A

44-year-old man was admitted unconscious to the Emergency Department. Shortly

after admission, he had a tonic-clonic seizure. Further exams led to the

diagnosis of status epilepticus, and he was treated with a drug that increased

the activity of a central neurotransmitter able to generate only inhibitory

postsynaptic potentials (IPSPs) by increasing Cl- or K+ conductance.

Which

neurotransmitter was most likely affected by the drug treatment?