Phencyclidine-induced cognitive deficits in mice are improved by subsequent subchronic administration of tropisetron: Role of alpha 7 nicotinic receptors
ABSTRACT We examined the effects of tropisetron, a 5-hydroxytryptamine (5-HT(3)) receptor antagonist and alpha7 nicotinic receptor agonist, on cognitive deficits in mice after repeated administration of the NMDA receptor antagonist phencyclidine (PCP). PCP (10 mg/kg/day for 10 days)-induced cognitive deficits were significantly improved by subsequent subchronic (2 weeks) administration of tropisetron, but not ondansetron. Effects of tropisetron were significantly antagonized by co-administration of the alpha7 nicotinic receptor antagonist methyllycaconitine, suggesting the role of alpha7 nicotinic receptors in the active mechanisms of tropisetron. These findings suggest that tropisetron could be a potential therapeutic drug for cognitive deficits in schizophrenic patients.
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ABSTRACT: In order to develop a model of persistent sensorimotor gating that did not require acute NMDA (N-methyl-D-aspartate) receptor blockade, adult female Sprague-Dawley rats were pre-treated with N-methyl-scopolamine (1 mg/kg s.c.), then administered MK-801 (dizocilpine, 5 mg/kg i.p.) along with two separate doses (5 mg/kg) of pilocarpine. The drug regimen was repeated four and eight days later. Controls received saline in lieu of any drug. Ten days after the last neurotoxic treatment, rats had a significant impairment (reduction) in pre-pulse inhibition (PPI). Each treatment group (neurotoxic treated and control) was then divided into two groups for treatment with saline or 0.5 mg/kg nicotine, administered s.c. twice daily from days 10 to 23. The rats were tested for sensorimotor gating on days 17 and 22 shortly after the morning nicotine administration. Nicotine did not affect the PPI in control animals. On day 17, PPI impairment was sustained in neurotoxically treated rats, regardless of saline or nicotine treatment. On day 22, however, the effect of neurotoxic treatment on PPI was totally absent in saline treated rats, whereas in nicotine treated rats, PPI impairment was still evident. Combination of nicotine and neurotoxic treatment also caused an up-regulation of high affinity nicotinic receptors in the cortex and the thalamus and apparent normalization of low affinity nicotinic receptors in the hippocampus. The findings indicate that muscarinic activation, in conjunction with neurotoxic NMDA receptor antagonism, produces relatively long-term impairment in auditory gating, a result relevant to modeling clinical observations of schizophrenia-associated symptoms. Contrary to expectation, nicotine administration in this model resulted in further impairment rather than amelioration of PPI. The results suggest a sustainable model of PPI impairment and possible role of nicotinic receptors in selective brain regions in this behavior.Neurotoxicity Research 09/2008; 13(3-4):151-61. DOI:10.1007/BF03033499 · 3.15 Impact Factor
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ABSTRACT: The aim of the present work is to assess the chemical and biological diversity of ligands reported in scientific articles or patents to be active against ion channels targets. A specific query of the AurSCOPE Ion Channel knowledge database was constructed to retrieve a set of the most active non-peptide ligands tested in binding or electrophysiology experiments against all ion channel families. A biological activity threshold cutoff expressed by K(i), IC(50), or EC(50) was set to 300 nM. This activity cutoff was selected such that we would retrieve a set of compounds, which contain the most active ligands for all target families, but is a reasonable number to analyze. To encode the chemical space for the entire active dataset (9897 molecules), ChemAxon's chemical fingerprints were computed and optimized and then employed to cluster the dataset at a variety of different similarity thresholds. Concurrently, the exploration of the biological space was performed by associating with each chemical cluster the corresponding target or target family. Tri-dimensional visualization of different voltage- and ligand-gated ion channel families projected into the active chemical space was obtained after a principal components analysis performed using selected molecular descriptors. The findings presented herein give a global picture of the realm of ion channels active ligands and link the knowledge on chemical structures with their respective biological activities.Channels (Austin, Tex.) 07/2007; 1(4):291-9. DOI:10.4161/chan.5099 · 2.32 Impact Factor