Altered magnetic resonance images of brain and social behaviors of hatchling, and expression of thyroid hormone receptor beta mRNA in cerebellum of embryos after Methimazole administration

作者：Haba Gen; Nishigori Hidekazu; Sasaki Makoto; Tohyama Koujiro; Kudo Kohsuke; Matsumura Yutaka; Sugiyama Toru; Kagami Keisuke; Tezuka Yu; Sanbe Atsushi; Nishigori Hideo

来源：Psychopharmacology, 2014, 231(1): 221-230.

DOI：10.1007/s00213-013-3229-z

• Chick
• MRI
• Cerebellum
• Methimazole
• Social behaviors
• Vocalization
• Aggregation
• Thyroid hormone receptor
• Inorganic pyrophosphatase
• Secernin

The effects of low thyroid hormone level during embryogenesis on MRI of the brain and social behaviors of hatchlings were examined using "fertilized hen's egg-embryo-chick" system.
Control and hatchlings treated with methimazole (20 mu mol/egg), which hatched 3 days later than controls were examined. The results are as follows:
1. The MRI examination of the midsagittal section of the brain on hatch day showed that the sizes, by T1- and ADC values by diffusion-weighted images, of the optic lobe and cerebellum of the MMI-hatchlings were significantly bigger than those of the controls.
2. The social behaviors o post-hatch day 3 were based on the following tests:
(a) Aggregation test: The speed of four chicks, individually isolated by cardboard barriers in a box, to make a group upon the removal of barriers.
(b) Belongingness tests: The speed of a chick isolated at a corner to join the group of three chicks placed at the opposite corner.
(c) Vocalization test: The number of decibel produced by a chick isolated at a corner using a sound meter. These tests demonstrated that MMI-hatchlings took longer times and had weaker vocalization than the controls, significantly.
Upregulation of THR beta mRNA after MMI treatment suggested that THR was necessary for cerebellum development.
The MMI exposure during the last week of embryogenesis possibly delayed the myelination of certain brain regions and impaired the social behaviors of hatchlings. The chick embryos can be easily induced with hypothyroidism without maternal influences, and the hatchling's behaviors were analyzed using a video camera. The present method will be useful for assessing the effects of unfavorable influences during embryogenesis on social behaviors in later life.

• 出版日期2014-1