Psychopharmacology is the study of drugs that affect brain and behaviour. The substances producing changes in behaviour are called as “psychoactive drugs.” Most of the psychoactive drugs influence the chemical reactions at nerve synapses to produce behavioural changes.
The drugs that enhance the neurotransmission are known as “agonists.” The drugs that reduce the neurotransmission are known as “antagonists.”
Thus, the blanks can be filled with synapses; agonists; antagonists.