Toxicological Evaluation of the Methanol Extract of Gmelina arborea Roxb. Bark in Mice and Rats.

OBJECTIVE: The present study was designed to evaluate acute and repeated dose toxicity of the methanol extract (ME) of the Gmelina arborea stem bark. MATERIALS AND METHODS: For the acute toxicity study, ME of G. arborea was orally administered to Swiss albino mice at a dose range of 300-5000 mg/kg. For the repeated dose toxicity study, the Wistar rats of either sex were orally administered with ME of G. arborea at the doses of 300, 1000, and 2000 mg/kg/day for a period of 28 days. The effects on body weight, food and water consumption, organ weight, hematology, clinical chemistry as well as histology were studied. RESULTS: The administration of ME from the G. arborea bark at 300-5000 mg/kg did not produce mortality or significant changes in the clinical signs. The no-observed adverse effect level (NOAEL) of ME was 5000 mg/kg. There were no significant differences in the general condition, growth, organ weights, hematological parameters, clinical chemistry values, or gross and microscopic appearance of the organs from the treatment groups as compared to the control group. CONCLUSION: ME of G. arborea was found safe in acute and repeated dose toxicity studies when tested in mice and rats.

A therapeutic approach to treat cardiovascular dysfunction of diabetes.

Diabetes greatly increases risk of cardiovascular dysfunction and interruptions of matrix metalloproteinase-2 (MMP-2) and matrix metalloproteinase-9 (MMP-9) have been shown to reduce the risk by alteration in extracellular matrix. We hypothesized that minocycline induced MMP-2 and MMP-9 inhibition can be enhanced by aspirin (through its COX and tPA inhibitory action) and this combination can reduce cardiovascular dysfunction of diabetes. Four weeks after diabetes induction (streptozotocin, 55 mg/kg, i.p.), rats were treated with minocycline (50 mg/kg, p.o.), aspirin (50 mg/kg, p.o.), or minocycline (50 mg/kg, p.o.) plus aspirin (50 mg/kg, p.o.) for a period of next four weeks. At the end of eighth week arterial pressure, heart rate and left ventricular pressure were recorded. Contractile response to phenylephrine (10(-5) M) and relaxation responses to acetylcholine (10(-9)-10(-4) M) were obtained from aortic rings of diabetic rats. Gel zymography was performed to evaluate MMP-2 and MMP-9 levels. Heart rate, mean arterial pressure, dp/dt(max) and dp/dt(min) were found significantly decreased in STZ diabetic rats when compared with normoglycemic group. Treatment with combination of minocycline and aspirin significantly ameliorate these compared to vehicle treated diabetic group. Endothelium-dependent relaxation responses induced by acetylcholine were decreased in diabetic rats and significantly higher in combination treated group. Collagen, MMP-2 and MMP-9 levels were significantly decreased in combined treated group when compared with diabetic control. Present study revealed that aspirin potentate minocycline induced MMP-2 and MMP-9 inhibition to ameliorate cardiovascular dysfunction of diabetes and this combination can be an approach for the treatment.

Toxicological assessments of aqueous extract of Eugenia jambolana stem bark.

Eugenia jambolana Lam. (Myrtaceae) is widely used in folk medicine as an antidiabetic, but there is a lack of information about its toxicity, especially for the stem bark. The present study evaluated acute oral and repeated-dose toxicity of the stem bark aqueous extract of Eugenia jambolana (EJ) in albino mice and Wistar rats. In the acute toxicity tests, mice received oral doses of EJ extract as 300, 2000, and 5000 mg/kg body weight. Mortality, signs of toxicity, body weight, food consumption, and gross findings were observed for 14 days post-treatment. In repeated toxicity, rats were orally treated with 300, 1000, and 2000 mg/kg body weight, and animals were observed till the 28th day of treatment. At the end of the study period, surviving animals were fasted overnight and anesthetized for blood collection and removal of some vital organs for histopathology. No significant differences were noted in body and organ weights between the control and treated groups from either of the studies. In addition, hematological parameters, e.g., red blood cell count (RBC), hemoglobin concentration (Hb), mean corpuscular hemoglobin concentration (MCHC), platelets (PLT), and white blood cell differential count, biochemical parameters, e.g., blood glucose, creatinine, blood urea nitrogen (BUN), alkaline phosphatase (ALP), bilirubin, total protein, and albumin, and ions, e.g., potassium, sodium, chloride, calcium, and phosphorus, were studied in the repeated-dose toxicity study. In conclusion, these investigations indicate the safety of acute and repeated oral administration of the aqueous extract of EJ stem bark, suggesting therefore that it may be continuously used safely.

