RESUMO
Two randomized, double-blind, placebo-controlled studies are reported that had the objective to evaluate the pharmacokinetics, pharmacodynamics, and safety of ASP015K (peficitinib), a Janus kinase (JAK) inhibitor, in healthy subjects. The single-dose study included 7 male groups (3-300 mg) and 2 female groups (30 or 200 mg), n = 8/group (6 on ASP015K and 2 on placebo in each group). The multiple-dose study included 1 female and 3 male groups, n = 12/group (9 on ASP015K and 3 on placebo in each group), who received ASP015K (30 mg) or placebo every 12 hours (twice a day) for 14 days. In the single-dose study, plasma ASP015K concentration increased dose-proportionally. Food increased ASP015K exposure (AUCinf ) by 27%. Mean peak JAK inhibition increased with dose, from 6% at 4 hours (median) following ASP015K 3 mg to 93% (range, 89%-98%) at 2 hours (median) after ASP015K 300 mg. In the multiple-dose study, ASP015K plasma exposure reached steady state by day 3. On day 14, mean ASP015K peak concentration was 38%-65% higher than after the first dose; peak JAK inhibition following 100 or 200 mg twice daily was >85%. The most common adverse events (AEs) were neutropenia, headache, and abdominal pain; no serious AEs occurred. The safety findings at pharmacologically effective doses of ASP015K support further clinical development.
Assuntos
Adamantano/análogos & derivados , Inibidores de Janus Quinases/farmacologia , Inibidores de Janus Quinases/farmacocinética , Niacinamida/análogos & derivados , Adamantano/efeitos adversos , Adamantano/farmacocinética , Adamantano/farmacologia , Adolescente , Adulto , Área Sob a Curva , Relação Dose-Resposta a Droga , Método Duplo-Cego , Feminino , Interações Alimento-Droga , Voluntários Saudáveis , Humanos , Inibidores de Janus Quinases/efeitos adversos , Masculino , Pessoa de Meia-Idade , Niacinamida/efeitos adversos , Niacinamida/farmacocinética , Niacinamida/farmacologia , Adulto JovemRESUMO
HIV seroconversion outcomes in preexposure prophylaxis (PrEP) trials of oral tenofovir (TFV)-containing regimens are highly sensitive to drug concentration, yet less-than-daily dosing regimens are under study. Description of TFV and its active moiety, TFV diphosphate (TFV-DP), in blood, vaginal tissue, and colon tissue may guide the design and interpretation of PrEP clinical trials. Six healthy women were administered a single oral dose of 300 mg tenofovir disoproxil fumarate (TDF) and 4.3 mg (12.31 MBq, 333 µCi) (14)C-TDF slurry. Blood was collected every 4 h for the first 24 h, then at 4, 8, 11, and 15 days postdosing. Colonic and vaginal samples (tissue, total and CD4(+) cells, luminal fluid and cells) were collected 1, 8 and 15 days postdose. Samples were analyzed for TFV and TFV-DP. Plasma TFV demonstrated triphasic decay with terminal elimination half-life median [interquartile range (IQR)] 69 h (58-77). Peripheral blood mononuclear cell (PBMC) TFV-DP demonstrated biphasic peaks (median 12 h and 96 h) followed by a terminal 48 h (38-76) half-life; Cmax was 20 fmol/million cells (2-63). One day postdose, the TFV-DP paired colon:vaginal tissue concentration ratio was 1 or greater in all subjects' tissue homogenates, median 124 (range 1-281), but was not sustained. The ratio was lower and more variable in cells extracted from tissue. Among all sample types, TFV and TFV-DP half-life ranged from 23 to 139 h. PBMC TFV-DP rose slowly in the hours after dosing indicating that success with exposure-driven dosing regimens may be sensitive to timing of the dose prior to exposure. Colonic tissue homogenate TFV-DP concentrations were greater than in vaginal homogenate at 24 h, but not in cells extracted from tissue. These and the other pharmacokinetic findings will guide the interpretation and design of future PrEP trials.
