The effect of the β-carboline FG 7142 on the behaviour of male rats in a living cage: An ethological analysis of social and nonsocial behaviour

The effects of FG 7142, a -carboline benzodiazepine receptor partial inverse agonist, on the social behavior of pair-housed rats were investigated. Four 6-min dyadic social encounters in a living cage were observed in a paradigm in which one member of a pair of rats was injected. The four injection groups (n=8) were vehicle control, and FG 7142 at 2.5, 5.0 and 10.0 mg/kg, respectively. All injections were administered 2 min before the start of the first observation trial. Compared to the effects of vehicle alone, FG 7142 decreased aggressive behaviour but did not change the level of total social interaction. Thus there were compensating increases in approaching and avoiding behaviours following the administration of FG 7142. Locomotion declined marginally and immobility increased in FG 7142-injected rats. FG 7142 decreased the incidence of self-grooming. The evidence is consistent with a relatively selective reduction in intraspecies aggression in male rats after the injection of the -carboline inverse agonist.     

Antagonism of the anticonflict effects of chlordiazepoxide by β-carboline carboxylic acid ethyl ester,Ro 15-1788 and ACTH(4–10)

The antagonism of the anticonflict effect of chlordiazepoxide (CDP) by -carboline carboxylic acid ethyl ester (BCCE), Ro 15-1788 and ACTH(_4–10) has been evaluated in the Geller-Seifter rat conflict test in which CDP increases punished (conflict), but not unpunished responding. BCCE (0.5–10 g ICV) produced a dose-dependent reduction in the anticonflict activity of CDP. This was also significantly reduced by Ro 15-1788 (25 mg/kg IP) and a high dose of ACTH(_4–10) (5 g ICV). None of these test compounds had a marked direct effect on punished or unpunished responding in the doses used. These experiments provide further physiological support for the suggestion from binding studies that BCCE and Ro 15-1788 act on benzodiazepine receptors. However, the ability of ACTH(_4–10) to reduce the anticonflict effect of CDP may be by some other, possibly opioid, mechanism.     

Self-administration of methohexital,midazolam and ethanol: effects on the pituitary–adrenal axis in rhesus monkeys

Rationale There is disagreement in the literature with respect to how drugs of abuse affect the functioning of the hypothalamic–pituitary–adrenal (HPA) axis, and whether these changes in endocrine function may be related to the rewarding effects of these drugs.Objectives To determine whether reinforcing drugs with different mechanisms of action affect HPA axis function at doses at which they serve as reinforcers.Methods Seven monkeys (6 male) were randomly assigned to self-administer methohexital—a barbiturate (n=4), midazolam—a benzodiazepine (n=3), or ethanol (n=5). Each monkey had a surgically implanted indwelling venous catheter, and was trained to respond on a fixed ratio of 30 lever presses to receive an injection of drug or saline. Blood samples were obtained before, during, and after the self-administration sessions for the measurement of ACTH and cortisol by radioimmunoassay.Results Although methohexital, midazolam, and ethanol all maintained self-administration behavior across a range of doses, they differed in their effects on ACTH and cortisol. Ethanol inhibited ACTH and cortisol secretion. Methohexital and midazolam both tended to decrease ACTH and cortisol at large doses, and increase these hormones at small doses, but the HPA effects of neither drug differed significantly from when saline was available.Conclusions The neutral overall effect of methohexital and midazolam on HPA activity is consistent with other monkey and human studies, whereas the inhibitory effect of self-administered ethanol in the monkey contrasts with both the rat and human literature. The data in this study suggest that a change in HPA axis activity is not a requirement for drug-reinforced behavior in monkeys.Results from this paper were first presented at the annual meeting of ISPNE, Quebec City, Canada, in August 2001.     

