Not all brands are created equal: a comparison of selected components of different brands of Serenoa repens extract

Recommendations regarding the use of plant-derived medications for the treatment of lower urinary tract symptoms (LUTS) associated with benign prostatic hyperplasia (BPH) state that every brand should be fully evaluated and considered separately. Disparity between a number of brands in terms of their stated and actual doses has been recently highlighted. The aim of this study was to fully quantify the variation in Serenoa repens extracts (SrE) commercially available for the treatment of BPH-associated LUTS. To this end, 14 brands of SrE were compared. Concentrations of free fatty acids (FFAs), methyl and ethyl esters, long-chain esters and glycerides were assessed using liquid and gas chromatography. Many of the brands showed a significantly different proportional content which may have an impact on their clinical efficacy and safety. The high concentrations of FFAs in particular, which previous research has suggested as comprising the active agent of SrE for the treatment of LUTS, may influence the clinical benefit derived from each product. Our findings lend further weight to recommendations by the 5th International Consultation on BPH that plant-derived treatments should be analysed and considered as independent entities despite their common origin. Only extracts with demonstrated pharmacological activities and proven clinical efficacy should be considered for the treatment of patients with BPH.

Directions in urological research and drug therapies

This meeting report summarizes advances and notable developments in the pharmaceutical management of urological diseases presented at various sessions during the Annual Meeting of the American Urological Association held in Anaheim, California, June 2-7, 2001. More than 10,000 attendees drawn from clinical and preclinical research deliberated on the latest trends in surgical and pharmacotherapeutic management in diverse areas of urology. In particular, several forums were dedicated to reviewing scientific trends, emerging concepts and therapies in urological diseases, such as overactive bladder, erectile dysfunction and lower urinary tract symptoms, which are the focus of this report.

Clinical trials design: protocols and endpoints

Over the last decade there has been a proliferation in clinical trials to test agents for the treatment of erectile dysfunction (ED). Many aspects of clinical trials design and conduct and guidelines for future conduct have been the subject of a recent comprehensive review (Rosen R et al. In: Proceedings of the 1st International Consultation on Erectile Dysfunction 1999). The present article attempts to extend that analysis from trials that focus purely on symptomatic improvement of ED to trials relevant to the management of the ED patient in the community. Although the regulatory approval process accounts for the bulk of the clinical trials undertaken, studies are also initiated for concept testing, post-marketing surveillance and for promotional and/or pricing reasons. The trial design can be dependent on which of the above objectives is being served. However, there are also many common features that are summarized below; the major focus is placed on regulatory-standard or 'pivotal' studies. International Journal of Impotence Research (2000) 12, Suppl 4, S53-S58.

alpha1-adrenoceptor selectivity: the North American experience

OBJECTIVE

The recent publication of multicentre US studies raises the possibility that the response to tamsulosin is dose-related and less than maximum at 0.4 mg. The objective of the present study was to calculate pharmacologically equivalent, alpha-blocking doses of doxazosin and tamsulosin in a clinical setting and thereby to examine further the concept of 'uroselectivity' and 'prostate selectivity'.

METHODS

Healthy male volunteers were monitored in controlled, crossover studies. The effects of placebo or alpha blocker on phenylephrine (PE)-induced urethral and vascular responses, were determined. These were related to plasma drug concentrations and used with in vitro radioligand binding data to derive receptor occupancy.

RESULTS

Doxazosin effectively blocked PE-induced vascular and urethral changes over the dose range 1-16 mg. There was no evidence for target organ selectivity. The degree of blockade of the PE-induced responses by tamsulosin was highly dependent on the time of measurement, post drug administration. The degree of observed blockade with tamsulosin at 0.4 mg was substantially less than that observed at 0.8 mg tamsulosin and/or 1 mg doxazosin.

CONCLUSIONS

These studies provide no evidence of prostate selectivity for tamsulosin. 0.4 mg tamsulosin is a sub-optimal blocking dose and is equivalent to 1 mg of doxazosin and terazosin (1-2 mg). It is recommended that future comparative studies on benefit/risk in patients should include a range of doses encompassing the ED50.

Transforming growth factor beta 1 transduced mouse prostate reconstitutions: II. Induction of apoptosis by doxazosin

BACKGROUND

To study the possible relationship between adrenergic activities and the pathogenesis of benign prostatic hyperplasia (BPH), we tested the effect of doxazosin, an alpha 1-adrenoceptor antagonist, on prostatic growth in vivo using a mouse model for BPH.