Assuntos
Adenina/análogos & derivados , Fármacos Anti-HIV/farmacocinética , Colo/química , Leucócitos Mononucleares/química , Organofosfonatos/farmacocinética , Plasma/química , Vagina/química , Adenina/administração & dosagem , Adenina/farmacocinética , Administração Oral , Adulto , Fármacos Anti-HIV/administração & dosagem , Radioisótopos de Carbono/análise , Feminino , Humanos , Marcação por Isótopo , Organofosfonatos/administração & dosagem , TenofovirRESUMO
BACKGROUND: Rational development of drugs to prevent human immunodeficiency virus (HIV) transmission benefits from an understanding HIV distribution in the female genital tract after intercourse. This study describes HIV distribution using surrogates of cell-free and cell-associated HIV and semen. METHODS: Apheresis-derived, autologous, lymphocyte-rich cells radiolabeled with 3.7-MBq (100-µCi) indium 111 ((111)In)-oxine (cell-associated HIV surrogate) and 18.5-MBq (500-µCi) technetium 99m ((99m)Tc)-sulfur colloid (HIV-sized 100-nm particle, cell-free HIV surrogate) were resuspended in 3 mL of hydroxyethylcellulose gel (semen simulant) with gadoteridol and dosed via artificial phallus after simulated intercourse. Postdosing dual-isotope single photon emission computed tomography with computed tomography (SPECT/CT) and magnetic resonance (MR) images were acquired to determine the surrogates' distribution. Seven hours after dosing, vaginal biopsy and luminal samples were collected at discrete locations in 8 subjects. RESULTS: SPECT/CT and MR analysis showed HIV and semen surrogate distribution with highest signal intensity in the vaginal pericervical area, without detectable signal in the uterus. One-third of the administered dose was retained in the female genital tract after 4 hours. Cell-free and cell-associated surrogate distribution coincided. CONCLUSIONS: We demonstrate the feasibility of dual-isotope SPECT/CT and MR imaging to determine the distribution of HIV and semen surrogates after simulated intercourse without disrupting vaginal contents. Surrogate distribution suggests topical microbicides do not need to reach the uterus for efficacy.
Assuntos
Coito/fisiologia , Infecções por HIV/transmissão , Sêmen/diagnóstico por imagem , Vagina/virologia , Adulto , Feminino , Infecções por HIV/virologia , Humanos , Imageamento por Ressonância Magnética , Masculino , Pessoa de Meia-Idade , Imagem Multimodal , Tomografia por Emissão de Pósitrons , Traçadores Radioativos , Compostos Radiofarmacêuticos , Sêmen/citologia , Estatísticas não Paramétricas , Coloide de Enxofre Marcado com Tecnécio Tc 99m , Fatores de Tempo , Tomografia Computadorizada por Raios X , Vagina/diagnóstico por imagem , Vagina/fisiologia , Adulto JovemRESUMO
OBJECTIVES: Describing the distribution and clearance of HIV surrogates within the gastrointestinal tract to inform rectal microbicide development. DESIGN: Radiolabeled simulated HIV-infected semen was administered, imaged, and biopsied to simulate and measure colonic HIV distribution after anal intercourse. METHODS: Healthy male subjects with a history of receptive anal intercourse and experience with the use of anal sex toys were recruited to this study. Apheresis isolated leukocytes were collected before simulated intercourse. These autologous leukocytes, radiolabeled with 9.25 MBq (111)Indium-oxine (cell-associated HIV surrogate), and sulfur colloid particles, labeled with 37 MBq (99m)Technectium (cell-free HIV surrogate), were mixed in 3 mL autologous seminal plasma. This simulated HIV-infected semen was administered to subjects via an artificial phallus with urethra after 5 minutes of simulated intercourse. Postdosing dual isotope Single photon emission computed tomography coupled with traditional computed tomography (SPECT/CT) images were acquired at 1, 4, 8, and 24 hours. At 5 hours postdosing, colon biopsies were collected, CD4 cells were extracted, and samples analyzed for radioactivity. RESULTS: SPECT/CT images showed similar luminal distribution for both surrogates, with migration limited to the rectosigmoid colon in all subjects. SPECT showed at least 75% overlap in distribution of both surrogates up to 4 hours after dosing. Biopsies indicate that 2.4% of CD4 cells extracted from rectosigmoid colon tissue were exogenously administered. CONCLUSIONS: Our HIV surrogates stayed within the rectosigmoid colon for 24 hours. Exogenously dosed autologous lymphocytes and HIV-sized particles migrate to similar locations and associate with the colonic tissue in the lumen.
