Reproductive phenology of Melastomataceae species with contrasting reproductive systems: contemporary and historical drivers.

Flowering and fruiting are key events in the life history of plants, and both are critical to their reproductive success. Besides the role of evolutionary history, plant reproductive phenology is regulated by abiotic factors and shaped by biotic interactions with pollinators and seed dispersers. In Melastomataceae, a dominant Neotropical family, the reproductive systems vary from allogamous with biotic pollination to apomictic, and seed dispersal varies from dry (self-dispersed) to fleshy (animal-dispersed) fruits. Such variety in reproductive strategies is likely to affect flowering and fruiting phenologies. In this study, we described the reproductive phenology of 81 Melastomataceae species occurring in two biodiversity hotspots: the Atlantic rain forest and the campo rupestre. We aim to disentangle the role of abiotic and biotic factors defining flowering and fruiting times of Melastomataceae species, considering the contrasting breeding and seed dispersal systems, and their evolutionary history. In both vegetation types, pollinator-dependent species had higher flowering seasonality than pollinator-independent ones. Flowering patterns presented phylogenetic signal regardless of vegetation type. Fruiting of fleshy-fruited species was seasonal in campo rupestre but not in Atlantic rain forest; the fruiting of dry-fruited species was also not seasonal in both vegetation types. Fruiting showed a low phylogenetic signal, probably because the influence of environment and dispersal agents on fruiting time is stronger than the phylogenetic affinity. Considering these ecophylogenetic patterns, our results indicate that flowering may be shaped by the different reproductive strategies of Melastomataceae lineages, while fruiting patterns may be governed mainly by the seed dispersal strategy and flowering time, with less phylogenetic influence.

High-performance liquid chromatography measurement of hyperforin and its reduced derivatives in rodent plasma.

A reverse-phase high-performance liquid chromatography method was developed for the determination of hyperforin and its reduced derivatives octahydrohyperforin and tetrahydrohyperforin in rodent plasma. The procedure includes solid-phase extraction from plasma using the Baker 3cc C8 cartridge, resolution on the Symmetry Shield RP8 column (150 mm x 4.6 mm, i.d. 3.5 microm) and UV absorbance detection at 300 nm. The assay was linear over a wide range, with an overall coefficient of variation less than 10% for all compounds. The precision and accuracy were within acceptable limits and the limit of quantitation was sufficient for studies preliminarily assessing the disposition of tetrahydrohyperforin and octahydrohyperforin in the mouse and rat.

Effects of chronic treatment with escitalopram or citalopram on extracellular 5-HT in the prefrontal cortex of rats: role of 5-HT1A receptors.

1 Microdialysis was used to study the acute and chronic effects of escitalopram (S-citalopram; ESCIT) and chronic citalopram (CIT), together with the 5-HT1A receptor antagonist WAY100,635 (N-[2-[methoxyphenyl)-1-piperazinyl]ethyl]-N-(2-pyridinyl) cyclohexane carboxamide trihydrochloride) and the 5-HT1A receptor agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), on extracellular 5-hydroxytryptamine (5-HT) levels in the rat prefrontal cortex. 2 Extracellular 5-HT rose to 234 and 298% of basal values after subcutaneous (s.c.) acute doses of 0.15 and 0.63 mg kg(-1) ESCIT. No further increase was observed at 2.5 mg kg(-1) ESCIT (290%). 3 The effect of 13-day s.c. infusion of 10 mg kg(-1) day(-1) ESCIT on extracellular 5-HT (422% of baseline) was greater than after 2 days (257% of baseline), whereas exposure to ESCIT was similar. In contrast, the increase in extracellular 5-HT induced by the infusion of CIT for 2 (306%) and 13 days (302%) was similar. However, brain and plasma levels of S-citalopram in rats infused with CIT for 13 days were lower than after 2 days. 4 Acute treatment with 2.5 mg kg(-1) ESCIT or 5 mg kg(-1) CIT raised extracellular 5-HT by 243 and 276%, respectively, in rats given chronic vehicle but had no effect in rats given ESCIT (10 mg kg(-1) day(-1)) or CIT (20 mg kg(-1) day(-1)) for 2 or 13 days, suggesting that the infused doses had maximally increased extracellular 5-HT. WAY100,635 (0.1 mg kg(-1) s.c.) increased extracellular 5-HT levels by 168, 174 and 169% of prechallenge values in rats infused with vehicle or ESCIT for 2 or 13 days, respectively. WAY100,635 enhanced extracellular 5-HT levels to 226, 153 and 164% of prechallenge values in rats infused with vehicle or CIT for 2 and 13 days, respectively. 5 8-OH-DPAT (0.025 mg kg(-1)) reduced extracellular 5-HT by 54% in control rats, but had no effect in those given ESCIT and CIT for 13 days. 6 This series of experiments led to the conclusion that chronic treatment with ESCIT desensitizes the 5-HT1A receptors, regulating the release of 5-HT in the prefrontal cortex and enhances the effect of the drug on extracellular 5-HT. They also indicate that chronic treatment with ESCIT and CIT did not prevent WAY100,635 from raising extracellular 5-HT.

