OBJECTIVETo explore the mechanism of postoperative fatigue syndrome(POFS) by detecting the change of central monoamine neurotransmitters in a rat model after major abdominal surgery.

METHODEighty-four rats were randomly divided into fatigue assessment groups (including model group and sham group) and experimental groups (including postoperative day 1, 3, 5, 7, and 14 recovery groups and the corresponding control groups). Postoperative fatigue was evaluated after surgery. The brains were removed thereafter to detect the levels of 5-hydroxytryptamine (5-HT), norepinephrine (NE), dopamine (DA) in the hippocampus, midbrain, hypothalamus by high performance liquid chromatography. Serum free tryptophan (f-Trp) and branched-chain amino acids (BCAA) were measured.

RESULTSThe level of 5-HT increased to the highest at postoperative day 3, but reduced rapidly to the minimum at postoperative day 5, and then gradually recovered to the preoperative level. There was significant difference of 5-HT among experimental groups (P<0.05), also between the postoperative 24 hrs group and control groups (P<0.05). f-Trp and the ratio of f-Trp/BCAA increased in the early postoperative period, reduced to minimum at postoperative day 5. f-Trp was still lower compared to the control group at postoperative day 14, while the ratio of f-Trp/BCAA and BCAA restored to control level. Both of them were significantly different among experimental groups (P<0.05), also between the experimental groups and control groups (P<0.05).

CONCLUSIONChanges of f-Trp, the ratio of f-Trp/BCAA, and central 5-HT may play an important role in the development of POFS.