Multicenter assessment of CSF-phosphorylated tau for the prediction of conversion of MCI.

BACKGROUND: The measurement of hyperphosphorylated tau (p-tau) in CSF has been proposed as a biomarker candidate for the prediction of Alzheimer disease (AD) in patients with mild cognitive impairment (MCI). However, a standard quantitative criterion of p-tau has not been evaluated. OBJECTIVE: To assess in a multicenter study the predictive accuracy of an a priori defined criterion of tau phosphorylated at threonine 231 (p-tau(231)) for the prediction of conversion from MCI to AD during a short-term observation interval. METHODS: The study included 43 MCI converters, 45 stable MCI (average follow-up interval = 1.5 years), and 57 healthy controls (at baseline only). Subjects were recruited at four international expert sites in a retrospective study design. Cox regression models stratified according to center were used to predict conversion status. Bootstrapped 95% CIs of classification accuracy were computed. RESULTS: Levels of p-tau(231) were a significant predictor of conversion (B = 0.026, p = 0.001), independent of age, gender, Mini-Mental State Examination, and ApoE genotype. For an a priori-defined cutoff point (27.32 pg/mL), sensitivity ranged between 66.7 and 100% and specificity between 66.7 and 77.8% among centers. The bootstrapped mean percentage of correctly classified cases was 79.95% (95% CI = 79.9 to 80.00%). Post hoc defined cutoff values yielded a mean bootstrapped classification accuracy of 80.45% (95% CI = 80.24 to 80.76%). CONCLUSIONS: An a priori defined cutoff value of p-tau(231) yields relatively stable results across centers, suggesting a good feasibility of a standard criterion of p-tau(231) for the prediction of Alzheimer disease.

Longitudinal CSF and MRI biomarkers improve the diagnosis of mild cognitive impairment.

The diagnosis of Alzheimer's disease (AD) in patients with mild cognitive impairment (MCI) is limited because it is based on non-specific behavioral and neuroimaging findings. The lesions of Alzheimer's disease: amyloid beta (Abeta) deposits, tau pathology and cellular oxidative damage, affect the hippocampus in the earlier stages causing memory impairment. In a 2-year longitudinal study of MCI patients and normal controls, we examined the hypothesis that cerebrospinal fluid (CSF) markers for these pathological features improve the diagnostic accuracy over memory and magnetic resonance imaging (MRI)-hippocampal volume evaluations. Relative to control, MCI patients showed decreased memory and hippocampal volumes and elevated CSF levels of hyperphosphorylated tau and isoprostane. These two CSF measures consistently improved the diagnostic accuracy over the memory measures and the isoprostane measure incremented the accuracy of the hippocampal volume achieving overall diagnostic accuracies of about 90%. Among MCI patients, over 2 years, longitudinal hippocampal volume losses were closely associated with increasing hyperphosphorylated tau and decreasing amyloid beta-42 levels. These results demonstrate that CSF biomarkers for AD contribute to the characterization of MCI.

Effects of the putative antidepressant, ABT 200, on the clearance of exogenous norepinephrine in rat cerebellum.