The effect of isoprenaline on plasma concentrations of immunoreactive β-endorphin and β-lipotropin in the conscious rat

Summary The effect of the -adrenoceptor agonist isoprenaline on the plasma concentrations of -endorphin (-E) and -lipotropin (-LPH) was investigated in conscious rats. Isoprenaline (i.m.) elevated plasma -endorphin-like immunoreactivity (-EI) as measured by radioimmunoassay of unextracted plasma, with peak values 24 min after drug administration. This effect was dose-dependent. The lowest effective dose of isoprenaline was 15 g kg^–1; 240 g kg^–1 exerted a maximum effect, raising plasma -EI about ten-fold above control values. Plasma vasopressin concentrations also increased in response to isoprenaline following a timecourse identical to that of plasma -EI. (±)-Propranolol (1 mg kg^–1) but not phentolamine (10 mg kg^–1) rendered isoprenaline (240 g kg^–1) injections almost ineffective. Because of the cross-reactivity of -LPH in the radioimmunoassay used, plasma was extracted by means of a cation exchange resin and subjected to gel chromatography on a Sephadex G-50 column, avoiding artefactual degradation of the peptides. In isoprenaline-treated rats about 50% of the -EI behaved similar to human -LPH, whereas 45% co-migrated with human -E; immunoreactivity corresponding to -LPH or -E comprised about 70% or 30%, respectively, in the plasma extract of vehicle-treated rats. Dexamethasone pretreatment reduced the isoprenaline-induced increase in plasma -EI by 87%, but left the simultaneous elevation of plasma vasopressin concentrations unchanged.These data demonstrate that isoprenaline stimulates -LPH and -E release in vivo. The possibility of an interrelationship between vasopressin and -E release is discussed.     

The discriminative stimulus effects of midazolam are resistant to modulation by morphine,amphetamine, dizocilpine,and γ-butyrolactone in rhesus monkeys

Rationale  

Although abuse of benzodiazepines alone is uncommon, it is high in polydrug abusers, including those who primarily use opioids or stimulants.     

The effects of a benzodiazepine receptor antagonist β-carboline ZK-93426 on scopolamine-induced impairment on attention,memory and psychomotor skills

The effects of a single dose of scopolamine alone and in combination with ZK 93426 (a -carboline antagonist at the GABA_A/BZ receptor complex with weak inverse agonist activity) were tested in two studies. In one study (study 1) the emphasis of enquiry was on different stages of information processing measured by a psychometric battery; in the second study (study 2) performance at different stages of memory and psychomotor abilities was tested and electroencephalogram recordings and video-tracking were also performed. Each study consisted of two parts, part I in which scopolamine (0.5 mg; 1 ml) or placebo were administered subcutaneously, and part II in which scopolamine (0.5 mg; 1 ml) was administered subcutaneously followed by an intravenous injection of ZK 93426 (0.04 mg; 0.04 ml/kg) or placebo. Thirty-six volunteers, who were randomly allocated to receive one of the two treatments (n=18 per treatment), participated in each part. In study 1 attention was measured by a continuous attention task and a rapid information processing task, vigilance was measured by a visual vigilance task, and working memory and reasoning were evaluated by a logical reasoning task. A visual memory task was also included to measure acquisition and retention. In study 2 acquisition and short term storage and retrieval were measured by a word lists-Buschke restricted reminding procedure, and retention was tested by delayed recall and recognition. Psychomotor performance was assessed by measuring tapping speed (related to gross motoric abilities) and a pegboard task (related to fine motoric abilities). A task to measure working memory, the Pauli test, was also included. In study 1 scopolamine significantly impaired performance in the attentional and vigilance tasks (P<0.05), but there was no effect in the logical reasoning task main measurements of time and accuracy. In study 2, scopolamine also impaired performance in the psychomotor tasks (P<0.05) and the Pauli test. ZK 93426 partially antagonised most of the effects of scopolamine on memory and attention, suggesting that an interaction between the GABA-ergic and cholinergic systems is reflected in measurements of both attention and memory. In general a dissociation was found in the effects of scopolamine on memory, i.e. scopolamine impaired performance during all acquisition measurements but left retention unaffected.     

