Enhancement of Solubility and Bioavailability of β-Lapachone Using Cyclodextrin Inclusion Complexes

Purpose. To explore the use of cyclodextrins (CD) to form inclusion complexes with -lapachone (-lap) to overcome solubility and bioavailability problems previously noted with this drug. Methods. Inclusion complexes between -lap and four cyclodextrins (-, -, -, and HP-CD) in aqueous solution were investigated by phase solubility studies, fluorescence, and ¹H-NMR spectroscopy. Biologic activity and bioavailability of -lap inclusion complexes were investigated by in vitro cytotoxicity studies with MCF-7 cells and by in vivo lethality studies with C57Blk/6 mice (18-20 g). Results. Phase solubility studies showed that -lap solubility increased in a linear fashion as a function of -, -, or HP-CD concentrations but not -CD. Maximum solubility of -lap was achieved at 16.0 mg/ml or 66.0 mM with HP-CD. Fluorescence and ¹H-NMR spectroscopy proved the formation of 1:1 inclusion complexes between -CD and HP-CD with -lap. Cytotoxicity assays with MCF-7 cells showed similar biologic activities of -lap in -CD or HP-CD inclusion complexes (TD₅₀ = 2.1 M). Animal studies in mice showed that the LD₅₀ value of -lap in an HP-CD inclusion complex is between 50 and 60 mg/kg. Conclusions. Complexation of -lap with HP-CD offers a major improvement in drug solubility and bioavailability.     

Effects of Topical Anandamide-Transport Inhibitors,AM404 and Olvanil,on Intraocular Pressure in Normotensive Rabbits

Purpose. To evaluate the effects of topically applied anandamide transport inhibitors, AM404 and olvanil, on the intraocular pressure (IOP) of normotensive rabbits. To determine if the ocular hypotension induced by topical anandamide (AEA) can be potentiated by co-administered AM404. Methods. Test compounds, in either hydroxypropyl--cyclodextrin (HP--CD) or propylene glycol, were administered unilaterally onto rabbit eyes. To determine if AM404 affects the IOP-profile of AEA, AM404 was administered ocularly 15 minutes before topical AEA. Phenylmethylsulfonyl fluoride (PMSF) (24 mg/kg, s.c.) was given 30 min before AEA to prevent its catabolism. IOPs of the treated and untreated eyes were measured. The cannabinoid agonist activities of AM404 and olvanil were studied by using [³⁵S]GTPS autoradiography. Results. Topical AM404 (62.5 g), in HP--CD vehicle, decreased IOP significantly in treated eyes. AM404 (62.5 g) induced a significant IOP increase without subsequent decrease when given in propylene glycol vehicle. Olvanil (312.5 g) caused a significant IOP reduction without provoking an initial hypertensive phase. These compounds did not significantly affect the IOP of untreated eyes. Co-administered AM404 (125 g in HP--CD) had no significant effect on the IOP profile of AEA (62.5 g). Conclusions. Ocular administration of AM404 or olvanil decreased IOP in rabbits, although AM404 can provoke an initial ocular hypertension and did not potentiate the IOP responses induced by exogenous AEA.     

The subjective,behavioral and cognitive effects of subanesthetic concentrations of isoflurane and nitrous oxide in healthy volunteers

A prospective, crossover, double-blind trial was conducted in nine healthy volunteers in which the subjective, psychomotor and memory effects of isoflurane (0.0, 0.3 and 0.6%) and nitrous oxide (N₂O) (0, 20 and 40%) were examined. Dependent measures included visual analog scales and a standardized drug effects inventory (subjective effects), reaction time and eye-hand coordination (e.g., psychomotor performance), and immediate and delayed free recall (memory). There were some similarities in subjective effects between the two inhaled drugs (e.g., increased ratings of drunk and spaced out), but isoflurane had effects which N₂O did not have. Isoflurane but not N₂O increased visual analog scale ratings of confused, sedated, and carefree, and decreased ratings of in control of thoughts and in control of body. An odor was detected with isoflurane and it was disliked. Psychomotor performance was more grossly impaired during isoflurane inhalation than during N₂O inhalation. Psychomotor recovery from both agents was rapid and complete so that 5 min after the inhalation period had ceased, performance had returned to baseline levels. Both isoflurane and nitrous oxide impaired immediate and delayed free recall. The feasibility of using isoflurane in conscious sedation procedures is discussed.     