ABT 200 [(RR,SS)-3-phenyl-1-[1',2',3',4'-tetrahydro-5',6'-methylenedioxy- 1'-naphthalenyl-methyl]-pyrrolidine methanesulfonate] is a potent alpha 2-adrenoceptor antagonist (Ki = 1.2 nM) with modest norepinephrine uptake-blocking activity (IC50 = 841 nM) that is currently under clinical evaluation as an antidepressant. The effects of ABT 200, nomifensine (an inhibitor of catecholamine uptake), and rauwolscine (a selective alpha 2-adrenoceptor antagonist) on the clearance of exogenous norepinephrine in the cerebellum of urethane-anesthetized rats was investigated using a vivo electrochemistry. Chronoamperometric recordings were continuously made at 5 Hz using Nafion-coated, single carbon fiber electrodes. When a calibrated amount of norepinephrine was pressure-ejected at 5-min intervals from a micropipette adjacent (290-330 microM) to the electrode, transient and reproducible norepinephrine signals were detected. In response to systemic ABT 200 (30 mg/kg i.p.) or nomifensine (30 mg/kg i.p.), the signals increased in both amplitude and time course, indicating significant inhibition of the norepinephrine transporter. A lower dose (15 mg/kg i.p.) of either ABT 200 or nomifensine had no effect in this paradigm. Local application of ABT 200 (400 microM) or nomifensine (400 microM) prior to pressure-ejection of norepinephrine also significantly increased the amplitude and time course of the norepinephrine signals. In contrast, systemic administration of rauwolscine (30 mg/kg i.p.) or vehicle solution, and local application of vehicle solution, had no effect on the norepinephrine signals. These data indicate that at the higher dose evaluated, both ABT 200 and nomifensine inhibit cerebellar norepinephrine uptake in vivo.

Preclinical pharmacological actions of (+/-)-(1'R*,3R*)-3-phenyl-1- [1',2',3',4'-tetrahydro-5',6'-methylene-dioxy-1'-naphthalenyl) methyl] pyrrolidine methanesulfonate (ABT-200), a potential antidepressant agent that antagonizes alpha-2 adrenergic receptors and inhibits the neuronal uptake of norepinephrine.

(+/-)-(1'R*,3R*)-3-phenyl-1-[(1',2',3',4'-tetrahydro-5',6'-methylene- dioxy-1'-naphthalenyl) methyl] pyrrolidine methanesulfonate (ABT-200) was evaluated in a number of biological tests to establish its pharmacological profile of activity. ABT-200 antagonized the uptake of [3H]-norepinephrine into synaptosomes of rat hypothalamus (IC50 = 841 nM) and blocked 4,alpha-dimethyl-m-tyramine- induced hypermotility in rats. In addition, ABT-200 potently inhibited binding of [3H]-rauwolscine to alpha-2 adrenergic receptors with a Ki value in radioligand binding assays of approximately 1 nM in the rat cortex and was much less potent at other receptor binding sites. ABT-200 antagonized alpha-2 receptors in vitro in the rat vas deferens and dog saphenous vein, where pA2 values of 7.7 and 8.2, respectively, were obtained. ABT-200 also antagonized clonidine-induced mydriasis and increased the overflow of [3H]-norepinephrine in guinea pig hippocampal slices, manifestations of blockade of alpha-2 adrenoceptors in the central nervous system. ABT-200 was active in antagonizing nocturnal hyperactivity in olfactory bulbectomized rats, a test for putative antidepressant activity. In cardiovascular studies, ABT-200 exhibited negligible activity in affecting hemodynamic parameters and was free of postural hypotensive activity. In both in vitro and in vivo, ABT-200 was devoid of antihistaminic or anticholinergic activity. This profile of activity of moderate inhibition of norepinephrine uptake with blockade of alpha-2 adrenoceptors suggests potential dual-action effects for ABT-200, which may represent a putative antidepressant with minimal cardiovascular side-effect liability.

Cardiovascular effects of orally administered ABBOTT-81988, an angiotensin II antagonist, in conscious spontaneously hypertensive rats.

