Effect of intracerebral serotonin administration on pituitary-thyroid function.
Thyroid function was investigated following intrahypothalamic implantation of cannulae containing 80 mug serotonin-creatine sulphate or after intraventricular injection of 100 mug of the same substance. Control animals received either needle implantations or intraventricular injections of creatine-sulphate. Thyroid/serum 131-I ratio, activity of the thyroid gland as evaluated histologically and thyrotrophic hormone (THS) content in the pituitary were significantly decreased in serotonin-treated animals. Thyrotrophic hormone releasing hormone (TRH) concentration of the hypothalamus was also significantly lowered in serotonin-treated animals when compared to intact controls. Creatine-sulphate injected rats showed a slight decrease of TSH content of the pituitary and of TRH concentration of the hypothalamus which is probably due to a stress effect caused by the intracranial intervention and/or by the intraventricular administration of a relatively large molecule, such as creatine sulphate. It is concluded that serotonin decreases the functional activity of the hypothalamo-pituitary-thyroid system by inhibiting the TRH-secretion of the hypothalamus.
D000818:Animals; D002552:Cerebral Ventricles; D003404:Creatinine / Q000494:pharmacology; D007031:Hypothalamus / Q000378:metabolism*; D007457:Iodine Radioisotopes; D008297:Male; D010902:Pituitary Gland / Q000378:metabolism*; D051381:Rats; D012701:Serotonin / Q000494:pharmacology*; D013961:Thyroid Gland / Q000033:anatomy & histology / Q000378:metabolism*; D013972:Thyrotropin / Q000378:metabolism; D013973:Thyrotropin-Releasing Hormone / Q000378:metabolism
D007457:Iodine Radioisotopes; D012701:Serotonin; D013973:Thyrotropin-Releasing Hormone; D013972:Thyrotropin; D003404:Creatinine