Phencyclidine decreases tickling-induced 50-kHz ultrasound vocalizations in juvenile rats: a putative model of the negative symptoms of schizophrenia?

The objective of the present study was to examine the idea that the decrease in 50-kHz ultrasonic vocalizations elicited by tickling in juvenile rats following the administration of the psychotomimetic drug phencyclidine (PCP) may represent a valid model of the negative symptoms of schizophrenia. Fifty-kilohertz calls in rodents have been suggested to represent an archaic model of human laughter. Our results showed that daily tickling sessions produced a gradual increase in 50-kHz vocalizations, an effect that reached statistical significance from day 3. Administration of PCP (1 mg/kg, intraperitoneally) attenuated the 50-kHz calls induced by 4 consecutive days of tickling. The ability of several clinically effective or potential antipsychotics to reverse the effects of PCP was investigated. The 5-HT1A receptor partial agonist, buspirone (0.3 and 1 mg/kg, intraperitoneally), the dual D2/5-HT1A receptor ligand, SSR181507 (0.5-0.75 mg/kg, intraperitoneally), but not the atypical antipsychotic, aripiprazole (0.1-1 mg/kg, intraperitoneally), the 5-HT2A receptor antagonist, eplivanserin (0.3-3 mg/kg, intraperitoneally), and the GlyT1 inhibitor, SSR103800 (0.3-3 mg/kg, intraperitoneally) significantly attenuated the effects of PCP on 50-kHz calls. Importantly, in animals not treated with PCP, none of the drugs affected 50-kHz calls elicited by a first handling-tickling session, indicating that the action of buspirone and SSR181507 cannot be explained by an intrinsic effect. To investigate further the specificity of these drug effects, we tested the anxiolytic and antidepressant agents, diazepam (0.1-1 mg/kg, intraperitoneally) and fluoxetine (1-10 mg/kg, intraperitoneally), respectively, in this procedure. Neither drug affected tickling-induced 50-kHz calls in naive or PCP-treated rats. In conclusion, the results of the present study confirm that 50-kHz calls elicited by several tickling sessions in rats can be reduced by acute administration of PCP, and that this effect can be reversed by previous administration of compounds with 5-HT1A receptor agonist properties. As evidence for clinical efficacy of both agents on the negative symptoms of schizophrenia is weak or lacking, the current findings do not allow a definite conclusion to be drawn on the validity of this procedure as a model of this aspect of schizophrenia.

Lipoprotein(a) Cellular Uptake Ex Vivo and Hepatic Capture In Vivo Is Insensitive to PCSK9 Inhibition With Alirocumab.

Lipoprotein(a) (Lp[a]) is the most common genetically inherited risk factor for cardiovascular disease. Many aspects of Lp(a) metabolism remain unknown. We assessed the uptake of fluorescent Lp(a) in primary human lymphocytes as well as Lp(a) hepatic capture in a mouse model in which endogenous hepatocytes have been ablated and replaced with human ones. Modulation of LDLR expression with the PCSK9 inhibitor alirocumab did not alter the cellular or the hepatic uptake of Lp(a), demonstrating that the LDL receptor is not a major route for Lp(a) plasma clearance. These results have clinical implications because they underpin why statins are not efficient at reducing Lp(a).

Tetravalent Bispecific Tandem Antibodies Improve Brain Exposure and Efficacy in an Amyloid Transgenic Mouse Model.

Most antibodies display very low brain exposure due to the blood-brain barrier (BBB) preventing their entry into brain parenchyma. Transferrin receptor (TfR) has been used previously to ferry antibodies to the brain by using different formats of bispecific constructs. Tetravalent bispecific tandem immunoglobulin Gs (IgGs) (TBTIs) containing two paratopes for both TfR and protofibrillar forms of amyloid-beta (Aß) peptide were constructed and shown to display higher brain penetration than the parent anti-Aß antibody. Additional structure-based mutations on the TfR paratopes further increased brain exposure, with maximal enhancement up to 13-fold in wild-type mice and an additional 4-5-fold in transgenic (Tg) mice harboring amyloid plaques, the main target of our amyloid antibody. Parenchymal target engagement of extracellular amyloid plaques was demonstrated using in vivo and ex vivo fluorescence imaging as well as histological methods. The best candidates were selected for a chronic study in an amyloid precursor protein (APP) Tg mouse model showing efficacy at reducing brain amyloid load at a lower dose than the corresponding monospecific antibody. TBTIs represent a promising format for enhancing IgG brain penetration using a symmetrical construct and keeping bivalency of the payload antibody.

