Abrupt nicotine cessation after chronic use disrupts monoaminergic systems and causes withdrawal signs/symptoms. In this study, the precursor of serotonin 5-hydroxytryptophan (5-HTP) relieved nicotine withdrawal signs. (-)-Nicotine bitartrate or equimolar sodium tartrate was infused into each rat via a s.c. osmotic minipump for 7 days. Somatic abstinence signs (teeth-chattering/chews and shakes, etc.) were counted one day after pump removal. Somatic signs were attenuated by the i.p. injection of 5-HTP, but not by NSD-1015, a centrally-acting L-aromatic amino acid decarboxylase inhibitor, indicating that 5-HTP mitigates somatic signs mainly through its conversion to 5-HT.