RESUMO
A series of N-benzylpiperidines (2a-d, 10) with novel isoxazole-containing tricycles has been prepared. This series has shown potent in vitro inhibition of the enzyme acetylcholinesterase (AChE), with IC50S = 0.33 - 3.6 nM. Compound 2a was the most potent inhibitor with an IC50 = 0.33 +/- 0.09 nM. Derivatives 2a-d and 10 displayed weak in vitro inhibition of butyrylcholinesterase (BuChE) with IC50S = 600 - 23,000 nM. The most selective compound was 2a with a BuChE/AChE ratio in excess of 4 orders of magnitude (> 10,000). Pyrrolobenzisoxazole 2a also displayed a favorable profile in vivo. In microdialysis experiments, 2a produced a 200% increase in extracellular levels of acetylcholine (ACh) at a dose of 0.4 mg/kg in freely moving, conscious rats. Peripheral side effects (salivation ED50 = 26 +/- 1.5 mg/kg) and acute lethality (LD50[1 h] = 42 mg/kg) were observed at > 60-fold higher doses. These data indicate that 2a is an AChE inhibitor with good central selectivity and a favorable margin of safety. Compound 2a, designated as CP-118,954, is currently in clinical development for the treatment of cognitive disorders.
Assuntos
Inibidores da Colinesterase/síntese química , Inibidores da Colinesterase/farmacologia , Isoxazóis/síntese química , Isoxazóis/farmacologia , Piperidinas/síntese química , Piperidinas/farmacologia , Animais , Butirilcolinesterase , Inibidores da Colinesterase/toxicidade , Isoxazóis/toxicidade , Masculino , Piperidinas/toxicidade , Ratos , Ratos Sprague-Dawley , Relação Estrutura-Atividade , Tacrina/farmacologia , Tacrina/toxicidadeRESUMO
The major signal transduction pathway for neurotensin (NT) receptors is the G-protein-dependent stimulation of phospholipase C, leading to the mobilization of intracellular free Ca2+ ([Ca2+]i) and the stimulation of cyclic GMP. We investigated the functional actions of an analog of NT(8-13), N alpha MeArg-Lys-Pro-Trp-tLeu-Leu (NT1), and other NT related analogs by quantitative measurement of the cytosolic free Ca2+ concentration in HT-29 (human colonic adenocarcinoma) cells using the Ca(2+)-sensitive dye fura-2/AM and by effects on cyclic GMP levels in rat cerebellar slices. The NT receptor binding affinities for these analogs to HT-29 cell membranes and newborn (10-day-old) mouse brain membranes were also investigated. Data obtained from HT-29 cell and mouse brain membrane preparations showed saturable single high-affinity sites and binding densities (Bmax) of 130.2 and 87.5 fmol/mg protein, respectively. The respective KD values were 0.47 and 0.39 nM, and the Hill coefficients were 0.99 and 0.92. The low-affinity levocabastine-sensitive site was not present (K1 > 10,000) in either membrane preparation. Although the correlation of binding between HT-29 cell membranes and mouse brain membranes was quite significant (r = 0.92), some of the reference agents had lower binding affinities in the HT-29 cell membranes. The metabolically stable compound NT1 plus other NT analogs and related peptides [NT, NT(8-13), xenopsin, neuromedin N, NT(9-13), kinetensin and (D-Trp11)-NT] increased intracellular Ca2+ levels in HT-29 cells, indicating NT receptor agonist properties. The effect of NT1 in mobilizing [Ca2+]i blocked by SR 48692, a non-peptide NT antagonist. Receptor binding affinities of NT analogs to HT-29 cell membranes were positively correlated with potencies for mobilizing intracellular calcium in the same cells. In addition, NT1 increased cyclic GMP levels in rat cerebellar slices, confirming the latter findings of its NT agonist action. These results substantiate the in vitro NT agonist properties of the hexapeptide NT analog NT1.
Assuntos
Química Encefálica , Cálcio/metabolismo , GMP Cíclico/biossíntese , Neurotensina/análogos & derivados , Oligopeptídeos/farmacologia , Receptores de Neurotensina/agonistas , Sequência de Aminoácidos , Animais , Animais Recém-Nascidos , Linhagem Celular/metabolismo , Membrana Celular/metabolismo , Humanos , Camundongos , Dados de Sequência Molecular , Neurotensina/fisiologia , Receptores de Neurotensina/metabolismoRESUMO
AIMS: To determine whether ziprasidone alters the metabolizing activity of the 2D6 isoenzyme of cytochrome P450 (CYP2D6). METHODS: Twenty-four healthy young subjects aged 18-45 years were screened for CYP2D6 metabolizing activity and shown to be extensive metabolizers of dextromethorphan. These subjects were then randomized to receive a single dose of ziprasidone 80 mg, paroxetine 20 mg or placebo, 2 h before receiving a dose of dextromethorphan. Urine samples for the determination of dextromethorphan concentrations were collected over the 8 h period following dextromethorphan dosing, and used for the determination of dextromethorphan/dextrorphan ratios. Blood samples were collected immediately before and up to 10 h after the administration of ziprasidone or paroxetine, and used to derive pharmacokinetic parameters of ziprasidone and paroxetine. RESULTS: There were no statistically significant changes in the urinary dextromethorphan/dextrorphan ratio in the ziprasidone group or the placebo group. By contrast, there was a 10-fold increase in the urinary dextromethorphan/dextrorphan ratio in the paroxetine group and this differed significantly from those in the ziprasidone and placebo groups (P = 0.0001). CONCLUSIONS: The findings of this study suggest that ziprasidone does not inhibit the clearance of drugs metabolized by CYP2D6.
