Anti-dyskinetic efficacy of 5-HT3 receptor antagonist in the hemi-parkinsonian rat model

Phytoconstituents Targeting the Serotonin 5-HT3 Receptor: Promising Therapeutic Strategies for Neurological Disorders

The 5-hydroxytryptamine-3 receptor (5-HT3R), a subtype of serotonin receptor, is a ligand-gated ion channel crucial in mediating fast synaptic transmission in the central and peripheral nervous systems. This receptor significantly influences various neurological activities, encompassing neurotransmission, mood regulation, and cognitive processing; hence, it may serve as an innovative target for neurological disorders. Multiple studies have revealed promising results regarding the beneficial effects of these phytoconstituents and extracts on conditions such as nausea, vomiting, neuropathic pain depression, anxiety, Alzheimer's disease, cognition, epilepsy, sleep, and dyskinesia via modulation of 5-HT3R in the pathophysiology of neurological disorder. The review delves into a detailed exploration of in silico, in vitro, and in vivo studies and clinical studies that discussed phytoconstituents acting on 5-HT3R and attenuates difficulties in neurological diseases. The diverse mechanisms by which plant-derived phytoconstituents influence 5-HT3R activity offer exciting avenues for developing innovative therapeutic interventions. Besides producing an agonistic or antagonistic effect, some phytoconstituents exert modulatory effects on 5-HT3R activity through multifaceted mechanisms. These include γ-aminobutyric acid and cholinergic neuronal pathways, interactions with neurokinin (NK)-1, NK2, serotonergic, and γ-aminobutyric acid(GABA)ergic systems, dopaminergic influences, and mediation of calcium ions release and inflammatory cascades. Notably, the phytoconstituent's capacity to reduce oxidative stress has also emerged as a significant factor contributing to their modulatory role. Despite the promising implications, there is currently a dearth of exploration needed to understand the effect of phytochemicals on the 5-HT3R. Comprehensive preclinical and clinical research is of the utmost importance to broaden our knowledge of the potential therapeutic benefits associated with these substances.

Ondansetron attenuates cisplatin-induced behavioral and cognitive impairment through downregulation of NOD-like receptor inflammasome pathway

Cisplatin is an effective and commonly used chemotherapeutic drug; however, its use is accompanied by several adverse effects, including chemobrain. Ondansetron is a 5-HT3 antagonist, commonly used in prophylactic against chemotherapy-induced nausea and vomiting. Moreover, it has been identified as a novel neuroprotective agent in different animal models. However, its protective role against chemotherapy-induced chemobrain has not been investigated. The current study was the first study that explored the potential neuroprotective effect of ondansetron against cisplatin-induced chemobrain in rats. Cisplatin (5 mg/Kg) was injected intraperitoneally, once weekly, for 4 weeks with the daily administration of ondansetron (0.5 and 1 mg/Kg). Compared to the cisplatin-treated group, ondansetron administration showed a significant decrease in the latency time and a significant increase in ambulation, rearing, and grooming frequency in the open field test (OFT). Moreover, a significant improvement in the latency time in the rotarod and passive avoidance tests, following ondansetron administration. In addition, ondansetron treatment increased the percentage of alternation in the Y-maze test. Also, ondansetron showed a remarkable enhancement in the biochemical parameters in the hippocampus. It increased the acetylcholine (Ach) level and decreased the level of the acetylcholine esterase enzyme (AchE). Ondansetron significantly decreased interleukin-1β (Il-1β), tumor necrosis factor-alpha (TNF-α), toll-like receptor-4 (TLR-4), NOD-like receptor-3 (NLRP3) inflammasome as well as caspase-1 and caspase-3 levels. Furthermore, ondansetron significantly decreased the levels of copper transporter-1(CTR1) expression in the hippocampus. Collectively, these findings suggest that ondansetron may exhibit a neuroprotective and therapeutic activity against cisplatin-induced chemobrain.

