Chronic Dosing Studies Research Articles

Acute pharmacodynamic effects of pimobendan in client-owned cats with subclinical hypertrophic cardiomyopathy

BackgroundPrior studies have suggested that pimobendan is associated with several positive effects in cats, including improved survival in cats with congestive heart failure and improved left atrial function in research colony cats with hypertrophic cardiomyopathy (HCM) and normal cats. However, there is still a paucity of pharmacodynamic data refuting or supporting the use of pimobendan in a clinical cat population. This clinical trial aimed to evaluate the pharmacodynamic effects and tolerability of a single dose of pimobendan in cats with HCM. Echocardiograms and Doppler-derived systolic blood pressures were performed in 21 client-owned cats with subclinical HCM at baseline and 90-min after oral administration of 1.25 mg of pimobendan (Vetmedin). Seven additional cats were evaluated post-placebo administration to account for intra-day variability.ResultsHeart rate, systolic blood pressure, and murmur grade were not significantly different between baseline and post-pimobendan evaluations. Left auricular blood flow velocity, left atrial size, and left ventricular fractional shortening were not significantly different between baseline and post-pimobendan evaluations.Mean (± standard deviation) tissue Doppler peak systolic velocity of the mitral annulus was significantly higher following pimobendan (7.4 cm/s ± 1.5 vs 8.5 ± 1.6; p = 0.02). Median (min, max) left-ventricular outflow tract maximum velocity was significantly higher following pimobendan [1.9 m/sec (1.5, 3.4) vs 2.6 m/sec (2.0, 4.0); p = 0.01]. Mean right-ventricular outflow tract maximum velocity was also significantly higher following pimobendan (1.5 m/s ± 0.51 vs 2.0 ± 0.53; p = 0.004). Mean left atrial fractional shortening was significantly higher following pimobendan (28% ± 6 vs 32% ± 7; p = 0.02).No adverse events were observed following pimobendan administration.Right ventricular outflow tract velocity was significantly higher following placebo in control cats (1.02 ± 0.21 versus 1.31 ± 0.31; p = 0.01). No other significant differences were detected.ConclusionsIn client-owned cats with HCM, pimobendan acutely increased left atrial function and mildly increased left ventricular systolic function. Left ventricular outflow tract velocity was increased after pimobendan. Pimobendan was well tolerated in the acute setting in cats with HCM. The findings of this prospective, acute-dosing study confirm previous findings in research animals and retrospective analyses and suggest that chronic dosing studies are safe and warranted.

Coffee and cigarette smoking interactions with lamotrigine

The objective of this analysis was to determine possible interactions between lamotrigine (LTG) and coffee or cigarette use. As part of the statistical analysis of factors influencing LTG pharmacokinetics (PK) in the Equigen chronic dose study, we collected prospective data from enrolled patients on their use of coffee and cigarettes. Subjects were part of a crossover replication study of generic LTG products with rigorous blood sampling and were instructed to not change their typical consumption of these products for the duration of the study. A total of 35 subjects were enrolled, with 33 subjects having sufficient data for analysis. Higher consumption of coffee was associated with a significantly lower area under the curve (AUC) and maximum concentration (Cmax) of lamotrigine (LTG). Higher cigarette use did not result in a significant change in AUC or Cmax. Coffee, but not cigarette use, either induces LTG metabolism or inhibits LTG absorption.

Pharmacokinetics of budesonide/glycopyrrolate/formoterol fumarate metered dose inhaler formulated using co-suspension delivery technology after single and chronic dosing in patients with COPD

