Testosterone and trenbolone enanthate increase mature myostatin protein expression despite increasing skeletal muscle hypertrophy and satellite cell number in rodent muscle.

The androgen-induced alterations in adult rodent skeletal muscle fibre cross-sectional area (fCSA), satellite cell content and myostatin (Mstn) were examined in 10-month-old Fisher 344 rats (n = 41) assigned to Sham surgery, orchiectomy (ORX), ORX + testosterone (TEST; 7.0 mg week-1 ) or ORX + trenbolone (TREN; 1.0 mg week-1 ). After 29 days, animals were euthanised and the levator ani/bulbocavernosus (LABC) muscle complex was harvested for analyses. LABC muscle fCSA was 102% and 94% higher in ORX + TEST and ORX + TREN compared to ORX (p < .001). ORX + TEST and ORX + TREN increased satellite cell numbers by 181% and 178% compared to ORX, respectively (p < .01), with no differences between conditions for myonuclear number per muscle fibre (p = .948). Mstn protein was increased 159% and 169% in the ORX + TEST and ORX + TREN compared to ORX (p < .01). pan-SMAD2/3 protein was ~30-50% greater in ORX compared to SHAM (p = .006), ORX + TEST (p = .037) and ORX + TREN (p = .043), although there were no between-treatment effects regarding phosphorylated SMAD2/3. Mstn, ActrIIb and Mighty mRNAs were lower in ORX, ORX + TEST and ORX + TREN compared to SHAM (p < .05). Testosterone and trenbolone administration increased muscle fCSA and satellite cell number without increasing myonuclei number, and increased Mstn protein levels. Several genes and signalling proteins related to myostatin signalling were differentially regulated by ORX or androgen therapy.

Mechanism of lipid bilayer perturbation by bactericidal membrane-active small molecules.

Membrane-active small molecules (MASMs) are small organic molecules designed to reproduce the fundamental physicochemical properties of natural antimicrobial peptides: their cationic charge and amphiphilic character. This class of compounds has a promising broad range of antimicrobial activity and, at the same time, solves some major limitations of the peptides, such as their high production costs and low in vivo stability. Most cationic antimicrobial peptides act by accumulating on the surface of bacterial membranes and causing the formation of defects when a threshold is reached. Due to the drastically different structures of the two classes of molecules, it is not obvious that small-molecule antimicrobials act in the same way as natural peptides, and very few data are available on this aspect. Here we combined spectroscopic studies and molecular dynamics simulations to characterize the mechanism of action of two different MASMs. Our results show that, notwithstanding their simple structure, these molecules act just like antimicrobial peptides. They bind to the membrane surface, below the head-groups, and insert their apolar moieties in the core of the bilayer. Like many natural peptides, they cause the formation of defects when they reach a high coverage of the membrane surface. In addition, they cause membrane aggregation, and this property could contribute to their antimicrobial activity.

Effects of the beta3-adrenoceptor (Adrb3) agonist SR58611A (amibegron) on serotonergic and noradrenergic transmission in the rodent: relevance to its antidepressant/anxiolytic-like profile.

SR58611A is a selective beta(3)-adrenoceptor (Adrb3) agonist which has demonstrated antidepressant and anxiolytic properties in rodents. The present study confirmed the detection of Adrb3 mRNA transcript in rodent brain sub-regions and evaluated the effect of SR58611A on serotonergic and noradrenergic transmission in rats and mice in an attempt to elucidate the mechanism(s) underlying these properties. SR58611A (3 and 10 mg/kg, p.o.) increased the synthesis of 5-HT and tryptophan (Trp) levels in several rodent brain areas (cortex, hippocampus, hypothalamus, striatum). Moreover, SR58611A (10 mg/kg, p.o.) increased the release of 5-HT assessed by in vivo microdialysis in rat prefrontal cortex. Systemic (3 mg/kg, i.v.) or chronic administration of SR58611A (10 mg/kg, p.o.), in contrast to fluoxetine (15 mg/kg, p.o.), did not modify the activity of serotonergic neurons in the rat dorsal raphe nucleus. The increase in 5-HT synthesis induced by SR58611A was not observed in Adrb3s knockout mice, suggesting a selective involvement of Adrb3s in this effect. SR58611A (3 and 10 mg/kg, p.o.) did not modify norepinephrine synthesis and metabolism but increased its release in rat brain. Repeated administration of SR58611A (10 mg/kg, p.o.) did not modify basal norepinephrine release in rat prefrontal cortex whereas it prevented its tail-pinch stress-induced enhancement similarly to reboxetine (15 mg/kg, p.o.). Finally SR58611A increased the firing rate of noradrenergic neurons in the rat locus coeruleus following systemic (3 mg/kg, i.v.) or local (0.01 and 1 microM) but not chronic (10 mg/kg, p.o.) administration. These results suggest that the anxiolytic- and antidepressant-like activities of SR58611A involve an increase of brain serotonergic and noradrenergic neurotransmissions, triggered by activation of Adrb3s.

