Acamprosate suppresses ethanol-induced place preference in mice with ethanol physical dependence.

The present study investigated the effect of acamprosate on ethanol (EtOH)-induced place preference in mice with EtOH physical dependence. The expression of EtOH (2 g/kg, intraperitoneally)-induced place preference in mice without EtOH treatment before the experiment was dose-dependently suppressed by acamprosate. The levels of protein kinase A (PKA) and phospho-cAMP response element binding protein (p-CREB) in the limbic forebrain after EtOH-conditioning in naïve mice was unchanged. Furthermore, mice on the 4th day of withdrawal from continuous EtOH vapor inhalation for 9 days showed transient and significant enhancement of EtOH (1 g/kg, intraperitoneally)-induced place preference, which was significantly suppressed by acamprosate (300 mg/kg, oral administration; p.o., once a day) administered daily for 3 days after withdrawal from EtOH inhalation and during EtOH-conditioning. PKA and p-CREB proteins in the limbic forebrain of EtOH-conditioned mice on 4th day of withdrawal from continuous EtOH inhalation for 9 days significantly increased, which were completely abolished by acamprosate. These findings suggest that the signal transduction pathway via the PKA-p-CREB pathway in the limbic forebrain may be functionally related to the development of sensitization of EtOH-induced place preference and provide a possible molecular basis for the pharmacological effect of acamprosate to prevent or reduce the relapse of alcohol dependence.

Expression of beta-adrenergic receptor up-regulation is mediated by two different processes.

Mechanisms of up-regulation of beta-adrenergic receptors (beta-ARs) induced by sustained exposure to 10(-8) M nadolol, a non-selective beta-AR antagonist, were examined using mouse cerebrocortical neurons. Nadolol dose- and time-dependently increased [3H]CGP-12177 bindings to the particulate fractions. This increase occurred 6 h and attained its plateau 12 h after the exposure, whereas beta1- and beta2-AR mRNA significantly increased 24 h and attained their plateaus 3 days after the exposure. Scatchard analysis revealed that the increased bindings were due to increase of receptor density. The [3H]CGP-12177 bindings to beta1- and beta2-ARs increased both 12 h and 5 days after the exposure. Although cycloheximide (CHX) decreased the bindings with or without nadolol, the extent of increase of the bindings induced by nadolol was not affected by CHX. Actinomycin D (AD) with nadolol showed no affects on the bindings 12 h after nadolol exposure, while AD treated 6 h after nadolol exposure significantly reduced the bindings 48 h after nadolol exposure. During 24 h after nadolol exposure, the increase in proteins of beta1- and beta2-ARs in the neuronal membrane was due to the increased receptor protein translocation from cytosol to membrane. These results indicate that the up-regulation of beta-ARs induced by nadolol is mediated by, at least, two different processes, one is increase in translocation of receptor proteins from cytosol to membrane with no changes in synthesis of receptor proteins and their mRNA and another is dependent on receptor protein synthesis with increased synthesis of their mRNA.

Functional role of inhibitory and excitatory nerves in the porcine lower urinary tract.

In the trigone (three portions) and proximal urethra isolated from castrated male pigs, transmural electrical stimulation (0.5-10 Hz) induced no or slight contractions followed by frequency-related relaxations. Atropine suppressed the contraction and potentiated the relaxation. N(G)-nitro-L-arginine methylester (L-NAME), a nitric oxide (NO) synthase inhibitor, depressed or abolished the relaxation induced by low frequency stimulation, but only slightly attenuated the response to high frequency stimulation. L-Arginine reversed the inhibitory effect. L-NAME-sensitive relaxation by 1 Hz stimulation was abolished by 1H-(1,2,4)oxadiazolo-(4,3-a)quinoxalin-1-one (ODQ), a guanylate cyclase inhibitor. Release of NO by nerve stimulation to trigonal strips was determined by increased formation of cyclic GMP in the incubation media containing guanylate cyclase and GTP. L-NAME-resistant relaxation by 10 Hz stimulation was not impaired by ODQ, capsaicin, chymotrypsin, K(+) channel inhibitors and beta-adrenoceptor antagonists. Similar results were obtained in the trigone and urethra from normal male and female pigs. Detrusor muscle responded to nerve stimulation with contraction followed by slight relaxation. Relaxations at 1 and 10 Hz stimulation under treatment with atropine and alpha,beta-methylene ATP were partially attenuated by L-NAME. It is concluded that there is no significant difference in the inhibitory responses, sensitive and resistant to L-NAME, to nerve stimulation in the trigone and proximal urethra from castrated and non-castrated male and female pigs. Relaxations to stimulation at 1 Hz seem to be mediated exclusively by neurogenic NO and cyclic GMP generation, whereas those to 10 Hz stimulation is mainly associated with non-NO relaxing factor(s), peptides, K(+) channel openers and beta-adrenoceptor agonist being unlikely involved.