METHODS

The mouse prostate reconstitution (MPR) model system with retroviral (BabeTGF-beta 1Neo) transduction of transforming growth factor beta 1 (TGF-beta 1) was used to induce focally hyperplastic BPH-like lesions and increase the number of catecholaminergic neurons. The mice were treated with daily intraperitoneal injections of doxazosin (3 mg/kg).

RESULTS

Doxazosin caused a significant reduction in the wet weight of BabeTGF-beta 1-infected MPRs. The percent of PCNA-positive epithelial cells was similar in the doxazosin-treated and water only, control groups. There was a significant increase in the number of epithelial cells undergoing programmed cell death, apoptosis, in the doxazosin group (apoptotic index = 4.7 for doxazosin group vs. 3.1 for control group, P < 0.05). The doxazosin-induced apoptosis was more apparent in TGF-beta 1 transduced MPRs than BAG alpha control MPRs, and was not seen in the prostates of the adult male mice into which the MPRs were engrafted.

CONCLUSIONS

Our data demonstrate a novel and potentially important biological activity of doxazosin in vivo in this mouse model of BPH.

Prostatic alpha 1-adrenoceptors and uroselectivity

BACKGROUND

alpha 1-adrenoceptor antagonists (blockers) are now commonly used in the treatment of the symptoms of lower urinary tract obstruction. Originally phenoxybenzamine, a non-selective antagonist at both alpha 1- and alpha 2-adrenoceptors, was used by Marco Caine. In an attempt to minimize side effects, selective alpha 1-antagonists, e.g. prazosin, were subsequently developed. More recently, agents such as alfuzosin, doxazosin, terazosin, and tamsulosin have been introduced and claims of "uroselectivity" and "prostate" selectivity have emerged.

METHODS

This review attempts to put these claims into perspective and represents a comprehensive analysis of all pre-clinical and clinical data including several papers from the Japanese literature. An attempt is made to define what is meant by selectivity at various levels including the test tube, in the laboratory animal and, most importantly, in the clinical context of the whole patient.

CONCLUSIONS

The conclusions are interpreted within the context of the subdivision of the alpha 1-adrenoceptor into alpha 1A, alpha 1B, and alpha 1D subtypes.

A comparison of the effects of doxazosin and terazosin on the spontaneous sympathetic drive to the bladder and related organs in anaesthetized cats

The effects of i.v. infusion of the alpha1-adrenoceptor antagonists doxazosin and terazosin (2 mg kg-1 h-1) on spontaneous hypogastric, renal and inferior cardiac nerve activity, spontaneous bladder contractions, blood pressure, heart rate and femoral arterial flow were investigated separately in alpha-chloralose-anaesthetized cats. Both drugs caused a reduction in hypogastric nerve activity associated with no overt changes in spontaneous bladder contractions. Doxazosin was more potent than terazosin, in that there was a significant reduction in hypogastric nerve activity after 20 min (0.67 mg kg-1) of infusion, while for terazosin this occurred after 40 min (1.33 mg kg-1). Both drugs also caused significant falls in blood pressure of 34 +/- 3 mm Hg and 33 +/- 4 mm Hg after 60 min. This was associated with no change in heart rate for doxazosin while terazosin caused an initial and significant increase in heart rate of 20 +/- 3 beats min-1 by 5 min, declining by 30 min to 1 +/- 5 beats min-1. This terazosin-induced tachycardia was associated with a significant increase in cardiac nerve activity of 128 +/- 22%. Both drugs caused increases in renal nerve activity however only for doxazosin was this increase significant. Femoral arterial conductance was also increased by both drugs, however, for doxazosin this increase was immediate and larger over the infusion period. These results demonstrate that alpha1-adrenoceptor antagonists can reduce sympathetic drive to the bladder and related organs.

Comparison of testosterone metabolism in benign prostatic hyperplasia and human prostate cancer cell lines in vitro

