Effect of SC-41930, a potent selective leukotriene B4 receptor antagonist, in the guinea pig model of middle ear inflammation

Arachidonic acid metabolites such as prostaglandins and leukotrienes have been shown to play an important role in the pathogenesis of otitis media (OM). Among these mediators, leukotriene B4 (LTB4) is one of the most potent inducers of inflammatory processes. SC-41930 has been shown to be a specific LTB4 receptor antagonist both in vitro and in vivo. In this study, anti-inflammatory effects of SC-41930 were investigated in a guinea pig model of OM induced by middle ear (ME) inoculation of killed Staphylococcus aureus. Outcome of treatment was determined by measurement of myeloperoxidase activity in the samples of ME mucosa, evaluation of temporal bone histopathology, and presence of ME fluids. Myeloperoxidase activity in the SC-41930-treated group was found to be significantly lower than that in the control group. Histopathology of temporal bones indicated decreased inflammation in the treated group as compared to the controls. In addition, ME fluids were absent in four out of six treated animals. These results demonstrate that SC-41930 can produce significant anti-inflammatory effects in this model of OM.     

A potent nonpeptide neuropeptide Y Y1 receptor antagonist, a benzodiazepine derivative

We describe here a nonpeptide neuropeptide Y Y1 receptor antagonist, 2,4-dioxo-1,5-bis(2-oxo-2-orthotolyl-ethyl)-3-[3-[3-([3-[3-(3-p iperidin-1-ylmethyl-phenoxy)-propylcarbamoyl]-propyl]-car bamoyloxymethyl)-phenyl]-ureido]-2,3,4,5-tetrahydro-1H-benzo[b][1,4]diaz epine (Compound 1), which was previously synthesized as a linked type of dual cholecystokinin (CCK)-B and histamine H2 receptor antagonist. Compound 1 competitively inhibited [125I]peptide YY (PYY) binding to Y1 receptors in human neuroblastoma SK-N-MC cells with Ki of 6.4 +/- 1.0 nM, while it had no effect on [125I]PYY binding to Y2 or Y5 receptors even at 1 microM. Functionally, Compound 1 inhibited the Y1 receptor-mediated increase in cytosolic free Ca2+ concentration and Y1 receptor-mediated attenuation of cAMP accumulation in a dose-dependent manner with IC50 values of 95 +/- 5 and 320 +/- 10 nM in SK-N-MC cells, respectively. Neither its CCK-B receptor antagonistic moiety of Compound 1 (Compound 2) nor its histamine H2 receptor antagonistic moiety of Compound 1 (Compound 3) had any effect on [125I]PYY binding, suggesting that the entire structure of Compound 1 is essential for Y1 receptor blocking activity. It showed no significant activity (IC50 > 1 microM) in 30 receptor binding assays and 5 enzyme assays, with the exception of CCK-B and histamine H2 receptors. We conclude that Compound 1 is a useful molecule not only for studying the physiological role of neuropeptide Y but also for exploring more specific Y1 receptor antagonists.     

New drugs in asthma treatment. Leukotriene receptor blockers and leukotriene synthesis inhibitors

Asthma is an inflammatory airway disease. The patient is characterised by increased mucus secretion, mucosal oedema, bronchial obstruction of varying degree and bronchial hyperresponsiveness. Several cell types and a large number of mediators are involved in asthma-related inflammation and constriction of the airways. The leukotrienes constitute an important group of mediators in asthmatic inflammation. The study of specific leukotriene receptor antagonists and biosynthesis inhibitors has not only shed light on the underlying mechanisms in asthma, but also opened up the way to new treatment alternatives. As zafirlukast, a leukotriene receptor antagonist has just been licensed in Finland, it is a suitable opportunity to review the importance of leukotrienes in asthma and the use of agents that affect them.     