Stimulation of the beta3-Adrenoceptor as a novel treatment strategy for anxiety and depressive disorders.

The characterization of the first selective orally active and brain-penetrant beta3-adrenoceptor agonist, SR58611A (amibegron), has opened new possibilities for exploring the involvement of this receptor in stress-related disorders. By using a battery of tests measuring a wide range of anxiety-related behaviors in rodents, including the mouse defense test battery, the elevated plus-maze, social interaction, stress-induced hyperthermia, four-plate, and punished drinking tests, we demonstrated for the first time that the stimulation of the beta3 receptor by SR58611A resulted in robust anxiolytic-like effects, with minimal active doses ranging from 0.3 to 10 mg/kg p.o., depending on the procedure. These effects paralleled those obtained with the prototypical benzodiazepine anxiolytic diazepam or chlordiazepoxide. Moreover, when SR58611A was tested in acute or chronic models of depression in rodents, such as the forced-swimming and the chronic mild stress tests, it produced antidepressant-like effects, which were comparable in terms of the magnitude of the effects to those of the antidepressant fluoxetine or imipramine. Supporting these behavioral data, SR58611A modified spontaneous sleep parameters in a manner comparable to that observed with fluoxetine. Importantly, SR58611A was devoid of side effects related to cognition (as shown in the Morris water maze and object recognition tasks), motor activity (in the rotarod), alcohol interaction, or physical dependence. Antagonism studies using pharmacological tools targeting a variety of neurotransmitters involved in anxiety and depression and the use of mice lacking the beta3 adrenoceptor suggested that these effects of SR58611A are mediated by beta3 adrenoceptors. Taken as a whole, these findings indicate that the pharmacological stimulation of beta3 adrenoceptors may represent an innovative approach for the treatment of anxiety and depressive disorders.

Additional evidence for anxiolytic- and antidepressant-like activities of saredutant (SR48968), an antagonist at the neurokinin-2 receptor in various rodent-models.

Central tachykinins have been shown to play a role in the modulation of stress-related behaviours. Saredutant, a tachykinin NK2 receptor antagonist, displayed mixed anxiolytic- and antidepressant-like activities in rodents. The present study aimed at further characterizing its psychotropic properties. Saredutant was tested in the rat social interaction test to further confirm its anxiolytic-like activity, and in a variety of behavioural models sensitive to antidepressant drugs. In the rat social interaction test, saredutant (20 mg/kg, i.p.) significantly increased the time spent in interaction, as did the prototypical anxiolytic agents, diazepam (1 mg/kg, i.p.) and buspirone (1 mg/kg, s.c.), but not the antidepressant, fluoxetine. In a differential reinforcement of low rate-72s task, saredutant (3 mg/kg, i.p.) displayed an antidepressant-like activity by increasing reinforced response rate and percentage of responses emitted in the inter-response time bin [49-96 s]. In bulbectomized rats, saredutant (20 mg/kg, i.p.) restored the deficit of acquisition of passive avoidance. In rat pups separated from their mother, saredutant (3-10 mg/kg, s.c.) reduced ultrasonic distress calls. Finally, in the chronic mild stress paradigm in mice, a 29-day treatment regimen with saredutant (10 mg/kg, i.p.) attenuated stress-induced physical degradation. Importantly, in the depression models, the effects of saredutant were comparable to those obtained under similar experimental conditions by reference antidepressants such as fluoxetine or imipramine. Together, these results suggest further that the NK2 receptor may represent an attractive target for the treatment of both depressive and anxiety disorders.

Characterization of SSR103800, a selective inhibitor of the glycine transporter-1 in models predictive of therapeutic activity in schizophrenia.

