1. Male Sprague-Dawley rats were made either hyper- or hypothyroid with thyroxine or 4-methyl-2-thiouracil, respectively. Bronchial smooth muscle (BSM) contractility and lung cyclic adenosine 3',5'-monophosphate (cAMP) content were measured in both conditions. 2. Bronchial smooth muscle contractility was significantly weaker in hyperthyroid rats, while the BSM contractility of hypothyroid rats was the same as controls. 3. The cAMP content of hyperthyroid rat lungs was similar to controls but was decreased in hypothyroid rats. 4. These studies demonstrated that both the hyper- and hypothyroid states affect respiration, although the mechanisms involved with different for each condition.
1. The effects of corticosteroid pretreatment on acetylcholine (ACH)-induced contraction of bronchial smooth muscle (BSM) were studied. 2. ACH dose-response curves for dexamethasone (DM)- and corticosterone (B)-treated but not deoxycorticosterone (DOC)-treated BSM were significantly shifted to the right; this provides evidence that glucocorticoid treatment reduced the sensitivity of BSM to ACH. 3. Morphine enhanced BSM contraction in response to ACH by 20%. DM suppressed this enhancement. 4. These findings correlated well with the reduction of muscarinic receptor numbers in BSM by glucocorticoids in our previous study. In addition, glucocorticoids reduced the sensitivity of BSM to opioids.
1. Debrisoquine hydroxylation phenotyping was carried out in 97 Chinese and 97 Malay healthy volunteers. 2. No poor metabolizer was found in the Chinese population. Using a metabolic ratio antimode of 10.0, two poor metabolizers were present amongst the Malays studied.
1. A series of experiments were conducted to investigate the effect of endogenous opioids on blood pressure of laboratory rats during stress. 2. Rats subjected to 120 min immobilization showed a significant drop in systolic pressure which could be prevented by pretreatment injections of naloxone. 3. Adrenalectomized rats subjected to the same kind of stress showed a drop in systolic pressure equivalent to only 30% of the systolic pressure drop in the intact animals. This decrease in systolic pressure could also be prevented by pretreatment injections of naloxone. 4. It was concluded that the decrease in systolic pressure in intact rats during immobilization was mostly due to endogenous opioids released from the adrenal glands, whereas opioids of other origins such as the pituitary gland, were also important.
Acute RyR2 activation by exchange protein directly activated by cAMP (Epac) reversibly perturbs myocyte Ca2+ homeostasis, slows myocardial action potential conduction, and exerts pro-arrhythmic effects. Loose patch-clamp studies, preserving in vivo extracellular and intracellular conditions, investigated Na+ current in intact cardiomyocytes in murine atrial and ventricular preparations following Epac activation. Depolarising steps to varying test voltages activated typical voltage-dependent Na+ currents. Plots of peak current against depolarisation from resting potential gave pretreatment maximum atrial and ventricular currents of -20.23 ± 1.48 (17) and -29.8 ± 2.4 (10) pA/μm2 (mean ± SEM [n]). Challenge by 8-CPT (1 μmol/L) reduced these currents to -11.21 ± 0.91 (12) (P .05). Assessment of the inactivation that followed by applying subsequent steps to a fixed voltage 100 mV positive to resting potential gave concordant results. Half-maximal inactivation voltages and steepness factors, and time constants for Na+ current recovery from inactivation in double-pulse experiments, were similar through all the pharmacological conditions. Intracellular sharp microelectrode membrane potential recordings in intact Langendorff-perfused preparations demonstrated concordant variations in maximum rates of atrial and ventricular action potential upstroke, (dV/dt)max . We thus demonstrate an acute, reversible, Na+ channel inhibition offering a possible mechanism for previously reported pro-arrhythmic slowing of AP propagation following modifications of Ca2+ homeostasis, complementing earlier findings from chronic alterations in Ca2+ homeostasis in genetically-modified RyR2-P2328S hearts.
