Drugs online research references
J Med Chem. 1998 Aug 13;41(17):3220-31.
Synthesis and pharmacological characterization of O-alkynyloximes of tropinone and N-methylpiperidinone as muscarinic agonists.
Xu R, Sim MK, Go ML.
Departments of Pharmacy and Pharmacology, National University of Singapore, 10 Kent Ridge Crescent, Republic of Singapore 119260.
A number of O-alkynyloximes of tropinone and N-methyl-4-piperidinone have been synthesized and evaluated for muscarinic activity. The affinities of these oximes were tested in homogenates of cerebral cortex, heart, and submandibulary glands from rats using [3H]pirenzepine and [3H]-N-methylscopolamine as radioligands. The oximes bind to the cortical muscarinic receptors with pKi values varying from 3 to 7. Higher binding affinities were observed for the O-alkynyl tropinone oximes than the corresponding piperidinone analogues. Binding to the muscarinic sites in the heart and submandibulary glands was also observed but with lower affinities. Good M1 subtype selectivity (10-fold or greater) was observed with some oximes (26a, 28a, 32a) at the cortical sites. These oximes also attenuated scopolamine-induced impairment of the water mask task in mice. Functional assays for M3 activity on the rat aorta showed that all oximes possessed M3 agonist action but M2 agonist activity was not observed at the endothelium-denuded rabbit aorta. Analysis of the quantitative structure-activity relationship (QSAR) indicated that the Connolly surface area is an important determinant of activity, accounting for 70% of the variation in cortical binding affinity among the oximes.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9703467&dopt=Abstract
uniroma2.it
1. Intracellular recordings were made from neurones in slice of rat striatum in vitro. 2. The forty-nine neurones studied were immunoreactive for choline acetyltransferase and had the electrophysiological characteristics typical of large aspiny interneurones. 3. Focal stimulation of the slice elicited a hyperpolarizing inhibitory postsynaptic potential in thirty-five neurones. This IPSP lasted 0.5-1 s and reversed polarity at a membrane potential which was dependent on the logarithm of the extracellular potassium concentration. 4. The IPSP was reversibly blocked by scopolamine and methoctramine, which has some selectivity for M2 subtype of muscarinic receptor. It was unaffected by 6-cyano-7-nitroquinoxaline-2,3-dione (10 microM), DL-2-amino-phosphonovaleric acid (30 microM) and bicuculline (30 microM). 5. Exogenous acetylcholine and muscarine also hyperpolarized the neurones, and this was blocked by methoctramine by not by pirenzepine, which is an M1 receptor-selective antagonist. 6. The findings demonstrate that muscarinic IPSPs occur in the central nervous system. The IPSP may mediate an 'autoinhibition' of striatal cholinergic neurone activity.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9705993&dopt=Abstract
Neurobiol Learn Mem. 1998 May;69(3):225-40.
Estrogen improves performance of reinforced T-maze alternation and prevents the amnestic effects of scopolamine administered systemically or intrahippocampally.
Fader AJ, Hendricson AW, Dohanich GP.
Department of Psychology, Tulane University, New Orleans, Louisiana, 70118, USA.
In a previous study, administration of high doses of estradiol benzoate (100 microgram/kg for 3 days im) to ovariectomized Long-Evans rats counteracted impairments of reinforced T-maze alternation induced by systemic administration of scopolamine, a muscarinic receptor blocker. In the current study, daily administration of lower doses of estradiol benzoate (5 microgram/kg for 3 weeks sc) increased the number of correct reinforced alternations during T-maze acquisition in ovariectomized rats compared to oil-treated controls and prevented impairments of reinforced alternation induced by injection of scopolamine hydrobromide (0.2 mg/kg ip). Furthermore, scopolamine (20 microgram) delivered bilaterally to the dorsal hippocampus reduced reinforced T-maze alternation in ovariectomized rats previously trained to complete this task while daily treatment with estradiol benzoate (5 microgram/kg sc) for 1 week prior to scopolamine infusion counteracted this impairment. In summary, physiological levels of estrogen improved performance during acquisition of reinforced T-maze alternation and prevented impairments induced by scopolamine administered systemically or intrahippocampally. Copyright 1998 Academic Press.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9707487&dopt=Abstract
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