A systematic scoping review of rodent models of catatonia: Clinical correlations, translation and future approaches

Catatonia is a psychiatric disorder, which subsumes a plethora of affective, motor and behavioral symptoms. In the last two decades, the number of behavioral and neuroimaging studies on catatonia has steadily increased. The majority of behavioral and neuroimaging studies in psychiatric patients suggested aberrant higher-order frontoparietal networks which, on the biochemical level, are insufficiently modulated by gamma-aminobutyric acid (GABA)-ergic and glutamatergic transmission. However, the pathomechanisms of catatonic symptoms have rarely been studied using rodent models. Here, we performed a scoping review of literature available on PubMed for studies on rodent models of catatonia. We sought to identify what we could learn from pre-clinical animal models of catatonia-like symptoms, their underlying neuronal correlates, and the complex molecular (i.e. genes and neurotransmitter) mechanisms by which its modulation exerts its effects. What becomes evident is that although many transgenic models present catatonia-like symptoms, they have not been used to better understand the pathophysiological mechanisms underlying catatonia so far. However, the identified neuronal correlates of catatonia-like symptoms correlate to a great extent with findings from neuroscience research in psychiatric patients. This points us towards fundamental cortical-striatal-thalamocortical and associated networks modulated by white matter inflammation as well as aberrant dopaminergic, GABAergic, and glutamatergic neurotransmission that is involved in catatonia. Therefore, this scoping review opens up the possibility of finally using transgenic models to help with identifying novel target mechanisms for the development of new drugs for the treatment of catatonia.

Broad Serotonergic Actions of Vortioxetine as a Promising Avenue for the Treatment of L-DOPA-Induced Dyskinesia

Parkinson's Disease (PD) is a neurodegenerative disorder characterized by motor symptoms that result from loss of nigrostriatal dopamine (DA) cells. While L-DOPA provides symptom alleviation, its chronic use often results in the development of L-DOPA-induced dyskinesia (LID). Evidence suggests that neuroplasticity within the serotonin (5-HT) system contributes to LID onset, persistence, and severity. This has been supported by research showing 5-HT compounds targeting 5-HT1A/1B receptors and/or the 5-HT transporter (SERT) can reduce LID. Recently, vortioxetine, a multimodal 5-HT compound developed for depression, demonstrated acute anti-dyskinetic effects. However, the durability and underlying pharmacology of vortioxetine's anti-dyskinetic actions have yet to be delineated. To address these gaps, we used hemiparkinsonian rats in Experiment 1, examining the effects of sub-chronic vortioxetine on established LID and motor performance. In Experiment 2, we applied the 5-HT1A antagonist WAY-100635 or 5-HT1B antagonist SB-224289 in conjunction with L-DOPA and vortioxetine to determine the contributions of each receptor to vortioxetine's effects. The results revealed that vortioxetine consistently and dose-dependently attenuated LID while independently, 5-HT1A and 5-HT1B receptors each partially reversed vortioxetine's effects. Such findings further support the promise of pharmacological strategies, such as vortioxetine, and indicate that broad 5-HT actions may provide durable responses without significant side effects.

Phylogenetic analyses of 5-hydroxytryptamine 3 (5-HT3) receptors in Metazoa

The 5-hydroxytrptamine 3 (5-HT3) receptor is a member of the 'Cys-loop' family and the only pentameric ligand gated ion channel among the serotonin receptors. 5-HT3 receptors play an important role in controlling growth, development, and behaviour in animals. Several 5-HT3 receptor antagonists are used to treat diseases (e.g., irritable bowel syndrome, nausea and emesis). Humans express five different subunits (A-E) enabling a variety of heteromeric receptors to form but all contain 5HT3A subunits. However, the information available about the 5-HT3 receptor subunit occurrence among the metazoan lineages is minimal. In the present article we searched for 5-HT3 receptor subunit homologs from different phyla in Metazoa. We identified more than 1000 5-HT3 receptor subunits in Metazoa in different phyla and undertook simultaneous phylogenetic analysis of 526 5HT3A, 358 5HT3B, 239 5HT3C, 70 5HT3D, and 173 5HT3E sequences. 5-HT3 receptor subunits were present in species belonging to 11 phyla: Annelida, Arthropoda, Chordata, Cnidaria, Echinodermata, Mollusca, Nematoda, Orthonectida, Platyhelminthes, Rotifera and Tardigrada. All subunits were most often identified in Chordata phylum which was strongly represented in searches. Using multiple sequence alignment, we investigated variations in the ligand binding region of the 5HT3A subunit protein sequences in the metazoan lineage. Several critical amino acid residues important for ligand binding (common structural features) are commonly present in species from Nematoda and Platyhelminth gut parasites through to Chordata. Collectively, this better understanding of the 5-HT3 receptor evolutionary patterns raises possibilities of future pharmacological challenges facing Metazoa including effects on parasitic and other species in ecosystems that contain 5-HT3 receptor ligands.

