has part has part has_part characteristic of has modifier serotonin abnormal serotonin level decreased serotonin level reduced serotonin level MPheno.ontology csmith reduction in the amount of biochemical messenger and regulator, found in the CNS, gastrointestinal tract, and produced by platelets that mediates neurotransmission, gastrointestinal motility, hemostasis, and cardiovascular integrity 2010-03-12T02:44:38Z decreased 5-hydroxytryptamine level decreased hippophaine level reduced serotonin concentration decreased serotonin concentration decreased 5-HT level MP:0010070 decreased hydroxytryptamine level decreased enteramine level decreased hormone level abnormal decreased amount