Don't forget the adrenergic receptors, even though the affinity is lower the stimulating effects are still there. Dopamine receptor binding on the other hand make the experience more rewarding and actually helps acquiring new behavior that came to mind during the experience. Dopamine receptor binding does cause some stimulation but my personal belief is that norepinephrine is a much more powerful stimulant and even a low-medium affinity to adrenergic receptors can cause the stimulation felt on LSD.