Vaccination with DNA containing tat coding sequences and unmethylated CpG motifs protects cynomolgus monkeys upon infection with simian/human immunodeficiency virus (SHIV89.6P).

Recent evidence suggests that a CD8-mediated cytotoxic T cell response against the Tat protein of human immunodeficiency virus (HIV)/simian immunodeficiency virus (SIV) controls primary infection after pathogenic virus challenge, and correlates with the status of long-term nonprogressor in humans. Due to the presence of unmethylated CpG sequences, DNA vaccination can boost the innate immunity driving more potent T cell-mediated immune responses. Therefore, cynomolgus monkeys were vaccinated with a tat-expressing vector containing defined unmethylated CpG sequences (pCV-tat). Here it is shown that the intramuscular inoculation of the pCV-tat contained primary infection with the highly pathogenic SHIV89.6P virus preventing the CD4(+) T cell decline in all the vaccinated monkeys. Undetectable virus replication and negative virus isolation correlated in all cases with the presence of anti-Tat CTLs. However, a CD8-mediated non cytolytic antiviral activity was also present in all protected animals. Of note, this activity was absent in the controls but was present in the monkey inoculated with the CpG-rich vector alone that was partially protected against viral challenge (i.e. no virus replication but positive virus isolation). These results suggest that a CTL response against Tat protects against primary infection by blocking virus replication at its early stage, in the absence of sterilizing immunity. Nevertheless, the boost of the innate immunity by CpG sequences can contribute to this protection both by driving more potent CTL responses and by inducing other CD8-mediated antiviral activities. Thus, the CpG-rich tat DNA vaccine may represent a promising candidate for preventive and therapeutic vaccination against AIDS.

Chronic treatment with reboxetine by osmotic pumps facilitates its effect on extracellular noradrenaline and may desensitize alpha(2)-adrenoceptors in the prefrontal cortex.

1. This study investigated the effect of acute (2 days) and chronic (14 days) treatment with a selective inhibitor of noradrenaline uptake, reboxetine (10 mg kg(-1) day(-1)) by osmotic pumps, on extracellular noradrenaline and the sensitivity of alpha(2)-adrenoceptors in the prefrontal cortex of rats. 2. The effect of continuous infusion of reboxetine for 14 days on cortical extracellular noradrenaline was significantly higher (599% of vehicle levels) than after 2 days (263% of vehicle levels). 3. Brain concentrations of reboxetine after 2 and 14 days of infusion were 37.9+/-17.8 and 37.1+/-7.7 ng g(-1), respectively. 4. Reboxetine infused for 2 and 14 days significantly increased extracellular dopamine in the prefrontal cortex, to a similar extent (257 and 342% of vehicle levels, respectively), whereas extracellular 5-HT was not modified by either treatment. 5. Clonidine (10 and 30 microg kg(-1) i.p.) reduced cortical extracellular noradrenaline similarly in animals treated with reboxetine or vehicle for 2 days whereas the effects in rats infused with reboxetine for 14 days were markedly less than in vehicle-treated animals. 6. Clonidine (0.05 and 0.2 microM), infused through the dialysis probe into the prefrontal cortex, reduced cortical extracellular noradrenaline much less in rats treated with reboxetine for 14 days than in vehicle-treated animals. 7. Reboxetine's effect on extracellular noradrenaline in the prefrontal cortex was greater after chronic treatment and could be associated with desensitization of terminal alpha(2)-adrenoceptors that normally serve to inhibit noradrenaline release.