BackgroundBudesonide/glycopyrrolate/formoterol fumarate metered dose inhaler (BGF MDI), formulated using co-suspension delivery technology, is a triple fixed-dose combination in late-stage clinical development for chronic obstructive pulmonary disease (COPD). MethodsWe conducted two studies to characterize the pharmacokinetic (PK) profile of BGF MDI in patients with COPD: (i) a phase I, open-label, single and chronic (7-day) dosing study (NCT03250182) with one treatment arm (BGF MDI 320/18/9.6 μg); and (ii) a PK sub-study of KRONOS (NCT02497001), a phase III, randomized, double-blind study in which patients received 24 weeks’ treatment with BGF MDI 320/18/9.6 μg, glycopyrrolate/formoterol fumarate (GFF) MDI 18/9.6 μg, budesonide/formoterol fumarate (BFF) MDI 320/9.6 μg, or budesonide/formoterol fumarate dry powder inhaler (BUD/FORM DPI) 320/9 μg. PK parameters in both studies included maximum observed plasma concentration (Cmax) and area under the plasma concentration–time curve from 0 to 12h (AUC0–12). ResultsIn the phase I PK study (30 patients), budesonide and glycopyrronium Cmax were comparable after single and chronic dosing of BGF MDI (accumulation ratio [RAC] 95% and 107%, respectively) whereas Cmax for formoterol was slightly higher after chronic dosing (RAC 116%). AUC0–12 for budesonide, glycopyrronium, and formoterol were higher following chronic versus single dosing, with an RAC of 126%, 179%, and 143%, respectively. After 7 days’ dosing, AUC0–12 and Cmax for all three components of BGF MDI were similar to those in the KRONOS PK sub-study (202 patients) at Week 24.In the latter sub-study, Cmax and AUC0–12 at Week 24 were generally comparable across treatments for budesonide (geometric mean ratios [GMR] of 96%–109% for BGF MDI vs BFF MDI or BUD/FORM DPI), glycopyrronium (GMR of 88%–100% for BGF MDI vs GFF MDI), and formoterol (GMR of 80%–113% for BGF MDI vs GFF MDI or BFF MDI). ConclusionsSteady-state PK parameters of budesonide, glycopyrronium, and formoterol were similar after 7 days’ dosing in the phase I PK study and after 24 weeks in the KRONOS PK sub-study. Systemic exposure to budesonide, glycopyrronium, and formoterol was generally comparable across treatments in the KRONOS PK sub-study, suggesting no meaningful drug–drug or within-formulation PK interactions.

Antioxidant, anti-inflammatory and hypoglycemic effects of Fagonia olivieri DC on STZ-nicotinamide induced diabetic rats - In vivo and in vitro study

Ethnopharmacological relevanceFagonia olivieri (Zygophyllaceae) is used in Pakistan for management of diabetes and for treatment of stress related disorders of liver and kidneys. The objective of present study was to evaluate antidiabetic activity of F. olivieri using streptozotocin-nicotinamide induced diabetic rat model. MethodsPowder of the whole plant of F. olivieri was extracted with methanol (FOME) and the residue was fractionated with n-hexane (FOHE), chloroform (FOCE), ethyl acetate (FOCE), n-butanol (FOBE) and the remaining soluble aqueous fraction (FOAE). The extract/fractions were evaluated for in vitro inhibition of α-amylase and α-glucosidase and for the antidiabetic studies in Sprague-Dawley rats. FOAE was evaluated in 21 day chronic multiple dose study. Glibenclamide (10 mg/kg) and FOAE were used at a concentration of 200 mg/kg (164.8 μg of catechin) and 400 mg/kg (329.6 μg of catechin) in streptozotocin (STZ)-induced diabetic rats. Various serum parameters, blood cell parameters and oxidative stress induced parameters of the liver and kidneys were investigated. ResultsResults showed that aqueous fraction of F. olivieri (FOAE) potentially inhibited activity of pancreatic α-amylase, intestinal maltase and sucrase. Administration of FOAE (200 mg/kg; 400 mg/kg) to diabetic rats for 21 days increased body weight, hemoglobin and its indices, RBCs, platelets, lymphocytes and neutrophils against diabetic group. In serum level of glucose, transaminases, ALP, LDH, total bilirubin, creatinine and lipids decreased while insulin, total protein and albumin increased in contrast to diabetic group. Further, level of cytokines; TGF-β1, TNF-α and IL-6 in serum and altered level of antioxidant enzymes, glutathione and lipid peroxides of liver and kidney tissues restored towards control animals. ConclusionThis study demonstrated that FOAE inhibited activity of digestive enzymes and exhibited antioxidant, anti-inflammatory and antihyperglycemic activity in STZ-nicotinamide prompted diabetic rats and suggested that FOAE might be used as a therapeutic agent for the management of type-2 diabetes.