ZD1542, a potent thromboxane A2 synthase inhibitor and receptor antagonist in vitro

1. The thromboxane A2 synthase (TXS) inhibitory activity and the thromboxane A2 (TP)-receptor blocking action of ZD1542 (4(Z)-6-[2S,4S,5R)-2-[1-methyl-1-(2-nitro-4-tolyloxy)ethyl]-4-(3- pyridyl)-1,3-dioxan-5-yl]hex-4-enoic acid) has been evaluated in vitro on platelets and whole blood from a range of species including man. Antagonist activity has also been investigated in vascular and pulmonary smooth muscle preparations in vitro. 2. ZD1542 caused concentration-dependent inhibition of human platelet microsomal thromboxane B2 (TXB2) production in vitro (IC50 = 0.016 microM); this inhibition was associated with an increase in prostaglandin E2 (PGE2) and PGF2 alpha formation. 3. ZD1542 also inhibited collagen-stimulated TXS in human, rat and dog whole blood giving IC50 values of 0.018, 0.009 and 0.049 microM respectively. The drug did not modify platelet cyclo-oxygenase activity as inhibition of TXB2 formation was associated with a concomitant increase in the levels of PGD2, PGE2 and PGF2 alpha. ZD1542 had little if any effect against cultured human umbilical vein endothelial cell (HUVEC) cyclo-oxygenase (IC50 > 100 microM) and prostacyclin (PGI2) synthase (IC50 = 18.0 +/- 8.6 microM). 4. ZD1542 caused concentration-dependent inhibition of U46619-induced aggregation responses of human, rat and dog platelets yielding apparent pA2 values of 8.3, 8.5 and 9.1 respectively. The drug was selective as, at concentrations up to 100 microM, it did not modify 5-hydroxytryptamine (5-HT) or the primary phases of adenosine diphosphate (ADP) and adrenaline-induced aggregation. Furthermore, ZD1542 (100 microM) modified only weakly the platelet effects of PGD2, PGE1 and PGI2. 5. ZD1542 also caused concentration-dependent inhibition of U46619-mediated contractions of rat thoracic aorta, guinea-pig trachea and lung parenchyma preparations giving apparent pA2 values of 8.6,8.3 and 8.5 respectively. At concentrations approaching three orders of magnitude greater than those required to block U46619-mediated contractions, the drug did not affect the actions of non-prostanoid agonists or exhibit agonist activity in any of the smooth muscle preparations employed; neither did it interact at EP- or FP-receptors.6. In conclusion, the present study demonstrates that ZD1542 is a drug that exhibits both potent,selective TXS inhibition and TXA2 receptor antagonism.     

X-ray structural characterization of SR 142948, a novel potent synthetic neurotensin receptor antagonist

In ob/ob mice, leptin deficiency results in hypogonadotrophic hypogonadism, impaired sexual maturation and infertility, which are all corrected by leptin administration. In humans, pubertal development and menarche are related to the attainment of a critical amount of body fat. To examine whether changes in circulating concentrations of leptin could be a hormonal signal influencing gonadotrophin secretion, we studied 98 adolescents and young adults of both sexes, aged 13-19 years, whose weight varied from normal to massively obese and whose sexual maturation was between Tanner stages 3 and 5. We measured leptin, sex steroids and circulating gonadotrophin concentrations in the basal state and in response to GnRH. In perimenarchial and young adult girls, we found that the LH and FSH responses to GnRH were negatively correlated with body mass index (BMI: r = -0.45 and -0.47 respectively, P < 0.0025) and circulating leptin (r = -0.53 and -0.49 respectively, P < 0.002). Decreased LH and FSH responses to GnRH were associated with increased adiposity and hyperleptinaemia. Our data do not establish, but are consistent with a direct neuroendocrine negative effect of excess leptin on the central reproductive system of obese girls. In boys of comparable adiposity, we found no influence of BMI or leptin on gonadotrophin concentrations, which is another aspect of the sexual dimorphism characterizing human leptin physiology.     

Pharmacological profile of T-0201, a highly potent and orally active endothelin receptor antagonist

The authors studied the pharmacological properties of N-(6-(2-(5-bromopyrimidin-4-yl)-4-(2-hydroxy-1, 1-dimethylethyl)benzensulfonamide sodium salt sesquihydrate (T-0201), a new nonpeptide endothelin (ET) receptor antagonist, in vitro and in vivo. In binding studies, T-0201 competitively antagonized the specific binding of [125I]-ET-1 to human cloned ETA receptors (the Ki value was 0.015 +/- 0.004 nM). T-0201 weakly inhibited [125I]-ET-1-binding to human cloned ETB receptors; the Ki value was 41 +/- 21 nM. T-0201 shifted the concentration-response curve of ET-1-induced contraction of the isolated rat aorta (ETA receptors) to the right (pA2 = 9.0 +/- 0.2). In the isolated rat trachea, a selective ETB agonist sarafotoxin S6c-induced contraction was inhibited by T-0201 (pA2 = 6.8 +/- 0.3). T-0201 also caused the inhibition of ET-1-induced contraction of the isolated rabbit pulmonary artery (pA2 = 5.7 +/- 0.3). In anesthetized rats, T-0201 (0.01-1 mg/kg) inhibited the pressor response to exogenous big ET-1 (1 nmol/kg i.v.), after both i.v. and p.o. administration, in a dose-dependent manner. The significant inhibitory effect of orally administered T-0201 on big ET-1-induced pressor response lasted for 4 hr at 0.1 mg/kg and for 8 hr at 1 mg/kg. Thus the present study demonstrates that T-0201 is a highly potent, long-lasting, orally active and selective ETA receptor antagonist.     

