Gender-related differential effect of tachykinin NK2 receptor-mediated visceral hyperalgesia in guinea pig colon.

BACKGROUND AND PURPOSE: The tachykinin NK2 receptor antagonist ibodutant is under Phase III clinical investigation to treat female patients with irritable bowel syndrome. The aim of this study was to investigate the NK2 receptor-related gender specificity in a model of colitis. EXPERIMENTAL APPROACH: Colitis was induced by rectal instillation of 2,4,6-trinitrobenzenesulfonic acid (TNBS, 0.5 mL, 30 mg·mL(-1) in 30% ethanol) in female and male guinea pigs. Electromyographic recording of the responses to colorectal distension (CRD) was made 3 days later. Ibodutant (0.33 , 0.65, 1.9 and 6.5 mg·kg(-1) ) was given s.c., 30 min before CRD. Release of neurokinin A and substance P from isolated mucosal and smooth muscle tissues following treatment with KCl (80 mM) or capsaicin (10 µM) was measured by EIA. Plasma pharmacokinetics of ibodutant following a single s.c. administration (0.73 or 2.1 mg·kg(-1) ) were measured over 24 h. KEY RESULTS: Ibodutant did not affect abdominal contractions in control animals. After TNBS-induced colitis, ibodutant prevented the increased visceral hypersensitivity to CRD in females, at lower doses than in males. Ibodutant pharmacokinetics did not differ between females and males. Tachykinins release was greater in smooth muscle than in mucosal samples. Capsaicin-stimulated release of tachykinins from inflamed mucosal samples from females was significantly lower than in males. CONCLUSIONS AND IMPLICATIONS: Ibodutant prevented abdominal nociception in a model of visceral hypersensitivity in guinea pigs with a greater efficacy in females than in males. Our results highlight a gender-related difference in colonic visceral hypersensitivity and mucosal nerve activation.

Nepadutant pharmacokinetics and dose-effect relationships as tachykinin NK2 receptor antagonist are altered by intestinal inflammation in rodent models.

Tachykinin NK2 receptor antagonists could reduce motility and symptoms during gastrointestinal diseases characterized by local inflammation such as diarrhea or colitis; however, how these conditions change pharmacodynamic and pharmacokinetic characteristics of NK2 receptor antagonists is unknown. We investigated the effect of the peptide NK2 receptor antagonist nepadutant on spontaneous intestinal motility or [betaAla8]NKA(4-10)-induced colonic and bladder contractions in rodent models of intestinal inflammation (enteritis induced by castor oil and rectocolitis induced by local instillation of acetic acid in rats, enteritis induced by bacterial toxins in mice). In the castor oil model, the oral/intraduodenal bioavailability of nepadutant was also determined. The intrarectal (i.r.) administration of nepadutant (100 nmol/kg) did not reduce [betaAla8]NKA(4-10) (10 nmol/kg i.v.)-induced colonic and bladder contractions in normal animals, but the same dose of nepadutant produced an inhibitory effect in the two organs following rectocolitis; in contrast, nepadutant is equieffective by the intravenous route in normal and colitic animals. In this model, nepadutant (100 nmol/kg i.r. or i.v.) decreased spontaneous colonic hypermotility, without affecting motility in controls. The intraduodenal administration of nepadutant (30 nmol/kg), which was ineffective on [betaAla8]NKA(4-10) (10 nmol/kg i.v.)-induced colonic and bladder contractions in control animals, abolished bladder contractions in castor oil-pretreated animals. In this latter group, the oral and intraduodenal bioavailability of nepadutant showed a 7- to 9-fold increase with respect to controls. Oral administration of nepadutant, in nanomolar or subnanomolar dosage, reduced diarrhea induced by bacterial toxins in mice. It is concluded that intestinal inflammation increases nepadutant absorption in the intestine, enhancing its activity. These results suggest that a drug with a limited oral bioavailability could be used for treating gastrointestinal diseases associated with a local inflammation.

Determination of the tricyclic compound adosupine and its three metabolites in plasma and brain of rat using high-performance liquid chromatography.