Acute buspirone dosing enhances abuse-related subjective effects of oral methamphetamine

There is not an approved pharmacotherapy for treating methamphetamine use disorder. This study sought to determine the effects of acute buspirone treatment on the subjective and cardiovascular effects of oral methamphetamine in order to provide an initial assessment of the utility, safety, and tolerability of buspirone for managing methamphetamine use disorder. We predicted that acute buspirone administration would reduce the subjective effects of methamphetamine. We also predicted that the combination of buspirone and methamphetamine would be safe and well tolerated. Ten subjects completed the protocol, which tested three methamphetamine doses (0, 15, and 30mg) in combination with two buspirone doses (0 and 30mg) across 6 experimental sessions. Subjective effects and physiological measures were collected at regular intervals prior to and after dose administration. Methamphetamine produced prototypical subjective and cardiovascular effects. Acute buspirone administration increased some of the abuse-related subjective effects of methamphetamine and also attenuated some cardiovascular effects. The combination of oral methamphetamine and buspirone was safe and well tolerated. Acute buspirone administration may increase the abuse liability of oral methamphetamine. Chronic buspirone dosing studies remain to be conducted, but given preclinical findings and the outcomes of this work, the utility of buspirone for treating methamphetamine use disorder appears limited.

Generic-to-generic lamotrigine switches in people with epilepsy: the randomised controlled EQUIGEN trial

Patients and clinicians share concerns that generic drug substitution might lead to loss of efficacy or emergence of adverse events. In this trial, we assessed US Food and Drug Administration (FDA) bioequivalence standards by studying the effects of switching between two disparate generic immediate-release lamotrigine products in patients with epilepsy. The Equivalence among Generic Antiepileptic Drugs (EQUIGEN) chronic-dose study was a randomised, double-blind, crossover study that enrolled adults (aged ≥18 years) with epilepsy from six epilepsy centres at academic institutions across the USA who were receiving immediate-release lamotrigine dosed at 100 mg, 200 mg, 300 mg, or 400 mg twice daily. Eligible patients were randomly allocated (1:1) to one of two treatment sequences (sequence 1 or sequence 2), comprising four study periods of 14 days each. During each 14-day treatment period, patients received balanced doses of an oral generic lamotrigine product every 12 h (200-800 mg total, identical to lamotrigine dose prior to study enrolment); after each 14-day period, patients were crossed over to receive the other generic product. Computer-based randomisation was done using random permuted blocks of size two or four for each site to prevent sequence predictability. Both patients and study personnel were masked to the generic products selected, their predicted exposure (ie, "high" vs "low"), and their group allocation. The primary outcome of this trial was bioequivalence between the generic products, which was assessed at the end of the study through a comparison of maximum plasma concentration (Cmax) and area under the concentration-time curve (AUC) for each product in the analysis population (all patients who completed all four treatment periods). Bioequivalence was established if the 90% CIs of the ratios of these two parameters for the two products were within equivalence limits (80-125%) in the analysis population. This study is registered with ClinicalTrials.gov\, number NCT01713777. Between April 25, 2013, and Aug 12, 2014, 35 eligible patients were enrolled and randomly assigned to treatment sequence 1 (n=15) or treatment sequence 2 (n=20). 33 patients completed all four treatment periods and were included in the primary outcome analysis. The 90% CIs of the ratios of both Cmax and AUC were within equivalence limits (AUC 90% CI 98-103, Cmax 90% CI 99-105), showing that lamotrigine exposures were equivalent between the generic products. No significant changes in seizure frequency or adverse events were recorded. No deaths, study-related serious adverse events, or changes in clinical laboratory values or vital signs occurred during this study. Disparate generic lamotrigine products in patients with epilepsy showed bioequivalence with no detectable difference in clinical effects, confirming that US Food and Drug Administration bioequivalence standards are appropriate. American Epilepsy Society, Epilepsy Foundation, and US Food and Drug Administration.

Differential effects of isomers of clomiphene citrate on reproductive tissues in male mice.

To determine, in a chronic dosing study, the oral toxicity potential of the test substances, enclomiphene citrate (ENC) and zuclomiphene citrate (ZUC), when administered to male mice by oral gavage. Mice were divided into five treatment groups. Group I, placebo; Group II, 40 mg/kg body weight/day ENC; Group III, 4 mg/kg/day ENC; Group IV, 40 mg/kg/day ZUC; Group V, 4 mg/kg/day ZUC. Serum samples and tissues were obtained from each mouse for analysis and body weights were measured. In this chronic dosing study in mice, profound effects on Leydig cells, epididymis, seminal vesicles, and kidneys were seen, as well as effects on serum testosterone, follicle-stimulating hormone and luteinising hormone levels that were associated with ZUC treatment only. Treatment with the isolated enclomiphene isomer had positive effects on testosterone production and no effects on testicular histology. The present study suggests that an unopposed high dose of zuclomiphene can have pernicious effects on male mammalian reproductive organs. The deleterious effects seen when administering ZUC in male mice, justifies the case for a monoisomeric preparation and the development of ENC for clinical use in human males to increase serum levels of testosterone and maintain sperm counts.

