Dopamine functions as a primary neurotransmitter that mediates motivation, reward processing, and hedonic pleasure in response to environmental stimuli.

Study: Striatal dopamine D2/D3 receptor regulation of human reward processing and behaviour

When scientists blocked dopamine signals in people’s brains, they became less motivated and less able to feel pleasure from good things. When they partly boosted dopamine, people stayed normal. This proves dopamine is key for feeling motivated and rewarded.

Study: Pharmacological Modulation of Dopamine Receptors Reveals Distinct Brain-Wide Networks Associated with Learning and Motivation in Nonhuman Primates

This study showed that blocking dopamine in monkeys made them less motivated to learn rewards from cues, proving dopamine is key for feeling driven by things in the environment. It doesn't measure 'pleasure' directly, but it shows dopamine is essential for motivation and reward learning.

Study: Hedonic hotspot in rat olfactory tubercle: map for mu-opioid, orexin, and muscimol enhancement of sucrose ‘liking’

This study found that tweaking a specific brain area in rats made them enjoy sweet tastes more, showing that pleasure comes from certain brain spots — which is exactly what dopamine is thought to help do in humans.

Study: Neurotransmitter and metabolic effects of interferon-alpha in association with decreased striatal dopamine in a Non-Human primate model of Cytokine-Induced depression

When the monkeys got sick from a drug that causes inflammation, their brain’s dopamine levels dropped, and they became less motivated — showing that dopamine is needed to feel driven and rewarded by things around us.