Immune activation in africa is environmentally-driven and is associated with upregulation of CCR5. Italian-Ugandan AIDS Project.

BACKGROUND: HIV infection in Africa is associated with immune activation and a cytokine profile that stimulates CCR5 expression. We investigated whether this immune activation is environmentally driven; if a dominant expression of CCR5 could indeed be detected in African individuals; and if R5 HIV strains would be prevalent in this population. METHODS: Freshly drawn peripheral blood mononuclear cells from HIV-uninfected African and Italian individuals living in rural Africa, from HIV-uninfected Africans and Italians living in Italy, and from HIV-infected African and Italian patients were analysed. Determinations of HIV coreceptor-specific mRNAs and immunophenotype analyses were performed in all samples. Virological analyses included virus isolation and characterization of plasma neutralizing activity. FINDINGS: Results showed that: immune activation is detected both in Italian and African HIV-uninfected individuals living in Africa but not in African subjects living in Italy; CCR5-specific mRNA is augmented and the surface expression of CCR5 is increased in African compared with Italian residents (CXCR4-specific mRNA is comparable); R5-HIV strains are isolated prevalently from lymphocytes of African HIV-infected patients; and plasma neutralizing activity in HIV-infected African patients is mostly specific for R5 strains. CONCLUSIONS: Immune activation in African residents is environmentally driven and not genetically predetermined. This immune activation results in a skewing of the CCR5 : CXCR4 ratio which is associated with a prevalent isolation of R5 viruses. These data suggest that the selection of the predominant virus strain within the population could be influenced by an immunologically driven pattern of HIV co receptor expression.

SHIV89.6P pathogenicity in cynomolgus monkeys and control of viral replication and disease onset by human immunodeficiency virus type 1 Tat vaccine.

The Tat protein of human immunodeficiency virus (HIV) is produced very early after infection, plays a key role in the virus life cycle and in acquired immunodeficiency syndrome (AIDS) pathogenesis, is immunogenic and well conserved among all virus clades. Notably, a Tat-specific immune response correlates with non-progression to AIDS. Here, we show that a vaccine based on the Tat protein of HIV blocks primary infection with the simian/human immunodeficiency virus (SHIV)89.6P and prevents the CD4 T cell decline and disease onset in cynomolgus monkeys. No signs of virus replication were found in five out of seven vaccinated macaques for almost 1 year of follow-up. Since the inoculated virus (derived from rhesus or from cynomolgus macaques) is shown to be highly pathogenic in cynomolgus macaques, the results indicate efficacy of Tat vaccination in protection against highly pathogenic virus challenge. Finally, the studies of the Tat-specific immunological responses indicate a correlation of protection with a cytotoxic T cell response. Thus, a Tat-based vaccine is a promising candidate for preventive and therapeutic vaccination in humans.

Non-nucleoside HIV-1 reverse transcriptase inhibitors: synthesis and biological evaluation of novel quinoxalinylethylpyridylthioureas as potent antiviral agents.