Assuntos
Colo/fisiologia , Homossexualidade Masculina , Comportamento Sexual/fisiologia , Adulto , Anti-Infecciosos/administração & dosagem , Infecções por HIV/etiologia , Humanos , Masculino , Pessoa de Meia-Idade , Imagem Multimodal , Tomografia por Emissão de Pósitrons , Traçadores Radioativos , Sêmen/citologia , Sêmen/virologia , Coloide de Enxofre Marcado com Tecnécio Tc 99m , Fatores de Tempo , Tomografia Computadorizada por Raios XRESUMO
The population pharmacokinetic (PK) profile of oral clonidine was characterized in newborns with neonatal abstinence syndrome, and significant covariates affecting its PK parameters were identified. Plasma clonidine concentration data were obtained from a clinical trial in which 36 newborns, aged 1 to 25 days (postnatal age, PNA) and weighing 2.1 to 3.9 kg, were enrolled to take multiple oral doses of clonidine. The population PK model of clonidine was developed by NONMEM, and significant covariates were identified, followed by nonparametric bootstraps (2000 replicates) and simulation experiments. A 1-compartment open linear PK model was chosen to describe plasma concentrations of clonidine, and body weight and PNA were significant covariates for apparent clearance (CL/F) as follows: CL/F (L/h) = 15.2 × [body weight (kg)/70](0.75) × [PNA (day)(0.441)/(4.06(0.441) + PNA (day)(0.441))]. Furthermore, CL/F of clonidine increased rapidly with PNA during the first month of life after body weight was adjusted. Any optimal dosage regimen for clonidine in term neonates should be based on infant's age and body weight, and 1.5 µg/kg every 4 hours is proposed starting the second week of life based on the simulation results.
Assuntos
Agonistas de Receptores Adrenérgicos alfa 2/farmacocinética , Clonidina/farmacocinética , Síndrome de Abstinência Neonatal/metabolismo , Administração Oral , Agonistas de Receptores Adrenérgicos alfa 2/administração & dosagem , Agonistas de Receptores Adrenérgicos alfa 2/sangue , Clonidina/administração & dosagem , Clonidina/sangue , Método Duplo-Cego , Humanos , Recém-Nascido , Taxa de Depuração Metabólica , Modelos Biológicos , Síndrome de Abstinência Neonatal/sangue , Síndrome de Abstinência Neonatal/tratamento farmacológico , Placebos , Estudos ProspectivosRESUMO
Microbicides, substances applied topically to prevent sexual HIV infection, are needed to empower receptive sexual partners with effective prevention methods. Several large microbicide trials, however, failed to demonstrate efficacy, thus motivating a reevaluation of the current microbicide development paradigm, which has been largely empirically based. Microbicide use occurs in a highly complex environment involving multi-level interactions, behavioral and biochemical, among host, virus, and drug, yet many details of these interactions remain unknown. Fundamental information regarding virus and drug distribution over time in sexually receptive body compartments that is necessary to design a microbicide able to outdistance and outlast the virus is largely absent. Recent efforts have been made to establish a simple conceptual framework for obtaining the knowledge that is likely to inform a more mechanistic, model-based development paradigm. These efforts have also advanced the development of numerous methodological approaches to obtain the knowledge needed to improve microbicide development.
