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Psychopharmacology (Berl). 1998 Jul;138(2):198-206.
Dose-dependent influence of buspirone on the activities of selective serotonin reuptake inhibitors in the mouse forced swimming test.

Redrobe JP, Bourin M.

GIS Medicament, JE 2027 Neurobiologie de l'Anxiete, Faculte de Medecine, Nantes, France.

Recent clinical data suggest that buspirone may enhance the efficacy and/or reduce the latency to therapeutic effect of selective serotonin reuptake inhibitors (SSRIs) in unipolar major depressive disorder. The present study, using the mouse forced swimming test, was performed to investigate further the mechanisms involved in the potential antidepressant-enhancing effects of buspirone. Prior administration of buspirone (0.06 mg kg(-1), i.p.) significantly enhanced the anti-immobility effects of subactive doses of fluvoxamine (4 mg kg(-1), i.p.; P < 0.01), paroxetine (4 mg kg(-1), i.p.; P < 0.01), citalopram (4 mg kg(-1), i.p.; P < 0.01) and sertraline (2 mg kg(-1), i.p.; P < 0.01) in the forced swimming test. However, pretreatment with buspirone did not induce antidepressant-like effects when tested in combination with fluoxetine (4 mg kg(-1), i.p.). Each antidepressant tested reduced immobility time in the forced swimming test [citalopram (16 mg kg(-1), i.p.; P < 0.01), fluoxetine (32 mg kg(-1), i.p.; P < 0.01), fluvoxamine (32 mg kg(-1), i.p.; P < 0.01), paroxetine (16 mg kg(-1), i.p.; P < 0.01) and sertraline (16 mg kg(-1), i.p.; P < 0.01)]. Pretreatment with buspirone (0.5 mg kg(-1), i.p.), or its major metabolite 1-PP (0.5 mg kg(-1), i.p.), attenuated all SSRI-induced anti-immobility effects (P < 0.01). Concomitant studies of locomotor activity ruled out any stimulant or sedative effects of the interactions. The results of the present study suggested that low dose buspirone enhanced the activity of subactive doses of SSRIs in the mouse forced swimming test, probably via an action at 5-HT1A receptors. On the other hand, a high dose of buspirone attenuated the antidepressant-like effects of active doses of these drugs, possibly via the generation of an active metabolite (1-PP) acting at alpha2-adrenoreceptors.

online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9718290&dopt=Abstract

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Neuroreport. 1998 Aug 3;9(11):2535-8.
Contrasting effects of chronic paroxetine on 5-HT1A control of dorsal raphe cell firing and 5-HT release.

Davidson C, Stamford JA.

Academic Department of Anaesthesia and Intensive Care, St Bartholomew's and the Royal London School of Medicine and Dentistry, Royal London Hospital, UK.

To test the role of 5-HT1A receptors in the action of antidepressants, we investigated the effect of chronic paroxetine (10 mg/kg, p.o. for 21 days) on functional assays of 5-HT1A sensitivity. We constructed cumulative concentration response curves to the selective 5-HT1A agonist (+)-8-OH-DPAT on both extracellular recordings of 5-HT neurones and electrically stimulated 5-HT release in dorsal raphe brain slices. Chronic paroxetine desensitized the 5-HT1A receptors controlling firing, with an increase in EC50 from 10.7 nM to 46.2 nM 8-OH-DPAT. Chronic paroxetine did not, however, desensitize the 5-HT1A receptors controlling 5-HT release but increased the 8-OH-DPAT Emax from 54.9% to 79.2% inhibition of 5-HT release. These data suggest that there are either two distinct populations of 5-HT1A receptors or separate second messenger systems, one controlling 5-HT release and another influencing firing. Furthermore chronic paroxetine treatment can differentially modulate these different populations.

online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9721928&dopt=Abstract

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Brain Res Mol Brain Res. 1998 Aug 15;59(1):66-73.
Expression and regulation of the human dopamine transporter in a neuronal cell line.

Zhang L, Elmer LW, Little KY.

Department of Psychiatry, University of Michigan, Ann Arbor, MI, USA.

Human cocaine users exhibit increased striatal [3H]WIN35428 binding to the dopamine transporter (DAT). However, the nature of the changes induced in the DAT are complex and may not result from a simple increase in number of DAT molecules. To better understand the regulation of DAT inhibitor binding sites and their relationship to the overall process of dopamine uptake, a neuronal model system expressing the human DAT has been developed. Initial experiments were attempted with native dopaminergic neurons so as to allow examination of DAT interactions with vesicular release and storage mechanisms. Dissociated fetal rat mesencephalic neurons, of various ages and mixtures with target cells, were grown to confluence. However, [3H]WIN35428 binding was of low affinity at all levels of maturity. Following this, a simpler model was assessed, using DAT cDNA transfected into neuroblastoma-derived Neuro2A cells. Initially, no specific and little non-specific [3H]WIN35428 or [3H]paroxetine binding was found in non-transfected cells. After transfection with the human DAT inserted in the pcDNA vector, both DAT binding and dopamine uptake were significantly and stably present. Treatment with (-)cocaine, 10-6 M for 24 h, increased DAT binding and uptake, which did not occur in parallel COS-7 experiments. Other experiments with Neuro2A cells also found that dopamine uptake was down-regulated by treatment with a PKC activator. These results suggest that the transfected Neuro2A neurons should be useful for ongoing experiments examining the regulation of the DAT by assorted treatments. Copyright 1998 Elsevier Science B.V.

online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9729282&dopt=Abstract

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