While specific D2 agonists are hard to come by [such as bromocryptine], Salvinorin A is a good example of the effects of D2 dopamine receptors. While the entirety of the unpleasant effects of Salvinorin A are due to its Kappa Opioid receptor agonism, the psychedelic effects are entirely due to D2 receptors. Salvinorin A is both a strong D2 agonist and a Kappa Opioid agonist. The Kappa Opioid receptor not only shuts down dopamine neurons in the area affected by opiates, but also very strongly upregulates D2 receptors. This means by being a Kappa Opioid agonist, Salvinorin A potentiates its psychedelic action at the D2 receptors.
The D2 dopamine receptor does not produce euphoria. It produces the following:
- Dissociation, similar to NMDA antagonism but not as thorough. It separates you from the outside world, giving you an inability to communicate or interact with it. This is due to changes in calcium levels affected by D2.
- Suppression of dopamine release in the body. This is related to dissociation: it disconnects you from the organic movement of your body. You literally move like a robot. Suppression of dopamine release in this case does not mean dysphoria, it simply occurs in the movement coordination areas.
- Closed Eye Visuals: At lower levels, two dimensional cartoon like artwork appears. Examples can be found on google. The artwork is present both in cannabis, and in salvia at low levels. At higher levels things get more visionary, as evidenced by salvia.
- Open Eye Visuals: At lower levels, D2 makes the entire world lose its sense of three dimensionality. It makes everything flat, yet somehow interconnected. It makes objects blurry and lose focus, and prevents your eyes from locking onto objects.
- Mind's Eye Visuals: Faces, numbers, and diamonds can be perceived. Waves of sky blue energy.
D2 very strongly stops the long term production of prolactin. When this happens, you regain the feeling of childhood magic that was lost when you became a teenager. Reality opens up to you. Things become FRESH. Prolactin suppresses global dopamine release in a way that suppresses how you felt as a child, the innocence you once had. This is one of the primary reasons phenethylamine is so tonic and antidepressive. Prolactin causes depression, and D2 relieves prolactin.