Abstract

Objectives: Hypothyroidism is believed to result in irreversible neurological and cognitive impairments. The aim of this study was to examine cognitive functions of male and female rat offspring exposed to 6-propyl-2-thiouracil (PTU) following levothyroxine-therapy. Materials and Methods: Wistar rats were used for the experiment. To induce chronic mild neonatal hypothyroidism in rat offspring, PTU (1.5, 3, and 6 ppm) was added to drinking water of the rat offspring from postnatal day 1 to week 12. In the separated group, levothyroxine (50 mg/kg. SC) was injected in the Hypo 6 ppm. Morris water maze (MWM) and novel object recognition (NOR) tests were performed at weeks 10 and 12 respectively. Results: In both male and female rats, there was an increase (P < 0.05) in neonatal hypothyroid rats' escape latency and traveled distance to find the hidden platform in MWM compared to those of control. Retrieval memory was impaired in the MWM and the NOR tests. Levothyroxine-therapy resulted in a non-significant difference in the traveled distance and latency delay and retrieval memory of the hypo 6 ppm group compared to controls (P > 0.05). Conclusions: Cognitive impairments following neonatal mild hypothyroidism can disturb hippocampusdependent learning and memory in both male and female rats. Treatment with levothyroxine induces an improvement in disorders of both male and female genders. © 2018 Mahdieh Taheri et al.