A leukotriene receptor antagonist, ONO-1078, modulates drug sensitivity and leukotriene C4 efflux in lung cancer cells expressing multidrug resistance protein

In this preliminary observation, a group of seven mentally and physically handicapped persons of chronological ages ranging from 15.4 yr. to 26.8 yr. experienced 15 sec. of physical rocking. For the further analysis, the poststimulus periods were classified into either those when the subjects' spontaneous head, mouth, and body movements had increased from the prestimulus period or those decreased. The median heart rates recorded in the poststimulus period were not significantly different from those in the prestimulus period on trials on which there was an observable increase in the rates of spontaneous head, mouth, and body movements; however, the median heart rates decreased during those trials on which a decrease in the rates of the movements occurred. Since it is said that rocking heightens arousal of persons with mental and physical handicaps, it is suggested that spontaneously emitted, aimless head, mouth, and body movements attributed to low arousal were reduced by heightened arousal rather than by a decline in participants' activities.     

SB209670, a potent endothelin receptor antagonist, prevents or delays axonal degeneration after spinal cord injury

We developed a rat spinal cord transection injury model and investigated whether endogenous endothelin takes part in axonal degeneration after injury, by using a potent nonselective endothelin receptor antagonist, SB209670. Light microscopic analysis showed that axonal degeneration of the spinal cord was clearly observed one week after injury, supported by immunohistochemical study with anti-neurofilament antibody. Electron microscopic observation showed enlargement and shrinking of spinal axons in the injured sites one week after injury. Application of SB209670 to the lesion sites markedly inhibited axonal damage after injury. These results suggest that endogenous endothelin plays a role in axonal degeneration after spinal cord injury and that SB209670 prevents or delays the axonal degeneration after CNS damage.     

Effects of cysteinyl-leukotriene receptor antagonist, thromboxane A2 receptor antagonist, and thromboxane A2 synthetase inhibitor on antigen-induced bronchoconstriction in patients with asthma

BACKGROUND: Leukotriene (LT) and thromboxane A2 (TXA2) receptor antagonists have been used in the treatment of asthma. OBJECTIVES: We examined the effects of an LT receptor antagonist, TXA2 receptor antagonist, and TXA2 synthetase inhibitor on bronchoprovocation test (BPT) in patients with mild-to-moderate atopic asthma. METHODS: BPT was performed four times in each of six asthmatics. Development of the immediate asthmatic reaction (IAR) and late asthmatic reaction (LAR) was confirmed on the first BPT (BPT1). After a 7-day washout period, an LT receptor antagonist (pranlukast, 450 mg/d), TXA2 receptor antagonist (seratrodast, 80 mg/d), or TXA2 synthetase inhibitor (ozagrel, 800 mg/d) was administered orally over 7 days at random using a cross-over method (BPT2-4). Blood levels of LTB4, LTC4, LTD4, 11-dehydrothromboxane B2, eosinophil cationic protein, and histamine were measured at reaction phases of pre-BPT, IAR, and LAR. RESULTS: Administration of pranlukast suppressed IAR by 80.5% (p < 0.0001) and LAR by 54.6% (p = 0.0391). Ozagrel significantly suppressed IAR by 39.5% (p = 0.0413), but the fall in FEV1 was >20% (21.56+/-4.173%). Seratrodast did not suppress IAR or LAR. Blood levels of chemical mediators did not correlate with the suppressive effects of the tested drugs. CONCLUSIONS: The LT receptor antagonist was considered to be the most effective. LT might play a more important role in the pathogenesis of asthma than TXA2. Our data showed that measurement of blood levels of chemical mediators is not useful in identifying the pathogenic mechanisms of asthma.     