Pathways of testosterone metabolism in tissue slices and cell suspensions of human benign hyperplastic prostate (BPH) tissue and human prostate cancer cell lines (DU145, HPC-36M, PC-3/MA2 and LNCaP) were investigated. Thin layer chromatography analysis was used to identify the following tritiated metabolites: testosterone, 5 alpha-dihydrostestosterone (DHT), 5 alpha-androstane-3 alpha/3 beta-17 beta-diol (androstanediols), 4-androstene-3,17-dione (androstenedione) and 5 alpha-androstanedione. The predominant pathway for testosterone metabolism in BPH was via 5 alpha-reductase producing 5 alpha-dihydrotestosterone (71% and 75% total metabolites in slices and suspensions incubated for 24 h, respectively). The cancer cell lines DU145 and HPC-36M resembled BPH by metabolizing testosterone predominantly to DHT (68% and 82% total metabolites, respectively), although the rate of metabolism was much lower in the cell lines (0.099 and 0.05 pmol testosterone/mg protein/h in DU145 and HPC-36M) compared to the BPH cell suspensions (6.4 pmol testosterone/mg protein/h). In contrast, PC-3/MA2 contained high 17 beta-HSD activity forming large amounts of 4-androstene-3,17-dione (84% total metabolites), converting testosterone at a rate faster (12.8 pmol testosterone/mg protein/h) than the BPH cell suspensions. LNCaP rapidly converted testosterone exclusively to a glucuronide conjugate (7.4 pmol testosterone/mg protein/h), although after incubation with [3H]-4-androstene-3,17-dione, 5 alpha-reductase activity was demonstrated. LNCaP was the only cell line whose growth and colony-forming ability was stimulated by testosterone and DHT. BPH and all the cell lines tested had 5 alpha-reductase activity, but only the prostate tissue and the cell lines DU145 and HPC-36M converted testosterone predominantly to DHT.

Effect of alpha 1 adrenoceptor antagonists on prostatic pressure and blood pressure in the anesthetized dog

OBJECTIVES

In the current study we have profiled a range of compounds at alpha 1 adrenoceptor subtypes in vitro and have assessed their effects in vivo using the anesthetized dog in an attempt to elucidate the predominant alpha 1 adrenoceptor subtype mediating contractile responses of the canine prostate.

METHODS

The affinity of compounds for alpha 1 adrenoceptor subtypes was determined by displacement of [3H] prazosin binding from stably transfected rat 1 fibroblasts expressing alpha 1A, alpha 1B, and alpha 1C, adrenoceptor subtypes. The potency of these agents was then assessed in vivo using an anesthetized dog model allowing simultaneous measurement of prostatic pressure and blood pressure following intravenous (i.v.) administration of phenylephrine (1 to 128 micrograms/kg).

RESULTS

All compounds examined in this study showed high and similar affinity for alpha 1 adrenoceptor subtypes, with the exception of 5-Methyl-urapidil, which was selective for alpha 1C (pKi = 9.3) over alpha 1B (pKi = 7.2) and alpha 1A (pKi = 8.1). Doxazosin, terazosin, alfuzosin, and tamsulosin were potent antagonists of phenylephrine responses and in vivo derived "pseudo pA2" determinations showed that the drugs did not discriminate between prostatic and vascular receptors. 5-Methyl-urapidil was also a potent antagonist of phenylephrine-induced responses but was selective for prostatic pressure ("pseudo pA2" = 8.7) over blood pressure ("pseudo pA2" = 7.2).

CONCLUSIONS

Data in the present study suggest a predominant role of the alpha 1C adrenoceptor subtype in the contractile response of the canine prostate to phenylephrine in vivo. This model therefore provides a suitable means of assessing putative prostate-selective antagonists for the treatment of benign prostatic hyperplasia.

Pharmacological properties of the cloned alpha 1A/D-adrenoceptor subtype are consistent with the alpha 1A-adrenoceptor characterized in rat cerebral cortex and vas deferens