An analytical method for the detection in biological samples of the novel tricyclic compound adosupine (10-acetoamido-5-methyl-5,6-dihydro-11H-dibenzo[b,e]azepin-6 ,11-dione), which is capable of influencing various forms of urinary bladder hyperreflexia has been developed using high-performance liquid chromatography with UV detection. Liquid-liquid extraction was used to isolate the parent compound, three metabolites and an analogue (added as internal standard) from plasma and brain of rat. Adosupine was well separated from its three metabolites with 0.01 M disodium hydrogenphosphate-acetonitrile-methanol-nonylamine (59.986:38:2:0.014) at pH 4.5 as mobile phase using a C18 reversed-phase column. The standard curves were linear in the range 50-5000 ng/ml (or ng/g) for adosupine and metabolites in both plasma and brain. The between- and within-assay variations for high and low concentrations of the parent compound and the three metabolites were 8.2-14%. In the range 50-5000 ng/ml (or ng/g) the accuracy of the method was satisfactory, with the relative error always lower than 10%. Analytical recoveries of added adosupine and the three metabolites were higher than 82%. The method has been applied successfully, to investigate the pharmacokinetics of the drug and its distribution in the central nervous system of rats.

Effect of enantiomers of propranolol on desipramine-induced anti-immobility in the forced swimming test in the rat.

The effect of d- and l-enantiomers of propranolol on desipramine-induced anti-immobility effects and on brain desipramine levels was studied in the rat. Intraperitoneal propranolol and desipramine were administered three times, 25, 6, 2 and 24, 5, 1 h respectively, before the test. It was found that l-propranolol but not d-propranolol, at the same doses (2.5 and 5 mg/kg), antagonized 20 mg/kg desipramine without altering desipramine brain levels. It is suggested that blockade of beta-adrenergic receptors rather than membrane-stabilizing or pharmacokinetic effects is responsible for the antagonism of propranolol toward desipramine.

Effect of serotoninergic drugs on stress-induced hyperthermia (SIH) in mice.

8-OH-DPAT (2.5-10 mg/kg) and buspirone (10 mg/kg) but not 5,7-DHT (200 micrograms/mouse), pCPA (75 and 150 mg/kg, three times), ritanserin (0.1 and 0.2 mg/kg), LY 53857 (1.5 and 3 mg/kg), GR 38032 F (0.1-100 micrograms/kg), TFMPP (5 and 20 mg/kg) and mCPP (2.5 and 5 mg/kg) antagonized the rise in body temperature that occurs to the last mice removed from their group housing, which was termed as stress-induced hyperthermia (SIH). Ro 15-1788, at a dose which blocked the effect of diazepam on SIH, did not reverse the anxiolytic effect of buspirione. Instead, when cerebral 5-HT content was reduced to 50% by 5,7-DHT-induced lesion, the effect of buspirone on SIH was decreased. TFMPP 5 mg/kg did not shorten significantly the onset of SIH as could have been expected by an anxiogenic drug, while the dose of 20 mg/kg did not modify the pattern of SIH at all. The lower dose of TFMPP evoked a hyperthermic and the higher a hypothermic response.

Cholinergic drug effects on antidepressant-induced behaviour in the forced swimming test.

The contribution of anticholinergic effects to the action of desipramine and nomifensine was investigated in the forced swimming test in rats. The immobility time was reduced by high doses of atropine (10-25 mg/kg i.p.) and scopolamine (1.5 mg/kg i.p., 1 and 0.5 h before the test, respectively) and was unaffected by physostigmine (0.25-0.5 mg/kg i.p., 1 h before the test). Unlike atropine (25 mg/kg), scopolamine (1.5 mg/kg) increased motor activity (open-field). The anti-immobility effect of i.p. desipramine (20 or 30 mg/kg) and nomifensine (2.5 or 5 mg/kg), administered 24, 5 and 1 h before the test, was potentiated by scopolamine (0.5-1.0 mg/kg) and antagonized by physostigmine (0.25-0.5 mg/kg). The brain levels of desipramine and nomifensine were unaffected by scopolamine or physostigmine. Motor performance was impaired in rats treated with physostigmine and desipramine whereas hypermotility was observed in rats treated with scopolamine and nomifensine. The anti-immobility effect of atropine (25 mg/kg) and scopolamine (1.5 mg/kg) was not antagonized by physostigmine (0.5 mg/kg). These results indicate that anticholinergic mechanisms alone are not sufficient to influence immobility time and suggest that the cholinergic system may control, the neural circuitry upon which desipramine and nomifensine act to reduce immobility time.