Assuntos
Antipsicóticos/farmacologia , Antipsicóticos/farmacocinética , Inibidores do Citocromo P-450 CYP2D6 , Inibidores Enzimáticos/farmacologia , Piperazinas/farmacologia , Piperazinas/farmacocinética , Tiazóis/farmacologia , Tiazóis/farmacocinética , Adolescente , Adulto , Antipsicóticos/sangue , Área Sob a Curva , Citocromo P-450 CYP2D6/metabolismo , Dextrometorfano/farmacocinética , Interações Medicamentosas , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Paroxetina/sangue , Paroxetina/farmacologia , Piperazinas/sangue , Inibidores Seletivos de Recaptação de Serotonina/sangue , Inibidores Seletivos de Recaptação de Serotonina/farmacologia , Tiazóis/sangueRESUMO
The localization of quaternized muscarinic receptor (mAChR) antagonists, [11C]methyl tropanyl benzilate ([11C]MTRB) and [11C]methyl quinuclidinyl benzilate ([11C]MQNB), in rat pituitary was compared to that of [11C]tropanyl benzilate ([11C]TRB), a neutral antagonist. The quaternized ligands localize via a mAChR-mediated mechanism as shown by 60% reduction in radioactivity concentrations in the presence of QNB. [11C]TRB appears to localize primarily by a non-mAChR specific mechanism. Induction of pituitary prolactinomas by diethylstilbestrol resulted in a reduction of [11C]MTRB pituitary localization compared to normals. Elevated serum prolactin levels due to prolactinoma presence had no measurable effect on myocardial [11C]MTRB uptake or on KD values. Bmax values for myocardial mAChR were similar for controls and for DES exposure of 10 weeks.
Assuntos
Dietilestilbestrol/farmacologia , Ligantes , Parassimpatomiméticos , Receptores Muscarínicos/efeitos dos fármacos , Animais , Encéfalo/metabolismo , Estudos de Avaliação como Assunto , Feminino , Miocárdio/metabolismo , Hipófise/metabolismo , Quinuclidinil Benzilato/análogos & derivados , Quinuclidinil Benzilato/farmacologia , Ratos , Ratos Endogâmicos F344 , Distribuição Tecidual , Tropanos/farmacocinéticaRESUMO
The receptor binding and biochemical effects of the putative dopamine (DA) partial agonist CI-1007 ([R(+)-1,2,3,6-tetrahydro-4-phenyl- 1-[(3-phenyl-3-cyclohexen-1-yl)methyl]pyridine] maleate) and potential antipsychotic were evaluated with a variety of biochemical methods. In receptor binding studies, CI-1007 bound to rat striatal DA receptors exhibiting a Ki of 3 nM as assessed by inhibition of [3H]N-propylnorapomorphine binding. CI-1007 also exhibited high affinity for cloned human D2L (Ki = 25.5 nM) and D3 (Ki = 16.6 nM) receptors with less affinity for D4.2 receptors (Ki = 90.9 nM). The affinity for serotonin-1A (5-HT-1A), alpha-2 adrenergic and 5-HT-2 receptors was moderate (submicromolar range) and slight or negligible for alpha-1, DA D1 and various other receptors. Unlike dopamine, the inhibition of [3H]spiperone binding was monophasic for CI-1007 and only slightly affected by the addition of Gpp-(NH)p. In vitro CI-1007 antagonized the forskolin-induced increases in cyclic AMP levels in GH4C1 cells expressing the human D2L receptor, having an intrinsic activity of 53% of that seen with the full agonist quinpirole. In vivo CI-1007 antagonized the gamma-butyrolactone (GBL)-induced accumulation of L-3,4-dihydroxyphenylalanine in striatum and mesolimbic regions of rat brain, causing a maximal 64% reversal in striatum, consistent with a partial agonist profile. In microdialysis studies it decreased DA overflow in both striatum and nucleus accumbens, indicating decreased release of DA. CI-1007 also reduced brain DA synthesis (DOPA accumulation), metabolism (DOPAC and HVA) and utilization (after tyrosine hydroxylase inhibition with alpha-methyl-p-tyrosine). CI-1007 did not affect striatal acetylcholine levels indicating lack of potent postsynaptic DA actions. CI-1007 seemed to be selective for DA neurons as it did not alter rat brain norepinephrine (NE) synthesis in the NE-enriched brainstem or NE utilization in the mesolimbic region. In addition, it did not affect in general 5-HT synthesis and metabolism in striatum and mesolimbic regions. These neurochemical results demonstrate that CI-1007 is a selective potent brain dopamine partial agonist with limited agonist activity at postsynaptic DA receptors.