Dipeptidyl peptidase IV inhibitory activity of protein hydrolyzates from <i>Amaranthus hypochondriacus</i> L. Grain and their influence on postprandial glycemia in Streptozotocin-induced diabetic mice.

Background: Type 2 diabetes is a chronic metabolic disorder. Recently, dipeptidyl peptidase IV (DPP-IV) inhibitors that protect incretin hormones from being cleaved by DPP-IV have been used as drugs to control glycemia. This study examined the potential hypoglycemic effect of amaranth grain storage protein hydrolyzates to control postprandial glycemia in streptozotocin (STZ)-induced diabetic mice as a model system of diabetes, and their inhibition mode on the enzyme. Material and Methods : Amaranth grain proteins were isolated and hydrolyzed and fractionated by gel filtration. The DPP-IV inhibitory activity of hydrolyzates as well as their kinetic parameters were assessed. Selected hydrolyzates (300 mg/kg body weight) were administered in a single administration-study (SAS) or in the same concentration during a four-week chronic daily dosing study (FWCDDS) in order to observe the effect on postprandial glycemia of diabetic mice. Results : Albumin 1, Globulin and Glutelin hydrolyzates (GluH) competitively inhibited DPP-IV in vitro (Ki= 0.11-5.61 mg/mL). GluH called Glu.III (IC 50 = 0.12±0.01 mg/mL) considerably inhibited DPP-IV activity. GluH identified as GluH24 improved glucose tolerance significantly (p<0.05), with remarkable increments in plasma insulin in SAS and FWCDDS (1.25 and 2.25 mg/mL, respectively). This effect could be compared to the one obtained from the mice group that was administered Sitagliptin (580 mg/kg body weight) as positive control (p<0.05). Conclusion : Amaranth Glutelin hydrolyzates yielded the highest enzyme inhibitory activity reported not only in vitro, but also in the STZ-induced diabetic mice in order to control postprandial glycemia. Key words : Amaranth protein hydrolyzate, DPP-IV inhibitory activity, diabetes

DIPEPTIDYL PEPTIDASE IV INHIBITORY ACTIVITY OF PROTEIN HYDROLYZATES FROM AMARANTHUS HYPOCHONDRIACUS L. GRAIN AND THEIR INFLUENCE ON POSTPRANDIAL GLYCEMIA IN STREPTOZOTOCIN-INDUCED DIABETIC MICE.

Background: Type 2 diabetes is a chronic metabolic disorder. Recently, dipeptidyl peptidase IV (DPP-IV) inhibitors that protect incretin hormones from being cleaved by DPP-IV have been used as drugs to control glycemia. This study examined the potential hypoglycemic effect of amaranth grain storage protein hydrolyzates to control postprandial glycemia in streptozotocin (STZ)-induced diabetic mice as a model system of diabetes, and their inhibition mode on the enzyme.&#x0D; Material and Methods: Amaranth grain proteins were isolated and hydrolyzed and fractionated by gel filtration. The DPP-IV inhibitory activity of hydrolyzates as well as their kinetic parameters were assessed. Selected hydrolyzates (300 mg/kg body weight) were administered in a single administration-study (SAS) or in the same concentration during a four-week chronic daily dosing study (FWCDDS) in order to observe the effect on postprandial glycemia of diabetic mice.&#x0D; Results: Albumin 1, Globulin and Glutelin hydrolyzates (GluH) competitively inhibited DPP-IV in vitro (Ki= 0.11-5.61 mg/mL). GluH called Glu.III (IC50= 0.12±0.01 mg/mL) considerably inhibited DPP-IV activity. GluH identified as GluH24 improved glucose tolerance significantly (p

P.11.1 Peptide-PMO induced exon-skipping restores muscle physiology in the mdx mouse