Stimulation of dopamine D-2 but not D-1 receptors reduces immobility time of rats in the forced swimming test: implication for antidepressant activity.

The involvement of dopamine D-1 and D-2 receptor mechanisms was investigated in the forced swimming test with rats. d,1-Sulpiride, a D-2 receptor antagonist, reported to reduce desipramine-induced anti-immobility, did not alter the brain levels of desipramine. In addition, the anti-immobility effect of desipramine was not antagonized by SCH 23390, a D-1 receptor antagonist. Amineptine (20 mg/kg i.p., 60 min before testing), a dopamine uptake blocker, and LY171555 (0.2 mg/kg i.p., 60 min before testing), a dopaminergic D-2 stimulant reduced immobility time in the forced swimming test, but benserazide + 1-DOPA (200 mg/kg p.o., 45 min before testing), which increases dopamine release, or SKF 38393A (20 mg/kg s.c., 60 min before testing), a D-1 agent, did not. The anti-immobility effect but not the stereotypy was increased following chronic (21 days) LY171555 (0.1 and 0.2 mg/kg i.p.) treatment. The effect of acute or repeated (7 days) LY171555 (0.2 mg/kg i.p.) treatment was antagonized by 1-sulpiride (50 mg/kg i.p., 90 min before testing), a D-2 receptor antagonist. Neither SKF 38393A (20 mg/kg s.c., 60 min before testing) nor SCH 23390 (0.05 mg/kg s.c., 30 min before testing) modified the acute anti-immobility effect of LY171555 (0.2 mg/kg i.p.) SCH 23390 (0.025 and 0.05 mg/kg) increased the immobility time at doses which decreased motor activity. The increase in immobility time brought about by SCH 23390 was not antagonized by SKF 38393A (20 mg/kg). The findings indicate that activation of dopamine D-2 receptors could reduce immobility time.

New method for recording cystometrograms in conscious, freely moving rats.

A new cystometric technique has been developed that is suitable for quantitative studies on physiopharmacology of micturition in conscious, freely moving rats. The method involves the transvesical infusion of warm saline at various filling rates through a catheter chronically implanted into the bladder dome. The various parameters of the collecting and voiding phase of the cystometrogram were recorded. Results obtained indicate that characteristics of the bladder voiding cycle of conscious, freely moving rats are qualitatively similar but quantitatively different from those described previously in anesthetized animals.

On the role of endogenous GABA in the forced swimming test in rats.

GABA content was reduced in the nucleus accumbens, cortex and brainstem of rats after 5 but not after 45, 120 min or 24 hr, from the termination of the pretest session. This reduction was not observed in rats performing on rotarod. Intraperitoneal AOAA (25 mg/kg; 24, 5 and 1 hr before the test), reduced at the same extent immobility time regardless whether the animals had been exposed to a pretest session. In pretested animals, reduction in immobility time produced by AOAA (25 mg/kg X 3 times) was similar to that observed following 50 mg/kg, 5 hr before testing. This reduction was not antagonized by GABA antagonists bicuculline (2 mg/kg) or picrotoxin (2 mg/kg), given intraperitoneally 30 and 20 min before the test respectively. Intraperitoneal sodium valproate (200 or 400 mg/kg; 24, 5 and 1 hr before the test) and isoniazide (200 mg/kg) or 4-deoxypyridoxine (400 mg/kg), administered 1 or 1.5 hr before the test, were ineffective. AOAA (25 mg/kg X 3 times) gave a similar increase in GABA levels to 50 mg/kg only once in the brainstem, nucleus accumbens and hypothalamus and a greater increase in the other brain areas. After 5 hr from single dosing, 25 mg/kg AOAA increased GABA levels less than 50 mg/kg AOAA in the brainstem, nucleus accumbens, frontal cortex and striatum, and increased it to same extent in the other areas. Sodium valproate (400 mg/kg X 3 times) increased GABA levels in all brain areas, except hippocampus, although to a lesser extent than AOAA.

Distribution of amiodarone and desethylamiodarone in a patient with acute myocardial infarction after intravenous administration.

