**4. Natural products and GABA**

Due to the different binding sites present on GABA (A) receptor, various receptor modulating compounds have been identified and depending on the mode of action, the affected binding site, and the compounds' affinity. Radioligand binding assays have been confirmed the capacity of the ligand for the displacement of a molecule from its binding site. Various studies helped us understand the link between modulation of the receptor and associated effects, such as anxiolytic, sedative, and anticonvulsive properties (**Figure 2**; **Table 1**).

Radioligand binding assays are simple but influential tool for reviewing receptors. They mainly analyze the interactions of hormones, neurotransmitters, growth factors, and related drugs with the receptors, studies of receptor interactions with second messenger systems, along with the characterization of regulatory changes in receptor number, subcellular distribution, and physiological function. So these assays are widely used in a numerous disciplines, including pharmacology, physiology, biochemistry, immunology, and cell biology. The fundamentals of the radioligand binding assay are fairly simple. The receptor of interest is incubated with an appropriate radioligand for a suitable period of time and then the radioactivity bound to the receptor is determined. There are three major types of experiments:

**Figure 2.** *Action of natural products on the specific site of GABA receptor.*



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