Antisense directed exon-skipping has been shown to be a powerful method to induce expression of dystrophin in dystrophic muscle for a range of species including man. Dystrophin expression can be induced in the mdx mouse by oligonucleotides targeting exon 23 which removes the premature stop mutation in the murine dystrophin gene. We had previously shown improved resistance to eccentric exercise (10% length change of the active muscle) following intramuscular delivery of a phosphorodiamidate morpholino oligomer (PMO) targeting exon 23 in the mdx mouse (Sharp et al., 2011). Little improvement was seen in specific force which is commonly only 60% of wild-type in the mdx mouse. We now report similar physiology results following a single intravenous treatment with a peptide-PMO (PPMO) using the Pip6a peptide. Importantly, repeated intravenous PPMO treatment every two weeks starting at 12 weeks old and continuing for 10 doses, completely prevented the force drop associated with eccentric exercise and significantly improved the specific force, albeit not quite to wild-type levels. Both the acute and chronic dosing results correlated with the increased expression of dystrophin in muscle fibres and decreased levels of TIMP-1 in the serum. The chronic dosing study also showed a reduction in inflammation, restoration of a more normal fibre type pattern and reduction in fibre size variability. These studies show the potential of the PPMO formulation to significantly improve the results of exon-skipping in clinical trials.

Abstract 936: Nonclinical safety and pharmacology of VX15/2503: a humanized IgG4 monoclonal antibody to SEMA4D

Abstract Vaccinex is developing VX15/2503, a humanized IgG4 anti-Semaphorin 4D (SEMA4D; CD100) antibody with approximately 5 nM affinity, for the treatment of patients with advanced solid tumors and for the treatment of patients with multiple sclerosis. SEMA4D is an important mediator of axonal growth cone guidance, angiogenesis, and T cell and B cell activation. Cellular SEMA4D (cSEMA4D) is expressed most abundantly on T cells and to a lesser extent on other lymphocytes as a 150 kDa transmembrane protein. SEMA4D is less abundantly present in serum as a 240 kDa, homodimeric soluble protein (sSEMA4D). VX15/2503 recognizes a discontinuous epitope in the homodimerzation domain of both the cellular and soluble forms of SEMA4D. This epitope is also located on the margin of the plexin B1 (PLXNB1) binding domain, the high affinity receptor of SEMA4D. Binding of SEMA4D by VX15/2503 blocks the binding of SEMA4D to PLXNB1 and reduces cSEMA4D by promoting internalization of approximately 60% over 24 hours. Evaluation of VX15/2503 or its murine progenitor (MAb 67-2) demonstrated that these anti-SEMA4D antibodies suppressed tumor growth, metastases and angiogenesis in syngeneic, xenograft, and transgenic tumor models. Single dose and one month toxicology studies utilizing VX15/2503 were performed in Sprague Dawley rats and cynomolgus macaques at doses of 0, 10, 30, or 100 mg/kg/dose. The no observed adverse effect level (NOAEL) in each study was determined to be 100 mg/kg/dose. A pivotal 6-month chronic dose study in rats is ongoing. Rats are being administered 26 weekly doses of VX15/2503 at 0, 30, 100, or 200 mg/kg/dose; data through 13 weeks have been analyzed. T cell associated SEMA4D remained saturated throughout this phase in mid and high dose animals. On average, high dose rats had a Cmax of 4,378 μg/mL and exposure of 330,878 μgαhr/mL (AUC0-168). Appetance, bodyweight, serum chemistry, behavior, general condition, and ophthalmologic parameters were unaffected by VX15/2503 administration. Treated animals mounted appropriate IgG response; however, low and high dose females produced a slight, but statistically significant lower IgM response than control animals five days following KLH administration. A statistically significant reduction of 33 to 80% was observed in circulating NK cell levels; no similar reduction was observed with macaques dosed weekly X 5 at 100 mg/kg or in ongoing clinical analyses of NK cell levels. Additionally, fewer splenic germinal centers and reduced lymphocyte infiltrates in hepatic parenchyma were observed in the tissues from high-dose animals. These pharmacologic effects did not result in frank toxicity in these animals. A Phase I trial with VX15/2503 is currently being conducted in adult patients with advanced solid tumors. A better understanding of antibody-antigen interactions as well as the nonclinical safety and pharmacology of this antibody will inform clinical development of VX15/2503. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 936. doi:1538-7445.AM2012-936