1. The pharmacological characteristics of cloned mammalian alpha 1A/D-, alpha 1B- and alpha 1C-adrenoceptor subtypes expressed in rat 1 fibroblasts were determined in comparison to the binding and functional properties of these subtypes in rat tissues. 2. Analysis of [3H]-prazosin binding to membrane homogenates from rat 1 fibroblast cells expressing each of the alpha 1-subtypes indicated high affinity binding to a single population of binding sites. Binding affinities were similar for alpha 1A/D-, alpha 1B- and alpha 1C-subtypes (Kds: 0.13, 0.10 and 0.15 nM respectively) although a higher density of alpha 1B- and alpha 1C-receptors (Bmax: 4068 and 10,323 fmol mg-1 protein respectively) were expressed in comparison to alpha 1A/D (838 fmol mg-1). 3. Displacement of [3H]-prazosin from membranes expressing cloned alpha 1-adrenoceptor subtypes revealed that 5-methyl-urapidil, WB 4101, benoxathian and phentolamine displayed high affinity and selectivity for alpha 1A/D- over alpha 1B-subtypes. These compounds also had high affinity and selectivity for alpha 1C- over alpha 1B-subtypes. 5-Methyl-urapidil showed selectivity for alpha 1C (Ki 0.60 +/- 0.16 nM) over both alpha 1A/D (Ki, 9.8 +/- 2.8 nM) and alpha 1B (Ki 57.2 +/- 12 nM) subtypes. Prazosin and doxazosin were not subtype selective. 4. In comparison to [3H]-prazosin a similar pharmacological profile was obtained with [125I]-HEAT using cloned alpha 1A/D-, alpha 1B- and alpha 1C-adrenoceptors expressed in rat 1 fibroblasts. 5. The affinities of prazosin, WB 4101, 5-methyl-urapidil, phentolamine and benoxathian at cloned alpha 1A/D-receptors were consistent with alpha 1A affinities determined with chlorethylclonidine-treated rat cortical membranes. Affinities at cloned XIB-receptors were consistent with alpha 1B affinities determined with rat liver membranes.6. Using the epididymal rat vas deferens as a functional measure of alpha 1A affinity, prazosin (pA29.23 +/- 0.28), WB 4101 (pA2 9.58 +/- 0.12), phentolamine (pKB 7.90 +/- 0.16), benoxathian (pKB 9.21 +/- 0.21)and 5-methyl-urapadil (pKB 8.51 +/-0.16) were potent antagonists of noradrenaline-induced contractions.7. At present, evidence from cloning studies suggests the existence of at least three alpha 1-adrenoceptor subtypes. In contrast to the recent proposal for alpha l-adrenoceptor classification, the pharmacology of the cloned alpha 1A/D (or alpha lD)-adrenoceptor is more consistent with that of an alpha 1A-adrenoceptor characterized in rat cerebral cortex and vas deferens.

The involvement of potassium channels in the action of ciclazindol in rat portal vein

1. In whole portal veins, ciclazindol (0.3-10 microM) increased the amplitude and duration, but decreased the frequency of spontaneous contractions. Glibenclamide (0.3-10 microM) produced a small increase in contraction amplitude and duration with a small reduction in contraction frequency. 2. In whole portal veins, ciclazindol (1-10 microM) antagonized the relaxant effects of BRL 38227 in a non-competitive manner. Under identical conditions, the effects of glibenclamide (0.3-10 microM) appeared to be competitive. 3. In whole portal veins loaded with 42K, ciclazindol itself (up to 3 microM) had no detectable effect on basal 42K exchange. However, the increase in 42K efflux produced by BRL 38227 (5 microM) was antagonized by ciclazindol (3 microM). Similar effects were produced by glibenclamide (up to 3 microM). 4. In freshly-isolated portal vein cells examined by the whole-cell voltage-clamp technique, ciclazindol (1-100 microM) inhibited the slowly-activating and inactivating transient outward current (ITO) which could be generated at potentials more positive than -30 mV. In addition ciclazindol (1-10 microM) inhibited the non-inactivating K-current (IKCO) induced by BRL 38227 (10 microM). 5. In freshly-isolated portal vein cells under current-clamp conditions, the hyperpolarization produced by BRL 38227 (10 microM) was reversed by ciclazindol (1-10 microM). 6. In porcine brain membrane fragments, glibenclamide (0.65 nM) displaced 50% of the binding of [3H]-glibenclamide whereas ciclazindol (up to 10 microM) had no effect. 7. It is concluded that ciclazindol is a K-channel blocker. Its action is not selective for the channel(s) which carry IKCO but also extends to those which carry ITO.Its inability to displace [3H]-glibenclamide from porcine brain fragments may indicate that antagonism of BRL 38227 by ciclazindol in smooth muscle is exerted at a site different from that of glibenclamide.

Disposition and pharmacokinetics of meptazinol in the CSF. Studies after intrathecal administration in the non-human primate Erythrocebus patas

A preliminary study is reported on the kinetics of meptazinol following intrathecal and i.m. administration in the Patas monkey. Following intrathecal administration (single dose of 0.5 mg) at T12/L1, meptazinol rapidly disappeared from the CSF with a T1/2 of 35 min. At 240 min after intrathecal injection, most of the meptazinol had been distributed within the spinal tissue near the region of the injection, with minimal amounts reaching the brain (less than 5% of the concentrations present in the lumbar and thoracic tissue). Following i.m. administration (16 mg kg-1) peak concentrations were present in the CSF and plasma within 60 min. Appreciable concentrations persisted in the CSF up to 180 min after i.m. administration. The results would suggest that meptazinol should give rapid but short acting pain relief following intrathecal injection with minimal CNS-related side effects.