The autopsy tissues concentration of amiodarone and desethylamiodarone of a man with acute myocardial infarction treated acutely with intravenous amiodarone is reported. Our data indicate that amiodarone is quickly distributed into all highly perfused tissues after intravenous administration with a high amiodarone/desethylamiodarone ratio. We also report here the autopsy case of a woman who died after 30 days of oral therapy with amiodarone. The increase in heart/plasma ratio of amiodarone and desethylamiodarone concentrations and the decrease in amiodarone/desethylamiodarone ratio after one month of therapy could explain the latency in the antiarrhythmic action of the drug.

Lack of relationship between effect of desipramine on forced swimming test and brain levels of desipramine or its demethylated metabolite in rats.

Animals were injected with 20 mg/kg desipramine (DMI) 1 h (acute) or 24, 5 and 1 h (subchronic) or once daily for 7 consecutive days (chronic) before the forced swimming test (FST). DMI was also injected at a dose of 40 mg/kg acutely. Animals were killed immediately after test for evaluation of brain concentrations of DMI and its demethylated metabolite desmethyldesipramine (DDMI). Acute and chronic DMI 20 mg/kg gave rise to similar brain concentrations but only chronic DMI was active on FST. Acute DMI 20 mg/kg and 40 mg/kg gave rise to different brain concentrations but similar effects on FST. DDMI concentrations were similar after the various DMI treatments. Results seem to indicate that no relationship exists between effect of DMI on FST and brain concentrations of either DMI or DDMI.

Amiodarone and desethylamiodarone distribution in the atrium and adipose tissue of patients undergoing short- and long-term treatment with amiodarone.

The time to onset of action of amiodarone is often long in patients treated for arrhythmias; one reason might be a slow entry of the drug into the target organ, the heart. Amiodarone and desethylamiodarone, its active metabolite, were measured in the plasma, atrial tissue and pericardial fat of patients undergoing cardiac surgery. Two groups were studied: patients treated with amiodarone for less than 28 days (short-term group) and those treated for 28 days or more (long-term group). Plasma levels of amiodarone in the two groups were not different, whereas levels of desethylamiodarone were significantly higher in the long-term group. Average concentrations of amiodarone in the atrium were higher with longer treatment periods (30.2 +/- 5.6 versus 13.2 +/- 2.5 micrograms/g wet weight of tissue); the same was true for desethylamiodarone (40.3 +/- 7.7 versus 15.7 +/- 3.7 micrograms/g). Amiodarone concentrations in fat were also significantly higher in the long-term than in the short-term group. Atrium/plasma concentration ratios of desethylamiodarone were higher than those of amiodarone, whereas fat plasma concentration ratios of desethylamiodarone were lower. In conclusion, the equilibration of amiodarone and desethylamiodarone concentrations between myocardium and plasma appears to occur slowly in patients undergoing long-term treatment with amiodarone.(ABSTRACT TRUNCATED AT 250 WORDS)

Physicochemical and analytical characteristics of amiodarone.

Data are reported on the analytical and physicochemical characteristics of amiodarone, for use in identifying and/or assaying this antiarrhythmic agent. The drug is highly soluble in chloroform and poorly soluble in water. Its acid-base constant (pKa) is 6.56, and its maximal lipid solubility range is from pH 3.5 to 5.5.

Blood levels and electrophysiological effects of intravenous amiodarone in patients with junctional reciprocating tachycardia. Preliminary observations.

The time course and the mode of antiarrhythmic action of Amiodarone was studied after acute i.v. injection of the drug (5 mg/kg in 5 min) to four patients with junctional reciprocating tachycardia. Electrophysiological studies were performed before and 1 and 2 hours after Amiodarone injection. It was impossible or considerably more difficult to induce junctional reciprocating tachycardia after Amiodarone, and the drug's effect was detectable mainly on the AV node. Kinetic analysis of blood levels of Amiodarone during the electrophysiological study did not support a direct association between blood concentration and its effects.

Acute overdosage of amiodarone in a suicide attempt.

Clinical and biochemical variables and blood levels of amiodarone and its metabolite are reported after acute self-intoxication in a young woman. Despite the huge amount of drug ingested no clinical side effects were documented over the monitored period of 3 months.