Risk factors for the development of adverse drug events in hospitalized patients

Adverse drug events in hospitalized patients lead to increased morbidity, mortality and costs. Early detection of adverse drug events could aid in the prevention of these adverse outcomes. A costeffective system for the early detection of adverse drug events should focus on high risk patients. A study was set up with the primary aim to identify characteristics that are associated with the development of adverse drug events (ADEs) in hospitalized patients.ADE reports were gathered from physicians and nurses (spontaneous reports) and from patients after intensive ward interviews by hospital pharmacists. All patients admitted to the internal medicine wards of two Dutch hospitals, during a two month period, were included.The following characteristics were analyzed for their potential relationship to the occurence of ADEs: age (categorized), gender, number of drugs prescribed during hospital stay, types of drugs used and changes in drug use on admission.Age was found to be inversely associated with the development of ADEs (OR 0.36, CI 0.210.61 for age category > 80 years; OR 0.56; CI 0.311.02 for age category 7580 years and OR 0.69; CI 0.421.11 for age category 6074 years). Furthermore, statistically significant associations were found for the number of drugs prescribed per hospitalized patient (for the class of 46 drugs per patient OR 2.61, CI 1.325.18), for newly prescribed drugs (OR 6.65, CI 2.6316.81) and for the cessation of drugs on hospital admission (OR 1.50, CI 1.022.20). The use of gastrointestinal drugs (OR 2.13, CI 1.323.45), central nervous system drugs (OR 1.66, CI 1.072.57) and antibiotics (OR 2.44, CI 1.653.60) were associated with the development of ADEs, when compared to all other drugs taken by the patients.In this study, the most important risk factors are the number of drugs used per patient and the starting of a new drug during hospitalization. As most hospitalized patients start new drug therapies while in hospital, this seems an inappropriate focus. However, careful monitoring of patients using more than 7 drugs at a time may be possible in a costeffective system for the early detection of ADEs.     

Rate of increase of plasma drug level influences subjective response in humans

This study addressed the commonly held, but seldom tested, notion that faster rates of increase of drug effects are associated with more positive subjective effects. Sodium pentobarbital was administered to normal healthy volunteers in either a single oral dose or in a series of divided, cumulating doses, and subjective responses were monitored. Twelve subjects participated in three weekly sessions, during which they received capsules containing placebo, 150 mg pentobarbital in a single dose (SIN) or 180 mg pentobarbital administered in six divided doses (DIV) of 30 mg every 30 min. Doses of pentobarbital in the SIN and DIV were selected to produce similar peak plasma levels. Blood samples were obtained at regular intervals for plasma drug level determinations, and throughout the session subjects completed self-report mood questionnaires (e.g., Profile of Mood States, visual analog ratings of drug liking and drug high) and psychomotor performance tests (e.g., Digit Symbol Substitution Test). As expected, the SIN and DIV conditions yielded similar peak levels of pentobarbital, but the peak was attained more rapidly in the SIN condition. Despite the similarity in peak plasma levels, subjects reached greater peaks in ratings of high and wanted more of the drug when they were in the SIN condition. On an end-of-session liking questionnaire they also reported significantly greater liking of the drug in the SIN condition. On other measures of drug effects (e.g., sedation and psychomotor impairment) no significant differences were observed between the conditions. Thus, the rate of increase of the drug's effects specifically influenced subjects' ratings on subjective measures (e.g., high and liking) that may be associated with risk for abuse. The results have implications for the relative abuse liability of different formulations of psychoactive drugs.     