Over the past 2 decades, knowledge of the role and clinical value of pharmacogenetic markers has expanded so that individualized pre-emptive therapy based on genetic background of patients could be within reach for clinical implementation. This is evidenced from the frequent updating of drug labels that incorporates pharmacogenetic information (where compelling data become available) by the regulatory agencies (such as the US FDA), and the periodical publication of guidelines of specific therapeutic recommendations based on the results of pharmacogenetic tests by the pharmacogenetics working groups or consortiums of professional bodies. Clinical relevance of the cytochrome P450 (CYP) polymorphism related to dose, effectiveness and/or toxicity of key drugs are presented in this review, including that of warfarin, clopidogrel, tricyclic antidepressants, and proton pump inhibitors. Prospect for routine clinical application of CYP genotyping before prescribing drugs is still currently unclear due to challenges and barriers associated with availability of well-defined and validated pharmacogenetic studies, the interpretation, result reporting and potential error of genotype testing, involvement of non-genetic factors, and other patient's demographic and disease conditions. Further studies to provide additional supporting clinical data and acceleration of pharmacogenetic testing standards and techniques should help improve the evidence base needed for clinical utility and hence move the implementation of genotype-guided therapy in clinical practice a step closer to reality.
Ageing is associated with increased prevalences of both atrial and ventricular arrhythmias, reflecting disruption of the normal sequence of ion channel activation and inactivation generating the propagated cardiac action potential. Experimental models with specific ion channel genetic modifications have helped clarify the interacting functional roles of ion channels and how their dysregulation contributes to arrhythmogenic processes at the cellular and systems level. They have also investigated interactions between these ion channel abnormalities and age-related processes in producing arrhythmic tendency. Previous reviews have explored the relationships between age and loss-of-function Nav 1.5 mutations in producing arrhythmogenicity. The present review now explores complementary relationships arising from gain-of-function Nav 1.5 mutations associated with long QT3 (LQTS3). LQTS3 patients show increased risks of life-threatening ventricular arrhythmias, particularly after 40 years of age, consistent with such interactions between the ion channel abnormailities and ageing. In turn clinical evidence suggests that ageing is accompanied by structural, particularly fibrotic, as well as electrophysiological change. These abnormalities may result from biochemical changes producing low-grade inflammation resulting from increased production of reactive oxygen species and superoxide. Experimental studies offer further insights into the underlying mechanisms underlying these phenotypes. Thus, studies in genetically modified murine models for LQTS implicated action potential recovery processes in arrhythmogenesis resulting from functional ion channel abnormalities. In addition, ageing wild type (WT) murine models demonstrated both ion channel alterations and fibrotic changes with ageing. Murine models then suggested evidence for interactions between ageing and ion channel mutations and provided insights into potential arrhythmic mechanisms inviting future exploration.
1. Andrographis paniculata (Burm. f) Nees, commonly known as 'king of bitters', is a herbaceous plant belonging to the Family Acanthaceae. It has been widely used for centuries in Asian countries like China, India, Thailand and Malaysia for the treatment of sore throat, flu and upper respiratory tract infections. 2. Andrographolide, 14-deoxy-11,12-didehydroandrographolide and neoandrographolide are examples of the major labdane diterpenoids isolated from A. paniculata. These bioactive molecules have exhibited varying degrees of anti-inflammatory and anticancer activities in both in vitro and in vivo experimental models of inflammation and cancer. 3. Extensive libraries of andrographolide analogues have been synthesised mainly by modifying the α,β-unsaturated γ-butyrolactone moiety, the two double bonds Δ(8,(17)) and Δ(12,(13)) and the three hydroxyls at C-3 (secondary), C-14 (allylic) and C-19 (primary). Many of these synthetic analogues exhibit superior anticancer activity over the naturally occurring andrographolides. 4. Andrographolide and its derivatives have been shown to have anti-inflammatory effects in experimental models of asthma, stroke and arthritis, as well as in patients with upper respiratory tract infections. Andrographolide reduces the production of cytokines, chemokines, adhesion molecules, nitric oxide and lipid mediators, probably via inhibition of the nuclear factor (NF)-κB signalling pathway. 5. The anticancer mechanisms for andrographolide include inhibition of Janus tyrosine kinases-signal transducers and activators of transcription, phosphatidylinositol 3-kinase and NF-κB signalling pathways, suppression of heat shock protein 90, cyclins and cyclin-dependent kinases, metalloproteinases and growth factors, and the induction of tumour suppressor proteins p53 and p21, leading to inhibition of cancer cell proliferation, survival, metastasis and angiogenesis. 6. Andrographolide drug discovery is a promising strategy for the development of a novel class of anti-inflammatory and anticancer drugs.