Involvement of central β2-adrenergic, NMDA and thromboxane A2 receptors in the pressor effect of anandamide in rats

Intravenous (i.v.) injection of the endocannabinoid anandamide induces triphasic cardiovascular responses, including a pressor effect mediated via unknown central and peripheral mechanism(s). The aim of the present study was to determine the central mechanism(s) responsible for the pressor response to anandamide. For this purpose, the influence of antagonists at thromboxane A₂ TP (sulotroban, daltroban, SQ 29548), NMDA (MK-801) and β₂-adrenergic receptors (ICI 118551) on the pressor effect induced by i.v. and intracerebroventricularly (i.c.v.) administered anandamide was examined in urethane-anaesthetized rats. Anandamide (1.5–3 µmol/kg, i.v.) or its stable analogue methanandamide (0.75 µmol/kg, i.v.) increased blood pressure by 25%. Anandamide (0.03 μmol per animal i.c.v.) caused a pure pressor effect (by 20%) but only in the presence of antagonists of CB₁ and TRPV1 receptors. The effects of cannabinoids (i.v. or i.c.v.) were diminished by i.v. daltroban, sulotroban (10 μmol/kg each), and/or SQ 29548 (1 μmol/kg). The effect of anandamide i.v. was reduced by SQ 29548 (0.02 μmol per animal i.c.v.) and by the thromboxane A₂ synthesis inhibitor furegrelate i.c.v. (1.8 µmol per animal). ICI 118551, MK-801 (1 µmol/kg i.v. each), and bilateral adrenalectomy diminished the effect of anandamide i.c.v. Sulotroban (i.v.) failed to affect the response to anandamide (i.v.) in pithed rats, and anandamide and methanandamide did not bind to TP receptors in rat platelets. The present study suggests that central β₂-adrenergic, NMDA and thromboxane A₂ receptors are involved in the anandamide-induced adrenal secretion of catecholamines and their pressor effect in urethane-anaesthetized rats.     

Pharmacokinetics of amosulalol,an α, β-adrenoceptor blocker,in rats,dogs and monkeys

1. The pharmacokinetics of an α,β-adrenoceptor blocker, amosulalol hydrochloride, were studied after i.v. and oral administration to rats, dogs and monkeys.

2. After an i.v. dose (1 mg/kg), the plasma concentration-time curve fitted a two-compartment open model with terminal half-lives of 2-5 h in rats, 21 h in dogs and 1-8 h in monkeys. The order of plasma clearances for amosulalol was: rats > dogs > monkeys.

3. After oral administration, the maximum plasma concentration was obtained at 0-5-1 h in rats (10-100mg/kg) and dogs (3-30mg/kg), and at l-7-2-7h in monkeys (3-10 mg/kg). A linear relationship between the area under the plasma concentration-time curve and dose administered was obtained for all three species. The systemic availabilities of the drug in rats, dogs and monkeys were 22-31%, 51-59% and 57-66%, respectively.

4. After repeated oral administration (10 mg/kg) to dogs for 15 days, the pharmaco-kinetic parameters did not differ significantly from those on the first day.     

The effects of ethanol in combination with the α2-adrenoceptor agonist dexmedetomidine and the α2-adrenoceptor antagonist atipamezole on brain monoamine metabolites and motor performance of mice

The time course of the effects of ethanol alone and in combination with the selective α₂-adrenoceptor agonist dexmedetomidine and the α-adrenoceptor antagonist atipamezole was studied in NIH-Swiss mice. Core body temperature, rotarod performance, motility and changes in the noradrenaline, dopamine, and 5-hydroxytryptamine (5-HT) metabolite contents of different brain parts (limbic forebrain, striatum, lower brainstem, the rest of the forebrain + midbrain and hypothalamus) were measured. Atipamezole (3 mg/kg) attenuated the hypothermia induced by either ethanol (3 g/kg) alone or ethanol in combination with dexmedetomidine (0.3 mg/kg). Atipamezole shortened the duration of the ethanol-impaired and ethanol + dexmedetomidine-impaired rotarod performance. Further, atipamezole prevented the decreased motility due to the combined treatment with ethanol and dexmedetomidine. Ethanol increased 3-methoxy-4-hydroxyphenylethylene glycol (MHPG), homovanillic acid (HVA) and 3,4-dihydroxyphenylacetic acid (DOPAC) values. Dexmedetomidine alone decreased MHPG and 5-hydroxyindoleacetic acid (5-HIAA) concentrations and increased DOPAC and HVA values. Dexmedetomidine combined with ethanol resulted in a further increase in DOPAC and HVA values. Pharmacokinetic parameters did not contribute to this antagonism of ethanol's effects by atipamezole, nor did the antagonism observed in rotarod performance or hypothermia seem to correlate with the changes seen in the brain noradrenaline and dopamine or 5-HT metabolism. In conclusion, these findings suggest that several ethanol effects are not mediated via direct activation of α₂-adrenoceptors, even though some of ethanol's behavioral and physiological effects may be antagonized by coadministration of α₂-adrenoceptor antagonists.     