Assuntos
Anti-Infecciosos Locais/uso terapêutico , Infecções por HIV/prevenção & controle , Farmacologia Clínica/tendências , Animais , Anti-Infecciosos Locais/farmacologia , Ensaios Clínicos como Assunto , Infecções por HIV/tratamento farmacológico , Humanos , Modelos Teóricos , Farmacologia Clínica/métodos , Terminologia como AssuntoRESUMO
STUDY OBJECTIVE: To compare steady-state pharmacokinetics and pharmacodynamics of methadone enantiomers when coadministered with fosamprenavir 700 mg-ritonavir 100 mg twice/day. DESIGN: Open-label, single-sequence, two-period crossover, drug-interaction study. SETTING: Two university-affiliated research centers. SUBJECTS: Twenty-six opioid-dependent, methadone-maintained, healthy adults. INTERVENTION: Subjects received their usual daily dose of methadone alone for 4 days (period 1). Subjects then received the same daily dose of methadone plus fosamprenavir 700 mg-ritonavir 100 mg twice/day for 14 days (period 2). MEASUREMENTS AND MAIN RESULTS: Blood was collected on days 1-4 (period 1) and on days 11-14 (period 2) for plasma R- and S-methadone concentrations; amprenavir concentrations were assessed during period 2. Opioid-effect measures were assessed in each study period. Subjects served as their own controls for comparison of period 1 with period 2. Coadministration of fosamprenavir-ritonavir with methadone reduced plasma total R-methadone area under the plasma concentration-time curve over the dosing interval at steady state (AUC tau-ss) by 18%, maximum concentration at steady state (Cmax-ss) by 21%, and concentration at the end of the dosing interval at steady state (Ctau-ss) by 11%; time to reach Cmax-ss (Tmax) was delayed by 1.75 hours. Coadministration of fosamprenavir-ritonavir with methadone also reduced plasma total S-methadone AUC tau-ss and Cmax-ss by 43% each, Ctau-ss by 41%, and delayed Tmax by 0.85 hours. Fosamprenavir-ritonavir administered with methadone did not alter plasma amprenavir pharmacokinetics compared with historical control data; nor did it alter the unbound R-methadone at 2 and 6 hours after methadone dosing. Pharmacodynamic indexes remained essentially unchanged after adding fosamprenavir-ritonavir to methadone. No subject demonstrated opioid intoxication or withdrawal, or requested methadone dosage modification. CONCLUSION: No adjustment in the dosages of either methadone or fosamprenavir 700 mg-ritonavir 100 mg twice/day is required during coadministration, on the basis of the small reduction in total R-methadone exposure, no change in unbound R-methadone, no clinically important opioid effects, and no change in amprenavir exposure.
Assuntos
Fármacos Anti-HIV/farmacologia , Carbamatos/farmacologia , Metadona/farmacologia , Entorpecentes/farmacologia , Organofosfatos/farmacologia , Pró-Fármacos/farmacologia , Ritonavir/farmacologia , Sulfonamidas/farmacologia , Adulto , Fármacos Anti-HIV/farmacocinética , Carbamatos/sangue , Carbamatos/farmacocinética , Estudos Cross-Over , Interações Medicamentosas , Feminino , Furanos , Humanos , Masculino , Metadona/química , Metadona/farmacocinética , Entorpecentes/química , Entorpecentes/farmacocinética , Organofosfatos/farmacocinética , Estereoisomerismo , Sulfonamidas/sangue , Sulfonamidas/farmacocinéticaRESUMO
AMD070, a CXCR4 antagonist, has demonstrated antiretroviral activity in human immunodeficiency virus-infected patients. Since AMD070 is a substrate of cytochrome P450 3A4 and P-glycoprotein, both of which may be affected by ritonavir, we tested for a ritonavir effect on AMD070 pharmacokinetics. Subjects were given a single 200-mg dose of AMD070 on days 1, 3, and 17. Ritonavir (100 mg every 12 h) was dosed from day 3 to day 18. Blood samples to test for AMD070 concentrations were collected over 48 h after each administration of AMD070. Twenty-three male subjects were recruited. Among them, 21 completed the study, and 2 were discontinued for reasons other than safety. All adverse events were grade 2 or lower. AMD070 alone had the following pharmacokinetic features, given as medians (ranges): 3 h (0.5 to 4 h) for the time to peak blood concentration, 256 ng/ml (41 to 845 ng/ml) for the peak concentration (C(max)), 934 h x ng/ml (313 to 2,127 h x ng/ml) for the area under the concentration-time curve from 0 h to infinity (AUC(0-infinity)), 214 liters/h (94 to 639 liters/h) for apparent body clearance, and 4,201 liters (1,996 to 9,991 liters) for the apparent volume of distribution based on the terminal phase. The initial doses of ritonavir increased the C(max) of AMD070 [geometric mean (90% confidence interval)] by 39% (3 to 89%) and the AUC(0-infinity) by 60% (29 to 100%). After 14 days of ritonavir dosing, the pharmacokinetic changes in AMD070 persisted. The plasma pharmacokinetics of ritonavir were consistent with previous reports. It is concluded that AMD070 concentrations were increased with concomitant ritonavir dosing for 14 days in healthy volunteers.