European study of asthma. Prevalence of atopy in young adults of 5 areas in Spain. Spanish Group of European Asthma Study

BACKGROUND: The aim of the current study is to show the prevalence of atopy in five Spanish areas, and its variability according to area, age and gender. PATIENTS AND METHODS: From a populational based sample of 16,884 individuals aged 20 to 44 years-old, we obtained a randomized 20% subsample (n = 3,310). Participants performed specific IgE measurements, skin prick tests, forced spirometries and metacholine challenges to measure bronchial hyperresponsiveness. The response rate was 40%, and 1,313 individuals were finally included in the study. Specific atopy to the following aeroallargens was determined: cat dander, Cladosporium, Dermatophagoides, Phleum, Parietaria, birch, Alternaria, ambrosia, olive, rye grass and dog dander. RESULTS: The global prevalence of atopy (detectable specific antibodies IgE in serum and/or skin reactivity) widely varied by area, skin reactivity ranking in males from a minimum in Albacete (24.6%; 95% CI: 18-33) to a maximum in Huelva (39.6%; 95% CI: 30-53), and in females ranking from a minimun in Galdakao (10.3%; 95% CI: 6-17) to a maximum in Barcelona (28.8%; 95% CI: 19-43). Considering separately seropositivity and skin reactivity we observed a similar trend. Males showed a higher prevalence of global atopy (40.1%) than females (29.4%). Our data indicate that there is a decrease in the prevalence of atopy according to age in the general population, but only significant in men. Dermatophagoides pteronyssinus is the most common allergen in all ares but Albacete, where the most common allergen is the olive pollen. CONCLUSIONS: By means of a standard methodology, we report population data of the prevalence of atopy in five Spanish areas. The distribution of the prevalence of atopy varies widely in the five areas surveyed, according to the composition of the most common environmental allergens.     

Oral glucocorticosteroid-sparing effect of budesonide administered by Turbuhaler: a double-blind, placebo-controlled study in adults with moderate-to-severe chronic asthma. Pulmicort Turbuhaler Study Group

The purpose of this study was to evaluate the correlation between alteration in telomere length and prognosis in patients with pathological stage I-II non-small cell lung cancer. We measured telomeric repeat length and telomerase activity by use of southern blot analysis of terminal restriction fragments and a non-radioactive ELISA-based assay, respectively. RESULTS: Alterations in TRF lengths were present in 17(29.8%) of 57 patients. Patients with altered TRF length had significantly shorter survival than did patients without (P = 0.0051). In multivariate analysis, only alteration in TRF length independently correlated with shortened survival (P = 0.0033).     

YF476 is a new potent and selective gastrin/cholecystokinin-B receptor antagonist in vitro and in vivo

Controversy exists as to whether the diabetic heart is more or less sensitive to ischemic injury. Although a considerable number of experimental studies have directly determined the effects of ischemia on the diabetic heart, there is still no general agreement as to whether metabolic changes within the myocardium contribute to the severity of ischemic injury. This paper reviews the evidence suggesting that the diabetic heart can actually be less sensitive to an episode of severe ischemia. Possible reasons for this decreased sensitivity to injury are discussed, which include a decreased accumulation of glycolytic products during ischemia (lactate and protons), as well as alterations in the regulation of intracellular pH in the diabetic heart. Based on existing studies, we suggest that although impaired glucose metabolism in the diabetic heart contributes to injury in hypoxic hearts or in hearts subjected to low-flow ischemia, diabetes-induced decreases in glycolysis can actually be beneficial to the diabetic heart during and following a severe ischemic episode. A decreased clearance of protons via the Na+/H+ exchanger may also contribute to the decreased sensitivity to ischemic injury in the diabetic heart.     

