Serotonin, 5-hydroxyindoleacetic acid and substance P content of discrete brain nuclei in rats made hypo- or hyperthyroid in the neonatal period: effect of growth hormone treatment.
In order to determine the role of growth hormone (GH) in the therapeutic effect of thyroxine (T4), we measured the content of serotonin (5-HT), 5-hydroxyindoleacetic acid (5-HIAA) and substance P in discrete brain nuclei of neonatally-induced hypothyroid rats and in neonatally-induced hypothyroid rats subsequently maintained on bovine growth hormone (b-GH) injections. Substance P was measured by radioimmunoassay whilst 5-HT and 5-HIAA levels were determined by HPLC with electrochemical detection. In neonatal hypothyroid rats, substance P concentration increased in 5 out of 11 brain nuclei dissected while 5-HT and 5-HIAA level increased in 7 out of 19 brain nuclei selected. Although b-GH-replacement therapy abolished the hypothyroid-induced accumulation of 5-HT and 5-HIAA in brain nuclei with exception of the substantia nigra zona reticulata, it did not influence the substance P accumulation. This suggests that the abnormal brain development observed during hypothyroidism may, in part, result from absence of growth hormone. We also observed that neonatal hyperthyroidism induced very little modification of 5-HT, 5-HIAA and substance P concentrations in discrete nuclei of the rat brain.
D000818:Animals; D000831:Animals, Newborn; D001923:Brain Chemistry; D013006:Growth Hormone / Q000627:therapeutic use*; D006897:Hydroxyindoleacetic Acid / Q000032:analysis*; D006980:Hyperthyroidism / Q000188:drug therapy / Q000378:metabolism; D007037:Hypothyroidism / Q000188:drug therapy / Q000378:metabolism; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D012701:Serotonin / Q000032:analysis*; D013373:Substance P / Q000032:analysis*; D013959:Thyroid Diseases / Q000188:drug therapy*
D012701:Serotonin; D013373:Substance P; D006897:Hydroxyindoleacetic Acid; D013006:Growth Hormone