Bandil, you can alkylate the piperazine-tryptamine with benzylchloride or p-methoxy-benzylchloride and you will get a sigma agonist, probably quite selectiver for sigma 2 receptor. A similar compound having two indol-3-yl-ethyl moieties attached on both sides of the piperazine was found psychoactive in animals already some 40 years ago. It is consistent with the SAR requirements for sigma 2 agonism as well as the above proposed benzylic version.
Anyway you can still acetylate it to block the basicity of the second piperazine nitrogen and check if the N'-acetyl compound has any serotoninergic activity. It would be very interesting nevertheless.