Stellate ganglion block may relieve hot flashes by interrupting the sympathetic nervous system.

Stellate ganglion block is routinely used in pain clinics. The mechanism of action of the stellate ganglion block is uncertain; the most common explanation is that it produces peripheral vasodilation, resulting in neural inhibition in the ganglion's sphere of innervation. However, the wide range of conditions that have been reported to respond favorably to stellate ganglion block suggest that its effectiveness may not be solely the result of increased blood flow nor restricted just to its sphere of innervation. We have found that stellate ganglion block is effective in the treatment of hot flashes in postmenopausal women, as well as those with estrogen depletion resulting from breast cancer treatment. Based on evidence that hot flashes may be centrally mediated and that the stellate ganglion has links with the central nervous system nuclei that modulate body temperature, we hypothesize that the stellate ganglion block provides relief of hot flashes by interrupting the central nervous system connections with the sympathetic nervous system, allowing the body's temperature-regulating mechanisms to reset. If this mechanism can be confirmed, this would provide women with intractable hot flashes with an effective, potentially long-lasting means of relieving their symptoms, and potentially widen the range of indications for stellate ganglion block to include other centrally mediated syndromes.

The effects of analogues of valproic acid on seizures induced by pentylenetetrazol and GABA content in brain of mice.

The effect of valproic acid and 10 close analogues (7 branched and 3 non-branched) were studied on the content of gamma-aminobutyric acid (GABA) in brain and on seizures induced by pentylenetetrazol (PTZ) in mice. All 8 branched fatty acids protected against seizures induced by pentylenetetrazol, but the 3 non-branched acids were inactive. A significant correlation was observed between side-chain length and anticonvulsant potency. However, sedative and toxic phenomena became apparent with longer chain lengths. The 3 non-branched fatty acids did not alter levels of GABA in brain, but there was a significant correlation between anticonvulsant activity and increased brain GABA levels, for the 8 branched fatty acids. Despite this correlation, one branched analogue, 2-ethylbutyric acid, possessed anticonvulsant activity but did not increase the content of GABA in brain.

Neuropharmacological profile of a novel and selective ligand of the sigma site: SR 31742A.

The biochemical, electrophysiological and behavioural effects of SR 31742A, a novel and selective ligand of sigma sites in brain, labelled with (+)-[3H]3PPP (Ki = 5.3 +/- 0.3 nM), were investigated in rodents and compared with those of DA antagonists having (haloperidol) or not (spiroperidol) a high affinity for sigma sites. Like haloperidol but unlike spiroperidol, SR 31742A, (ED50 = 0.065 mg/kg, i.p., and 0.21 mg/kg, p.o.) antagonized sigma-dependent turning behaviour in mice and inhibited (0.5 mg/kg, i.v.) the spontaneous firing of hippocampal (CA3) neurones in urethane-anaesthetized rats. In chloral hydrate-anaesthetized rats, like classical antipsychotic compounds, SR 31742A (0.625-5 mg/kg, i.p.) increased the number of spontaneously active A9 and A10 DA cells after single administration and produced an opposite effect after repeated injections. The drug SR 31742A reduced (2.5, 5, 10 mg/kg, i.p.) the hyperactivity elicited by various drugs including that produced by injection of (+)-amphetamine into the nucleus accumbens and impaired avoidance responses at doses (5, 10 mg/kg, i.p.), sparing escape behaviour. SR 31742A lacked affinity for DA receptors and neither did the compound induce catalepsy nor antagonize such effects elicited by apomorphine as climbing, hypothermia, stereotypy or the inhibition of firing of DA neurones. SR 31742A did not affect the basal metabolism of DA but at 10 mg/kg (i.p.) it significantly reduced the amphetamine-induced rise in levels of 3-MT in the striatum of mice. Together, these results indicate a modulatory role for sigma sites upon the activity of hippocampal and DA systems and that sigma ligands exert effects, which suggest antipsychotic potential.