1. The hypotensive effect of cross-fostering in spontaneously hypertensive rats (SHR) is thought to involve adjustments in renal function. However, its association with renal anti-oxidant/oxidant balance during cross-fostering is not known. 2. The present study examined the effect of cross-fostering and in-fostering of 1-day-old offspring between SHR and Wistar-Kyoto (WKY) dams on renal anti-oxidant/oxidant status and systolic blood pressure (SBP). Renal anti-oxidant/oxidant status and SBP were determined in the offspring from 4-16 weeks of age. 3. Cross-fostered SHR had significantly lower SBP than in-fostered SHR at 6, 8 and 12 weeks, but not at 16 weeks (127 ± 1 vs 144 ± 2, 138 ± 1 vs 160 ± 1, 174 ± 2 vs 184 ± 2 and 199 ± 2 vs 194 ± 3 mmHg at 6, 8, 12 and 16 weeks, respectively). No differences in SBP were evident between cross-fostered and in-fostered WKY rats. There were no significant differences in levels of thiobarbituric acid-reactive substances (TBARS), protein carbonyl and total anti-oxidant status (TAS) or superoxide dismutase, catalase, glutathione peroxidase (GPx), glutathione S-transferase and glutathione reductase activity between cross-fostered and in-fostered SHR or WKY offspring. However, compared with WKY rats, catalase activity was higher at 6 and 16 weeks, TAS was higher at 16 weeks and GPx activity and TBARS were lower at 16 weeks in SHR. 4. It appears that cross-fostering of SHR offspring to WKY dams during the early postnatal period causes a transient delay in the rise in blood pressure in SHR and that this does not involve the renal anti-oxidant/oxidant system.
1. Obesity is a metabolic disease of pandemic proportions largely arising from positive energy balance, a consequence of sedentary lifestyle, conditioned by environmental and genetic factors. Several central and peripheral neurohumoral factors (the major ones being the anorectic adipokines leptin and adiponecin and the orexigenic gut hormone ghrelin) acting on the anorectic (pro-opiomelanocortin and cocaine- and amphetamine-regulated transcript) and orexigenic (neuropeptide Y and agouti gene-related protein) neurons regulate energy balance. These neurons, mainly in the arcuate nucleus of the hypothalamus, project to parts of the brain modulating functions such as wakefulness, autonomic function and learning. A tilt in the anorectic-orexigenic balance, perhaps determined genetically, leads to obesity. 2. Excess fat deposition requires space, created by adipocyte (hypertrophy and hyperplasia) and extracellular matrix (ECM) remodelling. This process is regulated by several factors, including several adipocyte-derived Matrix metalloproteinases and the adipokine cathepsin, which degrades fibronectin, a key ECM protein. Excess fat, also deposited in visceral organs, generates chronic low-grade inflammation that eventually triggers insulin resistance and the associated comorbidities of metabolic syndrome (hypertension, atherosclerosis, dyslipidaemia and diabetes mellitus). 3. The perivascular adipose tissue (PVAT) has conventionally been considered non-physiological structural tissue, but has recently been shown to serve a paracrine function, including the release of adipose-derived relaxant and contractile factors, akin to the role of the vascular endothelium. Thus, PVAT regulates vascular function in vivo and in vitro, contributing to the cardiovascular pathophysiology of the metabolic syndrome. Defining the mechanism of PVAT regulation of vascular reactivity requires more and better controlled investigations than currently seen in the literature.
