Final answer:
Stimulants increase the release of neurotransmitters, intensifying brain cell activity. These include drugs like cocaine, amphetamines, and caffeine, which act mainly on the dopamine system.
Step-by-step explanation:
The drugs that cause more neurotransmitters to be released, thereby increasing the activity of brain cells, are stimulants. Stimulants like cocaine, amphetamines, and caffeine act as agonists of the dopamine neurotransmitter system, which is associated with reward and craving. These substances enhance neural activity by promoting the synthesis of neurotransmitters, reducing their reuptake from synapses, and mimicking their action by binding to receptors.