New heterocyclic derivatives of ethylpyridylthiourea, quinoxalinylethylpyridylthiourea (QXPT) and analogues, inhibited human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) activity and prevented HIV-1 cytopathogenicity in T4 lymphocytes. Several of these novel non-nucleoside RT inhibitors, with a substituted pyrroloquinoxalinone heteroaromatic skeleton, showed inhibitory activity against wild-type RT as well as against mutant RTs containing the single amino acid substitutions L1001, K103N, V106A, Y1811 and Y188L that was much greater than other non-nucleoside inhibitors such as nevirapine. Maximum potency in enzymatic assays was achieved with a fluoropyrroloquinoxaline skeleton linked to the ethylpyridylthiourea moiety (FQXPT). In cell-based assays on different cell lines and on human monocyte-macrophages, 6-FQXPT exhibited EC50 values in the nanomolar range, with a promising selectivity index. Moreover, 6-FQXPT showed synergistic antiviral activity with zidovudine.

Pyrroloquinoxaline derivatives as high-affinity and selective 5-HT(3) receptor agonists: synthesis, further structure-activity relationships, and biological studies.

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.

Control of SHIV-89.6P-infection of cynomolgus monkeys by HIV-1 Tat protein vaccine.

Vaccine strategies aimed at blocking virus entry have so far failed to induce protection against heterologous viruses. Thus, the control of viral infection and the block of disease onset may represent a more achievable goal of human immunodeficiency virus (HIV) vaccine strategies. Here we show that vaccination of cynomolgus monkeys with a biologically active HIV-1 Tat protein is safe, elicits a broad (humoral and cellular) specific immune response and reduces infection with the highly pathogenic simian-human immunodeficiency virus (SHIV)-89.6P to undetectable levels, preventing the CD4+ T-cell decrease. These results may provide new opportunities for the development of a vaccine against AIDS.

Orally administered ranitidine plasma concentrations before and after biliopancreatic diversion in morbidly obese patients.

BACKGROUND: Patients undergoing biliopancreatic diversion (BPD) may develop gastric ulcers, particularly within the first postoperative year. The prophylactic use of antisecretory compounds at the usual therapeutic doses, mainly conventional H2-receptor antagonists such as ranitidine, may reduce the incidence of this complication, which occurs in approximately 5% of patients after BPD. METHODS: The authors measured the plasma concentrations of ranitidine (300 mg orally) in obese patients, before and 8 months after BPD, and in control subjects of normal weight. The study included 11 obese patients undergoing BPD (age 45+/-14 years; preoperative and postoperative weights 124+/-21 and 92+/-11 kg) and 10 normal-weight subjects (age 37+/-13 years, weight 67+/-9 kg). RESULTS: Postoperative ranitidine plasma concentrations showed only minor differences from preoperative levels, with slightly higher maximum concentrations occurring sooner. The mean area under the curve was on the average 30% higher than preoperatively. All parameters, however, were similar to those in control subjects. CONCLUSIONS: BPD per se does not greatly affect the pharmacokinetic behavior of ranitidine, and therefore a conventional dosage regimen appears adequate for the prophylaxis and therapy of gastric ulcers associated with this operation.

Citalopram-induced hypophagia is enhanced by blockade of 5-HT(1A) receptors: role of 5-HT(2C) receptors.

The selective 5-hydroxytryptamine reuptake inhibitor citalopram (10 and 20 mg kg(-1), i.p.) significantly reduced food intake in male rats (CD-COBS) habituated to eat their daily food during a 4-h period. The 5-HT1A receptor antagonist WAY100635 (0.3 mg kg(-1)) administered systemically did not modify feeding but significantly potentiated the reduction in food intake caused by 10 mg kg(-1) i.p. citalopram. The dose of 5 mg kg(-1) i.p. citalopram was not active in animals pretreated with vehicle but significantly reduced feeding in animals pretreated with WAY100635. WAY100635 (0.1 microg 0.5 microl(-1)) injected into the dorsal raphe significantly potentiated the hypophagic effect of 10 mg kg(-1) citalopram. WAY100635 (1.0 microg 0.5 microl(-1)) injected into the median raphe did not modify feeding or the hypophagic effect of 10 mg kg(-1) citalopram. The 5-HT2B/2C receptor antagonist SB206553 (10 mg kg(-1), p.o.) slightly reduced feeding by itself but partially antagonized the effect of WAY100635 administered systemically (0.3 mg kg(-1), s.c.) or into the dorsal raphe (0.1 microg 0.5 microl(-1)) in combination with 10 mg kg(-1) i.p. citalopram. The hypophagic effect of 10 mg kg(-1) i.p. citalopram alone was not significantly modified by SB206553. Brain concentrations of citalopram and its metabolite desmethylcitalopram in rats pretreated with SB206553, WAY100635 and their combination were comparable to those of vehicle-pretreated rats, 90 min after citalopram injection. The hypophagic effect of citalopram was potentiated by blocking 5-HT1A receptors. Only the effect of the WAY100635/citalopram combination seemed to be partially mediated by central 5-HT2C receptors.