New therapeutic targets for rheumatoid arthritis

New insights into the pathogenesis of rheumatoid arthritis (RA) and consequently new targets of therapy are covered in a broad overview fashion. Shortterm significant beneficial effect on RA disease activity has been established in a small but rapidly growing number of doubleblind placebocontrolled trials now including recombinant human IL1 receptor antagonist, chimeric (mouse/human) monoclonal antibodies (mAb) against TNFa (cA2), humanised (human/mouse) antiTNFa mAb (CDP571) and recombinant human TNFreceptorFc fusion protein (TNFR : Fc). Placebocontrolled trials of antiT cells agents such as chimeric antiCD4 mAb (cMT412) and antiCD5 immunoconjugate, did not demonstrate clinical benefit. A placebocontrolled study of the antiT cell derived cytokine IL2 (DAB486IL2) showed only modes clinical improvement. Other antiT cell approaches such as autologous T cell vaccination and induction of tolerance by oral type II collagen have been unsuccessful. The one controlled trial with an antiinflammatory cytokine, recombinant human IFNg, showed modest clinical benefits. Controlled trials with IL4 and IL10 and with antiadhesion molecules are awaited.     

Subjective and behavioral responses to intravenous fentanyl in healthy volunteers

Fentanyl is a mu opiate agonist which is occasionally abused by medical personnel who have ready access to the drug. We examined in healthy volunteers (N=13) the subjective and psychomotor-impairing effects of intravenous fentanyl (0–100 µg/70 kg). A randomized, placebo-controlled, crossover design was used in which subjects were injected with 0, 25 (N=6), 50 and 100 µg/70 kg fentanyl in a double-blind fashion. Subjects completed several questionnaires commonly used in abuse liability testing studies before drug injection and at periodic intervals for up to 3 h after drug injection. Subjects also completed several psychomotor tests at these times. Some aspects of psychomotor functioning (e.g., eye-hand coordination) were impaired by fentanyl. Fentanyl produced dose-related increases in ratings of high and sedated, but also tended to produce dysphoria and somatic symptomatology. Most subjects reported liking the effects of the two higher doses of fentanyl for at least a brief time after injection, but they varied widely in their liking ratings across the 3-h post-drug injection period. Despite the transient increases in liking ratings, fentanyl did not increase scores on a widely-used measure of drug-induced euphoria (morphine-benzedrine group scale of the Addiction Research Center Inventory). The present results suggest that some medical personnel who experiment with fentanyl may like it, and thus be at increased risk for abusing the drug in the future.     

Cocaine-induced cocaine craving

In nine experienced users of cocaine, we examined the urge to use cocaine or other drugs following a 40 mg dose of intravenous (IV) cocaine with and without oral pretreatment with 2.5 mg bromocriptine. The urge to use cocaine was assessed with a questionnaire constructed to assess both wanting and craving for cocaine or other drugs. Fifteen minutes after the administration of cocaine (but not after placebo), subjects' ratings for both drug wanting and drug craving were significantly increased. Our results provide a laboratory demonstration of cocaine-induced increases in the urge to use drugs in humans. The findings, stressing the role of internal stimuli associated with drug administration, suggest the possibility of distinguishing among related, but perhaps distinct, components of the fluctuating levels of motivation to reuse drugs.     

Interaction of adenine nucleotides,UTP and suramin in mouse vas deferens: suramin-sensitive and suramin-insensitive components in the contractile effect of ATP