Cardioprotective and ß-adrenoceptor antagonistic activity of a newly synthesized aryloxypropanolamine derivative PP-36.

The present study was performed to evaluate the cardioprotective effects and pharmacological characterization of newly synthesized ß-adrenoreceptor antagonists 3-(3-tert-butylamino-2-hydroxypropoxy)-4-methoxybenzaldehyde (PP-36) in the rat model of coronary artery occlusion and reperfusion. Pre-ischemic administration (20 minutes before coronary occlusion) of PP-36 showed cardioprotective effects against ischemia/reperfusion injury in rats. PP-36 (6 mg kg(-1)) significantly reduced arrhythmia score (6.33 ± 0.55, P < 0.05), infarct size/left ventricle size (38.9 ± 3.2, P < 0.05) and no mortality compared to vehicle-treated control group (14.17 ± 1.83, 44.9 ± 4.6 and 17% respectively). In-vitro studies in rat isolated right atria, guinea-pig trachea and rat distal colon preparations, were carried out to investigate the potency of PP-36 towards different ß-adrenoceptor subtypes. pA2/pKB values of PP-36 for ß1-ß2-and ß3-adrenoceptors were 6.904 ± 0.190, 6.44 ± 0.129 and 5.773 ± 0.129, respectively. In conclusion, PP-36 is a ß-adrenoceptor antagonist possessing potent anti-arrhythmic and cardioprotective effects against ischemia/reperfusion injury in rats.

Migraine: current therapeutic targets and future avenues.

Migraine is characterized by attacks of intense pulsatile and throbbing headache, typically unilateral in nature with or without aura. Migraine affects a substantial fraction (10-20 %) of the world population (more women than men). With regard to the pathophysiology of migraine, several theories have been proposed; the major three are vascular (due to cerebral vasodilatation), neurological (abnormal neurological firing) and neurogenic dural inflammation (release of inflammatory neuropeptides). The drugs used to treat migraine can be divided into two groups: agents that abolish the acute migraine headache and agents aimed at prevention. The acutely acting antimigraine agents (5-HT(1B/1D) receptor agonists) stimulated research interest in the field of migraine. Currently prophylactic treatments for migraine include calcium channel blockers, 5-HT(2) receptor antagonists, beta-adrenoceptor blockers and gamma-amino butyric acid (GABA) agonists. Unfortunately, many of these treatments are non-specific and not always effective. Despite progress, the complex etiology of migraine requires further research, the condition often remains undiagnosed and available therapies are underused. In this review, the evidence that linked the different theories of migraine with its pathophysiology is considered. Furthermore, the present therapeutic targets and future approaches for the acute and prophylactic treatment of migraine are critically evaluated.

Preliminary mechanistic studies on the smooth muscle relaxant effect of hydroalcoholic extract of Curcuma caesia.