Examination of the relationship between the uptake system for 5-hydroxytryptamine and the high-affinity [3H]imipramine binding site--I. Inhibition by drugs

The relationship between the binding site for imipramine and the uptake system for 5-hydroxytryptamine was examined. This was determined from the interaction between various drugs (including tricyclic antidepressants) and the high affinity accumulation of [3H]5-hydroxytryptamine in cortical synaptosomes from the rat, and with the high affinity binding of [3H]imipramine to cortical membranes of the rat. Imipramine and clomipramine, but not desipramine, were potent inhibitors of both binding of [3H]imipramine and the uptake of [3H]5-hydroxytryptamine. However, ouabain, panuramine and 5-hydroxytryptamine itself, all inhibited the binding of [3H]imipramine only at concentrations greater than those required to inhibit the uptake of [3H]5-hydroxytryptamine. Kinetic analysis revealed that inhibitors of the uptake system for 5-hydroxytryptamine produced inhibition by different mechanisms, but this did not account for their differential potency against uptake and binding. It is concluded that the binding site for [3H]imipramine and the uptake site for 5-HT are not directly linked and that drugs may inhibit the uptake of 5-HT at sites other than the binding site for [3H]imipramine.

Subcellular site of action of imipramine in rodent brain

To determine the site of action of imipramine, the subcellular distribution of [3H]imipramine in rodents was followed after both in vivo administration and in vitro incubation with tissue slices under "physiological" conditions. Total [3H]imipramine (10-1,000 nM) binding was associated with all primary fractions, but in particular with the nuclear (P1) and mitochondrial (P2) pellets and the synaptosomal (P2B) and myelin (P2A) fractions. Using an excess of imipramine to define any nonspecific interactions, a specific association was observed mainly in those fractions containing isolated nerve terminals and to a lesser extent with the purified myelin fraction. Preparation of subsynaptosomal fractions by osmotic lysis indicated that [3H]imipramine was associated with the synaptic vesicle and microsomal fractions and also with synaptosomal membranes. The degree of binding to the vesicular and microsomal fractions was increased with the length of preparation time, whereas there was an inverse relationship between the length of preparation and the amount bound to the synaptosomal membrane fraction. There was no evidence of an intrasynaptosomal accumulation of [3H]imipramine at concentrations up to 1,000 nM. [3H]2-Nitroimipramine, a slowly dissociating imipramine derivative, was exclusively located in synaptic membrane fractions. Prior treatment of rats with a combination of 5,7-dihydroxytryptamine and desipramine reduced 5-hydroxytryptamine levels and the levels of [3H]imipramine associated with the synaptosomal fractions to the same extent. It is concluded that imipramine is associated with a binding site localised on 5-hydroxytryptaminergic nerve terminals and that there is a redistribution to other sites (vesicular and microsomal) during the isolation procedure.

A reassessment of the binding of [3H]rauwolscine to membranes from the rat cortex

In order to fully resolve the binding profile of [3H]rauwolscine to membranes from the cortex of the rat, saturation, competition and association-dissociation data were analysed by means of computerised curve-fitting techniques. The binding isotherm for [3H]rauwolscine was best fitted to a two-component model consisting of a high-affinity, saturable site (approx. Kd 1.8 nM) and a low-affinity, apparently non-saturable, component. Displacement experiments revealed shallow inhibition curves for both antagonist and agonist ligands with a rank order of potency indicative of an interaction at the alpha 2-adrenoceptor. Inclusion of spiroperidol, but not prazosin, markedly steepened the antagonist, but not the agonist inhibition curves. In addition, spiroperidol attenuated, but did not eliminate, the low-affinity component in saturation experiments. Dissociation and association data revealed a biphasic paradigm, the more slowly-associating/dissociating component of which was sensitive to spiroperidol. It was concluded that [3H]rauwolscine binds to two sites on membranes of the rat cortex; a high-affinity site corresponding to alpha 2-adrenoceptors and a low-affinity, spiroperidol-sensitive component. The possible identity of the low-affinity site is discussed with particular emphasis on displacement data for [3H]rauwolscine and the interaction with rauwolscine in isolated organs.

Is there a common, high-affinity opioid binding site in rat brain?

