I don't see how LSD compares to serotonin. What aspect of LSD fools the receptors in our brains to think it is serotonin?
LSD doesn't fool your brain into thinking it is serotonin. It acts as an agonist with serotonin receptors. This means that it triggers the release of serotonin. I don't know very much about biochemistry, so I'm sure that somebody else can provide a better explanation.
LSD most likely has an agonist/antagonist relationship with serotonin, agonistic to 5-HT1 receptors and antagonistic to 5-HT2 receptors, enhancing serotonin activity at 5-HT1 receptors while blocking 5-HT2 receptors from the more effective activation of serotonin.
lsd binds to several different receptors, from dopamine to H1 (histamine), with particular affinity to 5HT1 and 2. it has an indole base, as does 5HT, thus acts as a substrate at those sites