On native human, rat and mouse glycine transporter-1(GlyT1), SSR130800 behaves as a selective inhibitor with IC50 values of 1.9, 5.3 and 6.8 nM, respectively. It reversibly blocked glycine uptake in mouse brain cortical homogenates, increased extracellular levels of glycine in the rat prefrontal cortex, and potentiated NMDA-mediated excitatory postsynaptic currents in rat hippocampal slices. SSR103800 (30 mg/kg, p.o.) decreased MK-801- and PCP-induced locomotor hyperactivity in rodents. SSR103800 (1 and 10 mg/kg, p.o.) attenuated social recognition deficit in adult rats induced by neonatal injections of PCP (10 mg/kg, s.c., on post-natal day 7, 9 and 11). SSR103800 (3 mg/kg, p.o.) counteracted the deficit in short-term visual episodic-like memory induced by a low challenge dose of PCP (1 mg/kg, i.p.), in PCP-sensitized rats (10 mg/kg, i.p.). SSR103800 (30 mg/kg, i.p.) increased the prepulse inhibition of the startle reflex in DBA/1J mice. SSR103800 decreased defensive- and despair-related behaviors in the tonic immobility test in gerbils (10 and 30 mg/kg, p.o.) and in the forced-swimming procedure in rats (1 and 3 mg/kg, p.o.), respectively. These findings suggest that SSR103800 may have a therapeutic potential in the management of the core symptoms of schizophrenia and comorbid depression states.

The selective reversible FAAH inhibitor, SSR411298, restores the development of maladaptive behaviors to acute and chronic stress in rodents.

Enhancing endogenous cannabinoid (eCB) signaling has been considered as a potential strategy for the treatment of stress-related conditions. Fatty acid amide hydrolase (FAAH) represents the primary degradation enzyme of the eCB anandamide (AEA), oleoylethanolamide (OEA) and palmitoylethanolamide (PEA). This study describes a potent reversible FAAH inhibitor, SSR411298. The drug acts as a selective inhibitor of FAAH, which potently increases hippocampal levels of AEA, OEA and PEA in mice. Despite elevating eCB levels, SSR411298 did not mimic the interoceptive state or produce the behavioral side-effects (memory deficit and motor impairment) evoked by direct-acting cannabinoids. When SSR411298 was tested in models of anxiety, it only exerted clear anxiolytic-like effects under highly aversive conditions following exposure to a traumatic event, such as in the mouse defense test battery and social defeat procedure. Results from experiments in models of depression showed that SSR411298 produced robust antidepressant-like activity in the rat forced-swimming test and in the mouse chronic mild stress model, restoring notably the development of inadequate coping responses to chronic stress. This preclinical profile positions SSR411298 as a promising drug candidate to treat diseases such as post-traumatic stress disorder, which involves the development of maladaptive behaviors.

SSR180711, a novel selective alpha7 nicotinic receptor partial agonist: (II) efficacy in experimental models predictive of activity against cognitive symptoms of schizophrenia.

SSR180711 (4-bromophenyl 1,4diazabicyclo(3.2.2) nonane-4-carboxylate, monohydrochloride) is a selective alpha7 nicotinic receptor (n-AChR) partial agonist. Based on the purported implication of this receptor in cognitive deficits associated with schizophrenia, the present study assessed efficacy of SSR180711 (i.p. and p.o.) in different types of learning and memory involved in this pathology. SSR180711 enhanced episodic memory in the object recognition task in rats and mice (MED: 0.3 mg/kg), an effect mediated by the alpha7 n-AChR, as it was no longer seen in mice lacking this receptor. Efficacy was retained after repeated treatment (eight administrations over 5 days, 1 mg/kg), indicating lack of tachyphylaxia. SSR180711 also reversed (MED: 0.3 mg/kg) MK-801-induced deficits in retention of episodic memory in rats (object recognition). The drug reversed (MED: 0.3 mg/kg) selective attention impaired by neonatal phencyclidine (PCP) treatment and restored MK-801- or PCP-induced memory deficits in the Morris or linear maze (MED: 1-3 mg/kg). In neurochemical and electrophysiological correlates of antipsychotic drug action, SSR180711 increased extracellular levels of dopamine in the prefrontal cortex (MED: 1 mg/kg) and enhanced (3 mg/kg) spontaneous firing of retrosplenial cortex neurons in rats. Selectivity of SSR180711 was confirmed as these effects were abolished by methyllycaconitine (3 mg/kg, i.p. and 1 mg/kg, i.v., respectively), a selective alpha7 n-AChR antagonist. Additional antidepressant-like properties of SSR180711 were demonstrated in the forced-swimming test in rats (MED: 1 mg/kg), the maternal separation-induced ultrasonic vocalization paradigm in rat pups (MED: 3 mg/kg) and the chronic mild stress procedure in mice (10 mg/kg o.d. for 3 weeks). Taken together, these findings characterize SSR180711 as a promising new agent for the treatment of cognitive symptoms of schizophrenia. The antidepressant-like properties of SSR180711 are of added interest, considering the high prevalence of depressive symptoms in schizophrenic patients.