Effects of ageing and increased haemolysis on the levels of dolichol in rat spleen.

Dolichol is a long-chain polyisoprenoid. No enzyme pathway for dolichol degradation was discovered. Dolichol accumulates in human and rodent tissues during ageing. Red blood cells contain a larger amount of dolichol and red blood cell life span is shorter in older rats. The effects of age and of the load of dolichol from red blood cell degradation on the ageing-associated accumulation of dolichol in spleen were studied in 2, 6, 12, 18 and 24 month-old male Sprague Dawley rats fed ad libitum (AL) or on an anti-ageing dietary regimen (EOD). Tissue dolichol was extracted and assayed by HPLC [J. Gerontol. 53A (1998) B87]. Levels of dolichol increased in spleen, liver, kidney and muscle in parallel fashion from the age of 2 to 12 months. Unexpectedly, spleen dolichol decreased in older rats whereas liver, kidney and muscle dolichol increased significantly. The effects of haemolysis on spleen dolichol were tested by the administration of phenylhydrazine. Results show that haemolysis does not increase, but rather decreases the levels of dolichol in erythroclastic organs. It is concluded that the levels of spleen dolichol may decrease in the absence of any known enzymatic degradative pathway if the spleen and its resident phagocytes are forced to cope with a higher number of red blood cells to be cleared. Free-radical mediated decomposition of dolichol by phagocytic cells during erythrophagocytosis might be involved in the process.

EEG effects of i.v. infusion of pentylenetetrazol in rats: a model for screening and classifying antiepileptic compounds.

In order to validate a new animal model predictive of the profile of antiepileptic drugs, we studied the antagonism by standard antiepileptics of the EEG modifications induced by low-speed IV infusion of pentylenetetrazol (PTZ) in rats. The activity of the drugs was measured by their effects on temporal characteristics of the PTZ-induced EEG paroxysms. Most compounds had moderate to potent anti-PTZ effects, as shown by the changes in the EEG temporal parameters. However, these effects depended on the drugs and doses. Cluster analysis showed that drugs and doses which evoked similar changes were closely related and were included in separate clusters with respect to one another. In particular, the present results showed that benzodiazepines and antiepileptics cluster differently in their effects. Thus, this model could be a useful tool for assessing new antiepileptic drugs.

The CB1 cannabinoid receptor antagonist SR 141716A affects A9 dopamine neuronal activity in the rat.

CB1 receptors and their putative natural ligand anandamide, have been tentatively involved in the control of midbrain extrapyramidal function. Electrophysiological activity of dopamine neurones was measured after acute and repeated administration of the CB1 receptor antagonist SR 141716A (0.3-3 mg kg-1) in rats. Acute SR 141716A increased A9, but not A10 cell population response without affecting either their spontaneous firing rate or apomorphine-induced rate inhibition and prevented amphetamine-induced inhibition of A9, but not of A10 cell firing. After repeated administration SR 141716A (1 or 5 mg kg-1) decreased population response of A9 cells, which was reversed by apomorphine. These results suggest that CB1 receptor blockade by SR 141716A interrupts a cannabinoid-like endogenous tone controlling extrapyramidal function.

Electroencephalographic study of SR 95103, a GABAA antagonist: interaction with inhibitory amino acids and muscimol.