Summary Effects of various nucleotides, nucleosides and noradrenaline on smooth muscle tension were studied in the isolated mouse vas deferens. ,-Methylene-ATP, ATPS, noradrenaline, ATP and UTP elicited contraction, with potency decreasing in that order; there was no contractile response to adenosine or uridine (up to 100 mol/l). Prolonged incubation with ,-methylene-ATP (concentration increased stepwise from 0 to 15 mol/l) selectively reduced contractions induced by ATP and UTP but not those induced by noradrenaline, and there was cross-tachyphylaxis between ATP and UTP. Suramin (10–300 mol/l) did not alter the response to noradrenaline but shifted the concentration-response curves for ,-methylene-ATP, ATPS, UTP and lower concentrations of ATP (0.1–1 ol/l) to the right. The pA₂-values of suramin were 5.2 against ,-methylene-ATP, 4.8 against ATPyS, 5.1 against UTP and 5.4 against lower concentrations of ATP. The effects of higher concentrations of ATP were largely resistant to suramin. The results indicate that the mouse vas deferens possesses contraction-mediating smooth muscle P_2X-receptors. UTP also acts at this receptor, and there is no evidence for a separate UTP receptor. The selective inhibition of nucleotide- but not noradrenaline-induced contractions by suramin confirms the view that suramin is a selective P₂-antagonist. The resistance against suramin of part of the effect of ATP suggests that ATP activates a suramin-insensitive site in addition to the P_2X-receptor.Send offprint requests to I. von Kügelgen at the above address     

Factors influencing the reinforcing and subjective effects of ephedrine in humans

There has been little study of the abuse liability of ephedrine, a naturally occurring drug used in medicine for thousands of years and currently sold as a legal stimulant. The present study measured the reinforcing and subjective effects of ephedrine in a group of 27 adults (18 females and 9 males) with no history of drug dependence. A discrete-trial choice procedure was used to assess the reinforcing effects of a single oral dose of ephedrine selected to produce a moderate subjective response in each subject (range: 37.5-75 mg). A number of variables (gender, current and past drug use, personality, and baseline mood and arousal) were examined in an attempt to identify sources of variability in response to ephedrine. Of the 27 subjects, 5 chose ephedrine on either 2 or 3 out of a possible 3 occasions; overall, ephedrine was chosen on 17% of occasions. In the group as a whole, ephedrine had no effect on ratings of drug liking, but did increase ratings of high and scores on the MBG (euphoria) scale of the Addiction Research Center Inventory. Ephedrine also increased scores on a number of mood scales reflecting CNS stimulation and anxiety. Ephedrine choice was positively associated with current use of marijuana and lower levels of baseline anxiety and hunger, as well as with lower scores on two scales measuring dimensions of the personality trait of harm avoidance. Males and females differed in their response to ephedrine — males chose ephedrine more frequently than females and showed a more positive mood response to the drug. When compared to the results of a prior study of the same design withd-amphetamine, these results demonstrate that ephedrine produces a different profile of subjective effects and is a less efficacious reinforcer than amphetamine, suggesting that ephedrine has a lower liability for abuse.     

Structural and steric requirements for β-phenethylamines as agonists of the noradrenergic cyclic AMP generating system in the rat limbic forebrain

Summary The present studies were undertaken to assess the structural and steric requirements for -phenethylamines as agonists of the noradrenergic cyclic AMP generating system in slices of the rat limbic forebrain. Significant agonist activity of -phenethylamines requires a -3,4-dihydroxyphenethylamine with a -hydroxyl group in the R configuration. Thus, dopamine did not stimulate the system at concentrations up to 10^–3 M. Moreover, -hydroxyphenethylamines without a 3,4-catechol group (octopamine, phenylephrine, p-hydroxynorephedrine, metaraminol and methoxamine)-though exerting -agonist activity in peripheral tissues-lack agonist activity in this particular cyclic AMP generating system. The effects of (R)-norepinephrine and (R)-isoproterenol at maximal concentrations were not additive. The results lend further support to the view that the cyclic AMP generating system in slices of the limbic forebrain is part of a norepinephrine receptor coupled adenylate cyclase system with a subpopulation of receptors that are in nature.     

Is there a need for more precise definitions of bioavailability?