The effects of Vilazodone, YL-0919 and Vortioxetine in hemiparkinsonian rats

Parkinson's disease is a neurodegenerative disease often characterized by motor deficits and most commonly treated with dopamine replacement therapy. Despite its benefits, chronic use of L-DOPA results in abnormal involuntary movements known as L-DOPA-induced dyskinesia. Growing evidence shows that with burgeoning dopamine cell loss, neuroplasticity in the serotonin system leads to the development of L-DOPA-induced dyskinesia through the unregulated uptake, conversion, and release of L-DOPA-derived dopamine into the striatum. Previous studies have shown that coincident 5-HT_1A agonism and serotonin transporter inhibition may have anti-dyskinetic potential. Despite this, few studies have explicitly focused on targeting both 5-HT_1A and the serotonin transporter. The present study compares the 5-HT compounds Vilazodone, YL-0919, and Vortioxetine which purportedly work as simultaneous 5-HT_1A receptor agonists and SERT blockers. To do so, adult female Sprague Dawley rats were rendered hemiparkinsonian and treated daily for two weeks with L-DOPA to produce stable dyskinesia. The abnormal involuntary movements and forehand adjusting step tests were utilized as measurements for L-DOPA-induced dyskinesia and motor performance in a within-subjects design. Lesion efficacy was determined by analysis of striatal monoamines via high-performance liquid chromatography. Compounds selective for 5-HT_1A/SERT target sites including Vilazodone and Vortioxetine significantly reduced L-DOPA-induced dyskinesia without compromising L-DOPA pro-motor efficacy. In contrast, YL-0919 failed to reduce L-DOPA-induced dyskinesia, with no effects on L-DOPA-related improvements. Collectively, this work supports pharmacological targeting of 5-HT_1A/SERT to reduce L-DOPA-induced dyskinesia. Additionally, this further provides evidence for Vilazodone and Vortioxetine, FDA-approved compounds, as potential adjunct therapeutics for L-DOPA-induced dyskinesia management in Parkinson's patients.

Molecular Mechanisms and Therapeutic Strategies for Levodopa-Induced Dyskinesia in Parkinson's Disease: A Perspective Through Preclinical and Clinical Evidence

Parkinson's disease (PD) is the second leading neurodegenerative disease that is characterized by severe locomotor abnormalities. Levodopa (L-DOPA) treatment has been considered a mainstay for the management of PD; however, its prolonged treatment is often associated with abnormal involuntary movements and results in L-DOPA-induced dyskinesia (LID). Although LID is encountered after chronic administration of L-DOPA, the appearance of dyskinesia after weeks or months of the L-DOPA treatment has complicated our understanding of its pathogenesis. Pathophysiology of LID is mainly associated with alteration of direct and indirect pathways of the cortico-basal ganglia-thalamic loop, which regulates normal fine motor movements. Hypersensitivity of dopamine receptors has been involved in the development of LID; moreover, these symptoms are worsened by concurrent non-dopaminergic innervations including glutamatergic, serotonergic, and peptidergic neurotransmission. The present study is focused on discussing the recent updates in molecular mechanisms and therapeutic approaches for the effective management of LID in PD patients.