Assuntos
Compostos Heterocíclicos com 1 Anel/farmacocinética , Receptores CXCR4/antagonistas & inibidores , Ritonavir/farmacologia , Adolescente , Adulto , Aminoquinolinas , Área Sob a Curva , Benzimidazóis , Butilaminas , Relação Dose-Resposta a Droga , Inibidores da Protease de HIV/farmacologia , Compostos Heterocíclicos com 1 Anel/efeitos adversos , Compostos Heterocíclicos com 1 Anel/sangue , Humanos , Masculino , Taxa de Depuração Metabólica , Pessoa de Meia-IdadeRESUMO
The accessory glands of the male genital tract are the sites of several major health problems, including benign prostatic hyperplasia, prostate cancer, and human immunodeficiency virus (HIV) transmission. We aimed to validate and improve our noninvasive method for the quantitation of drug concentrations in these physiological subcompartments. Twenty-seven men were dosed with 100 mg desipramine (a weak base) and 975 mg aspirin (a weak acid) and ejaculated their semen in 1 pass across 5 compartments of a collection device 2.5 hours later. A Bayesian latent-variable model previously developed by our group was further advanced for the estimation of drug concentrations in prostate and seminal vesicles based on drug and biomarker concentrations in the split ejaculate. Under normality assumptions, desipramine concentration (with 95% credible intervals) in prostate and seminal vesicles were 27 (8.3-52) ng/mL and 7.6 (4.0-11) ng/mL, respectively; salicylate concentration in prostate and seminal vesicles were 2.0 (0.093-6.5) microg/mL, and 9.9 (8.2-12) microg/mL, respectively. The prostate-to-seminal vesicles concentration ratio was 0.20 (0.0087-0.75) for salicylate and 3.6 (0.91-9.9) for desipramine. We conclude that our quantitative analysis along with the split ejaculate method is sensitive, reproducible, and applicable for the assessment of pharmacokinetics of the accessory glands of the male genital tract.
Assuntos
Aspirina/farmacocinética , Desipramina/farmacocinética , Próstata/metabolismo , Glândulas Seminais/metabolismo , Administração Oral , Adolescente , Adulto , Algoritmos , Aspirina/administração & dosagem , Aspirina/sangue , Teorema de Bayes , Biomarcadores Farmacológicos/sangue , Cromatografia/métodos , Desipramina/administração & dosagem , Desipramina/sangue , Ejaculação/efeitos dos fármacos , Frutose/sangue , Infecções por HIV/diagnóstico , Infecções por HIV/metabolismo , Humanos , Masculino , Pessoa de Meia-Idade , Pacientes Ambulatoriais , Antígeno Prostático Específico/sangue , Reprodutibilidade dos Testes , Salicilatos/sangue , Sêmen/metabolismo , Disfunções Sexuais Fisiológicas/sangue , Disfunções Sexuais Fisiológicas/diagnóstico , Espectrometria de Massas em Tandem/métodosRESUMO
Food can change drug concentrations by several mechanisms, including some that are independent of absorption effects. This study tests the hypothesis that a meal decreases zidovudine (ZDV) concentration in blood plasma independent of an effect on drug absorption. The study was conducted as a substudy nested in a larger protocol in which ZDV was given to 7 healthy men by continuous infusion for 5 days starting on day 1. The subjects received only a standardized breakfast meal on day 2 and were fasted on day 3 until the 8-hour sampling period each day was finished. Blood samples were collected through an indwelling cannula in the arm contralateral to the ZDV infusion at the same time of day on both days. It was found that food decreased the blood plasma ZDV concentration at 1 hour postprandial by 14% (5.0%-22%; geometric mean change with 95% confidence interval). This decrease recovered by 6 hours postprandial. Similar changes were seen with the ZDV primary metabolite, zidovudine glucuronide. The authors conclude that food decreases blood plasma ZDV concentrations independent of any absorption effects. This effect may be due to the increased hepatic metabolism because feeding increases hepatic blood flow and because ZDV has a high hepatic extraction ratio with low affinity to blood plasma proteins.
