td-5108 and Memory-Disorders

Alzheimer's disease (AD) is a neurodegenerative disease characterized by memory decline and impaired hippocampal synaptic plasticity. The serotonin 5-HT4 receptor is involved in learning and memory processes. This study explored the effects of chronic stimulation of 5-HT4R on cognition, memory, long-term potentiation (LTP), paired-pulse ratio (PPR), and neuronal apoptosis in a rat model of amyloid-beta (Aβ)-induced AD. Thirty-five male Wistar rats were randomly divided into three groups as follows: the sham, Aβ, and Aβ + BIMU8 groups. Aβ (6 µg/µl) was administrated by intracerebroventricular (icv) injection. The animals were treated with BIMU8 (1 μg/μL, ICV) as a 5-HT4R agonist for 30 days. Memory and behavioral changes were assessed by the passive avoidance learning, novel object recognition, open field, and elevated plus maze tests. Hippocampal synaptic plasticity was evaluated in the dentate gyrus (DG) in response to the stimulation applied to the perforant pathway. Furthermore, neuronal apoptosis was measured in the hippocampus. Data were analyzed by SPSS version 19 using one-way ANOVA, followed by Tukey's post hoc test. Aβ induced memory deficits and neuronal loss and inhibited LTP induction. Aβ also increased the normalized PPR. BIMU8 enhanced the slope of the field excitatory postsynaptic potential in LTP and improved cognition behavior. Paired-pulse inhibition or facilitation was not affected by LTP induction in Aβ animals receiving the BIMU8. It can be concluded that the stimulation of the 5-HT

Topics: Amyloid beta-Peptides; Animals; Apoptosis; Avoidance Learning; Behavior, Animal; Benzimidazoles; Bridged Bicyclo Compounds, Heterocyclic; Dentate Gyrus; Excitatory Postsynaptic Potentials; Hippocampus; Male; Memory; Memory Disorders; Neuronal Plasticity; Neurons; Rats; Rats, Wistar; Receptors, Serotonin, 5-HT4; Serotonin 5-HT4 Receptor Agonists

Sleep is a circadian rhythm that is modulated by endogenous circadian clock located in the suprachiasmatic nucleus (SCN). Sleep modulates memory acquisition and promotes memory consolidation. Studies have shown that sleep deprivation (SD) impairs different types of memory including passive avoidance. Furthermore, the hippocampus plays a significant role in modulating passive avoidance memory. On the other hand, 5-HT4 receptors are expressed in the hippocampus and involved in learning and memory processes. In this study, we aimed to investigate the role of CA1 hippocampal 5-HT4 receptors in memory acquisition impairment induced by total sleep deprivation (TSD: 24 h) and REM sleep deprivation (RSD: 24 h). The water box apparatus was used to induce TSD, while multi-platform apparatus was applied to induce RSD. Passive avoidance memory test was also used to evaluate memory acquisition. The results showed that, intra-CA1 pre-training injection of RS67333 (5-HT4 agonist) and RS23597 (5-HT4 antagonist) at the doses of 0.01 and 0.1 µg/rat decreased memory acquisition, but did not alter pain perception and locomotor activity. Furthermore, TSD and RSD decreased memory acquisition; however, only TSD decreased locomotor activity and induced analgesic effect. The sub-threshold doses of RS67333 and RS23597, 0.001 and 0.0001 µg/rat, respectively, reversed the effect of TSD on memory acquisition and locomotor activity. In addition, only RS23597 reversed TSD-induced analgesia. In RSD condition, the subthreshold dose of RS23597 improved RSD-induced memory acquisition deficit. In conclusion, CA1 hippocampal 5-HT4 receptors play an important role in TSD/RSD-induced cognitive alterations.