ABBOTT-81988 (A-81988), 2-(N-propyl-N[(2'-[1H-tetrazol-5-yl]biphenyl- 4yl)methyl] amino) pyridine-3-carboxylic acid, a nonpeptide angiotensin II (AII) antagonist was studied in the conscious spontaneously hypertensive rate (SHR) (male, 18 to 21 weeks) for cardiovascular effects of oral administration. Oral A-81988 at 0.3 to 3 mg/kg produced a dose-related 10 to 29% decrease in mean arterial pressure (MAP) in SHR (control, 161 to 177 mm Hg; n = 19) for 12 to 24 h without changing heart rate. Oral A-81988 at 3 mg/kg daily maintained MAP in SHR at normotensive levels (97 to 120 mm Hg) during a 5-day protocol with no rebound hypertension at termination of treatment. There was an increase in plasma renin activity in nanograms AI/milliliter/hour in SHR treated with A-81988 (32 +/- 3, n = 6 v 5 +/- 2, n = 6 for vehicle) during its antihypertensive action. The oral potency of A-81988 was enhanced about 10-fold in furosemide-treated SHR. The pressor response to AII was inhibited selectively in SHR even after an 8-day treatment with A-81988 (approximately 3 mg/kg/day orally). Total peripheral resistance was lowered and cardiac output unchanged in SHR administered A-81988 (3 mg/kg/day orally for 2 days). A-81988 (3 mg/kg orally) did not cause orthostatic hypotension in SHR.(ABSTRACT TRUNCATED AT 250 WORDS)

[3H]A-81988, a potent, selective, competitive antagonist radioligand for angiotensin AT1 receptors.

Abbott-81988 (A-81988), 2-(N-n-Propyl-N-[(2'-[1H-tetrazol-5-yl]biphenyl-4- yl)methyl]amino)pyridine-3-carboxylic acid is a potent, competitive, non-peptidic antagonist of angiotensin AT1 receptors. A-81988 was labeled with tritium to high specific activity (16 Ci/mmol) and radioligand binding assays performed in rat liver membranes. [3H]A-81988 bound with high affinity (KD = 0.57 nM) and the KD determined from kinetics assays was similar. Non-specific binding (defined with 10(-6) M angiotensin-II) was very low (< 6% at the KD). The binding of [3H]A-81988 was competitive and exhibited appropriate pharmacological specificity for compounds acting at angiotensin AT1 receptors. These properties demonstrate that [3H]A-81988 will be a useful radioligand for studies of angiotensin AT1 receptors in various tissues.

Characterization of antihypertensive activity of ABBOTT-81988, a nonpeptide angiotensin II antagonist in the renal hypertensive rat.

2-(N-Propyl-N[(2'-[1H-tetrazol-5-yl]biphenyl-4yl)methyl]amin o) pyridine-3-carboxylic acid (ABBOTT-81988), a novel nonpeptide angiotensin II (AII) antagonist, was evaluated to characterize its antihypertensive activity in the conscious renal hypertensive rat. Oral or i.v. administration of ABBOTT-81988 at 0.03 to 0.3 mg/kg produced a dose-dependent, sustained decrease in mean arterial pressure (MAP; control 162-173 mm Hg, n = 27) of approximately 20 to 70 mm Hg. At a dose of 0.3 mg/kg p.o., ABBOTT-81988 lowered MAP to a normotensive level for more than 24 hr and did not change heart rate. During its antihypertensive effect (delta MAP, -28% approximately -35%), ABBOTT-81988 (0.1-03 mg/kg i.v.) decreased total peripheral resistance (delta resistance, -31% approximately -43%), and cardiac output remained either unchanged or slightly elevated. ABBOTT-81988 (0.3 mg/kg i.v.) produced an additional antihypertensive effect (delta MAP, -12 +/- 2%, n = 5) in captopril-pretreated (10 mg/kg i.v.) hypertensive rats, but captopril (10 mg/kg i.v.) had no effect in ABBOTT-81988-pretreated (0.3 mg/kg i.v.) rats. In the normotensive rat, ABBOTT-81988 (0.3 mg/kg p.o.) had no effect on basal MAP, but it inhibited the AII-induced (0.1 microgram/kg i.v.) pressor response by 51% to 91% for 24 hr, whereas the responses to norepinephrine (0.3 microgram/kg i.v.), vasopressin (0.03 IU/kg i.v.) and bradykinin (3 micrograms/kg i.v.) were not affected. It is concluded that ABBOTT-81988 is a safe and efficacious AII antagonist that may have use in the treatment of human hypertension.