SR 95103 has recently been described as a selective GABAA antagonist. In this study, the electroencephalographic (EEG) effects of SR 95103 were investigated as well as its central interaction with inhibitory amino acids and muscimol. Slow intravenous infusions of SR 95103 in rats induced epileptiform EEG activities which were antagonized by intracerebroventricularly injected muscimol, GABA and taurine whereas glycine did not modify and even facilitated the effects of SR 95103. These results suggest that the EEG effects of SR 95103 are due to the specific GABAA antagonistic properties of this compound.

Quantification of slow-wave EEG induced by atropine: effects of physostigmine, amphetamine and haloperidol.

The goal of this study was to investigate whether the atropine-induced slow waves in the rat EEG could be easily quantified and used to assess the action of drugs on the central cholinergic systems manifested at the cortical level. Cable-transmitted EEG recordings were made in freely-moving male rats over periods of 5-6 h. Visual inspection of the EEG led us to divide it into 2 states, according to frequency and amplitude criteria: desynchronized, low voltage activity was termed 'State 1', also including other arousal patterns like 'theta spindles'. Slow-wave, high voltage activity, as well as faster patterns like spindles of slow-wave sleep, were included in 'State 2'. The time spent in State 2 (chosen because slow waves are admittedly increased by atropine) was visually determined on the EEG paper tracings. Atropine per se, at increasing doses, (1, 3, 10, 30 and 100 mg/kg i.p.), induced an increased duration of State 2. By contrast, physostigmine per se at doses of 0.01, 0.1 and 0.3 mg/kg i.p. reduced this duration with increasing doses. The atropine (10 mg/kg i.p.)-induced increase of State 2 was markedly attenuated by physostigmine (0.1 and 0.3 mg/kg i.p.) and amphetamine (1 mg/kg i.p.), but potentiated by haloperidol (0.3 mg/kg i.p.). The effects of the different drugs and combinations on the general behavior were also noted. In conclusion, this approach appears to present a promising tool for the study of the interaction of drugs with central cholinergic systems.

The NK2 receptor antagonist SR48968 inhibits thalamic responses evoked by thermal but not mechanical nociception.

Extracellular recordings were made in the thalamic posterior nuclear group of anesthetized rats to study the effects of SR48968, a non-peptide NK2 receptor antagonist, on the responses evoked by thermal or mechanical nociceptive cutaneous stimulation. SR48968 (0.125-0.5 mg/kg, i.v. route) inhibited the responses to thermal stimulation while being ineffective on mechanically evoked responses in doses up to 2 mg/kg i.v. This effect was stereoselective since SR48965, the (R) enantiomer of SR48968 with a 2000-fold lower affinity for NK2 receptors, did not modify thermally evoked responses at a dose of 1 mg/kg i.v. These results support the notion that NK2 receptors are involved in thermal nociception.

In vitro and in vivo biological activities of SR140333, a novel potent non-peptide tachykinin NK1 receptor antagonist.

(S)1-(2-[3-(3,4-dichlorophenyl)-1-(3-isopropoxyphenylacetyl)pip eridin-3- yl]ethyl)-4-phenyl-1-azoniabicyclo[2.2.2]octane chloride (SR140333) is a new non-peptide antagonist of tachykinin NK1 receptors. SR140333 potently, selectively and competitively inhibited substance P binding to NK1 receptors from various animal species, including humans. In vitro, it was a potent antagonist in functional assays for NK1 receptors such as [Sar9,Met(O2)11]substance P-induced endothelium-dependent relaxation of rabbit pulmonary artery and contraction of guinea-pig ileum. Up to 1 microM, it had no effect in bioassays for NK2 ([beta Ala8]neurokinin A-induced contraction of endothelium-deprived rabbit pulmonary artery) and NK3 ([MePhe7]neurokinin B-induced contraction of rat portal vein) receptors. The antagonism exerted by SR140333 toward NK1 receptors was apparently non-competitive, with pD2' values (antagonism potency evaluated by the negative logarithm of the molar concentration of antagonist that produces a 50% reduction of the maximal response to the agonist) between 9.65 and 10.16 in the different assays. SR140333 also blocked in vitro [Sar9,Met(O2)11]substance P-induced release of acetylcholine from rat striatum. In vivo, SR140333 exerted highly potent antagonism toward [Sar9,Met(O2)11]substance P-induced hypotension in dogs (ED50 = 3 micrograms/kg i.v.), bronchoconstriction in guinea-pig (ED50 = 42 micrograms/kg i.v.) and plasma extravasation in rats (ED50 = 7 micrograms/kg i.v.). Finally, it also blocked the activation of rat thalamic neurons after nociceptive stimulation (ED50 = 0.2 micrograms/kg i.v.).