Summary After evaluation of the present definitions in a set of particular cases, it was agreed that there was no need for more precise definitions and that the current ones were adequate in the majority of cases. However, it was felt that the present definitions might be improved, in particular in view of the existence of non-systemically acting drugs and future targeted drugs. Thus, the FDA definition might be modified as follows: Bioavailability means the rate and extent to which the active drug ingredient or therapeutic moiety from a drug product becomes available at the site of drug action or in a biological medium believed to reflect accessibility to a site of action.     

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.     

Which smokers report most relief from craving when using nicotine chewing gum?

Seventy-seven smoker clinic clients who managed at least 2 weeks of smoking abstinence while chewing 2 mg nicotine gum reported the degree to which the gum reduced their craving for cigarettes, their daily gum consumption and the extent of urges to smoke despite the gum. Greatest relief from craving by the gum was reported by smokers with higher pre-abstinence expired-air carbon monoxide (CO) concentrations and higher stimulant and dependent scores on a smoking motivation questionaire but not greater usual daily cigarette consumption. Gum consumption correlated positively with expired-air CO, usual daily cigarette consumption, and stimulant and dependent smoking scores. Despite the gum, urges to smoke and difficulty not smoking were reported and the severity of these was associated with indulgent, stimulant and dependent smoking scores but not CO or usual daily cigarette consumption. The results are discussed in terms of the possible role of pharmacological and non-pharmacological factors in craving.     

The discriminative stimulus and subjective effects of d-amphetamine in humans

Seventeen normal, healthy adults were trained to discriminate between orally administered d-amphetamine (AMP; 10 mg) and placebo. Standardized subjective effects questionnaires were used to examine the relationship between the subjective and discriminative stimulus effects of AMP. Seven of the subjects were able to learn the discrimination reliably. These seven discriminators did not differ from the ten nondiscriminators in their subjective ratings of mood in the absence of drug. Discriminators were generally more sensitive than nondiscriminators to the subjective effects of AMP, although this difference in sensitivity reached statistical significance only for ratings of hungry. Stimulus substituion was tested in the discriminators with other doses of AMP (2.5 and 5 mg) and with 10 mg diazepam. The discriminative stimulus properties of AMP were dose-dependent, with 5 mg being the threshold dose. In five of the seven subjects the discriminative stimulus properties of diazepam did not substitute for those of AMP. The results demonstrate that the experimental paradigm can be used successfully to study the discriminative stimulus properties of drugs directly in humans.     

The selective P2X purinoceptor agonist, β,γ-methylene-L-adenosine 5′-triphosphate,discriminates between smooth muscle and neuronal P2X purinoceptors

The effects of the putative selective P_2X purinoceptor agonist, ,-methylene-l-adenosine 5-triphosphate (me-l-ATP), were determined at rat neuronal and smooth muscle P_2X purinoceptors.Me-l-ATP had no effect on the extracellularly recorded membrane potential of the rat isolated vagus nerve preparation at concentrations up to 300 M. In contrast, the archetypal P_2X purinoceptor agonist, , methylene ATP (meATP;1–100 M), produced concentration-related depolarisation responses with a mean EC₅₀ value of 10.8 M. The depolarising effects of meATP were not attenuated by me-l-ATP (100 M). In voltage clamp experiments on single nodose ganglion neurones, ATP (100 M), but not me-l.-ATP (1–300 M), evoked rapid ( < 20 ms onset) inward currents when applied using a concentration-clamp method. In receptor binding studies to rat brain membranes, me-d-ATP and meATP competed with high affinity for [³H]Lx meATP binding sites, with mean pIC₅₀ values of 7.7 and 8.3, respectively. However, me-l-ATP possessed low affinity for these sites and competed only at concentrations in excess of 10 M (mean pIC₅₀ value 4.1).In prostatic segments of the rat vas deferens, me-l-ATP (1–100 M) and meATP (0.3–100 M) each produced concentration-related contractile responses with mean EC₅₀ values of 17.1 and 3.6 M, respectively. Me-l-ATP (1–10 M) evoked fast inward currents in freshly dispersed vas deferens smooth muscle cells, indicative of an action at ligand-gated ion channels. Binding sites in vas deferens membranes labelled using 1 nM [³H]meATP exhibited high affinity for me-l-ATP, meATP and me-d-ATP with mean PIC₅₀ values of 7.7, 8.4 and 7.3, respectively.These results indicate that me-l-ATP exhibits neither agonist nor antagonist properties at P_2X purinoceptors on rat vagal neurones and possesses only very low affinity for [³H]meATP binding sites in rat brain. In contrast, me-l-ATP is a potent, high affinity agonist at smooth muscle P_2X purinoceptors of the rat vas deferens. This selective agonist action of me-l-ATP suggests that P_2X purinoceptors in smooth muscle and neurones are different and represent distinct P_2X purinoceptor subtypes.     

Vasopressin stimulates release of β-lipotropin and β-endorphin in conscious rats as measured by radioimmunoassay of unextracted plasma

Summary Using a newly developed radioimmunoassay to determine the -endorphin-like immunoreactivity (-EI) in unextracted plasma, the effect of vasopressin injections on plasma -EI was investigated in conscious rats. Arginine vasopressin caused a dose-dependent increase of plasma -EI from 34.5±7.8 fmol ml^–1 (n=6) in vehicle-treated animals to 205.0±36.1 fmol ml^–1 (n=7) after injection of the highest vasopressin dose employed (486 ng/100 g b.w.). In view of the appreciable cross-reactivity of -lipotropin (-LPH) in the radioimmunoassay used, plasma was extracted and subjected to gel chromatography on a Sephadex G-50 column. On average, about 70% of the -EI co-eluted with human -LPH and about 30% with human -endorphin in plasma extracts obtained from both control and vasopressin-treated rats. No peripheral conversion of human -LPH occurred under the experimental conditions, since after i.v. bolus injection of human -LPH 97% of the -EI comigrated with human -LPH during gel filtration. A similar blood pressure increase to that induced by the vasopressin injections, when elicited by noradrenaline or angiotensin II i.v., was not followed by an elevation of plasma -EI.These data indicate that vasopressin stimulates -lipotropin and -endorphin release into the systemic circulation in vivo.     

Adenosine receptor activation by adenine nucleotides requires conversion of the nucleotides to adenosine

Summary Adenine nucleotides cause adenosine receptor-mediated increases in cyclic AMP in the VA13 human fibroblast line. Levels of adenosine accumulated in the medium are insufficient to account for the responses to adenine nucleotides. Since rapid conversion of the nucleotides to adenosine by 5-nucleotidase in the vicinity of the receptor might account for the responses, six experimental methods were developed to distinguish between local conversion and direct action of the nucleotides. Results of all six methods favored local conversion. (1) 5-Nucleotidase inhibitors blocked the accumulations of cyclic AMP elicited by AMP, ADP, and ATP, but did not affect the response to adenosine. The most potent inhibitor of both conversion of AMP and response to AMP was ,-methylene-ADP (APCP). (2) Adenosine deaminase blocked the responses to AMP, ADP, ATP, and adenosine-containing coenzymes. (3) Theophylline, a specific competitive adenosine antagonist, was an insurmountable inhibitor of the increases in cyclic AMP caused by AMP, ADP, and ATP. The insurmountability was presumably due to substrate sataration of the converting enzyme 5-nucleotidase. (4) Although ADP and ATP had partial agonist-like dose-response curves, they did not inhibit the response to adenosine. (5) Nine cell lines which responded to adenosine were tested for response to AMP. Cell lines with high levels of 5-nucleotidase had large responses to AMP, those with intermediate levels of 5-nucleotidase had large or intermediate responses to AMP, and those with low 5-nucleotidase levels did not respond to AMP. (6) Inhibition of the uptake of labelled adenosine was used as an indicator of unlabelled adenosine concentrations near the cell membrane. Unlabelled AMP inhibited uptake nearly as effectively as unlabelled adenosine. APCP reversed the inhibition by AMP but not the inhibition by adenosine.The adenosine receptor is concluded to be an enity distinct from adenine nucleotide receptors.Submitted in partial fulfillment of the requirements for the degree Doctor of Philosophy in Neurosciences, University of California, San Diego. Supported by NIMH DA-00265 and PHS RR 05665. The author has been a NSF Graduate Fellow. An abstract of this material has been published (Bruns 1977)     