The antidepressant-like effects of the 3β-hydroxysteroid dehydrogenase inhibitor trilostane in mice is related to changes in neuroactive steroid and monoamine levels

In the present study, we analyzed the effects of a systemic treatment with the competitive 3β-hydroxysteroid dehydrogenase (3β-HSD) inhibitor trilostane on: (i) neurosteroid and monoamine levels in the brain, and (ii) the antidepressant activity of steroids and antidepressants in the forced swimming test (FST). 3β-HSD converts pregnenolone (PREG) into progesterone (PROG) or dehydroepiandrosterone (DHEA) into androstenedione. These neuroactive steroids are known to regulate neurotransmitters effects in the brain, particularly glutamate, γ-aminobutyric acid (GABA) and serotonin (5-HT), with consequences on mood and depression. We previously reported that trilostane showed antidepressant-like properties in the FST and concomitantly regulated plasma adrenocorticotropin (ACTH) and corticosterone levels, markers of the stress-induced hypothalamus-pituitary-adrenal (HPA) axis activation. We here observed that adrenalectomy/castration blocked the trilostane effect, outlining the importance of peripheral steroid levels. Trilostane (25 mg/kg) decreased hippocampus PROG contents and paradoxically increased circulating PROG levels. It also increased PREG levels in the hippocampus and frontal cortex. In the FST, a co-treatment with trilostane facilitated DHEAS (5-20 mg/kg) antidepressant activity, but showed only an additive, not facilitative, effect with PREGS (10-40 mg/kg), PROG (10-40 mg/kg) or allopregnanolone (ALLO, 1-8 mg/kg). Trilostane (25 mg/kg) treatment significantly increased 5-HT and (-)-norepinephrine (NE) turnovers in the hippocampus, an effect likely related to its antidepressant action. In co-administration studies, trilostane further decreased immobility following fluoxetine (30-60 mg/kg), sertraline (20-40 mg/kg) and imipramine (20-40 mg/kg), but not desipramine (20-40 mg/kg), treatments. A significant additive effect was observed for the selective 5-HT reuptake inhibitors (SSRI) at their highest dose. This study confirmed that a systemic administration of trilostane directly affected peripheral and brain levels in neuroactive steroids and monoamine turnover, resulting in antidepressant activity. The drug could be proposed as a co-treatment with SSRI. This article is part of a Special Issue entitled 'Anxiety and Depression'.     

The effect of β-adrenoceptor blocking agents on evolving myocardial necrosis in coronary ligated rats with and without reperfusion

Summary The left coronary artery of rats was ligated either permanently, or for a period of 40 or 60 min, with subsequent reperfusion. In experiments with permanent occlusion, the hearts were removed and investigated 5 h after the coronary ligation, or immediately after death in animals which died earlier. The hearts from the reperfusion experiments were investigated 60 min after reopening the occluded artery.The extent of the ischaemic and necrotic areas of the hearts was determined. A quantitative photometric method was developed, for this purpose, using negative staining with Evans blue for the ischaemic area, and negative staining with triphenyltetrazolium chloride for the necrotic area.In experiments in which ligation was permanent, the percentage of the ischaemic area which underwent necrosis increased with the time after coronary occlusion. In reperfusion experiments, myocardial necrosis was detected earlier than in experiments with permanent coronary ligation.The -adrenoceptor blocking agents pindolol, propranolol, and metoprolol significantly decreased the percentage of necrosis in experiments with permanent ligation of the coronary artery. The most selective of the -adrenoceptor blockers, i.e. metoprolol was tested in the reperfusion experiments. In these experiments, the amount of necrosis was also significantly decreased.An abstract was given at the Joint Meeting of the French and German Pharmacological and Toxicological Societies in Freiburg, 19–22 September 1983; W. Bernauer, Naunyn-Schmiedeberg's Arch Pharmacol, Supplement to Vol 324, R 9 (1983)     