Quantitative electroencephalographic profile of 3-(4-hydroxy-1-piperidinyl)-6-(2,4-dichlorophenyl)-pyridazine (SR 41378) in the rat.

Quantitative electroencephalographic (QEEG) analysis was performed in rats following the oral administration of SR 41378 [3-(4-hydroxy-1-piperidinyl)-6-(2,4-dichlorophenyl)-pyridazine], a novel aminopyridazine derivative, which has been shown to possess anticonvulsant, antianxiety and hypnotic activities in mice and rats. The EEG effects of SR 41378 (10, 30 and 100 mg/kg) were compared to those of secobarbital (30 and 60 mg/kg) and diazepam (1, 3 and 10 mg/kg). SR 41378 and secobarbital increased the power of the middle-frequencies (8-16 Hz) of the EEG, reduced that of 4-8 Hz (theta) activities and did not affect 1-4 Hz (delta) activities. Diazepam also increased the power of middle-frequency activities and decreased that of both delta and theta activities. Quantitative EEG profiles were calculated from the mean integrated power (MIP) of selected frequency bands. The QEEG profile of SR 41378 was found to share common characteristics with those of secobarbital and diazepam: dose-dependent decrease of theta band MIP and increase of 8-20 Hz (middle beta bands) MIP. However, both SR 41378 and secobarbital induced a reduction of the 28-32 Hz (fast beta bands) MIP, whereas diazepam diminished the delta band. These results suggest that SR 41378, a novel chemical structure, shares common psychotropic properties with barbiturates and benzodiazepines.

Cerebral-activating (EEG) properties of two inverse agonists and of an antagonist at the benzodiazepine receptor in the rat.

In order to assess the effects of inverse benzodiazepine agonists and antagonists on brain function, computerized EEG (CEEG) analysis was performed in rats following the i.p. administration of SR 95195 (7-phenyl-3-methyl-1,2,4 triazolo-[4,3-b]pyridazine) and CGS 8216 (2-phenylpyrazolo-[4,3c]-quinoline-3-[5H]-one) two benzodiazepine receptor inverse agonists (BRIAGs) and of flumazepil (Ro 15-1788), a benzodiazepine receptor antagonist (BRANT). The EEG effects of SR 95195 (3, 10, 30 and 60 mg/kg), CGS 8216 (10 and 30 mg/kg) and flumazepil (3, 10, 30 and 60 mg/kg) were compared to those of the psychostimulant drugs DL-amphetamine (0.1, 0.3 and 1 mg/kg), and caffeine (10 and 30 mg/kg) and those of aniracetam (100 and 300 mg/kg), a nootropic pyrrolidone derivative. The CEEG profiles of SR 95195, CGS 8216 and flumazepil were mainly characterized by a power increase in the 20-32 Hz frequency range and by a power reduction in the 8-16 Hz range. These effects were quite similar to those of the psychostimulants DL-amphetamine and caffeine as well as to those of the nootropic aniracetam. Other psychotropic drugs with CNS-depressant properties, namely diazepam (10 mg/kg p.o.), pentobarbital (30 mg/kg p.o.), chlorpromazine (10 mg/kg i.p.) and imipramine (10 mg/kg i.p.) induced quite different EEG power modifications. These results show that BRIAGs and BRANTs possess a marked intrinsic activity at the central level and suggest that this activity is CNS-activating in nature.

Neurobehavioural effects of SR 27897, a selective cholecystokinin type A (CCK-A) receptor antagonist.