Autoradiographic labelling of 5-HT3 receptors in the hemi-parkinsonian rat brain

L-3,4-dihydroxyphenylalanine (L-DOPA) is the mainstay treatment for Parkinson's disease, but its effectiveness during early disease is marred by the eventual development of L-DOPA induced dyskinesia. In hemi-parkinsonian rats, the serotonin type 3 (5-HT₃) antagonists ondansetron and granisetron alleviated dyskinesia induced by L-DOPA without impeding its anti-parkinsonian action; in parkinsonian marmosets, ondansetron alleviated dyskinesia and enhanced L-DOPA anti-parkinsonian action. Here, we sought to gain insight into the mechanisms governing the anti-dyskinetic action of 5-HT₃ antagonists and measured their levels across different brain, using [³H]GR65630 autoradiographic binding. Brain sections were chosen from 6-hydroxydopamine (6-OHDA)-lesioned rats exhibiting abnormal involuntary movements (AIMs), as well as L-DOPA-naïve 6-OHDA and sham-lesioned animals. [³H]GR65630 binding increased in the ipsilateral subthalamic nucleus of 6-OHDA-lesioned rats with mild and severe AIMs, (3-fold changes, P < 0.001). [³H]GR65630 binding also increased in the ipsilateral entopeduncular nucleus and thalamus of 6-OHDA-lesioned rats with severe AIMs (75% and 88%, P < 0.05). AIMs scores negatively correlated with [³H]GR65630 binding in the ipsilateral dorsolateral striatum and contralateral subthalamic nucleus (P < 0.05). These results suggest that alterations in 5-HT₃ mediated neurotransmission may contribute to the pathophysiology of L-DOPA induced dyskinesia.

Current Knowledge on the Background, Pathophysiology and Treatment of Levodopa-Induced Dyskinesia-Literature Review

Levodopa remains the primary drug for controlling motor symptoms in Parkinson’s disease through the whole course, but over time, complications develop in the form of dyskinesias, which gradually become more frequent and severe. These abnormal, involuntary, hyperkinetic movements are mainly characteristic of the ON phase and are triggered by excess exogenous levodopa. They may also occur during the OFF phase, or in both phases. Over the past 10 years, the issue of levodopa-induced dyskinesia has been the subject of research into both the substrate of this pathology and potential remedial strategies. The purpose of the present study was to review the results of recent research on the background and treatment of dyskinesia. To this end, databases were reviewed using a search strategy that included both relevant keywords related to the topic and appropriate filters to limit results to English language literature published since 2010. Based on the selected papers, the current state of knowledge on the morphological, functional, genetic and clinical features of levodopa-induced dyskinesia, as well as pharmacological, genetic treatment and other therapies such as deep brain stimulation, are described.

Amantadine: reappraisal of the timeless diamond-target updates and novel therapeutic potentials

The aim of the current review was to provide a new, in-depth insight into possible pharmacological targets of amantadine to pave the way to extending its therapeutic use to further indications beyond Parkinson's disease symptoms and viral infections. Considering amantadine's affinities in vitro and the expected concentration at targets at therapeutic doses in humans, the following primary targets seem to be most plausible: aromatic amino acids decarboxylase, glial-cell derived neurotrophic factor, sigma-1 receptors, phosphodiesterases, and nicotinic receptors. Further three targets could play a role to a lesser extent: NMDA receptors, 5-HT3 receptors, and potassium channels. Based on published clinical studies, traumatic brain injury, fatigue [e.g., in multiple sclerosis (MS)], and chorea in Huntington's disease should be regarded potential, encouraging indications. Preclinical investigations suggest amantadine's therapeutic potential in several further indications such as: depression, recovery after spinal cord injury, neuroprotection in MS, and cutaneous pain. Query in the database http://www.clinicaltrials.gov reveals research interest in several further indications: cancer, autism, cocaine abuse, MS, diabetes, attention deficit-hyperactivity disorder, obesity, and schizophrenia.

