Edit: If somebody (anybody) wants to add an answer so the bounty won't go to waste, please do so! The comments have already introduced me to the Kegg metabolism database, some interesting papers, and an amazing chapter on the biochemistry of cats. Thus, this question has been useful to me (and hopefully, to the community as well).
There is a question on Skeptics.SE that asks if "cats have a chemical in their brains that resembles LSD." I haven't found any similar claim online, but started wondering: 1. Do cats produce (natural) compounds that structurally resemble LSD? 2. Do cats produce (natural) compounds that functionally resemble LSD? Quickly glancing at the structure of LSD, it contains an indole ring. Hovering over the various indoles here found one substance that occurred in animals and was consumed as a psychedelic drug.
There is a paper that writes:
N,N-Dimethyltryptamine (DMT) is an indole alkaloid widely found in plants and animals. It is best known for producing brief and intense psychedelic effects when ingested. Increasing evidence suggests that endogenous DMT plays important roles for a number of processes in the periphery and central nervous system, and may act as a neurotransmitter.
The paper also proposed the role of DMT as a neurotransmitter. However, I haven't been able to confirm DMT is naturally produced by cats.
Do cats produce DMT? If so, what is the purpose of DMT in the cat?