The activity of SR 27897, a potent and selective CCK-A vs CCK-B receptor antagonist (Ki = 0.2 nM on guinea-pig pancreas vs 2000 nM on rat brain) was studied on behavioural, electrophysiological and biochemical effects induced by peripheral or central injection of CCK-8S. For comparative purposes, devazepide, a reference CCK-A receptor antagonist, was investigated in these same models. CCK-induced hypophagia and CCK-induced hypolocomotion in rats, two behavioural changes associated with the stimulation of peripheral CCK-A receptors, were dose-dependently antagonized by SR 27897 (ED50 = 0.003 and 0.002 mg/kg i.p., respectively) and devazepide (ED50 = 0.02 and 0.1 mg/kg i.p., respectively). CCK-induced decrease of cerebellar cGMP levels in mice was also reduced by SR 27897 (ED50 = 0.013 mg/kg) and by devazepide (0.084 mg/kg). The CCK-induced turning behaviour after intrastriatal injection in mice, and the potentiation of the rate suppressant activity of apomorphine on rat DA neurons, were blocked by higher doses of SR 27897 and devazepide, consistent with the probable central origin of these effects. The respective ED50s were 0.2 mg/kg i.p. for SR 27897 and 4.9 mg/kg i.p. for devazepide in the former model, while the respective minimal effective doses were 1.25 and 5 mg/kg i.p. in the latter test. In most tests the i.p./p.o. ratio for SR 27897 was near unity, suggesting a high oral bioavailability of the compound. Taken together, these findings support the notion that SR 27897 behaves as a potent CCK-A antagonist able to cross the blood brain barrier.

Arousal-enhancing properties of the CB1 cannabinoid receptor antagonist SR 141716A in rats as assessed by electroencephalographic spectral and sleep-waking cycle analysis.

The effects of the central (CB1) cannabinoid receptor antagonist SR 141716A on the sleep-waking cycle were investigated in freely-moving rats using time scoring and power spectral analysis of the electroencephalogram (EEG). Over a 4-hour recording period, SR 141716A (0.1, 0.3, 1, 3, and 10 mg/kg I.P.) dose-dependently increased the time spent in wakefulness at the expense of slow-wave sleep (SWS) and rapid eye movement sleep (REMS), delayed the occurrence of REMS but did not change the mean duration of REMS episodes. Moreover, the compound induced no change in motor behavior. At the efficient dose of 3 mg/kg I.P., SR 141716A reduced the spectral power of the EEG signals typical of SWS but did not affect those of wakefulness. Taken together, these results demonstrate that the EEG effects of SR 141716A reflect arousal-enhancing properties. In addition, the present study suggests that an endogenous cannabinoid-like system is involved in the control of the sleep-waking cycle.

Biochemical and electrophysiological properties of SR 57746A, a new, potent 5-HT1A receptor agonist.

SR 57746A (1-[2-(naphth-2-yl) ethyl]-4-(3-trifluoromethylphenyl)-1, 2, 5, 6 tetra-hydropyridine hydrochloride) binds competitively, and with high affinity (Ki = 2.0 +/- 0.7 nM) to 5-HT1A receptors from rat hippocampus in vitro, but has much less affinity for other 5-HT receptor subtypes (IC50 > 650 nM). SR 57746A produces a concentration-dependent inhibition of forskolin-stimulated adenylate cyclase activity in rat hippocampal homogenates, with a maximal effect identical to that of 8-OH-DPAT, suggesting that SR 57746A behaves as a full agonist in this experimental model. SR 57746A potently displaces [3H]8-OH-DPAT binding to rat hippocampal membranes ex vivo, with an ID50 of 11.1 mg/kg po, 30 min after administration, and 2.8 mg/kg po, 2 h after administration. This effect of SR 57746A is long-lasting (at least 24 hours at 10 mg/kg po). SR 57746A does not modify the levels of 5-HT or DA in various brain areas, but decreases the concentrations of 5-HIAA, and increases those of DOPAC, HVA and 3-MT. Following i.v. administration, SR 57746A (0.095 to 0.25 mg/kg) inhibits the spontaneous firing of dorsal raphe neurones, but does not modify the activity of DA neurones in the substantia nigra or ventral tegmental area. Thus, SR 57746A is a potent, selective and full agonist at 5-HT1A receptors in vitro and vivo.