Drugs online research references
Mol Pharmacol. 1995 Oct;48(4):623-9.
Presynaptic Ca2+/calmodulin-dependent protein kinase II: autophosphorylation and activity increase in the hippocampus after long-term blockade of serotonin reuptake.
Popoli M, Vocaturo C, Perez J, Smeraldi E, Racagni G.
Center of Neuropharmacology, University of Milan.
It is known that long-term treatment with antidepressants induces an enhancement of neurotransmission in the pathway projecting from raphe nuclei to the hippocampus. In the case of selective serotonin (5-HT) reuptake inhibitors, this enhancement is due to a desensitization of presynaptic 5-HT autoreceptors and a concomitant increase in 5-HT release in terminal areas. To investigate whether this effect is accompanied by adaptive changes in the molecular machinery regulating transmitter release at serotonergic terminals, autophosphorylation and activity of Ca2+/calmodulin-dependent protein kinase II were measured in subsynaptosomal fractions from hippocampus and total cortex. Long-term treatment with two selective serotonin reuptake inhibitors (paroxetine and fluvoxamine) and with a nonselective reuptake inhibitor (venlafaxine) induces a large increase of kinase autophosphorylation in synaptic vesicles and synaptic cytosol in the hippocampus but not in synaptosomal membranes. No significant change was detected in total cortex. The change is not reproduced by the direct addition of the drugs to the phosphorylation system and is not elicited by acute treatment of the animals. The increase in autophosphorylation is not accounted for by neosynthesis or translocation of the kinase to synaptic terminals. The change is restricted to the kinase located inside the terminals and is not detected in synaptosomal membranes, containing predominantly postsynaptic kinase, suggesting that only presynaptic kinase is affected. In the same fractions, the kinase activity is increased. These results are in agreement with reports suggesting a presynaptic effect for the SSRIs and disclose a new putative site of action for psychotropic drugs.
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war.wyeth.com
A LC-LC/MS/MS method has been developed that significantly increases the throughput in metabolism screening of drug candidates during lead optimization in discovery. This was accomplished by the reduction of sample preparation time through an on-line extraction of a drug and its metabolites from microsomal proteins using turbulent flow chromatography. Following its injection onto a column at turbulent flow, the drug and its metabolites are backwashed onto a reverse-phase column via on-line column switching and resolved chromatographically at a laminar flow of 2 mL/min. This tandem turbulent-laminar flow chromatographic system in a total cycle time of 8 min can achieve adequate separation of isomeric metabolites of venlafaxine, haloperidol, or adatanserin. Further improvement in throughput can be achieved by multiplexing both microsomal stability assessment and metabolite profiling into a single analysis. This is made possible by the ability of the ion-trap mass spectrometer to perform simultaneously multiple-reaction monitoring for microsomal stability and data-dependent multiple-stage mass spectrometric analysis for metabolite profiling within a single LC analysis. Such a LC-LC/MS/MS approach can dramatically shorten the time for providing metabolism feedback to the drug discovery process.
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ed.ac.uk
Chronic treatment with antidepressant drugs (2 weeks or longer) increases corticosteroid receptor mRNA expression in the hippocampus and reduces hypothalamic-pituitary-adrenal axis activity in parallel with improving mood and neuroendocrine function. Earlier effects are less well documented. We examined the effects of short term (9 days) treatment with fluoxetine (10 mg/kg) and venlafaxine (10 mg/kg) on hippocampal mineralocorticoid receptor (MR) and glucocorticoid receptor (GR) mRNA expression and spatial memory in adult rats. In situ hybridization histochemistry showed that the antidepressants decreased MR mRNA expression in all hippocampal subregions (e.g. 45% decrease in CA1 with venlafaxine, P<0.001), while GR mRNA expression was selectively reduced in the CA3 subregion. There was a trend for decreased plasma corticosterone levels following fluoxetine (50% fall, P=0.07) and venlafaxine (30% fall, P=0.18) but neither antidepressants affected spatial memory in the watermaze. Thus antidepressants can have complex and opposing actions on hippocampal corticosteroid receptor expression depending on the duration of treatment.
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