Development and validation of mechanical allodynia as a pain readout in a preclinical model of osteoarthritis

Development and validation of mechanical allodynia as a pain readout in a preclinical model of osteoarthritis

Drug Combinations in the Treatment of Hypertension

Not uncommonly, to effectively treat hypertension, multiple drugs must be given. Multidrug combinations that dominate clinical practice typically include a thiazide-type diuretic together with either an angiotensin-converting enzyme inhibitor, an angiotensin-receptor blocker, or less so a β-blocker. On the other hand, there are several approaches that can also incrementally reduce blood pressure (BP) but are used less regularly and, as such, go underappreciated as to their effectiveness. Such approaches may include within-class switching of diuretics, combining a thiazide-type diuretic with a calcium-channel blocker (CCB), using 2 CCBs from different subclasses, adding a peripheral α-blocker to an angiotensin-converting enzyme inhibitor, or tacking on an aldosterone receptor antagonist or nitrate therapy to any of several other drug classes. All of these presumably novel approaches offer useful options for treatment in the otherwise difficult-to-control hypertensive patient.1 These aforementioned fresh therapeutic approaches succeed in lowering BP based on the nature of the pharmacokinetic and pharmacodynamic interplay between select drug classes. A pharmacokinetic interaction that can be exploited clinically in the patient with difficult-to-treat hypertension is that of combining a dihydropyridine CCB, such as nifedipine, with a nondihydropyridine CCB, such as diltiazem or verapamil. The latter 2 compounds are known inhibitors of the cytochrome CYP3A4 isozyme. The dihydropyridine CCB nifedipine, as is the case for all CCBs, is extensively metabolized by CYP3A4 with little inhibitory effect on this isozyme itself. When nifedipine is combined with diltiazem or verapamil, the latter dose-dependently inhibits the clearance of nifedipine. This interaction occurs quickly, relates to the relatively steep dose-response relationship for nifedipine plasma levels and BP reduction when nifedipine is given in submaximal doses, and is nearly optimized within 3 days of …

Cholinergic system under aluminium toxicity in rat brain.

The present investigation envisages the toxic effects of aluminium on the cholinergic system of male albino rat brain. Aluminium toxicity (LD50/24 h) evaluated as per Probit method was found to be 700 mg/kg body weight. One-fifth of lethal dose was taken as the sublethal dose. For acute dose studies, rats were given a single lethal dose of aluminium acetate orally for one day only and for chronic dose studies, the rats were administered with sublethal dose of aluminium acetate once in a day for 25 days continuously. The two constituents of the cholinergic system viz. acetylcholine and acetylcholinesterase were determined in selected regions of rat brain such as cerebral cortex, hippocampus, hypothalamus, cerebellum, and pons-medulla at selected time intervals/days under acute and chronic treatment with aluminium. The results revealed that while acetylcholinesterase activity was inhibited, acetylcholine level was elevated differentially in all the above mentioned areas of brain under aluminium toxicity, exhibiting area-specific response. All these changes in the cholinergic system were subsequently manifested in the behavior of rat exhibiting the symptoms such as adipsia, aphagia, hypokinesia, fatigue, seizures, etc. Restoration of the cholinergic system and overt behavior of rat to the near normal levels under chronic treatment indicated the onset of either detoxification mechanisms or development of tolerance to aluminium toxicity in the animal which was not probably so efficient under acute treatment.

Zinc toxicity to aminergic neurotransmitters in rat brain

The present study was aimed to evaluate zinc toxicity to aminergic system in different areas of the brain of male albino rat, Rattus norvegicus. Zinc toxicity, evaluated as per Probit method was found to be 500 mg/kg body weight. For acute-dose studies, rats were given a single lethal dose of zinc chloride for one day only and for chronic-dose studies, the rats were administered with sub-lethal doses (1/10th of lethal dose) of zinc chloride every day for 90 days continuously. Various constituents of the aminergic system viz. dopamine, norepinephrine, and epinephrine and the catabolizing enzyme, monoamine oxidase (MAO) were determined in different regions of rat brain such as olfactory lobe, hippocampus, cerebellum, and pons-medulla on selected time intervals/days under acute and chronic treatment with zinc. The results revealed that while the levels of all aminergic neurotransmitters were elevated differentially in the above mentioned areas of brain, MAO activity registered nonsignificant inhibition in all brain regions under zinc toxicity. All these changes in the aminergic system were subsequently manifested in the behavior of rat exhibiting the symptoms of mild tremors, reduced locomotor activity and emotions, restlessness followed by lacrymation, salivation, etc. From these observations, it was obvious that zinc treatment caused severe perturbations in the functions of the nervous system. Restoration of the aminergic system along with behavior to the near normal levels under chronic treatment indicates the onset of detoxification mechanisms or development of tolerance to zinc toxicity in the animal which was not probably so efficient under acute treatment.

