The median raphe nucleus (also referred to as superior central nucleus, here abbreviated to MRN) is composed of polygonal, fusiform and pyriform neurons and exists rostral to the nucleus raphe pontis.

One trait of the MRN is its inhibition by lysergic acid diethylamide and psilocin

Psilocin

Psilocin , an aromatic compound, sometimes also spelled psilocine, psilocyn, or psilotsin, is a psychedelic mushroom alkaloid. It is found in most psychedelic mushrooms together with its phosphorylated counterpart psilocybin...

, two serotonin antagonist hallucinogens. The inactivation of the nucleus centralis superior via LSD

LSD

Lysergic acid diethylamide, abbreviated LSD or LSD-25, also known as lysergide and colloquially as acid, is a semisynthetic psychedelic drug of the ergoline family, well known for its psychological effects which can include altered thinking processes, closed and open eye visuals, synaesthesia, an...

 produces a dose dependent inactivation in the MRN, but not in the raphe pallidus.

The free-moving cats, in which this was discovered, exhibited dose dependent behavioral changes when researched by Dr. Michael Trulson of the neurology department at Texas A&M University Medical School..