Topics: Aniline Compounds; Animals; Avoidance Learning; CA1 Region, Hippocampal; Male; Memory Consolidation; Memory Disorders; Microinjections; Motor Activity; Pain Perception; Piperidines; Rats; Rats, Wistar; Receptors, Serotonin, 5-HT4; Serotonin 5-HT4 Receptor Agonists; Serotonin 5-HT4 Receptor Antagonists; Sleep Deprivation

It is widely assumed that the upcoming therapeutics for Alzheimer's disease will require to act on more than one target to be effective. We investigated here whether a combination of the nicotinic receptor allosteric modulator/cholinesterase inhibitor galantamine can act synergistically with the type 4 serotonin receptor (5-HT4R) partial agonist, RS-67333, to counterbalance deficits in short- and long-term memory. To select sub-efficacious doses of both drugs, dose-response studies were first performed on the scopolamine-induced deficits of spontaneous alternation in the Y-maze task and of acquisition and retrieval processes in a passive avoidance task.. For spontaneous alternation behavior, combination of 1 mg/kg galantamine and 0.5 mg/kg RS-67333 fully reversed the deficit. In the passive avoidance task, no sub-efficacious doses could be found in the retention paradigm, but a beneficial effect of the association has been demonstrated in the acquisition paradigm.. Mnesic effects of galantamine can be thus potentiated by activation of 5-HT4R. Such a combination treatment might (1) strengthen symptomatic relief, (2) attenuate adverse effects given the lower doses of each compound required, and (3) afford a disease-modifying effect given the known action of 5-HT4R on amyloidogenesis cascade.

Topics: Allosteric Regulation; Alzheimer Disease; Aniline Compounds; Animals; Cholinesterase Inhibitors; Galantamine; Male; Memory Disorders; Mice; Nicotinic Antagonists; Piperidines; Receptors, Nicotinic; Receptors, Serotonin, 5-HT4; Scopolamine; Serotonin 5-HT4 Receptor Agonists

The present study investigates the effects of 5-HT4 receptors of the nucleus accumbens (NAc) shell on the impairment of emotional memory consolidation induced by cannabinoid CB1 receptor stimulation. The elevated plus maze test-retest paradigm was used to assess memory in adult male Wistar rats. Intra-NAc shell administration of ACPA (selective cannabinoid CB1 receptor agonist 0.006 µg/rat) and RS23597 (5-HT4 receptor antagonist 0.01 µg/rat), immediately after training, decreased emotional memory consolidation, suggesting a drug-induced amnesia, whereas post-training intra-NAc shell microinjections of RS67333 (5-HT4 receptor agonist 0.016 µg/rat) increased emotional memory consolidation. Interestingly, RS67333 exerted a dual effect on ACPA-induced behaviors, potentiating and restoring amnesia caused by the subthreshold and effective doses of ACPA, respectively. However, neither RS23597 nor AM251 (CB1 receptor antagonist 30, 60 and 120 ng/rat) affected emotional memory consolidation. Nonetheless, a subthreshold dose of AM251 (120 ng/rat) reversed the amnesia induced by ACPA (0.006 µg/rat) and RS23597 (0.01 µg/rat). None of the above doses altered the locomotor activity. In conclusion, our results suggest that the NAc-shell 5-HT4 receptors are involved in the modulation of ACPA-induced amnesia.

Topics: Aniline Compounds; Animals; Arachidonic Acids; Cannabinoid Receptor Antagonists; Disease Models, Animal; Dose-Response Relationship, Drug; Emotions; Male; Maze Learning; Memory Consolidation; Memory Disorders; Motor Activity; Nootropic Agents; Nucleus Accumbens; Piperidines; Pyrazoles; Random Allocation; Rats, Wistar; Receptor, Cannabinoid, CB1; Receptors, Serotonin, 5-HT4; Serotonin 5-HT4 Receptor Agonists

5-HT4 receptors (5-HT4R) are suggested to affect learning and memory processes. Earlier studies have shown that animals treated with 5-HT4R agonists, often with limited selectivity, show improved learning and memory with retention memory often being assessed immediately after or within 24 h after the last training session. In this study, we characterized the effect of pre-training treatment with the selective 5-HT4R agonist SSP-002392 on memory acquisition and the associated long-term memory retrieval in animal models of impaired cognition. Pre-training treatment with SSP-002392 (0.3 mg/kg, 1.5 mg/kg and 7.5 mg/kg p.o.) dose-dependently inhibited the cognitive deficits induced by scopolamine (0.5 mg/kg s.c.) in two different behavioral tasks: passive avoidance and Morris water maze. In the Morris water maze, spatial learning was significantly improved after treatment with SSP-002392 translating in an accelerated and more efficient localization of the hidden platform compared to scopolamine-treated controls. Moreover, retention memory was assessed 24 h (passive avoidance) and 72 h (Morris water maze) after the last training session of cognitive-impaired animals and this was significantly improved in animals treated with SSP-002392 prior to the training sessions. Furthermore, the effects of SSP-002392 were comparable to galanthamine hydrobromide. We conclude that SSP-002392 has potential as a memory-enhancing compound.

Topics: Animals; Anxiety; Avoidance Learning; Benzofurans; Disease Models, Animal; Dose-Response Relationship, Drug; Fear; Galantamine; Male; Maze Learning; Memory Disorders; Mice, Inbred C57BL; Nootropic Agents; Piperidines; Random Allocation; Receptors, Serotonin, 5-HT4; Scopolamine; Serotonin 5-HT4 Receptor Agonists

Chronic constipation is very frequent in the general population. Although usually considered banal, this disorder has considerable personal, social and healthcare impact. Several studies have shown that the psychological impact exceeds that caused by rheumatoid arthritis or haemodialysis. Recently, prucalopride, a highly selective 5-HT4 receptor agonist has been shown to improve the symptoms of chronic constipation and to have a beneficial effect on social and healthcare impact. The drug was approved by the European Medicine Agency, in 2009 at a dose of 2 mg/day, 'for symptomatic treatment of chronic constipation in women in whom laxatives fail to provide adequate relief'. Neurological side effects or psychiatric disorders have not been reported previously with prucalopride. We present the case of a 61-year-old woman, who developed such adverse effects when given prucalopride for the treatment for chronic constipation.. A few hours after oral administration of this drug at therapeutic dose (2 mg/day), the patient experienced life-threatening neurological effects that included visual hallucination, loss of balance and memory, disorientation, exhaustion and suicidal ideation. Analysis with the Naranjo algorithm indicated a 'possible' relationship between prucalopride and these disorders.. This is the first report of prucalopride-induced neurological side effects and psychiatric disorders with prucalopride. The absence of other similar reports suggests that prucalopride rarely causes these adverse effects.

Topics: Benzofurans; Chronic Disease; Constipation; Female; Hallucinations; Humans; Memory Disorders; Mental Disorders; Middle Aged; Nervous System Diseases; Orientation; Postural Balance; Serotonin; Serotonin 5-HT4 Receptor Agonists; Suicidal Ideation

It is known that 5-HT(4) receptor agonists increase sAPPalpha levels in the cortex and hippocampus of mice as well as in a model of Alzheimer's disease (AD). As sAPPalpha is thought to have pro-mnesic properties, we assessed whether its increase induces cognitive improvement in a spatial memory task and whether it reverses a scopolamine-induced memory deficit. Mice treated or not treated with scopolamine were trained in the Morris water maze for 3 days. Before the probe test, they received an injection of either a 5-HT(4) receptor agonist (prucalopride or RS 67333), or an acetylcholinesterase inhibitor (donepezil), or both drugs. As expected, scopolamine decreased performance, an effect that was not reversed by the drugs tested when injected alone. However, prucalopride (5 mg kg(-1), s.c.) acted synergistically with donepezil (0.75 mg kg(-1), s.c.) to counteract completely scopolamine-induced amnesia. Western blot analysis of tissue homogenates in the cortex and hippocampus shows that sAPPalpha levels did not differ between saline- and scopolamine-treated mice. Furthermore, a region-dependent drug action was observed since the scopolamine-treated mice display a tendency to increase sAPPalpha levels in the hippocampus after donepezil or in the cortex after prucalopride. Our results suggest that a combined treatment with a 5-HT(4) receptor agonist with an acetylcholinesterase inhibitor has beneficial effects on memory in mice. Moreover, it seems to enhance sAPPalpha levels in two brain regions highly affected in AD. Thus, a drug polytherapy could be interesting not only to enhance cognitive performance and decrease drawbacks but also to get the best action in each brain region.