1. We believe that the ultimate goal of cardiovascular regulatory mechanisms is not the regulation of arterial blood pressure (BP), but the maintenance of tissue blood flows commensurate with metabolic requirements. Thus, elevated BP can potentially contribute to optimizing tissue blood flows under select circumstances; for example, when there are primary defects in autoregulation of tissue blood flows. 2. The hypothesis that a primary defect in autoregulation of tissue blood flows may be responsible for the development of hypertension is presented. It is argued that, in this context, at least part of the rise in BP may be reflexly driven by a 'metaboreflex', a homeostatic mechanism acting to regulate tissue blood flows. 3. We argue that in the context of primary defects in autoregulation of tissue blood flows, the ability to generate and sustain a hypertensive phenotype increases the lifespan of species (i.e. if it were not for this adaptive hypertensive phenotype, death due to circulatory failure would occur much earlier). 4. Experimental and clinical evidence that indirectly supports the hypothesis is reviewed briefly and a means for testing this hypothesis is suggested.
1. The present study was performed in order to determine the amino acid and fatty acid composition of an aqueous extract of the freshwater fish Channa striatus, obtained by soaking (1:2, w/v) fresh fillets overnight in a chloroform:methanol (2:1, v/v) solvent, to elucidate the mechanism responsible for its antinociceptive activity and to clarify the relationship between the presence of the amino and fatty acids and the expected activity. 2. The aqueous extract was found to contain all amino acids with the major amino acids glycine, alanine, lysine, aspartic acid and proline making up 35.77 +/- 0.58, 10.19 +/- 1.27, 9.44 +/- 0.56, 8.53 +/- 1.15 and 6.86 +/- 0.78% of the total protein, respectively. 3. In addition, the aqueous extract was found to have a high palmitic acid (C16:0) content, which contributed approximately 35.93 +/- 0.63% to total fatty acids. The other major fatty acids in the aqueous extract were oleic acid (C18:1), stearic acid (C18:0), linoleic acid (C18:2) and arachidonic acid (C20:4), contributing 22.96 +/- 0.40, 15.31 +/- 0.33, 11.45 +/- 0.31 and 7.44 +/- 0.83% of total fatty acids, respectively. 4. Furthermore, the aqueous extract was demonstrated to possess concentration-dependent antinociceptive activity, as expected, when assessed using the abdominal constriction test in mice. 5. It is concluded that the aqueous extract of C. striatus contains all the important amino acids, but only some of the important fatty acids, which are suggested to play a key role in the observed antinociceptive activity of the extract, as well as in the traditionally claimed wound healing properties of the extract.
1. There is a growing interest in the anti-oxidant characteristics and use of flavonoids in the management of cardiovascular diseases. The cardiovascular mechanism of action of these plant derivatives remains controversial. This study compared the effects of the flavonoid quercetin with those of the anti-oxidant vitamin ascorbic acid (vitamin C) on the reactivity of aortic rings from spontaneously hypertensive rats (SHR). 2. The phenylephrine (PE)-induced contractile and the endothelium-dependent and independent relaxant responses of aortic rings from 21 to 22 week old SHR and age-matched normotensive Wistar (WKY) rats were observed in the presence of quercetin or ascorbic acid. All the experiments were performed in the presence of the cyclooxygenase inhibitor, indomethacin (10 micromol/L). 3. The endothelium-dependent and independent relaxations to acetylcholine (ACh) and sodium nitroprusside (SNP), respectively, were significantly lesser in the SHR compared to the WKY tissues whereas the contractile responses to PE were similar in both tissues. Pretreatment of WKY rings with quercetin or ascorbic acid had no effect on the responses to ACh or PE. In the SHR tissues, however, quercetin or ascorbic acid significantly improved the relaxation responses to ACh and reduced the contractions to PE with greater potency for quercetin. Both compounds lacked any effects on the responses to SNP in either aortic ring types. N(omega)-nitro-L-arginine methyl ester (l-NAME, 10 micromol/L) significantly attenuated the vasodepressor effects of quercetin and ascorbic acid, raising the responses to PE to a level similar to that observed in the control SHR tissues. In l-NAME pretreated aortic rings, quercetin and ascorbic acid inhibited the contractile responses to PE with the same magnitude in WKY and SHR tissues. 4. The present results suggest that acute exposure to quercetin improves endothelium-dependent relaxation and reduces the contractile responses of hypertensive aortae with a greater potency than ascorbic acid. This suggests a better vascular protection with this flavonoid than ascorbic acid in the SHR model of hypertension and possibly in human cardiovascular diseases.