Light effect on the stability of β-lapachone in solution: pathways and kinetics of degradation

Objectives The purpose of this work was to study the chemical stability of the new antitumoral β‐lapachone (βLAP) to determine the degradation pathway/s of the molecule and the degradation kinetics in addition to identifying several degradation products. Method Samples of βLAP in solution were stored under conditions of darkness and illumination at 40°C at which the pseudo‐first order rate constants for the βLAP degradation were determined. Furthermore, drug degraded solutions were concentrated and purified using Sephadex LH‐20 and preparative thin‐layer chromatography and degradation products were identified by nuclear magnetic resonance spectroscopy. Key findings The results revealed that βLAP shows two different degradation routes: hydrolysis in the dark and photolysis under the light. The βLAP exposure to light accelerated the drug degradation about 140 fold, compared with the samples stored in the absence of light. The hydrolysis produced hydroxylapachol as the main degradation product. The photolysis yielded phthalic acid, 6‐hydroxy‐3methylene‐3H‐isobenzofuran‐1‐one and a benzomacrolactone together with a complex mixture of other phthalate‐derivatives such as 2‐(2‐carboxy‐acetyl)‐benzoic acid. Conclusions This study provides useful information for the development of βLAP dosage forms, their storage, manipulation and quality control.     

Influence of sildenafil on copulatory behaviour in sluggish or normal ejaculator male rats: a central dopamine mediated effect?

The present study investigates the effects induced by sildenafil (1 mg/kg, p.o.) and the dopamine agonist, SND 919 (0.1 mg/kg, i.p.) on copulatory behaviour of male rats, categorized, on the basis of seven consecutive mating pre-tests, as sluggish and normal ejaculators (SE and NE, respectively). The data obtained show that sildenafil modifies both sexual arousal and ejaculatory mechanisms of copulation. It appears that, although it induced a facilitatory effect on ejaculation of all rats, similarly to SND 919, the lowering of ejaculatory threshold was achieved by means of a reduction of mount frequency and intromission frequency in SE and NE groups, respectively. Differently from SND 919, sildenafil increased sexual arousal, diminishing post ejaculatory interval in SE animals and inter-intromission interval in both SE and NE rats. As the dopamine antagonist, (-)eticlopride (0.02 mg/kg, s.c.), significantly inhibited sildenafil-induced enhancement of sexual arousal in SE rats, it is suggested that the drug acts both peripherally and centrally.     

The effect of molecular weights of microencapsulating polymers on viability of mouse-cloned pancreatic β-cells: biomaterials,osmotic forces and potential applications in diabetes treatment

Introduction: Ideal cell-containing microcapsules should be capable of maintaining cell viability and exhibit significant structural stability to support cellular functionality. To date, such microcapsules remain unavailable; thus, this study used our well-established microencapsulating methods to examine a total of 32 different microencapsulating formulations and correlate polymers’ molecular weights (M_wt) and UDCA addition, with cell viability and microcapsules’ stability, postmicroencapsulation.

Methods: MIN6 mouse-cloned pancreatic β-cells were microencapsulated using control (n?=?16; without UDCA) and test (n?=?16; with UDCA) different polymers. Confocal microscopic imaging, cell viability, and microcapsules’ stability were assessed.

Results: Best cell viability (>50%) was obtained at average M_wt of 50,000?g/mol (poly-l-ornithine), followed by 110,000?g/mol (poly-l-lysine). There was no linear correlation between M_wt and viability. Confocal imagining showed similar microcapsules’ shape and cell distribution among all different polymers’ molecular weights, which suggests that the microencapsulating method was efficient and maintained microcapsules’ uniformity. UDCA addition resulted in enhanced osmotic stability of the microcapsules and improved cell viability, when the formulation contained 1% polylornithine, 1% polyethylene glycol, 20% Eudragit^® NM30D, 1% polytetrafluoroethylene, or 5% pentamethylcyclopentasiloxane.