Effects of iodoproxyfan, a potent and selective histamine H3 receptor antagonist, on alpha 2 and 5-HT3 receptors

We determined the affinity and/or potency of the novel H3 receptor antagonist iodoproxyfan at alpha 2 and 5-HT3 receptors. Iodoproxyfan and rauwolscine (a reference alpha 2 ligand) (i) monophasically displaced 3H-rauwolscine binding to rat brain cortex membranes (pKi 6.79 and 8.59); (ii) facilitated the electrically evoked tritium overflow from superfused mouse brain cortex slices preincubated with 3H-noradrenaline (pEC50 6.46 and 7.91) and (iii) produced rightward shifts of the concentration-response curve (CRC) of (unlabelled) noradrenaline for its inhibitory effect on the evoked overflow (pA2 6.65 and 7.88). In the guinea-pig ileum, iodoproxyfan 6.3 mumol/l failed to evoke a contraction by itself but depressed the maximum of the CRC of 5-hydroxytryptamine (pD'2 5.24). Tropisetron (a reference 5-HT3 antagonist) produced rightward shifts of the CRC of 5-hydroxytryptamine (pA2 7.84). In conclusion, the affinity/potency of iodoproxyfan at H3 receptors (range 8.3-9.7 [1]) exceeds that at alpha 2 receptors by at least 1.5 log units and that at 5-HT3 receptors by at least 3 log units.     

In-vitro characterization of YM872, a selective, potent and highly water-soluble alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate receptor antagonist

The in-vitro pharmacological properties of (2,3-dioxo-7-(1H-imidazol-1-yl)-6-nitro-1,2,3,4-tetrahydro-1-quinoxal inyl)-acetic acid monohydrate, YM872, a novel and highly water-soluble alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA)-receptor antagonist were investigated. YM872 is highly water soluble (83 mg mL(-1) in Britton-Robinson buffer) compared with 2,3-dihydroxy-6-nitro-7-sulphamoyl-benzo(F)quinoxaline (NBQX), 6-(1H-imidazol-1-yl)-7-nitro-2,3(1H,4H)-quinoxalinedione hydrochloride (YM90K) or 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX). YM872 potently inhibits [3H]AMPA binding with a Ki (apparent equilibrium dissociation constant) value of 0.096 +/- 0.0024 microM. However, YM872 had very low affinity for other ionotropic glutamate receptors, as measured by competition with [3H]kainate (high-affinity kainate binding site, concentration resulting in half the maximum inhibition (IC50) = 4.6 +/- 0.14 microM), [3H]glutamate (N-methyl-D-aspartate (NMDA) receptor glutamate binding site, IC50 > 100 microM) and [3H]glycine (NMDA receptor glycine-binding site, IC50 > 100 microM). YM872 competitively antagonized kainate-induced currents in Xenopus laevis oocytes which express rat AMPA receptors, with a pA2 value of 6.97 +/- 0.01. In rat hippocampal primary cultures, YM872 blocked a 20-microM AMPA-induced increase of intracellular Ca2+ concentration with an IC50 value of 0.82 +/- 0.031 microM, and blocked 300-microM kainate-induced neurotoxicity with an IC50 value of 1.02 microM. These results show that YM872 is a potent and highly water-soluble AMPA antagonist with great potential for treatment of neurodegenerative disorders such as stroke.     

Evaluation of efficacy of traditional Chinese medicines in the treatment of childhood bronchial asthma: clinical trial, immunological tests and animal study. Taiwan Asthma Study Group

Traditional Chinese medicines (TCM) have been used to treat bronchial asthma for several centuries and a certain degree of clinical benefit has been observed; however, scientific substantiation is lacking. A multicenter, double-blind and placebo-controlled study was therefore conducted to evaluate the clinical efficacy in terms of symptom score, medication score, morning and evening PEFRs, and changes of immunoregulatory function, such as distribution of lymphocyte subsets and in vivo and in vitro production of lymphokines (IFN-gamma and IL-4) and inflammatory mediators (histamine, PGE2 and LTC4). Furthermore, the protective effect of TCM on the late asthmatic reaction (LAR) was evaluated by using asthmatic guinea pigs. Three hundred and three asthmatic children were classified by Chinese doctors, according to a standardized questionnaire designed on the basis of basic logic of Chinese medicine, into three groups of specific constitution (group A, B and C). Group A consisted of 32 herb A-treated patients and 34 placebo-treated; group B, 74 herb B-treated and 64 placebo-treated; and group C, 55 herb C-treated and 44 placebo-treated. The study period was six months. The results were: 1) Both treatment group and placebo group showed an improvement in all clinical parameters, thus demonstrating a placebo effect. However, the improvement was usually greater in the former than the latter, although only the difference in PEFR was significant; 2) Herb A could increase total T cell and decrease B cell; 3) Herb A and B enhanced production of PGE2 but not LTC4, IFN-gamma and IL-4; 4) There was a general tendency for in vivo and in vitro production of histamine to decrease at the end of study in both treatment group and placebo group; however, the decrease was significantly greater in the former than the latter; 5) In asthmatic guinea pigs, 10-day's pretreatment with Chinese herbs could reverse the decrease of sGaw, suppress eosinophilia in bronchoalveolar lavage fluid (BALF), prevent the eosinophil infiltration of airways, increase PGE2 production and decrease LTC4 production in serum and BALF. Thus, traditional Chinese medicines did show a certain degree of clinical efficacy. The decreased production of histamine and LTC4, increased production of PGE2 that were found in both asthmatic children and asthmatic guinea pigs, and prevention of occurrence of LAR by suppressing eosinophil infiltration of airways and preserving airway conductance that were observed in asthmatic guinea pigs after allergen challenge might be used to account partly for the effectiveness.     