At low concentrations, 3H-naloxone apparently bound to two sites, of high (KD 0.50 nM) and low (KD 2.0 nM) affinity. Binding to the high affinity site was preferentially blocked by naloxonazine. This is consistent with the high and low affinity sites representing the mu 1 and mu 2 sites respectively. Binding of 3H-naloxone to the mu 1 and mu 2 sites was differentially inhibited by opioids. Compared to mu 2 binding, DADLE and DAGO preferentially inhibited mu 1 binding. DADLE inhibited the binding of 3H-DAGO potently and in a competitive manner. DAGO inhibited the binding of 3H-DADLE from two sites for which DAGO had high and low affinities. Scatchard analysis indicated that both 3H-DAGO and 3H-DADLE bound to one class of sites, with 3H-DADLE having a 2-3 fold greater Bmax. It is concluded that 3H-opioids bind to at least three sites--mu 1, mu 2 and delta. The mu 1 site represents a high affinity binding site for both opioid peptides and opioid alkaloids. DAGO is a selective ligand for the mu 1 site, whilst DADLE interacts with mu 1 and delta sites with similar affinities.

Assessment of noradrenaline and 5-hydroxytryptamine uptake in intact rat brain

A method for the measurement of 3H-monoamine [noradrenaline (NA) and 5-hydroxytryptamine (5-HT)] uptake into intact brain following intracerebroventricular injection is described. Most of the accumulated monoamine was associated with nerve terminals (synaptosomes). Radioactivity in the synaptosomal fraction was retained by 0.45-micron filters and was osmotically sensitive, features indicative of accumulation within particles rather than binding to membranes. [3H]5-HT associated with synaptosomes was reduced in animals pretreated with the neurotoxin 5,7-dihydroxytryptamine, in parallel with a reduction in endogenous 5-HT levels. Oral administration of tricyclic antidepressants including clomipramine, desipramine, and imipramine inhibited the synaptosomal accumulation of 3H-monoamines. Overall, the features of the accumulation of 3H-monoamines, after intracerebroventricular administration, displayed many of the characteristics expected of a physiological monoamine reuptake system.

Effects of histamine antagonists on noradrenaline-stimulated blood flow and oxygen consumption of brown adipose tissue in the rat

The effects of histamine antagonists on noradrenaline-stimulated metabolic rate, tissue blood flow (estimated from the distribution of radiolabelled microspheres) and brown adipose tissue (BAT) oxygen extraction were studied in male anaesthetised rats. Injection of cimetidine (H2-receptor antagonist), reduced the noradrenaline-stimulation of metabolic rate and the increase in blood flow to BAT, but did not affect blood flow to white adipose tissue, skin, leg muscle, kidney, brain, or testes. Following noradrenaline, in vivo oxygen consumption of BAT, estimated from blood flow and oxygen extraction was depressed to 31% of control values by treatment with cimetidine, blood pressure was unaffected. Injection of the histamine (H1-receptor) antagonist, mepyramine, did not affect tissue blood flow or metabolic rate. In conscious animals, cimetidine did not affect resting oxygen consumption, but depressed the thermogenic responses to noradrenaline. These data suggest that the stimulation of BAT blood flow and thermogenesis by noradrenaline may be mediated in part by histamine acting on an H2-type receptor.

Panuramine, a selective inhibitor of uptake of 5-hydroxytryptamine in the brain of the rat

The neurochemical profile of the novel inhibitor of uptake of 5-hydroxytryptamine (5-HT) panuramine (Wy 26002) has been investigated in the rat. In vitro, panuramine was found to be a potent and selective inhibitor of uptake of 5-HT with an IC50 of 22 +/- 4 nM. The IC50 for inhibition of uptake of noradrenaline was 848 nM and that for uptake of dopamine greater than 10 micron. Panuramine, in concentrations up to 10 micron did not displace the specific binding of either [3H]spiroperidol or [3H]5-HT and had no effect on the spontaneous or potassium-evoked release of 5-HT, suggesting that the compound had little effect on serotonergic transmission other than the inhibition of uptake of 5-HT. Panuramine also produced a dose-related antagonism of the depletion of 5-HT in brain induced by p-chloroamphetamine, confirming the ability of the drug to inhibit uptake of 5-HT in vivo.

Thermogenic properties of ciclazindol and mazindol in rodents

Ciclazindol, a noradrenaline (NA) uptake inhibitor originally introduced as an antidepressant, has recently been shown to produce weight loss in experimental animals and patients. Unlike CNS-stimulant anti-obesity drugs, such as amphetamine, ciclazindol may induce weight loss in animals by stimulating thermogenesis in brown adipose tissue (BAT), and it is known to stimulate resting metabolic rate (RMR) of rats and depress energetic efficiency. These effects can be achieved in the absence of overt CNS stimulation and with certain analogues of ciclazindol may be due to an exclusive peripheral action. Mazindol, a structural analogue of ciclazindol also produces an increase in RMR. However the increment is qualitatively and quantitatively different from that observed with ciclazindol and cannot be dissociated from central stimulant actions. In this report we examine some of the physiological and behavioural effects of ciclazindol and mazindol analogues in rats.