Plasma insulin levels and β-adrenoceptor antagonists

Summary The effect of -adrenoceptor antagonists on the intravenous glucose tolerance test was investigated in conscious dogs. dl-Celiprolol (cardioselective with ISA=intrinsic sympathomimetic activity) 200 and 1000 g/kg i.v., dl-metoprolol (cardio-selective without ISA) 200 and 1000 g/kg i.v., dl-pindolol (non-selective with ISA) 5 and 25 g i.v. and l-bupranolol (non-selective without ISA) 10 and 50 g/kg i.v. were used in the study. The influence of -adrenoceptor antagonists on the plasma glucose and immunoreactive insulin following the intravenous glucose tolerance test were evaluated by calculating the respective areas under the plasma curve.The present investigtion clearly demonstrates the marked difference between the various -adrenoceptor antagonists on heart rate and, especially on metabolic parameters. dl-Metoprolol, a -adrenoceptor antagonist with cardioselectivity and without ISA can be assumed not to alter plasma insulin level and glucose assimilation. l-Bupranolol, a non-selective -adrenoceptor antagonist without ISA reduces plasma insulin level and probably enhances peripheral glucose uptake, resulting in an unchanged glucose tolerance. dl-Celiprolol or dl-pindolol, -adrenoceptor antagonists with ISA, but cardioselective or non-selective enhance both, basal insulin level and insulin level after glucose stimulation but must be assumed to decrease peripheral glucose uptake since here too glucose tolerance was unchanged.     

Inhibition by ethanol of excitatory amino acid receptors and nicotinic acetylcholine receptors at rat locus coeruleus neurons

The frequency of spontaneous action potentials of locus coeruleus (LC) neurons was recorded extracellularly in pontine slices of the rat brain. Ethanol (1–100 mM) elevated the firing rate in most neurons; this effect was concentration-dependent. (S)--amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA; 0.03–1 M), kainate ( 0.1–3 M), N-methyl-D-aspartate (NMDA; 1–30 M), substance P 0.01–1 M, nicotine 0.1–10 M and ,-methylene ATP ,-meATP; 0.3–30 M, all increased the firing. Application of ethanol g10–100 mM to the superfusion medium for 10 min, reproducibly and concentration-dependently inhibited the facilitatory effect of NMDA g10 M. However, the inhibitory effect of ethanol (100 mM) decreased during a 30-min superfusion period and after the washout of ethanol the sensitivity of LC neurons to NMDA (10 M) tended to overshoot above their initial level. Although NMDA was more potent in the absence than in the presence of external Mg²⁺, ethanol (100 mM) continued to depress the facilitatory effect of a low concentration of NMDA (EM) in a Mg²⁺-free medium. By contrast, in a medium containing normal Mg²⁺, ethanol (100 mM) failed to significantly interfere with the increase in firing rate induced by a high concentration of NMDA (30 M). The effects of kainate (0.5 M), AMPA (0.3 M) and nicotine (1 M) were also depressed by ethanol (100 M), while the effects of substance P (0.03 M) and ,-meATP (30 M) were not changed. In conclusion, ethanol selectively counteracts the opening of cationic channels caused by excitatory amino acid (EAA) receptor agonists and nicotinic acetylcholine receptor agonists. During a longer lasting incubation with ethanol, the inhibition of the NMDA-induced excitatory effect declines, indicating the development of tolerance. Correspondence to: P. Illes at the above address