Granisetron, a selective 5-HT3 antagonist, reduces L-3,4-dihydroxyphenylalanine-induced abnormal involuntary movements in the 6-hydroxydopamine-lesioned rat

Administration of L-3,4-dihydroxyphenylalanine (L-DOPA) provides Parkinson's disease patients with effective symptomatic relief. However, long-term L-DOPA therapy is often marred by complications such as dyskinesia. We have previously demonstrated that serotonin type 3 (5-HT3) receptor blockade with the clinically available and highly selective antagonist ondansetron alleviates dyskinesia in the 6-hydroxydopamine (6-OHDA)-lesioned rat. Here, we sought to explore the antidyskinetic efficacy of granisetron, another clinically available 5-HT3 receptor antagonist. Rats were rendered hemi-parkinsonian by 6-OHDA injection in the medial forebrain bundle. Following induction of stable abnormal involuntary movements (AIMs), granisetron (0.0001, 0.001, 0.01, 0.1 and 1 mg/kg) or vehicle was acutely administered in combination with L-DOPA and the severity of AIMs, both duration and amplitude, was determined. We also assessed the effect of granisetron on L-DOPA antiparkinsonian action by performing the cylinder test. Adding granisetron (0.0001, 0.001, 0.01, 0.1 and 1 mg/kg) to L-DOPA resulted in a significant reduction of AIMs duration and amplitude, with certain parameters being reduced by as much as 38 and 45% (P < 0.05 and P < 0.001, respectively). The antidyskinetic effect of granisetron was not accompanied by a reduction of L-DOPA antiparkinsonian action. These results suggest that 5-HT3 blockade may reduce L-DOPA-induced dyskinesia without impairing the therapeutic efficacy of L-DOPA. However, a U-shaped dose-response curve obtained with certain parameters may limit the therapeutic potential of this strategy and require further investigation.

Selective blockade of the 5-HT3 receptor acutely alleviates dyskinesia and psychosis in the parkinsonian marmoset

In Parkinson's disease (PD), management of L-3,4-dihydroxyphenylalanine (l-DOPA)-related complications, such as l-DOPA induced dyskinesia and psychosis, remains inadequate, which poses a significant burden on the quality of life of patients. We have shown, in the hemi-parkinsonian rat model of PD, that the selective serotonin type 3 (5-HT₃) receptor antagonists ondansetron and granisetron decreased the severity of established dyskinesia, and ondansetron even attenuated the development of dyskinesia. Here, we seek to confirm these favourable data on dyskinesia and to explore the effect of ondansetron on the severity of psychosis-like behaviours (PLBs) in the gold standard model of PD, the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-lesioned non-human primate. We first determined the pharmacokinetic profile of ondansetron in the marmoset. Subsequently, six MPTP-lesioned marmosets were administered l-DOPA chronically until they exhibited stable and reproducible dyskinesia and PLBs upon each administration of l-DOPA. On behavioural assessment days, ondansetron (0.01, 0.1 and 1 mg/kg) or vehicle was administered in conjunction with l-DOPA, and the severity of dyskinesia, PLBs and parkinsonism was evaluated. Ondansetron 0.1 mg/kg alleviated global dyskinesia severity by 73% (P < 0.0001) and decreased duration of on-time with disabling dyskinesia by 88% (P = 0.0491). Ondansetron 0.1 mg/kg reduced the severity of global PLBs by 80% (P < 0.0001) and suppressed on-time with disabling PLBs (P = 0.0213). Ondansetron enhanced the anti-parkinsonian action of l-DOPA, reducing global parkinsonism by 53% compared to l-DOPA (P = 0.0004). These results suggest that selective blockade of the 5-HT₃ receptor with ondansetron may be an effective approach to alleviate l-DOPA-related complications.

Receptor Ligands as Helping Hands to L-DOPA in the Treatment of Parkinson's Disease

Levodopa (LD) is the most effective drug in the treatment of Parkinson’s disease (PD). However, although it represents the “gold standard” of PD therapy, LD can cause side effects, including gastrointestinal and cardiovascular symptoms as well as transient elevated liver enzyme levels. Moreover, LD therapy leads to LD-induced dyskinesia (LID), a disabling motor complication that represents a major challenge for the clinical neurologist. Due to the many limitations associated with LD therapeutic use, other dopaminergic and non-dopaminergic drugs are being developed to optimize the treatment response. This review focuses on recent investigations about non-dopaminergic central nervous system (CNS) receptor ligands that have been identified to have therapeutic potential for the treatment of motor and non-motor symptoms of PD. In a different way, such agents may contribute to extending LD response and/or ameliorate LD-induced side effects.