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Sigma (sigma) and phencyclidine (PCP) receptor ligands, apart from their main effects on sigma receptors and NMDA receptor-mediated neurotransmission, have been found to interact with catecholamine systems in several central and peripheral tissues. In the present study the binding profile of [3H]nisoxetine ([3H]NIS), a selective marker of the noradrenaline transporter, has been characterized in rat vas deferens membranes to further study its modulation by a number of characteristic sigma and PCP ligands. The binding of [3H]NIS was found to be of high affinity (Kd = 1.63 +/- 0.36 nM), saturable, sodium-dependent and to a single population of binding sites (nH = 1.003 +/- 0.017). The maximal binding capacity was 1,625 +/- 500 fmol/mg of protein. Kinetic experiments gave a k(+1) of 3.9 x 10(7) min(-1)M(-1) and a k(-1) of 0.005 min(-1). The [3H]NIS binding was totally inhibited, with IC50 values in the micromolar range, by all the sigma and PCP ligands tested, with the following order of potency: haloperidol > dextromethorphan > dizocilpine > dextrorphan > (+)-3-PPP > PCP > tenocyclidine. This order correlates well with that described in other tissues using [3H]desmethylimipramine. The inhibition by all these compounds, except that of (+)-3-PPP, was competitive. These results suggest that sigma and PCP ligands bind, at low micromolar concentrations, to a site in the noradrenaline transporter that is labelled by [3H]NIS.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9489512&dopt=Abstract
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J Neurochem. 1998 Mar;70(3):1077-87.
Release and uptake rates of 5-hydroxytryptamine in the dorsal raphe and substantia nigra reticulata of the rat brain.
Bunin MA, Prioleau C, Mailman RB, Wightman RM.
Department of Chemistry, University of North Carolina, Chapel Hill 27599-1108, USA.
Fast scan cyclic voltammetry with carbon fiber electrodes has been used to investigate the dynamics of the neurotransmitter 5-hydroxytryptamine (5-HT) in the extracellular fluid of two brain regions: the dorsal raphe and the substantia nigra reticulata. The method used previously was shown to be optimized to allow the time course of 5-HT concentration changes to be measured rapidly. Measurements were made in slices prepared from the brains of rats with the carbon fiber electrode inserted into the tissue and a bipolar stimulating electrode placed on the slice surface. Identification of 5-HT as the detected substance in both regions was based on voltammetric, anatomical, physiological, and pharmacological evidence. Autoradiography using [3H]paroxetine revealed highest 5-HT transporter binding densities in the regions in which voltammetric measurements were made. Evaluation of the pharmacological actions of tetrodotoxin and tetrabenazine, as well as the effects of calcium removal, suggested that 5-HT storage was vesicular and that the release process was exocytotic. The effects of fluoxetine (0.5 microM) were typical of a competitive uptake inhibitor, changing Km with little effect on Vmax. Release of 5-HT was found to be maximal with wide (2-ms) stimulus pulses in both regions, as expected for release from small unmyelinated processes, and to increase linearly with the number of pulses when high frequencies (100 Hz) were used. At lower frequencies, the concentration observed was a function of both release and uptake. Kinetic simulations of the data revealed that the major difference in 5-HT neurotransmission between the two regions was that release and uptake rates are twice as large in the dorsal raphe ([5-HT] per pulse = 100 +/- 20 nM, Vmax = 1,300 +/- 20 nM/s for dorsal raphe; [5-HT] per pulse = 55 +/- 7 nM, Vmax = 570 +/- 70 nM/s for substantia nigra reticulata). When normalized to tissue content, uptake rates in both regions were identical and similar to rates previously reported for dopamine in dopamine terminal regions. Nonetheless, compared with dopaminergic transmission in terminal regions such as the striatum, the absolute clearance rates in the substantia nigra reticulata and dorsal raphe were lower, resulting in a longer lifetime of 5-HT in the extracellular fluid and allowing long-range interactions.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9489728&dopt=Abstract
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Psychopharmacol Bull. 1997;33(4):755-60.
Treatment-emergent changes in sexual function with selective serotonin reuptake inhibitors as measured with the Rush Sexual Inventory.
Zajecka J, Mitchell S, Fawcett J.
Woman's Board Depression Treatment and Research Center, Rush-Presbyterian-St. Luke's Medical Center, Chicago, IL 60612, USA.
Rates of antidepressant-associated treatment emergent changes in sexual function and satisfaction vary with method of ascertainment. We used the Rush Sexual Inventory (RSI) to assess the effect of SSRIs on sexual function and satisfaction. The RSI is a comprehensive, succinct, patient-rated scale designed to provide an accurate depiction of premorbid, current, and followup changes in sexual function and satisfaction. We assessed 42 outpatients, diagnosed with major depressive disorder with or without comorbid obsessive-compulsive disorder, over their first 8 weeks of treatment with paroxetine 20 mg/day, sertraline 50-200 mg/day, or fluoxetine 20-60 mg/day. Males and females were found to experience similar rates of treatment emergent sexual dysfunction at 60 percent and 57 percent, respectively. Despite the same mechanism of action, medication treatment groups experienced varying levels of changes in sexual function and satisfaction over time. No variation existed between responders and nonresponders over time.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9493488&dopt=Abstract
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