Antidiabetic effects of dipeptidyl peptidase–IV inhibitors and sulfonylureas in streptozotocin-nicotinamide–induced mildly diabetic mice

The present study investigated the antidiabetic effects of the dipeptidyl peptidase (DPP)–IV inhibitors ASP8497 and vildagliptin, and the sulfonylureas glibenclamide and gliclazide in streptozotocin-nicotinamide–induced mildly diabetic mice. A single administration of ASP8497 and vildagliptin significantly improved glucose tolerance by increasing plasma insulin and glucagon-like peptide–1 levels. In addition, a single administration of glibenclamide and gliclazide also caused significant improvement in glucose tolerance with an accompanying increase in the plasma insulin level. Subsequently, the effects of a 1-week chronic daily dosing of DPP-IV inhibitors and sulfonylureas were investigated. All drugs significantly improved glucose tolerance on day 1 of chronic daily dosing. After 1 week of chronic daily dosing, the DPP-IV inhibitors caused a significant improvement in glucose tolerance similar to those observed on day 1 by increasing the plasma insulin and glucagon-like peptide–1 levels. In contrast, the sulfonylureas had no significant improving or insulinotropic effect. Furthermore, ASP8497 also had an antihyperglycemic effect and improved pancreatic histopathologic lesions in a 4-week chronic daily dosing study. These results suggest that chronic daily dosing of sulfonylureas had virtually no antidiabetic effects because of marked attenuation of the insulinotropic action in streptozotocin-nicotinamide–induced mildly diabetic mice. In contrast, the antidiabetic efficacy of DPP-IV inhibitors, including ASP8497, did not change even after chronic daily dosing; therefore, DPP-IV inhibitors are useful as a therapeutic agent for impaired glucose tolerance and type 2 diabetes mellitus.

Acute and chronic toxicity of a lyophilised aqueous extract of Tanacetum vulgare leaves in rodents

Aim of the study The present investigation was carried out to evaluate the safety of an aqueous extract of tansy (Tanacetum vulgare L.) leaves by determining its potential toxicity after acute and chronic administration in rodents. Materials and Methods For the acute study, a lyophilized aqueous extract of tansy leaves was administered to mice in single doses of 0-13 g/kg given by gavage as well as intraperitoneal doses of 0–4.5 g/kg. General behavior adverse effects and mortality were determined for up to 14 days. In the chronic dose study, the extract was administered orally at doses of 0, 100, 300 and 600 mg/kg daily for 90 days to rats. Biochemical and hematological parameters were determined after 30 and 60 days, and then at the end of 90 days of daily administration. Results In the acute study in mice, the crude aqueous extract of tansy leaves caused dose-dependent general behavior adverse effects and mortality. The no-observed adverse effect levels (NOAEL) of the tansy extract were 7.0 g/kg and 1.0 g/kg, and the lowest-observed adverse effect levels (LOAEL) were 9.0 g/kg and 1.5 g/kg, when given by the oral and intraperitoneal routes, respectively. Mortality increased with increasing doses, with LD 50 of 9.9 g/kg and 2.8 g/kg for the oral and intraperitonal modes of administration, respectively. In the chronic study in rats, daily oral administration of the crude aqueous extract of tansy leaves for up to 90 days did not result in death or significant changes in the biological (except for hypoglycemia) and hematological parameters. Conclusions Because of the relatively high NOAEL values in the acute study in mice, and lack of significant effect on biological and hematological parameters in rats after 90 days of daily doses, the tansy extract does not appear to have significant toxicity. In view of the dose of tansy consumed in traditional medicine, there is a wide margin of safety for the therapeutic use of the aqueous extract of Tanacetum vulgare leaves.

Pharmacokinetics, toxicity, and functional studies of the selective Kv1.3 channel blocker 5-(4-phenoxybutoxy)psoralen in rhesus macaques.