Simvastatin is a lipid lowering drug whose beneficial role on bone metabolism was discovered in 1999. Several in vivo studies evaluated its role on osteoporosis and fracture healing, however, controversial results are seen in the literature. For this reason, Simvastatin has not been the focus of any clinical trials as yet. This systematic review clears the mechanisms of action of Simvastatin on bone metabolism and focuses on in vivo investigations that have evaluated its role on osteoporosis and fracture repair to find out (i) whether Simvastatin is effective on treatment of osteoporosis and fracture repair, and (ii) which of the many available protocols may have the ability to be translated in the clinical setting. Simvastatin induces osteoinduction by increasing osteoblast activity and differentiation and inhibiting their apoptosis. It also reduces osteoclastogenesis by decreasing both the number and activity of osteoclasts and their differentiation. Controversial results between the in vivo studies are mostly due to the differences in the route of administration, dose, dosage and carrier type. Local delivery of Simvastatin through controlled drug delivery systems with much lower doses and dosages than the systemic route seems to be the most valuable option in fracture healing. However, systemic delivery of Simvastatin with much higher doses and dosages than the clinical ones seems to be effective in managing osteoporosis. Simvastatin, in a particular range of doses and dosages, may be beneficial in managing osteoporosis and fracture injuries. This review showed that Simvastatin is effective in the treatment of osteoporosis and fracture healing.
Peptidyl-prolyl cis/trans isomerases (PPIases) are a conserved group of enzymes that catalyse the conversion between cis and trans conformations of proline imidic peptide bonds. These enzymes play critical roles in regulatory mechanisms of cellular function and pathophysiology of disease. There are three different classes of PPIases and increasing interest in the development of specific PPIase inhibitors. Cyclosporine A, FK506, rapamycin and juglone are known PPIase inhibitors. Herein, we review recent advances in elucidating the role and regulation of the PPIase family in vascular disease. We focus on peptidyl-prolyl cis/trans isomerase NIMA-interacting 1 (Pin1), an important member of the PPIase family that plays a role in cell cycle progression, gene expression, cell signalling and cell proliferation. In addition, Pin1 may be involved in atherosclerosis. The unique role of Pin1 as a molecular switch that impacts on multiple downstream pathways necessitates the evaluation of a highly specific Pin1 inhibitor to aid in potential therapeutic drug discovery.
Psychosocial stress is reported to be one of the main causes of obesity. Based on observations in studies that relate stress and gut inflammation to obesity, the present study hypothesized that chronic stress, via inflammation, alters the expression of nutrient transporters and contributes to the development of metabolic syndrome. Rats were exposed to restraint stress for 4 h/day for 5 days/week for eight consecutive weeks. Different segments of rat intestine were then collected and analysed for signs of pathophysiological changes and the expression of Niemann-Pick C1-like-1 (NPC1L1), sodium-dependent glucose transporter-1 (SLC5A1, previously known as SGLT1) and facilitative glucose transporter-2 (SLC2A2, previously known as GLUT2). In a separate experiment, the total anti-oxidant activity (TAA)-time profile of control isolated intestinal segments was measured. Stress decreased the expression of NPC1L1 in the ileum and upregulated SLC5A1 in both the jejunum and ileum and SLC2A2 in the duodenum. Inflammation and morphological changes were observed in the proximal region of the intestine of stressed animals. Compared with jejunal and ileal segments, the rate of increase in TAA was higher in the duodenum, indicating that the segment contained less anti-oxidants; anti-oxidants may function to protect the tissues. In conclusion, stress alters the expression of hexose and lipid transporters in the gut. The site-specific increase in the expression of SLC5A1 and SLC2A2 may be correlated with pathological changes in the intestine. The ileum may be protected, in part, by gut anti-oxidants. Collectively, the data suggest that apart from causing inflammation, chronic stress may promote sugar uptake and contribute to hyperglycaemia.