BACKGROUND AND OBJECTIVES: Curcuma caesia (family Zingiberaceae) is widely used in India as both an anti-inflammatory and anti-asthmatic in Ayurvedic medicine. However, there are no published pharmacological data on Curcuma caesia on its potential anti-asthmatic activity. Hence, the objective of the present investigation is to study the mechanisms by which the hydroalcoholic extract of Curcuma caesia relaxes the smooth muscle in the bronchioles and vasculature of the respiratory tract. METHODS: The hydroalcoholic extract of Curcuma caesia (CC extract) was tested for its per se relaxant effect in guinea pig trachea and also in the presence of various receptor antagonists and enzyme inhibitors namely propranalol, 2', 5'-dideoxyadenosine, methylene blue, glibenclamide, N(omega)-nitro-L-arginine (L-NNA) and alpha-chymotrypsin. Furthermore, the possible role of hydroalcoholic extract in calcium channel modulation was investigated in depolarized rabbit aorta. RESULTS: The CC extract concentration dependently relaxed the carbachol (1 microM)-induced pre-contractions; the IC50 value was found to be 239.36 microg/ml and the incubation of either receptor antagonists or enzyme inhibitors did not exhibit any effect on the relaxation. In the isotonic Ca2+-free high-K+ (60 mM) depolarized aorta, CC extract (30 microg/ml) inhibited concentration-response curves of cumulative Ca2+ (0.1-30 mM) and the PD'2 value was found to be 4.11 microg/ml. INTERPRETATION AND CONCLUSION: The extract showed a dose-dependent, non-specific relaxation of pre-contracted isolated guinea pig trachea. The non-specific relaxant effect of the extract may be due to its ability to modulate calcium activity.

Migraine: current concepts and emerging therapies.

Migraine is a recurrent incapacitating neurovascular disorder characterized by attacks of debilitating pain associated with photophobia, phonophobia, nausea and vomiting. Migraine affects a substantial fraction of world population and is a major cause of disability in the work place. Though the pathophysiology of migraine is still unclear three major theories proposed with regard to the mechanisms of migraine are vascular (due to cerebral vasodilatation), neurological (abnormal neurological firing which causes the spreading depression and migraine) and neurogenic dural inflammation (release of inflammatory neuropeptides). The modern understanding of the pathogenesis of migraine is based on the concept that it is a neurovascular disorder. The drugs used in the treatment of migraine either abolish the acute migraine headache or aim its prevention. The last decade has witnessed the advent of Sumatriptan and the 'triptan' class of 5-HT1B/1D receptor agonists which have well established efficacy in treating migraine. Currently prophylactic treatments for migraine include calcium channel blockers, 5-HT2 receptor antagonists, beta adrenoceptor blockers and gamma-amino butyric acid (GABA) agonists. Unfortunately, many of these treatments are non specific and not always effective. Despite such progress, in view of the complexity of the etiology of migraine, it still remains undiagnosed and available therapies are underused. In this article, the diverse pieces of evidence that have linked the different theories of migraine with its pathophysiology are reviewed. Furthermore, the present therapeutic targets and futuristic approaches for the acute and prophylactic treatment of migraine, with a special emphasis to calcitonin gene-related peptide, are critically evaluated.

Effect of Sapindus trifoliatus on hyperalgesic in vivo migraine models.

Phytotherapies have offered alternative sources of therapy for migraine and gained much importance in prophylactic treatment. Sapindus trifoliatus is a medium-sized deciduous tree growing wild in south India that belongs to the family Sapindaceae. The pericarp is reported for various medicinal properties. A thick aqueous solution of the pericarp is used for the treatment of hemicrania, hysteria or epilepsy in folklore medicine. We have investigated the antihyperalgesic effects of the lyophilized aqueous extract of S. trifoliatus in animal models predictive of experimental migraine models using morphine withdrawal-induced hyperalgesia on the hot-plate test and on 0.3% acetic acid-induced abdominal constrictions in adult male Swiss albino mice. The extract significantly (N = 10, P < 0.05) increased the licking latency in the hot-plate test when administered i.p. at 10 mg/kg (6.70 +/- 0.39 s in saline control vs 18.76 +/- 0.96 s in S. trifoliatus-treated animals) and significantly (N = 10, P < 0.001) reduced the abdominal constrictions when administered i.p. at 2 and 10 mg/kg (40.20 +/- 1.36 in saline control vs 30.20 +/- 1.33 and 23.00 +/- 0.98 for 2 and 10 mg/kg, i.p., respectively, in S. trifoliatus-treated animals). Furthermore, when administered i.p. at 20 and 100 mg/kg, the extract significantly (N = 10, P < 0.05) inhibited the apomorphine-induced climbing behavior in mice (climbing duration 15.75 +/- 5.0 min for saline control vs 11.4 +/- 1.28 and 3.9 +/- 1.71 min for 20 and 100 mg/kg, respectively, in S. trifoliatus-treated animals). In receptor radioligand-binding studies, the extract exhibited affinity towards D2 receptors. The findings suggest that dopamine D2 antagonism could be the mechanism involved in the antihyperalgesic activity of the aqueous extract of S. trifoliatus.