Antihypertensive activity of ABBOTT-81282, a nonpeptide angiotensin II antagonist, in the renal hypertensive rat.

ABBOTT-81282, 4-(N-butyl-N-[(2-'-[1H-tetrazol-5yl]biphenyl-4-yl)methyl]ami no) pyrimidine-5-carboxylic acid is a novel nonpeptide angiotensin II (AII) antagonist. In vivo studies were performed to evaluate ABBOTT-81282 for its antihypertensive effect, pharmacological mechanism(s) of action, and cardiovascular safety. In the conscious renal artery-ligated (RAL) hypertensive rat, a model of high renin hypertension, ABBOTT-81282 (1-10 mg/kg p.o. and 0.1-1.0 mg/kg i.v.) lowered mean arterial pressure (MAP) in a dose-dependent manner with the ED30 values of 2.2 mg/kg for p.o. administration and 0.08 mg/kg for i.v. administration. At 10 mg/kg p.o., ABBOTT-81282 lowered blood pressure in the RAL rat (delta MAP 66 +/- 9 mm Hg from control MAP 167 +/- 7 mm Hg, n = 6) to a normotensive level (MAP, 115 +/- 5 mm Hg) for greater than 24 h and did not change heart rate. The i.v. administration of 1 mg/kg of ABBOTT-81282 also produced a sustained, long-lasting decrease (delta MAP 27-52 mm Hg) in blood pressure that was significantly different from the vehicle group at 8 h postdosing (143 +/- 3 mm Hg, n = 4 for ABBOTT-81282 vs. 181 +/- 3 mm Hg, n = 6 for vehicle group, p < 0.01). When blood pressure in the renal hypertensive rat was maximally lowered (delta MAP 72 +/- 9 mm Hg, n = 4) following the 1 mg/kg i.v. dose (cumulative) of ABBOTT-81282, additional administration of captopril (3 mg/kg i.v.) produced no further decline in blood pressure. In the conscious normotensive rat, 10 mg/kg p.o. of ABBOTT-81282 had no effect on basal MAP (119 +/- 3 vs. 115 +/- 4 mm Hg, pre- vs. 3.5 h postdosing, n = 4) and heart rate (364 +/- 18 vs. 363 +/- 14 beats/min, pre- vs. 3.5 h postdosing, n = 4) but inhibited the AII (0.1 micrograms/kg i.v.)-induced increase in MAP by 64-70%, while the MAP responses to norepinephrine (0.3 micrograms/kg i.v.), vasopressin (0.03 IU/kg i.v.) and bradykinin (3 micrograms/kg i.v.) remained intact. ABBOTT-81282 was also administered to conscious normotensive rats (n = 4) instrumented with ECG telemetry transmitters. At an i.v. dose of 10 mg/kg, which is 125 times greater than the i.v. ED30, ABBOTT-81282 caused a minimal decrease (< 14%) in MAP and had no effect on ECG waveforms. These data demonstrate that ABBOTT-81282 is a safe and efficacious antihypertensive agent with selective AII antagonism.(ABSTRACT TRUNCATED AT 400 WORDS)

A-69024: a non-benzazepine antagonist with selectivity for the dopamine D-1 receptor.