Tumour invasion and metastasis have been recognized as major causal factors in the morbidity and mortality among cancer patients. Many advances in the knowledge of cancer metastasis have yielded an impressive array of attractive drug targets, including enzymes, receptors and multiple signalling pathways. The present review summarizes the molecular pathogenesis of metastasis and the identification of novel molecular targets used in the discovery of antimetastatic agents. Several promising targets have been highlighted, including receptor tyrosine kinases, effector molecules involved in angiogenesis, matrix metalloproteinases (MMPs), urokinase plasminogen activator, adhesion molecules and their receptors, signalling pathways (e.g. phosphatidylinositol 3-kinase, phospholipase Cγ1, mitogen-activated protein kinases, c-Src kinase, c-Met kinases and heat shock protein. The discovery and development of potential novel therapeutics for each of the targets are also discussed in this review. Among these, the most promising agents that have shown remarkable clinical outcome are anti-angiogenic agents (e.g. bevacizumab). Newer agents, such as c-Met kinase inhibitors, are still undergoing preclinical studies and are yet to have their clinical efficacy proven. Some therapeutics, such as first-generation MMP inhibitors (MMPIs; e.g. marimastat) and more selective versions of them (e.g. prinomastat, tanomastat), have undergone clinical trials. Unfortunately, these drugs produced serious adverse effects that led to the premature termination of their development. In the future, third-generation MMPIs and inhibitors of signalling pathways and adhesion molecules could form valuable novel classes of drugs in the anticancer armamentarium to combat metastasis.
1. Free radicals generated by ferric nitrilotriacetate (FeNTA) can activate osteoclastic activity and this is associated with elevation of the bone resorbing cytokines interleukin (IL)-1 and IL-6. In the present study, we investigated the effects of 2 mg/kg FeNTA (2 mg iron/kg) on the levels of serum IL-1 and IL-6 with or without supplementation with a palm oil tocotrienol mixture or alpha-tocopherol acetate in Wistar rats. 2. The FeNTA was found to elevate levels of IL-1 and IL-6. Only the palm oil tocotrienol mixture at doses of 60 and 100 mg/kg was able to prevent FeNTA-induced increases in IL-1 (P < 0.01). Both the palm oil tocotrienol mixture and alpha-tocopherol acetate, at doses of 30, 60 and 100 mg/kg, were able to reduce FeNTA-induced increases in IL-6 (P < 0.05). Therefore, the palm oil tocotrienol mixture was better than pure alpha-tocopherol acetate in protecting bone against FeNTA (free radical)-induced elevation of bone-resorbing cytokines. 3. Supplementation with the palm oil tocotrienol mixture or alpha-tocopherol acetate at 100 mg/kg restored the reduction in serum osteocalcin levels due to ageing, as seen in the saline (control) group (P < 0.05). All doses of the palm oil tocotrienol mixture decreased urine deoxypyridinoline cross-link (DPD) significantly compared with the control group, whereas a trend for decreased urine DPD was only seen for doses of 60 mg/kg onwards of alpha-tocopherol acetate (P < 0.05). 4. Bone histomorphometric analyses have shown that FeNTA injections significantly lowered mean osteoblast number (P < 0.001) and the bone formation rate (P < 0.001), but raised osteoclast number (P < 0.05) and the ratio of eroded surface/bone surface (P < 0.001) compared with the saline (control) group. Supplementation with 100 mg/kg palm oil tocotrienol mixture was able to prevent all these FeNTA-induced changes, but a similar dose of alpha-tocopherol acetate was found to be effective only for mean osteoclast number. Injections of FeNTA were also shown to reduce trabecular bone volume (P < 0.001) and trabecular thickness (P < 0.05), whereas only supplementation with 100 mg/kg palm oil tocotrienol mixture was able to prevent these FeNTA-induced changes.