Acid-catalysed hydrolysis and benzodiazepine-like properties of 5-(dialkylamino)- and 5-(alkylthio)-substituted 8-chloro-6-phenyl-6H-[1,2,4]triazolol[4,3-a][1,5]benzodiazepines in mice.

The in-vitro and in-vivo hydrolysis of two benzodiazepine compounds has been studied to evaluate their in-vivo activity in mice. Compounds RL 218 and RL 236, selected as representative examples of N,N-dialkyl-8-chloro-6-phenyl-6H-[1,2,4]triazolo[4,3-a][1,5]benzodiaz epin-5-amines (1) and of their 5-(alkylthio) substituted analogues (2), were rapidly hydrolysed to the corresponding 8-chloro-6-phenyl-4H-[1,2,4]triazolo[4,3-a][1,5]benzodiazepin-5(6H )-one 3 (RL 214) in aqueous acidic solution at pH 1.5. This reaction also occurred extensively in mice when compounds RL 218 and RL 236 were given orally but not intraperitoneally. Both compounds were active against pentylenetetrazole-induced lethal convulsions in mice only when administered orally. After administration of pharmacologically effective oral doses (ED50, the dose protecting 50% of mice), at the time of assessment of the anti-pentylenetetrazole activity, mean brain concentrations of RL 218 and RL 236 were below the limits of sensitivity of the analytical procedure whereas brain concentrations of their metabolite RL 214 were comparable with that present after an oral equiactive dose of this compound itself. RL 214 but not RL 218 or RL 236 had in-vitro affinity for brain benzodiazepine receptors. These results indicate that the anticonvulsant activity of RL 218 and RL 236 in mice depends essentially on their in-vivo transformation into the common active metabolite RL 214 which most probably arises as a result of acid catalysed hydrolysis in the gastric juice.

Evolution of the dystrophin muscular promoter and 5' flanking region in primates.

About 1.6 kb of the noncoding region upstream of the muscular dystrophin gene was sequenced in human and other primates. The alignment showed the existence of many stretches of conserved sequences among the compared species distributed all along the investigated fragment, including the 5' end. In correspondence to these conserved boxes, we identified several new putative cis-acting elements that have similarity to known control regions of other muscle-specific genes. In some cases, however, the conserved sequences did not correspond to any known transcription factor binding sites. The rate of evolution estimated site by site all along the investigated region revealed a nonhomogeneous distribution of the substitution rate, several sequences exhibited a very slow rate of evolution suggesting that evolutionary forces of different nature may be at work. On the basis of the sequence alignment, we reconstructed the phylogenetic relationships within the hominoid lineage. In addition, we estimated the relative rate of evolution between hominoid and Old World monkeys, confirming the existence of an evolutionary slowdown in the hominoid lineage.

Brain-to-blood partition and in vivo inhibition of 5-hydroxytryptamine reuptake and quipazine-mediated behaviour of nefazodone and its main active metabolites in rodents.