Parasympathethic effects on diet-induced thermogenesis

Injection of atropine methyl nitrate or atropine sulphate enhanced the acute thermogenic response to food in rats. The main effector of diet-induced thermogenesis is brown adipose tissue (BAT), but acetylcholine (determined by bioassay) and acetylcholinesterase activity (determined histochemically) were not detected in BAT. This suggests that BAT has no parasympathetic innervation, and atropine must therefore act elsewhere to affect thermogenesis.

Influence of thyroid hormone on diet-induced thermogenesis in the rat

Energy balance and brown adipose tissue (BAT) metabolism were studied in rats maintained on stock or 'cafeteria' diet, and injected with either saline or triiodothyronine (T3, 10 micrograms/100 g b.wt./d) for 14 d. Cafeteria-fed rats showed large increases in metabolizable energy intake, energy expenditure and BAT mass, Na+, K+-ATpase activity and mitochondrial GDP binding. In stock fed rats, T3 also stimulated energy intake, metabolic rate and BAT mass and Na+, K+-ATPase activity, but did not affect GDP binding. Hyperthyroidism potentiated the effects of cafeteria feeding on energy expenditure and BAT mass, but BAT Na+, K+-ATPase activity was only slightly higher than that of the euthyroid cafeteria rats, and GDP binding was similar for both groups. These results confirm the involvement of BAT in diet-induced thermogenesis and show that this is potentiated by hyperthyroidism. The data also suggest that thyroid thermogenesis may result, at least partly, from stimulation of BAT.

Influence of chronic administration of ciclazindol on energy balance and brown adipose tissue in adult 'cafeteria'-fed rats

The effects of chronic oral administration of ciclazindol on energy balance and brown adipose tissue (BAT) activity were studied in adult rats maintained on a palatable cafeteria diet. Treatment with 1 mg ciclazindol/kg/day produced small, but not significant, reductions in body energy gain and increases in BAT mass and protein content. Administration of 3.4 and 11 mg/kg/day of ciclazindol depressed weight gain and caused a substantial (42%) reduction in body energy gain. These effects were partly due to a lower food intake, but also resulted from a marked decrease in energetic efficiency. Rats treated with 3.4 and 11 mg/kg/day of the drug showed significant increases in BAT protein content, Na+, K+-ATPase activity and mitochondrial proton conductance, assessed from GDP-binding capacity. These results show that the reduced body weight produced by ciclazindol is due to a lower energetic efficiency, which is associated with activation of BAT, and also a depressed food intake.

Critical assessment of noradrenaline uptake in synaptosomal preparations

Synaptosomes and other subcellular organelles were prepared from rat brain using a vertical rotor. The preparation time was reduced by up to 60% compared to conventional techniques. Uptake of [3H]-(-)-noradrenaline into subcellular fractions was characterized. The characteristics of this uptake were dependent on the subcellular composition and anatomical origin. Various methods of correction for energy independent processes were compared, but only sodium ion removal from the medium selectively inhibited the energy dependent uptake mechanism. Kinetic analysis of data revealed that high and low affinity uptake systems were dependent on the fraction under analysis. Noradrenaline uptake was not exclusively localised in noradrenergic terminals. Selective inhibitors of the noradrenaline uptake process (tricyclic antidepressants) inhibited energy dependent uptake completely only in purified synaptosomes prepared from cortex. In whole brain synaptosomal fractions, noradrenaline was partially accumulated into dopaminergic neurones; this uptake process was not inhibited by tricyclic antidepressants.

Restoration of mean arterial pressure in endotoxic shock by meptazinol. Contributions from lysosomal membrane stabilisation, opiate antagonism and noradrenaline release

Meptazinol elevated mean arterial pressure in rats which had been treated with endotoxin. The drug also reduced the titer of circulating lysosomal enzymes. This effect was secondary to the restoration of mean arterial pressure (MAP). In vitro, meptazinol stabilised lysosomal membranes, increased noradrenaline release and interacted with the opiate receptor (naloxone-binding site) as an antagonist. The relevant contributions of these phenomena to the restoration of MAP are discussed.

