Central nervous system (CNS) disorders, such as Alzheimer's disease (AD), Parkinson's disease (PD), multiple sclerosis (MS), and migraines, rank among the most prevalent and concerning conditions worldwide. Despite ongoing research, the pathophysiology of these disorders remains incompletely understood, primarily due to their complex etiology. Current pharmacological treatments mainly focus on alleviating symptoms rather than addressing the underlying causes of these diseases. CNS disorders are marked by impairments in neurocognitive and neuromuscular functions, and cognitive processes like learning and memory. This deterioration not only impacts the quality of life of affected individuals but also places a significant burden on their families. Neuroplasticity is a key property of the nervous system that enables brain repair and functional recovery. However, in CNS disorders, neuroplasticity is often compromised. Neuroplasticity, which is regulated by gene expression, is also modulated by environmental factors and epigenetic mechanisms, thereby reshaping neuronal networks in response to various biological and environmental stimuli and brain function. Importantly, neuroplasticity plays a critical role in repairing the brain, especially in the context of neurodegenerative diseases, where damaged neurons can reorganize and re-establish lost functions. Targeting neuroplasticity mechanisms holds significant potential for developing therapeutic interventions to improve treatment outcomes and prevent CNS disorders. A deeper understanding of neuroplasticity in neurological diseases could open new avenues for enhancing patient quality of life. This review aims to provide a comprehensive overview of synaptic function and the neuroplasticity mechanisms that are disrupted in neurological disorders.
Epilepsy is characterized by an imbalance in neurotransmitter activity; an increased excitatory to an inhibitory activity. Acetylcholine (ACh), serotonin, and norepinephrine (NE) may modulate neural activity via several mechanisms, mainly through its receptors/transporter activity and alterations in the extracellular potassium (K+) concentration via K+ ion channels. Seizures may disrupt the regulation of inwardly rectifying K+ (Kir) channels and alter the receptor/transporter activity. However, there are limited data present on the immunoreactivity pattern of these neurotransmitter receptors/transporters and K+ channels in chronic models of epilepsy, which therefore was the aim of this study. Changes in the immunoreactivity of epileptogenesis-related neurotransmitter receptors/transporters (M2, 5-HT2B, and NE transporter) as well as Kir channels (Kir3.1 and Kir6.2) were determined in the cortex, hippocampus and medulla of adult Wistar rats by utilizing a Pentylenetetrazol (PTZ)-kindling chronic epilepsy model. Increased immunoreactivity of the NE transporter, M2, and 5-HT2B receptors was witnessed in the cortex and medulla. While the immunoreactivity of the 5-HT2B receptor was found increased in the cortex and medulla, it was decreased in the hippocampus, with no changes observed in the M2 receptor in this region. Kir3.1 and Kir6.2 staining showed increase immunoreactivity in the cerebral cortex, but channel contrasting findings in the hippocampus and medulla. Our results suggest that seizure kindling may result in significant changes in the neurotransmitter system which may contribute or propagate to future epileptogenesis, brain damage and potentially towards sudden unexpected death in epilepsy (SUDEP). Further studies on the pathogenic role of these changes in neurotransmitter receptors/transporters and K+ channel immunoreactivity may identify newer possible targets to treat seizures or prevent epilepsy-related comorbidities.