A volumetric analysis of the brain and hippocampus of rats rendered perinatal hypothyroid

Abstract

The thyroid hormone is essential for the proper development of the central nervous system (CNS). Hormone deficiency during CNS development causes neurological abnormalities in the brain. The hippocampus is one of the brain regions vulnerable to hormone deficiency, and the volume of dentate gyrus (DG) and cornu ammonis (CA) are reduced by transient hypothyroidism during CNS development. However, it remains unclear whether transient hypothyroidism specifically reduces the whole hippocampal volume. In the present study, we used magnetic resonance imaging (MRI) to examine the effects of perinatal hypothyroidism on the ratio of hippocampal volume to brain volume as well as brain and hippocampal volumes overall. Perinatal hypothyroidism was induced by adding the anti-thyroid drug, methimazole, to the drinking water of pregnant dams from gestational day 15 to postnatal day 21. The MRI experiment was conducted when the rats were between 7 and 11 months old. The results showed reductions of the hippocampal and brain volume of the treated group. However, the ratio of hippocampal volume to brain volume was comparable between the control and treated groups. These results indicate that perinatal hypothyroidism minimizes the brain as a whole, but does not minimize the hippocampus in particular.

Hippocampal Volume Is Decreased in Adults with Hypothyroidism

“…However, they also noted that when they looked at hippocampal volume as a percentage of total volume, differences were no longer evident. This suggests that hypothyroid rats had smaller head sizes than control rats, which was also supported by Hasegawa et al (23). In contrast, the results of the current study provide evidence that patients with untreated adult-onset hypothyroidism have reduced hippocampal volumes, and that these differences remain following correction for intracranial volume due to head size and sex differences, in comparison to age-matched controls.…”

“…Reported alterations in animals include a reduction in the weight of the hippocampus, a reduction in the number of cells found, damaged growth of axons and dendrites, and a reduction in the volume of the hippocampus (16). However, it is important to note that some of these differences did not remain following correction for overall brain volume (23,24). Rabie et al (43) demonstrated a difference of up to 30% in hippocampal volume between 35-day-old (propylthiouracil (PTU)-induced) hypothyroid rats and control rats.…”

Scaling of cerebral blood perfusion in primates and marsupials

“…Whether primates differ from mammals in general is not known, because we Values are obtained from the literature (L) and the present study (P). Mean of four studies (Bailey et al, 2004;Hasegawa et al, 2010;Karbowski, 2007;Tajima et al, 1993); 11 Mean of four studies (Nakao et al, 2001;Ohno et al, 1979;Sakurada et al, 1978;Takagi et al, 1987); 12 Sato et al, 1999; 13 Macgowan et al, 2015;14 Christopher Macgowan (personal communication); ICA lumen radius from three mice; Foramen radius calculated from ICA lumen radius×1.4 (see note 6). are unable to gauge brain perfusion in other groups with the technique of this study.…”

Deformation-based brain morphometry in rats

“…The ROI-based manual outlining of individual brain structures enables the estimation of absolute volumes but requires well-reasoned and time-consuming area demarcation, and the outlining protocols may not be compatible between different laboratories (Foldi et al, 2010;Hasegawa et al, 2010;Henke et al, 2008;Nagel et al, 2004;Sawiak et al, 2009a;Schubert et al, 2008Schubert et al, , 2009. Unfortunately, manual approaches fail if the volumes of selected structures differ partially by small amounts.…”