Catecholamine and thyroid hormone influence on brown fat Na+, K+-ATPase activity and thermogenesis in the rat

Resting oxygen consumption (VO2) before and after injection of noradrenaline (NA), and plasma triiodothyronine levels were elevated in hyperthyroid and hyperphagic cafeteria fed rats, but were reduced in 4d-fasted and hypothyroid animals compared to controls. Refeeding fasted rats with a single carbohydrate meal caused all of these parameters to increase towards control levels. In vivo turnover, and in vitro release of NA brown adipose tissue (BAT) was elevated in cafeteria fed rats but remained unaltered in other groups and levels and uptake of NA in BAT were similar for all rats. Basal and NA stimulated Na+,K+-ATPase activity in BAT was increased in cafeteria and hyperthyroid rats and reduced in fasted and hypothyroid animals compared to control and refed groups. A highly significant correlation (r = 0.977), (P less than 0.001), found between the in vitro activity of this enzyme and resting VO2 in all rats, indicates that BAT Na+,K+-ATPase may be involved in the thermogenic responses to diet, catecholamines and thyroid hormones.

Resolution of monoamine uptake into binding and translocation components

Kinetic analysis of the energy-independent accumulation of noradrenaline as determined by either sodium omission or osmotic lysis, revealed two components: a) a low affinity system which may represent extraneuronal uptake and b) a high affinity component which was characteristic of the physiological re-uptake process. A comparison between intact and lysed synaptosomes suggested that this high affinity system may represent binding to the carrier protein which was no dependent on external sodium. Qualitatively similar results were observed for serotonin. The results are discussed in relation to models of neuronal re-uptake.

Dopaminergic mechanisms in diet-induced thermogenesis and brown adipose tissue metabolism

The role of dopamine (DA) in diet-induced thermogenesis was examined. DA was found in, and released from the sympathetic nerves supplying brown adipose tissue. However, the release of DA was only approximately 10% of that of noradrenaline. No significant re-uptake of DA was observed. Hyperphagic, cafeteria-fed rats exhibited higher rates of resting oxygen consumption (VO2) and increased DA release and turnover in brown adipose tissue relative to control animals. Pimozide completely abolished the difference in VO2 between the two groups and DA (0.5 mg . kg-1 s.c.) stimulated VO2 in control and cafeteria animals.

Sympathetic mechanisms in diet-induced thermogenesis: modification by ciclazindol and anorectic drugs

1 The sympathetic noradrenergic activation of brown adipose tissue and the biochemical mechanisms involved in diet-induced thermogenesis were studied in rats. 2 A close correlation was found between brown adipose tissue Na+, K+-adenosinetriphosphatase (Na+, K+-ATPase) activity in vitro and in vivo measurements of resting oxygen consumption (VO2). The effects of noradrenaline on in vitro NA+, K+-ATPase activity in brown adipose tissue and in vivo VO2 could be mimicked by a variety of agents. These included beta-adrenoceptor agonists and agents known to induce the release of noradrenaline or inhibit the noradrenaline uptake process. The pharmacological evidence suggests that dopaminergic mechanisms may also be involved in the control of thermogenesis. 3 Amphetamine did not increase VO2 in rats without causing associated increases in locomotor activity. Ciclazindol at doses of 3-30 mg/kg intraperitoneally increased VO2 but did not appear to increase locomotor activity or evoke any other signs of CNS stimulation including lengthening of time to sleep onset or stereotypy. Separation of metabolic and CNS effects occurred only at the lowest dose of mazindol used (0.3 mg/kg i.p.). These results are probably a reflection of (a) the relative abilities of these drugs to inhibit brain and brown adipose noradrenaline uptake processes and (b) the relatively high accumulation of ciclazindol in brown adipose. 4 Of the drugs tested, only ciclazindol was a more potent inhibitor of the noradrenaline uptake system in brown adipose tissue (BAT) than in brain. Kinetic analysis also revealed that the actions of ciclazindol on the NA uptake system and Na+, K+-ATPase in BAT differed from those of mazindol. 5 These findings suggest that ciclazindol may produce an energy wasting effect in rodents without causing overt CNS stimulation; the implications of these findings in terms of human obesity are discussed.

The rapid preparation of synaptosomes, using a vertical rotor

A rapid method for the preparation of isolated nerve terminals (synaptosomes) is described. The material, prepared using a vertical rotor, is compared biochemically with material prepared by conventional techniques. The synaptosomes possess many characteristics expected of isolated nerve terminals, including noradrenaline release and transport against a concentration gradient.