Pharmacological studies of the aqueous extract of Sapindus trifoliatus on central nervous system: possible antimigraine mechanisms.

The aqueous extract of pericarp of fruits of Sapindus trifoliatus (ST) Linn., family Sapindaceae was evaluated for its potential effects on central nervous system in mice. The extract at doses 20 and 100 mg/kg, i.p. significantly (p < 0.001) reduced the spontaneous locomotor activity and at 100 mg/kg, increased the thiopental-induced sleeping time. In rota-rod motor co-ordination test, ST at 100 mg/kg, i.p. significantly (p < 0.05-0.01) reduced the endurance time. Further ST exhibited no protection against maximal electroshock (MES)- and pentylenetetrazole (PTZ)-induced convulsions in mice. In receptor radioligand binding studies, ST exhibited affinity towards dopaminergic, alpha-adrenergic and muscarnic receptors. The findings suggest that, ST may possess principles with potential neuroleptic properties.

Effect of Sapindus trifoliatus on hyperalgesic in vivo migraine models

Phytotherapies have offered alternative sources of therapy for migraine and gained much importance in prophylactic treatment. Sapindus trifoliatus is a medium-sized deciduous tree growing wild in south India that belongs to the family Sapindaceae. The pericarp is reported for various medicinal properties. A thick aqueous solution of the pericarp is used for the treatment of hemicrania, hysteria or epilepsy in folklore medicine. We have investigated the antihyperalgesic effects of the lyophilized aqueous extract of S. trifoliatus in animal models predictive of experimental migraine models using morphine withdrawal-induced hyperalgesia on the hot-plate test and on 0.3 percent acetic acid-induced abdominal constrictions in adult male Swiss albino mice. The extract significantly (N = 10, P < 0.05) increased the licking latency in the hot-plate test when administered ip at 10 mg/kg (6.70 ± 0.39 s in saline control vs 18.76 ± 0.96 s in S. trifoliatus-treated animals) and significantly (N = 10, P < 0.001) reduced the abdominal constrictions when administered ip at 2 and 10 mg/kg (40.20 ± 1.36 in saline control vs 30.20 ± 1.33 and 23.00 ± 0.98 for 2 and 10 mg/kg, ip, respectively, in S. trifoliatus-treated animals). Furthermore, when administered ip at 20 and 100 mg/kg, the extract significantly (N = 10, P < 0.05) inhibited the apomorphine-induced climbing behavior in mice (climbing duration 15.75 ± 5.0 min for saline control vs 11.4 ± 1.28 and 3.9 ± 1.71 min for 20 and 100 mg/kg, respectively, in S. trifoliatus-treated animals). In receptor radioligand-binding studies, the extract exhibited affinity towards D2 receptors. The findings suggest that dopamine D2 antagonism could be the mechanism involved in the antihyperalgesic activity of the aqueous extract of S. trifoliatus.

In vitro pharmacological investigations of Sapindus trifoliatus in various migraine targets.

Phytotherapies have offered alternative sources of therapy for migraine and gained much importance in prophylactic treatment. The aqueous extract of pericarp of fruits of Sapindus trifoliatus Linn (ST), family Sapindaceae was evaluated for its affinity for 5-HT(1B/1D) receptors in rabbit saphenous vein, alpha-adrenoceptors in rabbit aorta, GABA receptors in guinea pig ileum, 5-HT(2B) receptors in rat fundus and vanilloid receptors in guinea pig trachea. The calcium blocking effect was studied in rabbit aorta while the modulatory role of ST on platelet serotonin release was evaluated in human platelets. The aqueous extract of Sapindus trifoliatus exhibited significant 5-HT(2B) receptor inhibition and moderate platelet serotonin release inhibition.

