In vivo microdialysis and single-cell extracellular recordings were used to assess the involvement of

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1These authors contributed equally to the work.Abbreviations used: 6-OHDA, 6-hydroxydopamine; AD, Alzheimer's disease; Ab42, amyloid-b (1-42) peptide; DCFH-DA, 2¢,7¢-dichlorofluorescein diacetate; DS, Down syndrome; H 2 O 2, hydrogen peroxide; MTT, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide; NAC, N-acetylcysteine; PD, Parkinson's disease; RES, resveratrol; a-syn, alpha-synuclein. AbstractHuman sirtuins are a family of seven conserved proteins (SIRT1-7). The most investigated is the silent mating type information regulation-2 homolog (SIRT1, NM_012238), which was associated with neuroprotection in models of polyglutamine toxicity or Alzheimer's disease (AD) and whose activation by the phytocompound resveratrol (RES) has been described. We have examined the neuroprotective role of RES in a cellular model of oxidative stress, a common feature of neurodegeneration. RES prevented toxicity triggered by hydrogen peroxide or 6-hydroxydopamine (6-OHDA). This action was likely mediated by SIRT1 activation, as the protection was lost in the presence of the SIRT1 inhibitor sirtinol and when SIRT1 expression was down-regulated by siRNA approach.RES was also able to protect SK-N-BE from the toxicity arising from two aggregation-prone proteins, the AD-involved amyloidb (1-42) peptide (Ab42) and the familiar Parkinson's disease linked a-synuclein(A30P) [a-syn(A30P)]. Alpha-syn(A30P) toxicity was restored by sirtinol addition, while a partial RES protective effect against Ab42 was found even in presence of sirtinol, thus suggesting a direct RES effect on Ab42 fibrils. We conclude that SIRT1 activation by RES can prevent in our neuroblastoma model the deleterious effects triggered by oxidative stress or a-syn(A30P) aggregation, while RES displayed a SIRT1-independent protective action against Ab42.

The synthesis, pharmacological evaluation, and structure-activity relationships (SARs) of a series of novel pyrroloquinoxalines and heteroaromatic-related derivatives are described. The new pyrroloquinoxaline-related ligands were tested in rat cortex, a tissue expressing high density of 5-HT(3) receptors, and on NG108-15 cells and exhibited IC(50) values in the low nanomolar or subnanomolar range, as measured by the inhibition of [(3)H]zacopride binding. The SAR studies detailed herein delineated a number of structural features required for improving affinity. Some of the ligands were employed as "molecular yardsticks" to probe the spatial dimensions of the lipophilic pockets L1, L2, and L3 in the 5-HT(3) receptor cleft, while the 7-OH pyrroloquinoxaline analogue was designed to investigate hydrogen bonding with a putative receptor site H1 possibly interacting with the serotonin hydroxy group. The most active pyrroloquinoxaline derivatives showed subnanomolar affinity for the 5-HT(3) receptor. In functional studies ([(14)C]guanidinium accumulation test in NG108-15 hybrid cells, in vitro) most of the tested compounds showed clear-cut 5-HT(3) agonist properties, while some others were found to be partial agonists. Several heteroaromatic systems, bearing N-substituted piperazine moieties, have been explored with respect to 5-HT(3) affinity, and novel structural leads for the development of potent and selective central 5-HT(3) receptor agonists have been identified. Preliminary pharmacokinetic studies indicate that these compounds easily cross the blood-brain barrier (BBB) after systemic administration with a brain/plasma ratio between 2 and 20, unless they bear a highly hydrophilic group on the piperazine ring. None of the tested compounds showed in vivo anxiolytic-like activity, but potential analgesic-like properties have been possibly disclosed for this new class of 5-HT(3) receptor agonists.

Fluoxetine (FL) is being used in neuropharmacology as a tool for studying various functional roles of serotoninergic neurons. Its kinetics was studied in rats, a species widely used in neurochemical studies, after IV (2.5-10 mg/kg) and oral (5-20 mg/kg) administration. When injected IV the drug followed apparent first-order kinetics up the 10 mg/kg dose. Its volume of distribution was large and total body clearance was relatively high compared to liver blood flow. The mean elimination half-lives (t1/2) of FL and its active metabolite norfluoxetine (NFL) were about 5 and 15 h, respectively. The mean blood:plasma concentration ratios of FL and NFL approached unity and plasma protein binding was 85-90% for both compounds. After oral doses the kinetics of FL were complex. At the lowest dose tested (5 mg/kg) the drug was efficiently extracted by the liver (extraction ratio about 60%), resulting in bioavailability of only about 38%. Plasma areas under the curve (AUC) of the metabolite were approximately the same as after IV injection of the same dose; consequently the metabolite-to-parent drug ratio after oral administration (about 5) was approximately twice that after IV injection of FL (about 2.5). At higher doses, however, the oral bioavailability (e.g. Cmax and AUC) appeared greater than expected, possibly because of transient saturation of FL first-pass metabolism in the case of the 10 mg/kg dose and concomitant saturation of elimination kinetics at the higher dose (20 mg/kg). The apparent elimination t1/2 of FL markedly increased and the metabolite-to-parent drug ratio declined with the higher dose, this also being consistent with saturable elimination.(ABSTRACT TRUNCATED AT 250 WORDS)