Study of The Effect of Polyphenol Plantagin On Calcium Transport in The Presence of NMDA Receptor Agonists and Antagonists

Аннотация

This study investigated the effect of Plantagin polyphenol on NMDA receptor binding sites using glycine, Mg2+ and Zn2+ ions. A suspension of rat brain synaptosomes was isolated by differential centrifugation. Changes [Ca2+]in concentration in the suspension medium of rat brain synaptosomes were measured using the fluorescent probe Fluo-4 AM. It was noted that synaptosomal Ca2+ transport remained virtually unchanged under the influence of plantago polyphenols in Zn2+ and Mg2+ in rat brain synaptosomal suspensions incubated with L- glutamate-Fluo-4 AM. The polyphenol Plantagin competes with glycine for binding to the glycine site of NMDA receptors, reducing the likelihood of full receptor activation even in the presence of glutamate, which leads to a limitation of Ca²⁺ influx, and therefore plays an important role in preventing excitotoxicity. Keywords: Plantagin polyphenol, NMDA receptor, Mg2+, Zn2+, synaptosome. Introduction: NMDA receptors are present in all parts In clinical and experimental neurology, divalent cations of the central nervous system, located mainly in the such as Mg2+ and Zn2+ are widely used as NMDA postsynaptic and partly in the presynaptic membrane receptor modulators [6,7]. [1]. NMDA receptors have also been found to function Mg2+ ions, which are usually considered endogenous in astrocytes in the cerebral cortex [2]. modulators, have been found to be more likely to bind The structure of the NMDA receptor consists of a to a specific site of the NMDA receptor at a highly complex of 4 separate basic subunits that form an ion negative membrane potential. Zn2+ ions bind to the channel in the central part that is permeable to Ca2+ GluN2A/GluN2B subunits [7]. ions. NMDA receptor subunits differ in their It is known that magnesium ions play an important role physiological and pharmacological properties, and in regulating the activity of NMDA receptors. They are seven subunits have been identified within the potential-dependent receptor blockers, preventing complex, including NR1, NR2A–D, NR3A, and NR3B. The excessive calcium influx and reducing excitotoxicity. NR1 subunit, which binds to glycine, has 8 isomeric Adequate amounts of Mg2+ are necessary for normal forms in the NMDA receptor structure, and the NR2A– NMDA receptor function and synaptic plasticity. Zinc D subunit, which binds to 1 or 2 glutamic acid and (Zn2+) ions can also modulate the activity of NMDA provides the receptor with the function of an ion receptors. They act as positive allosteric modulators, channel, are the functionally basic structures [3,4]. It is enhancing the response of glutamate receptors. suggested that the NR3A and NR3B subunits expand However, excessive levels of Zn2+ can lead to the spectrum of functional properties of the NMDA neurotoxicity and dysfunction of NMDA receptors. receptor [5,6]. NMDA receptors are heteromeric tetrameric proteins American Journal Of Biomedical Science & Pharmaceutical Innovation 11 https://theusajournals.com/index.php/ajbspi American Journal of Applied Science and Technology (ISSN: 2771-2745) composed of GluN1 and GluN2 subunits, which contain located in the presynaptic membrane [13]. D-serine/glycine and glutamate binding sites, Method for studying changes [Ca2+]in concentration respectively. in rat brain synaptosomes. In addition to D-serine/glycine and glutamate binding The change [Ca2+]in concentration in the suspension sites, they have several regulatory sites sensitive to medium of rat brain synaptosomes was calculated polyamines, Zn2+, protons and glutathione [2,7,8,9]. using the method developed by Grynkiewicz et al. [14]. It has been found that Mg2+ and Zn2+ ions have an To determine the intracellular calcium concentration inhibitory effect on NMDA receptors. These ions can (1×108 cl/ml) in synaptosomes, the highly sensitive block the NMDA receptor channel and reduce its fluorescent probe Fluo-4 AM was used. activation by the neurotransmitter glutamate. Studies In our experiments, 1 mg of Fluo-4 AM powdered show that the inhibitory effects of Mg2+ and Zn2+ on fluorescent probe was dissolved in 135 μL of DMSO to NMDA receptors are not the same. It has been found obtain 1 mM Fluo-4 AM reagent solution. Before the that the blocking of the channel by Zn2+ is faster than experiment, the Fluo-4 AM solution in DMSO was kept by Mg2+. at room temperature [15] and 80 μl synaptosomes and In addition, the effect of Mg2+ and Zn2+ ions on NMDA 12 μl Fluo-4 AM were added to 2 ml Krebs-Ringer buffer receptors may depend on changes in pH. Therapeutic and incubated for 30 min at 37°C. Fluo-4 AM is a approaches identified through studies of the effects of fluorescent Ca2+ chelator with high affinity for calcium. Mg2+ and Zn2+ on NMDA receptors suggest that by Fluo-4 AM can specifically detect intracellular calcium regulating Mg2+ and Zn2+ levels, NMDA receptor ions with high sensitivity, low cytotoxicity and high activity can be modulated and neurological diseases content of acetyl methyl