A group of ISOQUINOLINES in which the nitrogen containing ring is protonated. They derive from the non-enzymatic Pictet-Spengler condensation of CATECHOLAMINES with ALDEHYDES.

Synonyms: 0, Tetrahydro-Isoquinoline, Tetrahydro Isoquinolines, Tetrahydro Isoquinoline, Tetrahydro-Isoquinolines, Tetrahydroisoquinolines, 1,2,3,4-Tetrahydroisoquinolines, Isoquinolines, 1,2,3,4-tetrahydro-