A-69024 HBr, 1-(2-bromo-4,5-dimethoxybenzyl)-7-hydroxy-6-methoxy-2-methyl-1,2,3,4- tetrahydroisoquinoline hydrobromide, is a selective antagonist of the dopamine D-1 receptor. A-69024 HBr shows an apparent affinity toward the D-1 receptor (identified using [125I]SCH 23390) of 12.6 (4.15-38.3) nM (mean (90% CL), n = 3); the apparent affinity toward the D-2 receptor (identified using [3H]spiroperidol is 1 290 (1,200-1,380) nM (n = 3); using [125I]lysergic acid diethylamine to identify the 5-HT1C receptor gives apparent affinity of 17,800 (9,700-32,600) nM (n = 3). In assays of adenylate cyclase activity, A-69024 HBr antagonizes the D-1 receptor with a calculated affinity of 43.9 (17.5-110) nM (n = 5), while the molecule antagonizes the D-2 receptor with a calculated affinity greater than 400 nM. Behavioral studies demonstrate that A-69024 HBr (5 mg/kg s.c.) is able to block both amphetamine-induced locomotor activity and apomorphine-induced stereotypy. Furthermore, A-69024 HBr blocks SF&F 38393-, but not quinpirole-, induced rotation in rats having unilateral 6-hydroxydopamine lesions of the substantia nigra. When administered at behaviorally effective doses. A-69024 HBr neither increases the concentration of serum prolactin nor potentiates dihydroxyphenylalanine (DOPA) accumulation in the caudate-putamen of rats pretreated with the DOPA decarboxylase inhibitor NSD 1015. Because A-69024 is a dopamine receptor antagonist discriminating between the D-1 and D-2 receptors, it may be a useful research tool.

A new nasal decongestant, A-57219: a comparison with oxymetazoline.

2-(4-Amino-3,5-dichlorobenzyl)imidazoline hydrochloride (A-57219), has alpha 1-agonist/alpha 2-antagonist activity and was more effective and long-acting than oxymetazoline on canine nasal mucosa, in-vitro and in-vivo. Upon intranasal administration to dogs, the compound was devoid of systemic effects up to a concentration 1000 times that needed for local decongestant effect (1.65 micrograms, atomized from a 1 microgram mL-1 solution) suggesting limited mucosal absorption. After nasal administration to rats for 15 days at a concentration 1000 times greater than that required for nasal decongestion, no mucosal tissue toxicity or systemic effects were seen.

Conformationally defined adrenergic agents. 5. Resolution, absolute configuration, and pharmacological characterization of the enantiomers of 2-(5,6-dihydroxy-1,2,3,4-tetrahydro-1-naphthyl)imidazoline: a potent agonist at alpha-adrenoceptors.

(+/-)-2-(5,6-Dimethoxy-1,2,3,4-tetrahydro-1-naphthyl)imidazoline has been resolved into its (+) and (-) enantiomers, and the absolute configuration was established by single-crystal X-ray diffraction studies. The more active isomer has been assigned the R absolute configuration. Cleavage of the respective (+)- and (-)-dimethyl ethers with boron tribromide provided the corresponding (+)- and (-)-2-(5,6-dihydroxy-1,2,3,4-tetrahydro-1-naphthl)imidazoline hydrobromides and these were pharmacologically characterized. In various preparations, the R enantiomer has been shown to be an extremely potent alpha agonist with preferential activity at the alpha 2-adrenergic receptor.

Conformationally defined adrenergic agents. 4. 1-(aminomethyl)phthalans: synthesis and pharmacological consequences of the phthalan ring oxygen atom.

The synthesis of a series of 1-(aminomethyl)phthalans 1b is reported. The radioligand binding to alpha 1- and alpha 2-receptors and the in vitro pharmacology in alpha 1 (rabbit aorta) and alpha 2 (phenoxybenzamine-pretreated dog saphenous vein) tissues were determined and were compared to the activity of the corresponding 1-(aminomethyl)indans. The activity of this series of phthalans was found to be consistent with the electrostatic repulsion hypothesis that was used to design the parent indan (ERBCOP) compounds. The effect of the phthalan ring oxygenation was to somewhat improve alpha 1-receptor potency relative to the 6-ERBCOP indans without having a general effect on the alpha 2-receptor potency. We conclude from the overall pattern of activity that while the norepinephrine type beta-hydroxyl group may be beneficial for binding to the alpha 1-adrenoceptor, it is not required for strong binding to or full stimulation of the alpha 2-adrenergic receptor, provided that the conformational mobility associated with the phenylethylamine is restricted and maintained in a favorable conformation for receptor interaction.

