The GABA (gamma amino butyric acid) is an inhibitory neurotransmitter. Anti-anxiety and sedative-hypnotic drugs such as benzodiazepines (BDZ’s) act through GABAA receptors, which causes hyperpolarization by enhancing the chloride ion influx.
For example, the binding of BDZ’s cause’s chloride ion influx, which causes hyperpolarization of the cell. So, they produce inhibitory responses, they are mainly used as anxiolytics and sedatives.
Thus, the blanks can be filled with GABAA; chloride ions.