Randomly, I saw this diagram of a serotenergic neuron. Rageboy wonders about the similarities between LSD and SSRIs.

Well, LSD is a 5HT agonist (5HT is neurochemical shorthand for serotonin, also known as 5-hydroxytryptamine) In contrast, something like Prozac™ is a selective serotonin reuptake inhibitor. What this means is that Prozac™ merely increases the amount of serotonin present in the synapse but does not directly activate the postsynaptic receptor. In the short run, this will increase the likelihood that the postsynaptic neuron will fire, just like LSD will, but eventually, both the postsynaptic and the presynaptic neuron sense that there’s a lot of serotonin in the synapse, so that the postsynaptic neuron will downregulate its receptors, and the presynaptic neuron will make less serotonin, and you will reach a new steady state where the neurons will fire less frequently, but when they do, they will do so with more potency.

Interestingly, it has recently been discovered that 5HT antagonists also help with depression.

On the other hand, repeated use of LSD will probably downregulate the postsynaptic receptors as well, but it won’t necessarily downregulate how much serotonin gets produced. If LSD is anything like MDMA, eventually you will nuke your serotonergic neurons, and that tends to be very bad.

I think I have a nice theory here, accounting for the different effects of SSRIs vs LSD, and several experiments have been performed in animals and in humans, but I really don’t know.

All I know is that I haven’t heard of anyone tripping out on Prozac™ yet.