Investigations into the antinociceptive activity of Sapindus trifoliatus in various pain models.

The effect of the aqueous extract of Sapindus trifoliatus (ST) on chemical, thermal-induced pain, nitroglycerin-induced hyperalgesia and pain on inflamed tissue was investigated. The extract (20 and 100 mg x kg(-1), i.p.) significantly inhibited acetic-acid-induced abdominal constrictions, formalin-induced pain licking and hotplate-induced pain in mice. Furthermore, the extract significantly increased the response latencies of nitroglycerin-induced hyperalgesia by the tail-flick method and mechanical pain on carrageenan-induced inflamed paw in rats. The data suggest that ST has an inhibitory activity on both peripheral and central pain mechanisms and has a modulatory role in NO-mediated nociceptive transmission.

5-HT3 receptors in selective animal models of cognition.

Role of 5-HT3 receptors in cholinergic hypofunctional models of cognitive impairment in the elevated plus maze model and a passive avoidance model is studied. Cognitive impairment was caused by scopolamine (1 mg/kg, ip) in mice and 5-HT3 ligands mCPBG (1 and 5 mg/kg, ip) and ondansetron (0.5 and 5 mg/kg, ip) were administered before the pre-learning phase to study the effects on acquisition, while post-learning administration was used to determine the effects on consolidation. Ondansetron improved acquisition and retention in cholinergic hypofunctional models while mCPBG potentiated selected impaired cognitive indices. The results indicate the role of 5-HT3 receptors in cognition and that an ideal evaluation of 5-HT3 ligands in cognition should distinguish true cognitive effects from locomotor, motivational and emotional effects.

Synthesis of new arylaminoquinoxalines and their antimalarial activity in mice.

2-Arylaminoquinoxalines were prepared by the condensation of 2-chloroquinoxaline with the appropriate Mannich bases in the presence of HCl. To synthesize the Mannich bases, 4-acetamidophenol was reacted with formaldehyde and dialkylamine to yield 3-[(dialkylamino) methyl]-4-hydroxyacetanilide, followed by hydrolysis. Antimalarial activities of the new arylaminoquinoxalines were evaluated against the rodent malaria parasite Plasmodium yoelii at a dose of 75 mg kg(-1). Three compounds synthesized (2-[3-[(diethylamino) methyl]-4-hydroxyanilino]-quinoxaline dihydrochloride (2b), 2-[3-[(pyrrolidinyl) methyl]-4-hydroxyanilino]-quinoxaline dihydrochloride (2f), and 2-[3-[(piperidinyl) methyl]-4-hydroxyanilino]-quinoxaline dihydrochloride (2g)) showed moderate antimalarial activity.

Synthesis and preliminary pharmacological investigations of 1-(1,2-dihydro-2-acenaphthylenyl)piperazine derivatives as potential atypical antipsychotic agents in mice.

In research towards the development of new atypical antipsychotic agents, one strategy is that the dopaminergic system can be modulated through manipulation of the serotonergic system. The synthesis and preliminary pharmacological evaluation of a series of potential atypical antipsychotic agents based on the structure of 1-(1,2-dihydro-2-acenaphthylenyl)piperazine (7) is described. Compound 7e, 5-{2-[4-(1,2-dihydro-2-acenaphthylenyl)piperazinyl]ethyl}-2,3-dihy dro-1H- indol-2-one, from this series showed significant affinities at the 5-HT1A and 5-HT2A receptors and moderate affinity at the D2 receptor. 7e exhibits a high reversal of catalepsy induced by haloperidol indicating its atypical antipsychotic nature.

MgCl2-sensitive and Gpp(NH)p-sensitive antagonist binding states of rat heart muscarinic receptors: preferential detection at ambient temperature assay and location in two subcellular fractions.