Assuntos
Ingestão de Alimentos , Absorção Intestinal , Fígado/metabolismo , Período Pós-Prandial , Inibidores da Transcriptase Reversa/farmacocinética , Zidovudina/farmacocinética , Alimentos , Humanos , Masculino , Fatores de TempoRESUMO
A series of exceptionally potent agonists at neuronal nicotinic acetylcholine receptors (nAChRs) has been investigated. Several N-(3-pyridinyl) derivatives of bridged bicyclic diamines exhibit double-digit-picomolar binding affinities for the alpha 4 beta 2 subtype, placing them with epibatidine among the most potent nAChR ligands described to date. Structure-activity studies have revealed that substitutions, particularly hydrophilic groups in the pyridine 5-position, differentially modulate the agonist activity at ganglionic vs central nAChR subtypes, so that improved subtype selectivity can be demonstrated in vitro. Analgesic efficacy has been achieved across a broad range of pain states, including rodent models of acute thermal nociception, persistent pain, and neuropathic allodynia. Unfortunately, the hydrophilic pyridine substituents that were shown to enhance agonist selectivity for central nAChRs in vitro tend to limit CNS penetration in vivo, so that analgesic efficacy with an improved therapeutic window was not realized with those compounds.
Assuntos
Analgésicos/síntese química , Diaminas/síntese química , Compostos Heterocíclicos de Anel em Ponte/síntese química , Agonistas Nicotínicos/síntese química , Piridinas/síntese química , Analgésicos/química , Analgésicos/farmacologia , Animais , Ligação Competitiva , Encéfalo/efeitos dos fármacos , Encéfalo/metabolismo , Linhagem Celular , Diaminas/química , Diaminas/farmacologia , Dopamina/metabolismo , Compostos Heterocíclicos de Anel em Ponte/química , Compostos Heterocíclicos de Anel em Ponte/farmacologia , Técnicas In Vitro , Ligantes , Modelos Moleculares , Agonistas Nicotínicos/química , Agonistas Nicotínicos/farmacologia , Dor/tratamento farmacológico , Dor/etiologia , Medição da Dor , Doenças do Sistema Nervoso Periférico/tratamento farmacológico , Piridinas/química , Piridinas/farmacologia , Ratos , Receptores Nicotínicos/metabolismo , Estereoisomerismo , Relação Estrutura-AtividadeRESUMO
AMD070 is an oral CXCR4 antagonist with in vitro activity against X4-tropic human immunodeficiency virus type 1. Thirty fasting healthy male volunteers received oral doses of AMD070 ranging from a single 50-mg dose to seven 400-mg doses given every 12 h (q12h). Nine subjects received a 200-mg dose during fasting and prior to a meal. Subjects were monitored for safety and pharmacokinetics. AMD070 was well tolerated, without serious adverse events. Transient headaches (13 subjects) and neurocognitive (8 subjects) and gastrointestinal (7 subjects) symptoms were the most common complaints. Seven subjects had sinus tachycardia, and two were symptomatic. AMD070 plasma concentrations peaked 1 to 2 h after patient dosing. The estimated terminal half-life ranged from 11.2 to 15.9 h among cohorts. Dose proportionality was not demonstrated. Less than 1% of the drug appeared unchanged in the urine. Food reduced the maximum concentration of drug in serum and the area under the concentration-time curve from 0 to 24 h by 70% and 56%, respectively (P < or = 0.01). A dose-dependent elevation of white blood cells (WBC) demonstrated a maximum twofold increase over baseline (95% confidence interval, 2.0- to 2.1-fold) in an E(max) model. In healthy volunteers, AMD070 was well tolerated and demonstrated mixed-order pharmacokinetics, and food reduced drug exposure. AMD070 induced a dose-related elevation of WBC which was attributed to CXCR4 blockade. Using leukocytosis as a surrogate marker for CXCR4 inhibition, this dose-response relationship suggests that the doses used in this study were active in vivo, though not maximal, throughout the dosing interval. Trough concentrations with the 400-mg dose q12h exceeded the antiviral in vitro 90% effective concentration of AMD070.