Acamprosate {monocalcium bis(3-acetamidopropane-1-sulfonate)} reduces ethanol-drinking behavior in rats and glutamate-induced toxicity in ethanol-exposed primary rat cortical neuronal cultures.

Acamprosate, the calcium salt of bis(3-acetamidopropane-1-sulfonate), contributes to the maintenance of abstinence in alcohol-dependent patients, but its mechanism of action in the central nervous system is unclear. Here, we report the effect of acamprosate on ethanol-drinking behavior in standard laboratory Wistar rats, including voluntary ethanol consumption and the ethanol-deprivation effect. After forced ethanol consumption arranged by the provision of only one drinking bottle containing 10% ethanol, the rats were given a choice between two drinking bottles, one containing water and the other containing 10% ethanol. In rats selected for high ethanol preference, repeated oral administration of acamprosate diminished voluntary ethanol drinking. After three months of continuous access to two bottles, rats were deprived of ethanol for three days and then presented with two bottles again. After ethanol deprivation, ethanol preference was increased, and the increase was largely abolished by acamprosate. After exposure of primary neuronal cultures of rat cerebral cortex to ethanol for four days, neurotoxicity, as measured by the extracellular leakage of lactate dehydrogenase (LDH), was induced by incubation with glutamate for 1h followed by incubation in the absence of ethanol for 24h. The N-methyl-D-aspartate receptor blocker 5-methyl-10,11-dihydro-5H-dibenzo[a,d]-cyclohepten-5,10-imine, the metabotropic glutamate receptor subtype 5 antagonist 6-methyl-2-(phenylethynyl)pyridine and the voltage-gated calcium-channel blocker nifedipine all inhibited glutamate-induced LDH leakage from ethanol-exposed neurons. Acamprosate inhibited the glutamate-induced LDH leakage from ethanol-exposed neurons more strongly than that from intact neurons. In conclusion, acamprosate showed effective reduction of drinking behavior in rats and protected ethanol-exposed neurons by multiple blocking of glutamate signaling.

[Current status and perspectives on the development of therapeutic agents for Alzheimer's disease].

Acetylcholinesterase inhibitors have beneficial effects to improve the cognitive impairment in patients with mild to moderate Alzheimer's disease (AD). In addition, a channel blocker of N-methyl-D-aspartate receptor, memantine hydrochloride, was approved as a therapeutic agent for patients with moderate to severe AD in both EU countries in 2002 and USA in 2003, while the clinical development is still ongoing in Japan. In contrast, the pharmacotherapy for a prime cure against AD is not available in the market, although there has been a worldwide search for novel compounds. The most plausible mechanism for the treatment of AD is the reduction of the amyloid beta-peptide (Abeta) plaques, one of the pathological markers of AD, in the brain. For this purpose, the inhibitors of beta-secretase and gamma-secretase, which cleave amyloid precursor protein (APP) to release Abeta, has been developed to interfere with APP processing. The beta-sheet breaker and metal chelators for the breakdown of aggregated Abeta have also been synthesized as well as the immunotherapeutic approach using Abeta vaccine. On the other hand, some nonsteroidal anti-inflammatory drugs, such as ibuprofen and sulindac, noncompetitively inhibited Abeta production but not Notch cleavage. The development of Abeta-lowering drugs is highly expected for the treatment of AD.

[Current state on development of neuroprotective agents for cerebral ischemia].

The improvement of decreased cerebral blood flow using thrombolytic agents, anti-thrombin drugs, and antiplatelet drugs has been essential for acute ischemic stroke. Edaravone, a free radical scavenger, has been commercially available as a novel neuroprotective agent for ischemic stroke in Japan from 2001. The appearance of a neuroprotective agent implies that therapeutic strategy can be expanded through a combination with thrombolysis. In the previous development, several cases have reported that neuroprotective compounds failed in clinical trials. However, recent studies have clarified that the cerebral ischemia induced the neuronal cell death by mediating multiple mechanisms with necrosis and/or apoptosis. The cytotoxicity derived from the NO/peroxynitrite/free radical generating system, one of intracellular Ca2+ signaling, is a typical event in ischemic injury, which is protected by edaravone. Furthermore, it is suggested that suppression of excessively activated voltage-dependent Na+ and Ca2+ channels is effective as a strategy for neuroprotection, since abnormal excitatory stimuli in the neuronal network result in the cerebral infarction. The development of several compounds having different mechanisms of action for acute stroke is in progress. It is therefore prospected that the various novel neuroprotective agents will be provided for assuring the option of therapeutic strategy, since the reinforcement of medical stroke care including diagnosis contributes to the prolongation of the therapeutic time window.