Study on plasticity of visual system by thyroid hormone

已知甲状腺激素影响发育中大鼠视觉皮层的形态完整性以及包括精神状态在内的神经功能。为了探讨甲状腺激素对中枢神经系统功能的影响，我们对处于不同甲状腺状态的大鼠视觉系统进行了光重复刺激。使用正常（<I>）、实验前3至11周切除甲状腺（<II>）和补充甲状腺切除<T_4>（0.1 mg/kg）（<III>）。用戊巴比妥钠（55 mg/kg）麻醉后，给予光刺激（2焦耳，间隔5秒，25 cm）。为了记录由光刺激引起的诱发电位（Ep），将玻璃电极插入视皮层Ve（前额叶-8.5-9.5 mm，<lambda>3.0 mm，d 0.2-0.5 mm）和外侧膝状体核（LGN）。第二组大鼠在VC（+28.0%）和LGN（+29.1%）的Ep潜伏期延长，两个区域的p&lt;0.01。早在注射（0.05 mg/kg）后2天和1天就观察到这些变化<T_4><T_3>，表明需要甲状腺激素来维持视觉系统的功能完整性。

It has been known that thyroid hormone affects morphological integrity of the visual cortex of developing rats as well as nervous functions including mental states. In order to find the functional changes in the central nervous system, caused by thyroid hormone, we applied photic repetitive stimulation to the visual system of rats in various thyroid states. Normal ( <I> ), thyroidectomized 3 to 11 week prior to the experiments ( <II> ) and thyroidectomized- <T_4> (0.1 mg/kg) supplemented ( <III> ) were used. After anesthesia with Nembutal (55 mg/kg), photic stimulation (2 joules, 5 sec interval, 25 cm) was given to the rats. To record evoked potentials (Ep) elicited by the photic stimulation a glass electrode was inserted into the visual cortex Ve (Bregma-8.5-9.5 mm, <lambda> 3.0 mm, d 0.2-0.5 mm) and also the lateral geniculate nucleus (LGN). Group II rats showed a prolonged latency in Ep at VC (+28.0%) and also at LGN (+29.1%) at the levels of p<0.01 in both areas. These changes were observed as early as 2 days after <T_4> and also 1 day after <T_3> (0.05 mg/kg) injections, suggesting that thyroid hormone is required to maintain the functional integrity of the visual system.