Skip to main content
  • Poster presentation
  • Open access
  • Published:

Propylthiouracil causes behavioral changes in rats: the role of serotonin


Propylthiouracil is an antithyroid drug that inhibits thyroidal T4 production and peripheral conversion of T4 to T3. The manifestations of hypothyroidism are low metabolic rate, lethargy, bradycardia, sensitivity to cold and mental impairment.

The aim of this study was to determine behavior and endocrine effects after chronic application of propylthiouracil and to measure the serotonin levels in the brain of rats, pre-treated or not with 5-hydroxy-tryptophan.

Materials and methods

Male Wistar Albino rats (140 - 160 g) were allowed free access to drinking water containing 0,02 % Propylthiouracil for 5 weeks. The experimentally PTU- induced hypothyroidism was confirmed by a significant decrease of FT3 and FT4, and increase of TSH plasma levels. We performed Forced swimming test (FST) before and after 5-day-treatment with 5-hydroxy-tryptophan (50 mg/kg/i.p). The serotonin levels in the brain were also measured before and after 5-hydroxy-tryptophan application.


The chronic exposure of Propylthiouracil leaded to alteration of rat behavior and changes in hypothalamic-pituitary-thyroid axis. A statistically important prolongation of the immobilization time was found in hypothyroid rats compared to controls. We also observed decrease of food intake and body weight. Brain serotonin levels of experimentally induced hypothyroid rats were decreased statistically significant (0,3366 + 0,04829 g/g). Aftermg/g) in comparison with healthy controls (0,8178 + 0,0536 m 5-hydroxy-tryptophan treatment serotonin levels increased and depressive symptoms in rats diminished.


Our results indicate that PTU-induced hypothyroidism causes behavioral changes and depressive behavior in rats possibly via central serotoninergic hypofunction. Depressive symptoms could be avoided via application of serotoninergic drugs.

Author information

Authors and Affiliations


Rights and permissions

Open Access This article is published under license to BioMed Central Ltd. This is an Open Access article is distributed under the terms of the Creative Commons Attribution 2.0 International License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Reprints and permissions

About this article

Cite this article

Bocheva, G., Varadinova, M. & Boyadjieva, N. Propylthiouracil causes behavioral changes in rats: the role of serotonin. Ann Gen Psychiatry 7 (Suppl 1), S351 (2008).

Download citation

  • Published:

  • DOI: