o., respectively. Intraperitoneal administration of 5-HT and 5-methoxytryptamine, but not 2-methyl-5-HT, produced a dose-related increase in the incidence of diarrhea in fasted mice. 5-HT (0.32 mg/kg i.p.)-induced diarrhea was also inhibited by FK1052, ondansetron and granisetron, with ED50 values of 0.09, 2.3 and 0.88 mg/kg p.o., respectively. These findings suggest that 5-HT3 and 5-HT4 receptors may have an important role in colonic function and FK1052 may have therapeutic potential in the treatment of gastrointestinal dysfunction such as irritable bowel syndrome.

Pharmacological characterization of FK1052, a dihydropyridoindole derivative, as a new serotonin 3 and 4 dual receptor antagonist

(+)-8,9-Dihydro-10-dihydro-10-methyl-7-[(5-methyl-4-imidazolyl) methyl]pyrido-[1,2-a]indol-6(7H)-one hydrochloride (FK1052) is a newly designed and synthesized 5-hydroxytryptamine (5-HT)3 receptor antagonist with 5-HT4 receptor antagonistic activity. This compound, as well as ondansetron and granisetron, dose-dependently inhibited the von Bezold-Jarish reflex, a 5-HT3 receptor-mediated response, after intravenous (i.v.) and intraduodenal (i.d.) dosing to rats. The ID50 values showed FK1052 (0.28 microgram/kg, i.v., 5.23 micrograms/kg, i.d.) to be more potent than ondansetron (5.23 micrograms/kg, i.v., 170 micrograms/kg, i.d.) and granisetron (0.70 micrograms/kg, i.v., 66 micrograms/kg, i.d.). Furthermore, bioavailabilities of the test drugs by ID50 ratio (i.d./i.v.) showed that FK1052(17) was better absorbed than ondansetron(33) and granisetron(94) and possessed a similar duration of action to that of ondansetron and granisetron. We also examined the effects on 2-methyl-5-HT-, 5-HT- and 5-methoxytryptamine-induced contractions of guinea pig isolated ileum. FK1052, ondansetron and granisetron concentration-dependently inhibited 2-methyl-5-HT, a 5-HT3 agonist-induced contraction. The pA2 values for the 5-HT3 receptor indicated that FK1052 (8.36) was 40 times and three times more potent than ondansetron (6.79) and granisetron (7.86), respectively. FK1052, unlike ondansetron and granisetron, inhibited the 5-HT4-mediated component of concentration-response curve to 5-HT. Furthermore, FK1052 suppressed 5-methoxytryptamine, a 5-HT4 agonist-induced contraction in a concentration-dependent but insurmountable manner.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of perfusion flow rate, prostaglandin F2 alpha, phenylephrine, and serotonin on isolated, perfused brains of spontaneously hypertensive rats

Effects of perfusion flow rate and three vasoconstrictors, phenylephrine, prostaglandin F2 alpha (PGF2 alpha) and serotonin, on isolated, perfused brain preparations of spontaneously hypertensive (SHR) and normotensive Wistar-Kyoto rats (WKY) were investigated. The basal perfusion pressure of the cerebral vascular beds at a flow rate of 2.5 ml/min was 48 +/- 3 mm Hg (n = 11) in SHR and 32 +/- 2 mm Hg (n = 12) in WKY (P less than 0.005). The perfusion pressures at all flow rates tested (2.5-6.5 ml/min) in SHR were significantly greater than those in WKY. Concentration-perfusion pressure curves for the vasoconstrictors showed that the brain vascular bed was much more reactive to serotonin compared with phenylephrine and PGF2 alpha. EC50 values (-logM) for serotonin in the perfused brains of SHR and WKY were 7.0 +/- 0.06 (n = 10) and 6.5 +/- 0.06 (n = 11), respectively (P less than 0.01). There were no differences in EC50 values for phenylephrine or PGF2 alpha between SHR and WKY. Exogenous serotonin and phenylephrine caused significantly greater maximal vasoconstrictor responses in SHR compared with WKY, while the pressor response to PGF2 alpha was very weak and no significant difference between SHR and WKY preparations was observed. These results indicate that cerebral vascular beds in SHR exhibit higher cerebrovascular resistance than those in WKY. and that reactivity and sensitivity to serotonin and reactivity to phenylephrine in SHR rats are enhanced to a greater extent compared to WKY.

Relationship between endotoxaemia and protein concentration of ascites in cirrhotic patients

Endotoxaemia was investigated by the Limulus assay in 42 cirrhotic patients with ascites and in 33 without ascites. The incidence of endotoxaemia in the former group (59.5%) was significantly (P less than 0.05) higher than in the latter (36.4%). Correlation between endotoxaemia and specific gravity and concentrations of total protein, albumin, and globulin in ascitic fluid was studied in the group with ascites. The specific gravity of ascites in 25 patients with endotoxaemia was significantly greater than that in 17 patients without endotoxaemia (P less than 0.01). The concentration of total protein in patients with endotoxaemia (13.95 +/- 7.18 milligram, mean +/- SD) was nearly twice as high (P less than 0.01) as in patients without endotoxaemia (7.49 +/- 3.60 milligram). The protein content of those who showed reactions greater or equal to 2(+) in the Limulus assay (16.78 +/- 7.14 milligram) was a significantly (P less than 0.05) higher than in those with 1(+) reaction (11.26 +/- 6.33 milligram). Moreover, the concentration of albumin in patients with endotoxaemia (7.68 +/- 4.60 milligram) was more than twice that of the patients without endotoxaemia (3.39 +/- 1.58 milligram, P less than 0.01). On the other hand, globulin concentration in patients with endotoxaemia was 1.6 times that of patients without endotoxaemia (P less than 0.01). Similar differences were noted between endotoxaemic and non-endotoxaemic patients in the ascites-to-serum ratio in protein, albumin, and globulin. These results suggest that in liver cirrhosis endotoxaemia may cause an increase in protein concentrations in ascitic fluid, and that it may be a precipitating factor in the formation of ascites.