SSR180711, a novel selective alpha7 nicotinic receptor partial agonist: (1) binding and functional profile.

In this paper, we report on the pharmacological and functional profile of SSR180711 (1,4-Diazabicyclo[3.2.2]nonane-4-carboxylic acid, 4-bromophenyl ester), a new selective alpha7 acetylcholine nicotinic receptor (n-AChRs) partial agonist. SSR180711 displays high affinity for rat and human alpha7 n-AChRs (K(i) of 22+/-4 and 14+/-1 nM, respectively). Ex vivo (3)[H]alpha-bungarotoxin binding experiments demonstrate that SSR180711 rapidly penetrates into the brain (ID(50)=8 mg/kg p.o.). In functional studies performed with human alpha7 n-AChRs expressed in Xenopus oocytes or GH4C1 cells, the compound shows partial agonist effects (intrinsic activity=51 and 36%, EC(50)=4.4 and 0.9 microM, respectively). In rat cultured hippocampal neurons, SSR180711 induced large GABA-mediated inhibitory postsynaptic currents and small alpha-bungarotoxin sensitive currents through the activation of presynaptic and somato-dendritic alpha7 n-AChRs, respectively. In mouse hippocampal slices, the compound increased the amplitude of both glutamatergic (EPSCs) and GABAergic (IPSCs) postsynaptic currents evoked in CA1 pyramidal cells. In rat and mouse hippocampal slices, a concentration of 0.3 muM of SSR180711 increased long-term potentiation (LTP) in the CA1 field. Null mutation of the alpha7 n-AChR gene totally abolished SSR180711-induced modulation of EPSCs, IPSCs and LTP in mice. Intravenous administration of SSR180711 strongly increased the firing rate of single ventral pallidum neurons, extracellularly recorded in anesthetized rats. In microdialysis experiments, administration of the compound (3-10 mg/kg i.p.) dose-dependently increased extracellular acetylcholine (ACh) levels in the hippocampus and prefrontal cortex of freely moving rats. Together, these results demonstrate that SSR180711 is a selective and partial agonist at human, rat and mouse alpha7 n-AChRs, increasing glutamatergic neurotransmission, ACh release and LTP in the hippocampus.

The mGluR2 positive allosteric modulator, SAR218645, improves memory and attention deficits in translational models of cognitive symptoms associated with schizophrenia.

Normalization of altered glutamate neurotransmission through activation of the mGluR2 has emerged as a new approach to treat schizophrenia. These studies describe a potent brain penetrant mGluR2 positive allosteric modulator (PAM), SAR218645. The compound behaves as a selective PAM of mGluR2 in recombinant and native receptor expression systems, increasing the affinity of glutamate at mGluR2 as inferred by competition and GTPγ35S binding assays. SAR218645 augmented the mGluR2-mediated response to glutamate in a rat recombinant mGluR2 forced-coupled Ca2+ mobilization assay. SAR218645 potentiated mGluR2 agonist-induced contralateral turning. When SAR218645 was tested in models of the positive symptoms of schizophrenia, it reduced head twitch behavior induced by DOI, but it failed to inhibit conditioned avoidance and hyperactivity using pharmacological and transgenic models. Results from experiments in models of the cognitive symptoms associated with schizophrenia showed that SAR218645 improved MK-801-induced episodic memory deficits in rats and attenuated working memory impairment in NMDA Nr1neo-/- mice. The drug reversed disrupted latent inhibition and auditory-evoked potential in mice and rats, respectively, two endophenotypes of schizophrenia. This profile positions SAR218645 as a promising candidate for the treatment of cognitive symptoms of patients with schizophrenia, in particular those with abnormal attention and sensory gating abilities.

Selective blockade of the hydrolysis of the endocannabinoid 2-arachidonoylglycerol impairs learning and memory performance while producing antinociceptive activity in rodents.