Assuntos
Compostos Heterocíclicos com 1 Anel/administração & dosagem , Compostos Heterocíclicos com 1 Anel/farmacocinética , Receptores CXCR4/antagonistas & inibidores , Administração Oral , Adolescente , Adulto , Aminoquinolinas , Área Sob a Curva , Benzimidazóis , Butilaminas , Estudos de Coortes , Relação Dose-Resposta a Droga , Jejum , Meia-Vida , Cefaleia/induzido quimicamente , Compostos Heterocíclicos com 1 Anel/efeitos adversos , Compostos Heterocíclicos com 1 Anel/sangue , Compostos Heterocíclicos com 1 Anel/urina , Humanos , Leucócitos/efeitos dos fármacos , Masculino , Pessoa de Meia-Idade , Fatores de TempoRESUMO
Different nicotinic acetylcholine receptor subtypes appear to modulate dopamine release from the striatum and prefrontal cortex. In this study a combination of subtype-selective antagonists and agonists were used to extensively characterize the nAChRs involved in dopamine release from slice preparations of these two brain regions. alpha-conotoxin-MII inhibited nicotine-evoked [3H]dopamine (DA) release from striatum by 45%, but did not affect cortical dopamine release. Neither methyllycaconitine, alpha-bungarotoxin, nor alpha-conotoxin-ImI affected nicotine-evoked [3H]DA release from either striatum or prefrontal cortex. MG 624, a novel selective nAChR antagonist, inhibited cortical [3H]DA by 53%, but had no effect on striatal release. Compared to nicotine, (+/-)-UB-165 showed less efficacy with respect to dopamine release from striatum, and had no effect on cortical dopamine release. (+/-)-UB-165-evoked striatal dopamine release was completely blocked by mecamylamine, partially blocked (up to 55%) by alpha-conotoxin-MII, and unaffected by methyllycaconitine or alpha-conotoxin-ImI. alpha4beta2* and alpha6beta2beta3* nAChRs appear to play a role in striatal dopamine release, whereas alpha4beta2* nAChRs modulate release from prefrontal cortex. alpha7* nAChRs do not appear to play a role in nAChR-mediated dopamine release from either brain region.