The small molecule 5-(4-phenoxybutoxy)psoralen (PAP-1) is a selective blocker of the voltage-gated potassium channel Kv1.3 that is highly expressed in cell membranes of activated effector memory T cells (TEMs). The blockade of Kv1.3 results in membrane depolarization and inhibition of TEM proliferation and function. In this study, the in vitro effects of PAP-1 on T cells and the in vivo toxicity and pharmacokinetics (PK) were examined in rhesus macaques (RM) with the ultimate aim of utilizing PAP-1 to define the role of TEMs in RM infected with simian immunodeficiency virus (SIV). Electrophysiologic studies on T cells in RM revealed a Kv1.3 expression pattern similar to that in human T cells. Thus, PAP-1 effectively suppressed TEM proliferation in RM. When administered intravenously, PAP-1 showed a half-life of 6.4 hrs; the volume of distribution suggested extensive distribution into extravascular compartments. When orally administered, PAP-1 was efficiently absorbed. Plasma concentrations in RM undergoing a 30-day, chronic dosing study indicated that PAP-1 levels suppressive to TEMs in vitro can be achieved and maintained in vivo at a non-toxic dose. PAP-1 selectively inhibited the TEM function in vivo, as indicated by a modest reactivation of cytomegalovirus (CMV) replication. Immunization of these chronically treated RM with the live influenza A/PR8 (flu) virus suggested that the development of an in vivo, flu-specific, central memory response was unaffected by PAP-1. These RM remained disease-free during the entire course of the PAP-1 study. Collectively, these data provide a rational basis for future studies with PAP-1 in SIV-infected RM.

Assessing the dynamics of nuclear glucocorticoid-receptor complex: adding flexibility to gene expression modeling.

A retrospective analysis was performed to modify our fourth-generation pharmacodynamic model for glucocorticoid receptor (GR) dynamics with incorporation of more physiological features. This modified model was developed by integrating previously reported free cytosolic GR and GR mRNA data following single (10, 50 mg/kg) and dual (50 mg/kg at 0 and 24 hr) intravenous doses of methylprednisolone (MPL) in adrenalectomized (ADX) male Wistar rats with several in vitro studies describing real-time kinetics of the transfer of rat steroid-receptor complex from the cell cytosol to the nucleus. Additionally, free hepatic cytosolic GR and its mRNA data from a chronic infusion dosing study of MPL (0.1 and 0.3 mg/kg/hr) in male ADX Wistar rats were used to verify the predictability of the model. Incorporation of information regarding in vitro receptor kinetics allowed us to describe the receptor-mediated pharmacogenomic effects of MPL for a larger variety of genes in rat liver from microarray studies. These included early responsive gene like CCAAT/enhancer binding protein-beta (CEBP-beta), a transcription factor, as well as the later responsive gene for tyrosine aminotransferase (TAT), a classical biomarker of glucocorticoid (GC) genomic effects. This more mechanistic model of GR dynamics can be applied to characterize profiles for a greater number of genes in liver.

The role of GABAAβ2 subunit‐containing receptors in mediating the anticonvulsant and sedative effects of loreclezole

The majority of inhibitory neurotransmission in the brain is mediated by the gamma-aminobutyric acid (GABA) type A (GABA(A)) receptor. The anticonvulsant loreclezole largely acts by potentiating GABA(A) receptors containing beta2 and beta3 subunits. We used a genetically modified mouse containing a loreclezole-insensitive beta2 subunit (beta2N265S) to determine the role of this subunit in mediating the sedative and anticonvulsive effects of loreclezole. Sedation was assessed by measuring spontaneous locomotor activity and beam walking performance, and anticonvulsant efficacy was determined by pentylenetetrazole (PTZ) and amygdala kindling-induced seizures. The beta2N265S mice did not exhibit loreclezole-mediated sedation as shown by normal locomotor activity and beam walking performance. However, loreclezole also failed to provide significant protection against PTZ-induced seizures in the beta2N265S mice. Reduced efficacy against amygdala-kindled seizures, both acutely and over a 13-day chronic dosing study, was also observed in beta2N265S mice. These results suggest that the majority of the sedative effects and a significant proportion of the anticonvulsant efficacy of loreclezole are mediated via beta2-containing GABA(A) receptors.