Monoacylglycerol lipase (MAGL) represents a primary degradation enzyme of the endogenous cannabinoid (eCB), 2-arachidonoyglycerol (2-AG). This study reports a potent covalent MAGL inhibitor, SAR127303. The compound behaves as a selective and competitive inhibitor of mouse and human MAGL, which potently elevates hippocampal levels of 2-AG in mice. In vivo, SAR127303 produces antinociceptive effects in assays of inflammatory and visceral pain. In addition, the drug alters learning performance in several assays related to episodic, working and spatial memory. Moreover, long term potentiation (LTP) of CA1 synaptic transmission and acetylcholine release in the hippocampus, two hallmarks of memory function, are both decreased by SAR127303. Although inactive in acute seizure tests, repeated administration of SAR127303 delays the acquisition and decreases kindled seizures in mice, indicating that the drug slows down epileptogenesis, a finding deserving further investigation to evaluate the potential of MAGL inhibitors as antiepileptics. However, the observation that 2-AG hydrolysis blockade alters learning and memory performance, suggests that such drugs may have limited value as therapeutic agents.

SSR181507, a dopamine D2 receptor antagonist and 5-HT1A receptor agonist. II: Behavioral profile predictive of an atypical antipsychotic activity.

SSR181507 ((3-exo)-8-benzoyl-N-(((2S)7-chloro-2,3-dihydro-1,4-benzodioxin-1-yl)methyl)-8-azabicyclo(3.2.1)octane-3-methanamine monohydrochloride) is a novel tropanemethanamine benzodioxane that displays antagonist activity at dopamine D(2) receptors and agonist activity at 5-HT(1A) receptors. SSR181507 antagonized apomorphine-induced climbing in mice and stereotypies in rats (ED(50) of 2 and 3.4 mg/kg i.p., respectively) and blocked D-amphetamine-induced hyperlocomotion in rats at lower doses (0.3-1 mg/kg i.p.). At 1-10 mg/kg, it was found to disrupt active avoidance in mice. SSR181507 did not induce catalepsy in rats (MED>60 mg/kg i.p.) and antagonized (3-10 mg/kg i.p.) haloperidol-induced catalepsy. SSR181507 was also active in two models sensitive to antidepressant/anxiolytic drugs: in a guinea-pig pup/mother separation test, it decreased (1-3 mg/kg i.p.) the time spent vocalizing during the separation episode, and in a lithium-induced taste aversion procedure in rats, it partially reversed (3 mg/kg i.p.) the decrease of intake of a saccharin solution. Furthermore, SSR181507 increased (3 mg/kg i.p.) the latency time to paradoxical sleep in rats, an effect commonly observed with antidepressants. Coadministration of the selective 5-HT(1A) blocker SL88.0338 produced catalepsy and antagonized the effects of SSR181507 in the depression/anxiety tests, confirming the view that activation of 5-HT(1A) receptors confers an atypical profile on SSR181507, and is responsible for its antidepressant/anxiolytic properties. Finally, SSR181507 (1-3 mg/kg) did not affect memory performance in a Morris water maze task in rats. The pharmacological profile of SSR181507 suggests that it should control the symptoms of schizophrenia, in the absence of extrapyramidal signs and cognitive deficits, with the additional benefit of antidepressant/anxiolytic activities.

The neurokinin NK2 antagonist, saredutant, ameliorates stress-induced conditions without impairing cognition.

The current work extends our previous findings in stress-related disorders, but also addresses the impact of a neurokinin-2 (NK2) antagonist on cognition. Besides efficacy in mood disorders, an NK2 antagonist may have the potential to lack the disinhibitory components and adverse side effects associated with existing clinical treatments. Saredutant (3-30 mg/kg, per os, p.o.) was tested for anxiolytic-like potential in three mouse models: holeboard, stress-induced hyperthermia (SIH) and four-plate. In the holeboard model saredutant (30 mg/kg) showed a trend to increase head dipping without affecting general activity. In the SIH model, saredutant demonstrated a significant reduction in stress-induced temperature at 30 mg/kg, while the number of punished crossings in the four-plate was increased at all doses tested (3-30 mg/kg). While chlordiazepoxide (CDP) demonstrated anxiolytic-like effects in these models, the adverse side effects of benzodiazepines, such as sedation, disinhibition and cognitive deficits are well-documented. Saredutant produced no detrimental effect in three models of cognition: Morris Water Maze (MWM) in rats, spontaneous alternation in a Y-maze in mice and novel objection recognition in mice. In contrast, the benzodiazepine, diazepam (DZM), produced cognitive impairments. NK2 receptor antagonists like saredutant may therefore yield beneficial effects for mood disorders without the adverse effects of current treatments.