Assuntos
Química Encefálica/fisiologia , Corpo Estriado/metabolismo , Dopamina/metabolismo , Córtex Pré-Frontal/metabolismo , Receptores Nicotínicos/fisiologia , Animais , Química Encefálica/efeitos dos fármacos , Hidrocarbonetos Aromáticos com Pontes/farmacologia , Bungarotoxinas/farmacologia , Conotoxinas/farmacologia , Relação Dose-Resposta a Droga , Interações Medicamentosas , Masculino , Nicotina/farmacologia , Agonistas Nicotínicos/farmacologia , Antagonistas Nicotínicos/farmacologia , Piridinas/farmacologia , Compostos de Amônio Quaternário/farmacologia , Ratos , Ratos Sprague-Dawley , Receptores Nicotínicos/classificação , Estilbenos/farmacologia , Trítio/metabolismoRESUMO
The mechanism of nicotinic acetylcholine receptor (nAChR)-induced hippocampal dopamine (DA) release was investigated using rat hippocampal slices. nAChRs involved in hippocampal DA and norepinephrine (NE) release were investigated using prototypical agonists and antagonists and several relatively novel compounds: ABT-594 [(R)-5-(2-azetidinylmethoxy)-2-chloropyridine], (+/-)-UB-165 [(2-chloro-5-pyridyl)-9-azabicyclo [4.2.1]non2-ene], and MG 624 [N,N,N-triethyl-2-[4-(2 phenylethenyl)phenoxy]-ethanaminium iodine]. (+/-)-Epibatidine, (+/-)-UB-165, anatoxin-a, ABT-594, (-)-nicotine, 1,1-dimethyl-4-phenyl-piperazinium iodide, and (-)-cytisine (in decreasing order of potency) evoked [(3)H]DA release in a mecamylamine-sensitive manner. Aside from (+/-)-UB-165, all the agonists displayed full efficacy relative to 100 microM (-)-nicotine in [(3)H]DA release. In contrast, (+/-)-UB-165 was a partial agonist, evoking 58% of 100 microM (-)-nicotine response. Mecamylamine, MG 624, hexamethonium, d-tubocurare, and dihydro-beta-erythroidine (in decreasing order of potency), but not alpha-conotoxin-MII, methyllycaconitine, alpha-conotoxin-ImI, or alpha-bungarotoxin, attenuated 100 microM (-)-nicotine-evoked [(3)H]DA release in a concentration-dependent manner. (+/-)-UB-165, ABT-594, and MG 624 exhibited different pharmacologic profiles in the [(3)H]NE release assay when compared with their effect on [(3)H]DA release. ABT-594 was 4.5-fold more potent, and (+/-)-UB-165 was a full agonist in contrast to its partial agonism in [(3)H]DA release. MG 624 potently and completely blocked NE release evoked by 100 microM (-)-nicotine and 10 microM (+/-)-UB-165, whereas it only partially inhibited (-)-nicotine-evoked [(3)H]DA release. In conclusion, we provide evidence that [(3)H]DA can be evoked from the hippocampus and that the pharmacologic profile for nAChR-evoked hippocampal [(3)H]DA release suggests the involvement of alpha3beta4(*) and at least one other nAChR subtype, thus distinguishing it from that of nAChR-evoked hippocampal [(3)H]NE release.
Assuntos
Dopamina/metabolismo , Hipocampo/metabolismo , Receptores Nicotínicos/fisiologia , Animais , Azetidinas/farmacologia , Hidrocarbonetos Aromáticos com Pontes/farmacologia , Masculino , Antagonistas Nicotínicos/farmacologia , Norepinefrina/metabolismo , Piridinas/farmacologia , Compostos de Amônio Quaternário/farmacologia , Ratos , Ratos Sprague-Dawley , Estilbenos/farmacologia , Receptor Nicotínico de Acetilcolina alfa7RESUMO
Small conductance, Ca(2+)-activated K(+) channels (SK channels) regulate neuronal excitability. We used patch clamp to study the actions of the neuroprotective drug riluzole on recombinant SK2 channels expressed in HEK293 cells and native SK channels underlying the afterhyperpolarization current (I(AHP)) in cultured hippocampal neurons. External riluzole activated whole-cell SK2 channel currents in HEK293 cells dialyzed with a Ca(2+)-free intracellular solution. When applied to the intracellular aspect of the membrane of giant inside-out patches, riluzole enhanced the membrane current activated by 100 nM Ca(2+) in a reversible and concentration-dependent manner; 30 microM riluzole applied to the intracellular aspect of the patches sensitized the channels to activation by Ca(2+), resulting in a leftward shift of the Ca(2+) activation curve. Riluzole also enhanced the I(AHP) and reduced the spontaneous action potential frequency in chemically stimulated neurons. Modulation of SK channel activity by riluzole may contribute to its cellular, behavioral, and clinical effects.