Conclusions: UDCA addition improved microenvironmental conditions within the microcapsules but this effect was largely dependent on the polymer systems used.     

The effects of Δ9-tetrahydrocannabinol alone and in combination with cannabidiol on fixed-interval performance in rhesus monkeys

It has been reported that cannabidiol (CBD) antagonizes the effects of ⁹-tetrahydrocannabinol (THC) on operant behavior in rats and pigeons. We have replicated this finding with rhesus monkeys. Four rhesus monkeys were trained to lever press on a fixedinterval 5-min schedule of food presentation with a 1-min limited hold and 1-min time out between successive intervals. The effects of 0.3 and 1.0 mg/kg THC alone were determined three times during the experiment; before the CBD-THC interaction, after the CBD-THC interaction and once with the CBD vehicle. A dose of 30 mg/kg CBD, which alone resulted in a 24% reduction in responding, completely antagonized the response rate reduction produced by 0.3 mg/kg THC. The effects of THC revealed a rate-dependent effect that did not conform to the log-linear rate-dependency plots described for most other drugs.This research was reported at the FASEB Meeting in Atlantic City, NJ in 1978 [Fed. Proc. 37: 739 (Abs.) 1978]     

The effect of luteolin-7-O-β-d-glucuronopyranoside on gastritis and esophagitis in rats

This study evaluated the inhibitory action of luteolin-7-O-beta-D-glucuronopyranoside, luteolin which was isolated from Salix gilgiana leaves, and omeprazole on reflux esophagitis and gastritis in rats. Reflux esophagitis and gastritis were induced surgically and by the administration of indomethacin, respectively. The intraduodenal administration of luteolin-7-O-beta-D-glucuronopyranoside decreased the ulcer index, injury area, gastric volume and acid output, and increased the gastric pH compared with luteolin. Luteolin-7-O-beta-D-glucuronopyranoside significantly decreased the size of the gastric lesions that had been induced by exposing the gastric mucosa to indomethacin. The malondialdehyde content, which is the end product of lipid peroxidation, was increased significantly after inducing of reflux esophagitis. The malondialdehyde content was decreased by Luteolin-7-O-beta-D-glucuronopyranoside but not luteolin or omeprazole. Luteolin-7-O-beta-D-glucuronopyranoside has a more potent antioxidative effect than luteolin. Luteolin-7-O-beta-D-glucuronopyranoside is a promising drug for the treatment of reflux esophagitis and gastritis.     

Disposition and metabolism of amosulalol hydrochloride,a new combined α- and β-adrenoceptor blocking agent,in rats,dogs and monkeys

1. The disposition and metabolism of amosulalol hydrochloride, a combined α- and β-adrenoceptor blocking agent, were studied in rats, dogs and monkeys.

2. After oral administration of [¹⁴C]amosulalol hydrochloride, the plasma concentration of radioactivity reached a maximum at 05 to 1 h in all species and declined with half-lives of about 2 h in both rats and monkeys, and of about 4 h in dogs. The ratios of unchanged drug to total radioactivity in the rat and dog plasma were 8 and 43% at 05 h after administration, respectively. The radioactivity in the rat tissues was high in the liver, kidney, blood and pancreas after oral administration.

3. Following oral dosage, the urinary excretion of radioactivity was 26-34% of the dose in rats, 45% in dogs and 46% in monkeys in 48 h. The biliary excretion after oral dosage amounted to 66% and 41% in rats and dogs, respectively.

4. Six metabolites were isolated and identified from the urine of rats and dogs. They were derived from one or two of the following pathways: I, hydroxylation of the 2-methyl group of the methylbenzenesulphonamide ring; II, demethylation of the o-methoxy group of the methoxyphenoxy ring; III, hydroxylation at the 4 or 5 position of the methoxy-phenoxy ring; IV, oxidative cleavage of the C—N bond yielding o-methoxyphenoxy acetic acid. Moreover, some metabolites were metabolized to glucuronide or sulphate.