The glycine transporter-1 inhibitor SSR103800 displays a selective and specific antipsychotic-like profile in normal and transgenic mice.

Schizophrenia has been initially associated with dysfunction in dopamine neurotransmission. However, the observation that antagonists of the glutamate N-methyl-D-aspartate (NMDA) receptor produce schizophrenic-like symptoms in humans has led to the idea of a dysfunctioning of the glutamatergic system via its NMDA receptor. As a result, there is a growing interest in the development of pharmacological agents with potential antipsychotic properties that enhance the activity of the glutamatergic system via a modulation of the NMDA receptor. Among them are glycine transporter-1 (GlyT1) inhibitors such as SSR103800, which indirectly enhance NMDA receptor function by increasing the glycine (a co-agonist for the NMDA receptor) levels in the synapse. This study aimed at investigating the potential antipsychotic-like properties of SSR103800, with a particular focus on models of hyperactivity, involving either drug challenge (ie, amphetamine and MK-801) or transgenic mice (ie, NMDA Nr1(neo-/-) and DAT(-/-)). Results showed that SSR103800 (10-30 mg/kg p.o.) blocked hyperactivity induced by the non-competitive NMDA receptor antagonist, MK-801 and partially reversed spontaneous hyperactivity of NMDA Nr1(neo-/-) mice. In contrast, SSR103800 failed to affect hyperactivity induced by amphetamine or naturally observed in dopamine transporter (DAT(-/-)) knockout mice (10-30 mg/kg p.o.). Importantly, both classical (haloperidol) and atypical (olanzapine, clozapine and aripiprazole) antipsychotics were effective in all these models of hyperactivity. However, unlike these latter, SSR103800 did not produce catalepsy (retention on the bar test) up to 30 mg/kg p.o. Together these findings show that the GlyT1 inhibitor, SSR103800, produces antipsychotic-like effects, which differ from those observed with compounds primarily targeting the dopaminergic system, and has a reduced side-effect potential as compared with these latter drugs.

SL65.0155, a novel 5-hydroxytryptamine(4) receptor partial agonist with potent cognition-enhancing properties.

SL65.0155 [5-(8-amino-7-chloro-2,3-dihydro-1,4-benzodioxin-5-yl)-3-[1-(2-phenyl ethyl)-4-piperidinyl]-1,3,4-oxadiazol-2(3H)-one monohydrochloride] is a novel benzodioxanoxadiazolone compound with high affinity for human 5-hydroxytryptamine (5-HT)(4) receptors (K(i) of 0.6 nM) and good selectivity (greater than 100-fold for all other receptors tested). In cells expressing the 5-HT(4(b)) and 5-HT(4(e)) splice variants, SL65.0155 acted as a partial agonist, stimulating cAMP production with a maximal effect of 40 to 50% of serotonin. However, in the rat esophagus preparation, SL65.0155 acted as a 5-HT(4) antagonist with a pK(b) of 8.81. In addition, SL65.0155 potently improved performance in several tests of learning and memory. In the object recognition task, it improved retention at 24 h when administered i.p. or p.o. (0.001-0.1 mg/kg). This effect was antagonized by the 5-HT(4) antagonist SDZ 205,557, itself without effect, demonstrating that the promnesic effects of SL65.0155 are mediated by 5-HT(4) agonism. SL65.0155 also reversed the cognitive deficits of aged rats in the linear maze task and the scopolamine-induced deficit of mice in the water maze task. Furthermore, the combined administration of an inactive dose of SL65.0155 with the cholinesterase inhibitor rivastigmine resulted in a significant promnesic effect, suggesting a synergistic interaction. SL65.0155 was devoid of unwanted cardiovascular, gastrointestinal, or central nervous system effects with doses up to more than 100-fold higher than those active in the cognitive tests. These results characterize SL65.0155 as a novel promnesic agent acting via 5-HT(4) receptors, with an excellent preclinical profile. Its broad range of activity in cognitive tests and synergism with cholinesterase inhibitors suggest that SL65.0155 represents a promising new agent for the treatment of dementia.