EFFECT OF L-THYROXINE AND CARBIMAZOLE ON BLOOD-LEVELS OF BIOGENIC-AMINES IN RAT

Circulating levels of 5-hydroxytryptamine (5HT), histamine, monoamine oxidase (MAO), histaminase, tri-iodothyronine (T3) and thyroxine (T4) were studied in L-thyroxine and carbimazole treated rats. Increased co ncentrations of 5-HT, histamine, glutamate, T3 and T4 were recorded in L-thyroxine-treated rats while plasma gamma-aminobutyric acid (GABA), MAO and histaminase levels were significantly decreased. Considerable reduction in 5-HT, glutamate, T3 and T4 with trend towards the rise i n plasma levels of MAO and histaminase was noticed in carbimazole trea ted group. There was a significant correlation between these amines an d thyroid hormone values. The findings suggest that alterations in the metabolism of thyroid hormones may have a link with the altered metab olism of biogenic amines.