ABSTRACT
NADPH-d (nicotinamide-adenine dinucleotide phosphate-diaphorase) neurons are thought to migrate improperly during development in the brains of schizophrenic patients. This enzyme is a nitric oxide synthase (NOS). Nitric oxide (NO) is known to affect neurodevelopmental processes in the CNS. Therefore, we hypothesized that interference of NO generation during development may produce some aspects of schizophrenia symptomatology in a rat model. In these experiments, neonatal rats were challenged with a NOS inhibitor (L-nitroarginine 1-100 mg/kg s.c.) daily on post-natal days 3-5. L-Nitroarginine (L-NoArg) treated male rats developed a hypersensitivity to amphetamine in adulthood versus vehicle treated controls, whereas female rats did not. However, L-NoArg treated female rats developed a hypersensitivity to phencyclidine (PCP) at juvenile and adult ages versus vehicle treated controls, whereas male animals did not. L-NoArg treated male rats also had deficits in pre-pulse inhibition of startle whereas adult female rats did not. The results are discussed in terms of a new neurodevelopmental model of schizophrenia and male/female differences inherent in this disease.
Subject(s)
Disease Models, Animal , Enzyme Inhibitors/pharmacology , NADPH Dehydrogenase/antagonists & inhibitors , Nitric Oxide Synthase/antagonists & inhibitors , Nitroarginine/pharmacology , Schizophrenia/chemically induced , Animals , Animals, Newborn , Female , Male , Motor Activity/drug effects , Rats , Rats, Sprague-Dawley , Schizophrenia/enzymology , Sex CharacteristicsABSTRACT
1-[(3-Fluoro-4-pyridinyl)amino]-3-methyl-1(H)-indol-5-yl methyl carbamate (P10358) is a potent, reversible acetylcholinesterase inhibitor that produces central cholinergic stimulation after oral and parental administration in rats and mice. P10358 is a 2.5 times more potent acetylcholinesterase inhibitor than THA in vitro (IC50 = 0.10 +/- 0.02 microM vs. IC50 = 0.25 +/- 0.03 microM). It also inhibits butyrylcholinesterase activity as potently as THA (IC50 = 0.08 +/- 0.05 microM vs. IC50 = 0.07 +/- 0.01 microM). Ex vivo, P10358 (0.2 - 20 mg/kg, p.o.) produced dose-dependent inhibition of brain acetylcholinesterase activity. At 10 and 20 mg/ kg, it produced profound and long-lasting hypothermia in mice. P10358 enhanced performance in rats in a step-down passive avoidance task (0.62 and 1.25 mg/kg) and in a social recognition paradigm (0.32, 0.64 and 1.25 mg/kg) in mice. It reversed scopolamine-induced deficits in the Morris Water maze in rats (1.25 and 2.5 mg/kg) and a higher dose elevated striatal homovanillic acid levels. These behavioral and biochemical effects are consistent with central cholinergic stimulation. Hemodynamic studies in the rat demonstrated a 16-fold separation between behaviorally active doses (1.25 mg/kg) and those that elevated arterial pressure (20 mg/kg). Lethality in rats occurred at an oral dose of 80 mg/kg, but not at lower doses. Chemically, P10358 is an N-aminoindole and may not have the hepatotoxic liability associated with aminoacridine structure of tacrine. P10358 had weak affinity (>10 microM) at a variety of aminergic and peptidergic receptors and uptake carriers. These properties suggest that P10358 may be a safe and promising symptomatic treatment for Alzheimer's disease.
Subject(s)
Aminopyridines/toxicity , Brain/metabolism , Carbamates/toxicity , Cholinesterase Inhibitors/toxicity , Dopamine/metabolism , Hypothermia, Induced , Maze Learning/drug effects , Acetylcholinesterase/metabolism , Administration, Oral , Alzheimer Disease/drug therapy , Aminopyridines/administration & dosage , Aminopyridines/therapeutic use , Animals , Avoidance Learning/drug effects , Brain/drug effects , Butyrylcholinesterase/metabolism , Carbamates/administration & dosage , Carbamates/therapeutic use , Cholinesterase Inhibitors/administration & dosage , Cholinesterase Inhibitors/therapeutic use , Corpus Striatum/metabolism , Female , Humans , Kinetics , Male , Memory , Mice , Mice, Inbred Strains , Ovariectomy , Prosencephalon/enzymology , Rats , Rats, Wistar , Scopolamine/pharmacology , Social Behavior , Space Perception , Time FactorsABSTRACT
Acetylcholinesterase (AChE) inhibitors from several chemical classes have been tested for the symptomatic treatment of Alzheimer's disease; however, the therapeutic success of these compounds has been limited. Recently, another AChE inhibitor, galanthamine hydrobromide (GAL), has shown increased clinical efficacy and safety. Using biochemical, behavioral and pharmacokinetic analyses, this report compares GAL with two of its analogs, 6-O-acetyl-6-O-demethylgalanthamine hydrochloride (P11012) and 6-O-demethyl-6-O[(adamantan-1-yl)-carbonyl]galanthamine hydrochloride (P11149), for their therapeutic potential. P11012 and P11149 were found to be potent, competitive and selective inhibitors of AChE, demonstrating central cholinergic activity, behavioral efficacy and safety. P11012 and P11149, though pharmacokinetic analyses, were shown to act as pro-drugs, yielding significant levels of 6-O-demethylgalanthamine. In vitro, 6-O-demethylgalanthamine was 10- to 20-fold more potent than GAL as an inhibitor of AChE, and it demonstrated greater selectivity for inhibition of AChE vs. butyrylcholinesterase. Like GAL, both P11012 and P11149 showed central cholinergic activity biochemically, by significantly inhibiting rat brain AChE; physiologically, by causing hypothermia; and behaviorally, by attenuating scopolamine-induced deficits in passive avoidance. In addition, GAL, P11012 and P11149 enhanced step-down passive avoidance, another measure of behavioral efficacy. By comparing efficacious doses with primary overt effects, P11012 and P11149 had better oral therapeutic indices than GAL. Oral pharmacokinetic analyses of GAL, P11012 and P11149 revealed differences. Although P11012 and P11149 exhibited similar area under the curve values, 191149 had slower, lower and more sustained concentration maximum levels. P11012 and GAL rapidly reached their concentration maximums, but GAL, in brain had the highest area under the curve and concentration maximum. Because of its composite profile, including duration of action, oral therapeutic index and pharmacokinetics, P11149 is considered the better therapeutic candidate for the treatment of Alzheimer's disease.
Subject(s)
Alzheimer Disease/drug therapy , Cholinesterase Inhibitors/pharmacology , Galantamine/pharmacology , Animals , Avoidance Learning/drug effects , Body Temperature/drug effects , Cholinesterase Inhibitors/therapeutic use , Galantamine/analogs & derivatives , Galantamine/pharmacokinetics , Humans , Male , Mice , Rats , Rats, Sprague-Dawley , Rats, Wistar , Scopolamine/pharmacologyABSTRACT
A series of 5-amino-5,6,7,8-tetrahydroquinolinones was designed and synthesized as acetylcholinesterase inhibitors. The compounds are related to hyperzine A, a naturally occurring cholinesterase inhibitor. They inhibit acetylcholinesterase in vitro, and many are active in vivo in reversing a scopolamine-induced impairment of 24 h memory in a passive avoidance paradigm. Although these compounds were designed as partial structures of huperzine A, it is unlikely that they bind to the enzyme in a similar fashion, since they lack the unsaturated three-carbon bridge of huperzine A and both the quinolinone nitrogen and the amino group must be substituted in order to obtain good enzyme affinity.
