The Neuroprotective Effects of Agomelatine in a 3-Nitropropionic Acid-Induced Rat Model of Huntington’s Disease via Brain-Derived Neurotrophic Factor (BDNF)/tropomyosin-Related Kinase Receptor Type B (TrKB)/Phosphoinositide 3-Kinase (PI3K)/Protein Kinase B (AKT) Activation and Rho-Associated Protein Kinase 1 (ROCK1) Pathway Inhibition

The accumulation of CAG nucleotide duplicates in the huntingtin (HTT) gene triggers a neurological ailment described as Huntington's disease (HD), which is an irreversible, progressive, and inherited condition and affects both motor and cognitive abilities, resulting in a range of symptoms, including irregular gestures (chorea, dyskinesia), psychological disorders, and advanced dementia. Agomelatine is a novel antidepressant and melatonin analog. It exerts a synergistic pharmacological mechanism, combining stimulation of both MT1/MT2 melatonergic receptors with inhibition of 5-HT2C receptors. It was evaluated for its potential neuroprotective impact against HD triggered by 3-nitropropionic acid (3-NP) in rats. Four groups were established using a total of 40 rats: Group I (CTRL), Group II (AGO), Group III (3-NP), and Group IV (AGO + 3-NP). Deficits in motor function provoked by 3-NP were alleviated by agomelatine, as evidenced by increased ambulation and rearing frequencies, alongside a notable decline in immobility time of the open field assessment, elevated final falloff time of the rotarod assessment, and improved grip strength. Agomelatine also improved synaptic plasticity and neuronal survival by optimizing the expression and activity of the BDNF/TrKB/PI3K/AKT pathway and inhibiting apoptosis, microglial, and astrocytic activation. Furthermore, agomelatine administration reduced the expression of ROCK1, suppressing the release of inflammatory responses. Finally, agomelatine possessed neuroprotective activity, as proved by enhancing motor activity and histopathological abnormalities via improving the BDNF/TrKB/PI3K/AKT survival cascade and suppressing the ROCK1 inflammatory pathway.