Conformationally defined adrenergic agents. 3. Modifications to the carbocyclic ring of 5,6-dihydroxy-1-(2-imidazolinyl)tetralin: improved separation of alpha 1 and alpha 2 adrenergic activities.

A series of modifications to positions 1, 2, and 4 of the tetralin ring of 5,6-dihydroxy-1-(2-imidazolinyl)tetralin (1, A-54741) succeeded in improving the separation of the potent alpha 1 and alpha 2 adrenergic agonism observed for the parent compound 1. In particular 5,6-dihydroxy-4,4-dimethyl-1-(2-imidazolinyl)tetralin (7) was found to be a specific alpha 1 adrenergic agonist, and 7,8-dihydroxy-4-(2-imidazolinyl)chroman (2) was found to have improved alpha 2 adrenergic agonistic selectivity relative to the parent compound 1.

Conformationally defined adrenergic agents. 2. Catechol imidazoline derivatives: biological effects at alpha 1 and alpha 2 adrenergic receptors.

The synthesis and pharmacology of 2-(5,6-dihydroxy-1,2,3,4-tetrahydro-1-naphthyl)imidazoline (A-54741, 4), a very potent alpha-adrenergic agonist, are described. The change in biological activity resulting from variation of the carbocyclic ring size of 4 from four through seven members (2-5) is presented, as well as an explanation that accounts for this change in activity by considering the "exactness of fit" of these compounds to both the alpha 1- and alpha 2-adrenergic receptors. Compound 4 was found in vitro to be a full agonist with greater potency at the alpha 2 receptor (ED50 norepinephrine (NE)/ED50 4 = 188 +/- 22) than at the alpha 1 receptor (ED50 NE/ED50 4 = 13 +/- 2).

Adrenergic and dopaminergic properties of dopamine sulfoconjugates.

UNLABELLED: The 3- and 4-sulfate esters of dopamine (DA-3-SO4 and DA-4-SO4, respectively), the two main metabolites of DA, were evaluated for potential intrinsic or indirect catecholaminergic activities. Both compounds lacked any appreciable affinities for alpha 1, alpha 2, beta 1, beta 2 and DA-2 receptors. In the superfused [3H]norepinephrine-preloaded dog saphenous vein, both dopamine sulfates were devoid of any intrinsic inhibitory activity such as observed with dopamine pre- and postsynaptically. In addition, they did not displace the labeled vesicular neurotransmitter as did dopamine. In anesthetized dogs the two compounds failed to stimulate either the dopaminergic receptors (DA-1) of mesenteric vascular beds or the adrenergic receptors mediating the vasodilatory and pressor responses to dopamine. CONCLUSION: In our experimental conditions DA-3-SO4 and DA-4-SO4, the products of dopamine sulfoconjugation, lacked any demonstrable intrinsic affinity and/or efficacy on the dopaminergic and adrenergic receptors directly or indirectly through their metabolic transformation or through displacement of endogenous neurotransmitter.

Conformationally defined adrenergic agents. 1. Design and synthesis of novel alpha 2 selective adrenergic agents: electrostatic repulsion based conformational prototypes.

A previous report of the adrenergic selectivity of 2- and 6-fluoronorepinephrine prompted us to formulate a hypothesis that accounted for this selectivity on the basis of a conformational preference induced by electrostatic repulsion between the aromatic fluorine atom and the side-chain hydroxyl group. A series of nitrogen-substituted catechol (aminomethyl)benzocyclobutenes, indanes, tetralins, and benzocycloheptenes were prepared, and when their radioligand binding affinities were determined, it was found that the overall pattern of binding affinity results supported the electrostatic repulsion hypothesis. The radioligand binding assay also revealed several highly alpha 2 selective adrenergic agents among these compounds, with the binding selectivity maximizing for compounds having nitrogen substituted with a group no larger than methyl and having a five-membered carbocyclic ring (i.e., 16, 17, and 19).