1. Nitric oxide (NO) is formed enzymatically from l-arginine in the presence of nitric oxide synthase (NOS). Nitric oxide is generated constitutively in endothelial cells via sheer stress and blood-borne substances. Nitric oxide is also generated constitutively in neuronal cells and serves as a neurotransmitter and neuromodulator in non-adrenergic, non-cholinergic nerve endings. Furthermore, NO can also be formed via enzyme induction in many tissues in the presence of cytokines. 2. The ubiquitous presence of NO in the living body suggests that NO plays an important role in the maintenance of health. Being a free radical with vasodilatory properties, NO exerts dual effects on tissues and cells in various biological systems. At low concentrations, NO can dilate the blood vessels and improve the circulation, but at high concentrations it can cause circulatory shock and induce cell death. Thus, diseases can arise in the presence of the extreme ends of the physiological concentrations of NO. 3. The NO signalling pathway has, in recent years, become a target for new drug development. The high level of flavonoids, catechins, tannins and other polyphenolic compounds present in vegetables, fruits, soy, tea and even red wine (from grapes) is believed to contribute to their beneficial health effects. Some of these compounds induce NO formation from the endothelial cells to improve circulation and some suppress the induction of inducible NOS in inflammation and infection. 4. Many botanical medicinal herbs and drugs derived from these herbs have been shown to have effects on the NO signalling pathway. For example, the saponins from ginseng, ginsenosides, have been shown to relax blood vessels (probably contributing to the antifatigue and blood pressure-lowering effects of ginseng) and corpus cavernosum (thus, for the treatment of men suffering from erectile dysfunction; however, the legendary aphrodisiac effect of ginseng may be an overstatement). Many plant extracts or purified drugs derived from Chinese medicinal herbs with proposed actions on NO pathways are also reviewed.
1. This study was carried out to determine the effect of short-term and long-term ingestion of glycyrrhizic acid on the response to 2 h of restraint stress by measuring locomotor activity and plasma corticosterone levels. 2. Male Sprague-Dawley rats were randomly assigned into four groups, each group having eight rats. Group 1 (control) was given ordinary tap water, while groups 2 (short term), 3 and 4 (both long term) were given tap water containing 1 mg/mL glycyrrhizic acid to drink for 10 days, 4 weeks and 9 weeks, respectively. All the rats were subjected to 2 h of restraint stress and the locomotor activity assessed using an activity test in an open field arena followed by blood sampling to determine the plasma corticosterone level. These procedures were repeated daily for 14 days. 3. The basal locomotor activity scores for rats given glycyrrhizic acid for 10 days or 4 weeks were similar to those of controls; however, that of the rats treated long term with glycyrrhizic acid was significantly lower (21.0 +/- 3.0 squares crossed; P < 0.0005). Following the first period of restraint stress there was a highly significant decrease in locomotor activity, which remained significantly lower until the seventh and subsequent periods, indicating an adaptation to the repeated stress had occurred. Although the decrease in locomotor activity was partially blocked and adaptation to repetitive stress was enhanced in the rats given glycyrrhizic acid for 10 days, this was not seen in rats treated with glycyrrhizic acid for 4 or 9 weeks. The corticosterone levels in control rats were significantly elevated for 4-5 days following the exposure to repetitive stress but decreased gradually from day 7 onwards. However, both short- and long-term glycyrrhizic acid-treated rats had higher plasma corticosterone levels than the controls (P < 0.05). 4. In conclusion, repetitive restraint stress caused decreased locomotor activity associated with increased plasma corticosterone levels, both of which, in normal rats, decreased with adaptation to stress. The stress response was partially blocked and adaptation enhanced in rats given glycyrrhizic acid for 10 days, but not in rats given glycyrrhizic acid for 4 and 9 weeks. Glycyrrhizic acid ingestion caused high plasma corticosterone.