Evidence suggests that the addictiveness of some drugs, including cocaine and nicotine, is related to increases in the activity of which neurotransmitter?.

The answer is "Dopamine".

Some drugs fundamentally influence one neurotransmitter or class of neurotransmitters. For instance, prescription opioids and heroin deliver impacts that are like (however more articulated than) those created by the neurotransmitters endorphin and enkephalin: expanded absence of pain, reduced readiness, and low breath. Different medications upset more than one sort of neurotransmitter. Cocaine, for instance, joins to structures that manage dopamine, prompting increments in dopamine activity and creating euphoria; it likewise delivers changes in norepinephrine and glutamate frameworks that cause stimulant impacts.