Effects of KW-3902, a selective and potent adenosine A1 receptor antagonist, on renal hemodynamics and urine formation in anesthetized dogs

Smyth line (SL) chickens develop a spontaneous, autoimmune, posthatch loss of pigment cells (vitiligo) in regenerating feather tissue. Smyth line vitiligo (SLV) is associated with lymphocyte infiltrations prior to and throughout the development of the disorder. It was the purpose of this study to determine the type, relative amounts, and proportions of pulp-infiltrating lymphocytes at various times throughout the growth of regenerating feathers. Feathers were plucked from 8-week-old chickens with and without SLV. Feather pulp cell suspensions were prepared when the regenerating feathers were 2, 3, 4, and 6 weeks of age. Cells were fluorescently labeled using a panel of mouse monoclonal antibodies specific for chicken lymphocytes. Both T and B cells infiltrated the feather pulp of chickens with SLV. T cell levels remained elevated throughout the 6 weeks of feather growth, while B cell levels steadily declined to control levels over the same time. The pulp-infiltrating cells were primarily T cells with an alphabeta T cell receptor expressing the Vbeta1 gene (TCR2+). The ratio between CD4+ and CD8+ cells was 1.42 and 0.75 in 2- and 6-week-old regenerating feathers from chickens with autoimmune SLV, respectively. In non-vitiliginous chickens this ratio was always near 1. These data suggest that TCR2+ T cells play an important role in SLV. CD4+ cells may play a recruiting/activating role, whereas CD8+ cells may have cytotoxic activity specifically directed against melanocytes. Additionally, this is the first report demonstrating the infiltration of B cells into the feather pulp of vitiliginous chickens. These B cells may directly/indirectly contribute to melanocyte destruction in SLV.     

Binding characteristics of a potent AMPA receptor antagonist [3H]Ro 48-8587 in rat brain

A new AMPA receptor antagonist, Ro 48-8587, was characterized pharmacologically in vitro. It is highly potent and selective for AMPA receptors as shown by its effects on [3H]AMPA, [3H] kainate, and [3H] MK-801 binding to rat brain membranes and on AMPA- or NMDA-induced depolarization in rat cortical wedges. [3H]Ro 48-8587 bound with a high affinity (KD = 3 nM) to a single population of binding sites with a Bmax of 1 pmol/mg of protein in rat whole brain membranes. [3H]Ro 48-8587 binding to rat whole brain membranes was inhibited by several compounds with the following rank order of potency: Ro 48-8587 > 6-nitro-7-sulphamoylbenzo[f] quinoxaline-2,3-dione (NBQX) > YM 90K > 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) > quisqualate > AMPA > glutamate > kainate > NMDA. The distribution and abundance of specific binding sites (approximately 95% of total) in sections of rat CNS, revealed by quantitative receptor radioautography and image analysis, indicated a very discrete localization. Highest binding values were observed in cortical layers (binding in layers 1 and 2 > binding in layers 3-6), hippocampal formation, striatum, dorsal septum, reticular thalamic nucleus, cerebellar molecular layer, and spinal cord dorsal horn. At 1 nM, the values for specific binding were highest in the cortical layers 1 and 2 and lowest in the brainstem (approximately 2.6 and 0.4 pmol/mg of protein, respectively). Ro 48-8587 is a potent and selective AMPA receptor antagonist with improved binding characteristics (higher affinity, selectivity, and specific binding) compared with those previously reported.