The brain/plasma partition of nefazodone, hydroxynefazodone (OHNFZ) and m-chlorophenyl-piperazine (mCPP) and their antagonism of p-chloroamphetamine (PCA)-induced 5-hydroxytryptamine (5-HT) depletion and quipazine-induced head twitches were compared in rodents. Nefazodone (30 mg kg(-1), i.p.) rapidly entered the brain but concentrations were exceeded by mCPP, the metabolic ratio being 47 and 10 in the mouse and rat respectively. OHNFZ was detectable in plasma but never in brain. Brain concentrations of OHNFZ in the mouse (30 mg kg(-1), i.p.) were less than 10% of those in plasma, confirming a poor blood-brain barrier penetration. Concentrations of its metabolite mCPP were similar to those after 5 mg kg(-1)(i.p.) mCPP. In the mouse, nefazodone (30 mg kg(-1)) antagonized the 5-HT depleting effect of PCA 2 h after dosing, when it had disappeared from brain but when mCPP concentrations were similar to those after 5 mg kg(-1) (i.p.) mCPP. However, mCPP antagonized PCA less than nefazodone. In the rat, nefazodone pretreatment (30 mg kg(-1), 15 min) prevented (97% of inhibition) quipazine-induced head twitches. The effect was weaker (65% of inhibition) but significant when only mCPP was detected in brain. Analysis of brain concentrations of the two compounds after their ED50 against quipazine indicated that both contributed to the effect, although nefazodone was more active than mCPP in terms of concentrations required to obtain a comparable reduction of twitches. These findings show that mCPP concentrates in the brain following injection of nefazodone and may play a role in preventing quipazine-induced behaviour and PCA-induced 5-HT depletion. In contrast OHNFZ poorly enters the brain and its in vivo activity is mostly due to its biotransformation to mCPP.

Conservation of a putative AP1 binding site and complete homology to a fetal brain EST in a region upstream of the core muscle promoter in the human dystrophin gene.

A region of 744 basepairs (bp) upstream of the muscular dystrophin promoter (UMDP) was amplified by inverse-polymerase chain reaction (PCR), cloned and sequenced. Analysis of this sequence for the presence of putative transcriptional control elements identified several similarities with known cis-acting sequence motifs including two MyoD and two Ap1 motifs. One of these Ap1 motifs was found to be completely conserved within an otherwise highly variable region among five primate species. Complete homology to a human fetal brain expressed sequence tag (EST) was also observed over 201 bp at the 5' end of the UMDP region. Northern blot analysis using a radiolabelled EST probe identified a 1 kb mRNA expressed in human placenta and at lower levels in the heart. These results raise the possibility that additional transcriptional regulatory elements are located upstream of the core muscle promoter, and provide the first evidence for the existence of a gene that overlaps the human dystrophin gene.

Augmented serum neutralizing activity against primary human immunodeficiency virus type 1 (HIV-1) isolates in two groups of HIV-1-infected long-term nonprogressors.

Neutralizing activity against primary human immunodeficiency virus type 1 (HIV-1) isolates from 17 persons who were long-term disease nonprogressors (LTNPs) and 13 persons who were fast progressors (FPs) was compared. Sera from LTNPs showed higher neutralizing activity both in titer and in host spectrum than did sera from FPs. However, LTNP sera had limited neutralizing activity against HIV-1 subtypes from different geographic areas. Sera collected 6 years earlier from both groups had limited neutralizing activity, indicating that early responses are not predictive for disease progression. LTNPs had very low virus loads, as reflected by only one positive isolation, which was an MT-2-negative phenotype. Virus was isolated from all FPs, and the isolates showed a phenotype switch from MT-2 negative to MT-2 positive. Development of high-titer, broadly cross-reactive neutralizing antibodies is associated with control of virus replication and low virus load in HIV-1-infected LTNPs.

Novel and highly potent 5-HT3 receptor agonists based on a pyrroloquinoxaline structure.