Topics: Amyloid beta-Protein Precursor; Analysis of Variance; Aniline Compounds; Animals; Benzofurans; Cerebral Cortex; Cholinesterase Inhibitors; Donepezil; Drug Synergism; Hippocampus; Indans; Male; Maze Learning; Memory Disorders; Mice; Mice, Inbred C57BL; Motor Activity; Nootropic Agents; Piperidines; Scopolamine; Serotonin 5-HT4 Receptor Agonists; Statistics, Nonparametric

Bilateral intradentate injections of 3.0microg of colchicine induced a substantial loss of granule cells and damage to the overlying pyramidal cell layer in region CA1 in adult male Long-Evans rats. All rats with such lesions showed a significant associative learning deficit in an olfactory discrimination task, while being unimpaired in the procedural component of this task. Injection of a partial selective 5-HT(4) agonist (SL65.0155; 0.01mg/kg, i.p., vs. saline) before the third of six training sessions enabled complete recovery of associative learning performance in the lesioned rats. Activation of 5-HT(4) receptors by a selective agonist such as SL65.0155 might therefore provide an opportunity to reduce learning and memory deficits associated with temporal lobe damage, and could be useful for the symptomatic treatment of memory dysfunctions related to pathological aging such as Alzheimer's disease.

Topics: Animals; Association Learning; Behavior, Animal; Colchicine; Denervation; Dentate Gyrus; Dioxanes; Discrimination Learning; Male; Memory Disorders; Oxadiazoles; Pyramidal Cells; Rats; Rats, Long-Evans; Receptors, Serotonin, 5-HT4; Reversal Learning; Serotonin 5-HT4 Receptor Agonists; Smell

The present study was conducted to determine the effects of two potent 5-HT4 receptor agonists, BIMU 1 (1 (3-ethyl-2,3-dihydro-N-[endo-8-methyl-8-azabicyclo (3.2.1)-oct-3-yl]-2-oxo-1H) benzimidazole-1-carboxamide hydrochloride; 1, 3, 10 mg/kg, i.p.) and RS 67333 (1-(4-amino-5-chloro-2-methoxyphenyl)-3-(1-n-butyl-4-piperidinyl)-1-propanone; 0.25, 0.5, 1 mg/kg, i.p.) on the learning impairment induced by the muscarinic acetylcholine receptor antagonist, scopolamine (1 mg/kg) in mice. Working memory was examined by observing spontaneous alternation behavior in the Y-maze test. Both BIMU 1 (10 mg/kg) and RS 67333 (1 mg/kg) prevented the scopolamine-induced alternation deficits, whereas no effect could be evidenced on locomotor or emotional indices. The reversal actions of BIMU 1 and RS 67333 on this cognitive dysfunction were abolished by the selective 5-HT4 receptor antagonist GR 125487 (1-[2-[(methyl sulfonyl)-amino]-ethyl]-4-piperidinyl-methyl-5-fluoro-2-methoxy-1H-indole-3-carboxylate; 10 mg/kg, i.p.). When given alone at the same doses, none of the three serotonergic agents had any measurable effect. These results demonstrate the ability of 5-HT4 receptor agonists to reverse spontaneous working memory deficits and further confirm the therapeutic potential of such ligands in the treatment of cognitive alterations that associate short-term working memory disorders and cholinergic hypofunction.

Topics: Aniline Compounds; Animals; Benzimidazoles; Bridged Bicyclo Compounds, Heterocyclic; Dose-Response Relationship, Drug; Locomotion; Male; Memory; Memory Disorders; Mice; Piperidines; Receptors, Serotonin, 5-HT4; Scopolamine; Serotonin 5-HT4 Receptor Agonists