REDUCTION OF GASTROINTESTINAL SEROTONIN IN ALLOXAN-DIABETIC RATS - REVERSAL BY 5-HYDROXYTRYPTOPHAN TREATMENT

A rat model of alloxan-induced diabetes was used to investigate the ef fect of diabetic state on serotonin (5-HT) levels in peripheral body c ompartments, gastrointestinal (GI) and platelet, and the metabolic res ponse of these compartments to serotonin precursor (5-hydroxytryptopha n, 5-HTP) loading in diabetes. In all segments of diabetic gut a massi ve reduction in 5-HT concentration (to 45-64% at 6th week after induct ion of diabetes, with further progression to 30-52% at 14th week) was shown. After parenteral loading with 5-HTP for 6 days (30 mg/kg per da y) 5-HT concentration in all parts of the GI tract returned to the con trol values (82-108%), indicating reduced serotonin precursor availabi lity in diabetes. Platelet serotonin levels (PSL) in diabetic rats dem onstrated a slight gradual reduction that became significant at 14th w eek of diabetic state. On the mentioned 5-HTP challenge only blunted r esponse of PSL in diabetics, as contrasted to control animals (54% vs. 113%) was shown, indicating possible suppression of the membrane 5-HT transporter. The observed alterations in peripheral 5-HT homeostasis in diabetic rats as well as the possibility of their reversal by 5-HTP treatment could be of clinical interest.