**2.4 Gamma-amino butyric acid (GABA) receptors**

The GABA receptors are located in the nervous system of many insects. It is an oligomer of 5 subunits (**Figure 9**), each being polypeptide with a large domain in their N-terminal and 4 transmembrane domains [49]. The binding of GABA on its receptors leads to the inhibition of the nerve impulse. GABA acts by binding to its specific transmembrane receptors (GABA-gated chloride channels) present in the plasma membrane of neurons, opens the chloride (Cl− ) channels to allow the flow of Cl− into the neurons. This results in a negative charge on the transmembrane potential causing hyperpolarization and a reduction in membrane entry resistance. Pesticides by binding to insect GABA receptors, decrease or increase Cl− influx into neurons, and kill insects by causing excessive excitation or inhibition of the nervous system (hyperactivity, hyperexcitability, convulsions, production of prolonged high frequency discharges, etc.) [50, 51].

#### **Figure 9.**

*Representation of the GABAA receptor structure. (a). The inhibitory GABAA receptor consists of five subunits that together form a ligand-gated chloride (Cl− ) channel. (b). The most common subtype is a pentamer with 2α,2β, and 1 γ-subunit [48].*