Some novel observations dealing with antagonist binding to cardiac particulate muscarinic receptors are described. Gpp(NH)p increased (2-3 fold) the specific binding of [3H]-QNB or [3H]-NMS, both potent muscarinic antagonists, to washed particles (WP), but not microsomes (MIC), when the binding was conducted at 30 degrees C. Magnesium, on the other hand, increased (2-3 fold) the binding of these antagonists to MIC, but not to WP, under the same condition. The treatment of subcellular fractions with 0.2 mM N-ethylmaleimide (NEM), a sulfhydryl reagent, failed to significantly modify the respective stimulatory actions of either Gpp(NH)p on WP binding or of magnesium on MIC binding of these antagonists; treatment with dithiothreitol (1 mM) was also ineffective in this regard. Gpp(NH)p decreased Kd (WP) while magnesium increased Kd (MIC) for [3H]-QNB. Repeated freezing/thawing of isolated subcellular fractions abolished the stimulatory effect of magnesium on antagonist binding to MIC but not of Gpp(NH)p on WP antagonist binding; the freeze/thaw procedure per se increased MIC binding but not WP binding of these antagonists. When the binding was conducted at 4 degrees C (24 hr), the stimulatory effect of Gpp(NH)p on [3H]-QNB binding was enhanced (6-fold) in the case of WP and was detectable (80%) in the case of MIC. Under this condition, the stimulatory effect of magnesium on [3H]-QNB binding was also enhanced (5-fold) in the case of MIC and became evident (200%) in the case of WP. The results of this work support the following views: (a) antagonist-occupied cardiac muscarinic receptors are capable of interaction with guanine nucleotide binding proteins (G protein like Gi, Go) and such interaction influences antagonist binding properties (e.g. increased affinity) of the cardiac membrane-associated muscarinic receptors (b) magnesium influences (decreased affinity) antagonist binding properties by interacting with multiple sites of which some are likely associated with components other than G proteins of the particulate fractions (c) a pool of NEM-sensitive sulfhydryls involved in the regulation of Gpp(NH)p-sensitive agonist binding to cardiac muscarinic receptors is not involved in the regulation by either Gpp(NH)p or magnesium of antagonist binding in these subcellular fractions and (d) membrane fluidity and microenvironment surrounding the receptor and G proteins contribute to the actions of Gpp(NH)p and magnesium on antagonist binding.

Pharmacological nature of newer imidazoli(di)nes on rat anococcygeus muscle.

The Pharmacological nature of newer imidazoli(di)nes (clonidine analogs) on rat anococcygeus muscle (RA) was investigated. Clonidine analogs produced dose-dependent (1 X 10(-3) to 1 X 10(-5) M) contractions on RA. The relative affinity (pD2) values were in the rank order of ST 375 greater than ST 567 greater than ST 608 greater than CLO greater than ST 600 greater than ST 363 greater than noradrenaline (NA) greater than ST 91 greater than ST 93. The intrinsic activity (alpha E) values of ST 93, ST 91, ST 600 and clonidine were comparable to alpha E of NA while the other analogs showed lower values. The responses of the clonidine analogs and NA on RA were antagonised in the presence of phentolamine and prazosin but were unaffected by yohimbine. Propranolol, atropine, cyproheptidine, mepyramine and metiamide had no effect on the responses. Reserpine pretreatment did not inhibit the responses of clonidine analogs on RA. The data suggests that newer clonidine analogs exhibited differences for their receptor occupation and receptor activation. The excitatory effects of newer clonidine analogs on RA are mediated through the stimulation of postsynaptic alpha (alpha 1) adrenoceptors.

Protective effect of ST-93 against ouabain induced arrhythmias in guinea pigs.

ST-93, a clonidine analog was studied for its antiarrhythmic activity in anaesthetised guinea pigs against ouabain induced arrhythmia. The amount of ouabain required (micrograms/kg) for the production of ventricular premature best. Ventricular fibrillation and cardiac arrest was recorded in control and drug treated group of animals. Both ST-93 and clonidine produced significant antiarrhythmic effect in guinea pigs. This protective effect was significantly blocked by yohimbine, suggesting that the antiarrhythmic effect is mediated through presynaptic alpha 2-adrenoceptors.