T-HCA, or trans-4-hydroxycrotonic acid, is a drug used in scientific research. It is structurally related to GHB and binds to the GHB receptor with 4-fold higher affinity than GHB itself,[1] but is not an agonist for the primary sedative target of GHB, the GABAB receptor, and so does not produce sedative effects, instead causing convulsions thought to be mediated through increased glutamate release.[2] It may also be naturally produced in the mammalian CNS and is suspected to be an endogenous ligand for the GHB receptor.[3]

See also