Thesis (M.Sc.)--Chulalongkorn University, 2012

Serotonin mediating valvular disease is widely known in human medicine, but it is still unclear in canine degenerative mitral valve disease (DMVD). The Purpose of this study was to compare circulating serotonin concentrations between normal dogs and dogs with DMVD. Twenty healthy and twenty-three newly confirmed DMVD dogs, small breed less than 10 kilograms and older than 7 years old, were collected for the blood samples. Serum, plasma and platelet serotonin concentrations were measured by the serotonin ELISA test. Median plasma and platelet serotonin concentrations were not significantly different between the normal dogs and dogs with DMVD. While, median serum serotonin concentration in dogs with DMVD was significant lower than the normal dogs (p < 0.01). Age, platelet count, and echocardiographic indices showed no significant correlation with the circulating serotonin concentration. From the plasma and platelet results, the serotonin concentrations were unchanged between normal and DMVD group. Even though the difference had found in serum serotonin concentration, the serum sample does not represent the real circumstance in the body. In conclusion, circulating serotonin is unlikely to be a major source of serotonin in DMVD. Local serotonin signaling is suggested in mediating canine DMVD. Further study about the local serotonin blockage or other serotonin pathways mediating DMVD is warranted.