The synthesis and the biological evaluation of a series of novel pyrroloquinoxaline derivatives are described. In binding studies several compounds proved to be potent and selective 5-HT3 receptor ligands. The most active pyrroloquinoxalines, 11d and 11e, showed a subnanomolar affinity for 5-HT3 receptor and were able to functionally discriminate the central and peripheral 5-HT3 receptor, being agonists and antagonists, respectively. In functional studies ([14C]-guanidinium accumulation test in NG 108-15 cells, in vitro) most of the synthesized compounds showed clear-cut 5-HT3 agonist properties. In in vivo studies on the von Bezold-Jarisch reflex test (a peripheral interaction model) the behavior of the tested compounds ranged from agonist to antagonist, while clear agonist properties were obtained with 12a on cortical acetylcholine release in freely moving rats. Pharmacokinetic studies with 11e and 12c indicate that the compounds easily cross the blood-brain barrier (BBB) after systemic administration with a brain/plasma ratio of 17.5 and 37.5, respectively. Thus compounds 11e and 12c represent the most potent central 5-HT3 agonists identified to date that are able to cross the blood-brain barrier.

Neuropharmacological effects of low and high doses of repeated oral dexfenfluramine in rats: a comparison with fluoxetine.

The neuropharmacological effects of repeated oral doses of dexfenfluramine (DF; 1.25-10 mg/kg, twice daily for 21 days) were examined in rats and related to the drug brain levels. Results were compared with fluoxetine (FL) given at similar doses relative to its anorectic ED50. Both drugs dose-dependently slowed body weight gain and reduced brain serotonin (5-HT). However, at 1.25 mg/kg DF caused only a slight and transient decrease in cortical 5-HT. Comparable doses of FL (6.25-12.5 mg/kg) lowered 5-HT more than DF, besides slightly reducing striatal dopamine. At higher doses DF markedly reduced 5-HT in all regions, and to a lesser extent noradrenaline in hippocampus. There was a negative relationship between 5-HT and log total active drug levels and the indole was approximately halved at drug levels about 50 times lower with DF than FL. However, the ratio between drug levels causing marked 5-HT reductions and those considered anorectic was similar for DF and FL because brain levels at the anorectic ED50 were higher with FL than DF. Long-lasting reductions of 5-HT were also observed but recovery was only consistently slow beginning from 5 mg/ kg DF. Comparable doses of FL could not be used because its general toxicity leads to the death of rats after only 2-4 multiples of its anorectic ED50.

Effects of chronic treatment with fluoxetine and citalopram on 5-HT uptake, 5-HT1B autoreceptors, 5-HT3 and 5-HT4 receptors in rats.

The effect in rats of chronic treatment with two specific 5-HT reuptake inhibitors (SSRI) with antidepressant properties, citalopram (10 mg/kg, i.p. twice a day for 14 days, one day washout) and fluoxetine (15 mg/kg, p.o. twice a day for 21 days, 7 days washout), was evaluated on some mechanisms involved in central 5-HT neurotransmission. No adaptive modifications of brain 5-HT uptake (sites) were found by measuring functional [3H]5-HT uptake and [3H]citalopram binding in cortical and hippocampal synaptosomes, and by [3H]citalopram binding autoradiography in the raphe nuclei (5-HT cell bodies) and the ventral tegmental area (5-HT axonal pathway). Chronic treatments had no effect on presynaptic 5-HT1B autoreceptors, functionally evaluated by measuring 5-HT1B-mediated inhibition of depolarization-induced [3H]5-HT release from cortical and hippocampal synaptosomes. Chronic citalopram or fluoxetine did not significantly affect the binding of [3H]BRL-43694 to 5-HT3 receptors in the rat brain cortex. Citalopram had no effect on [125I]SB-207710 binding to 5-HT4 receptors, measured by autoradiography in the substantia nigra. Negative results, such as those reported in the present study, could be due to a number of variables including the animal species, the treatment schedule or the brain areas considered, thus explaining the differences from some previous reports of significant effects of SSRI. However, our negative data are in agreement with many other published studies, suggesting that adaptive modifications of brain 5-HT transporters, terminal 5-HT1B receptors, 5-HT3 and 5-HT4 receptors may not be a general effect induced by all SSRI.