Michalkiewicz M, Dey M, Huffman L J, Hedge G A
Department of Physiology, West Virginia University Health Sciences Center, Morgantown 26506-9229, USA.
Thyroid. 1998 Nov;8(11):1071-7. doi: 10.1089/thy.1998.8.1071.
In the present study, we tested the hypothesis that the neuropeptides, vasoactive intestinal peptide (VIP) and neuropeptide Y (NPY), which are present in the thyroid nerves, act as physiological neurotransmitters involved in the regulation of thyroid hormone secretion and thyroid blood flow. Specifically, we examined whether these neuropeptides can be released into thyroid blood vessels by electrical stimulation of the major thyroid nerves or whether their expression is altered by changes in iodine intake. Sprague-Dawley rats were used in this study. The cervical sympathetic trunk or the superior laryngeal nerve was stimulated by bipolar electrodes in anesthetized rats. During nerve stimulation, blood samples were withdrawn from the thyroid vein. Thyroid blood flow was monitored by laser Doppler blood flowmetry. Sympathetic stimulation caused a marked decrease in thyroid blood flow, which was associated with a significant increase in release of norepinephrine. However, these effects were not accompanied by any change in NPY release into the thyroid vein. Stimulation of the superior laryngeal nerve was not associated with changes in thyroid blood flow or VIP release into the thyroid vein. In a separate experiment, rats were fed a diet containing low-, high-, or normal iodine concentrations. Triiodothyronine (T3) and thyroxine (T4) levels in thyroid venous plasma were significantly reduced in rats fed a low-iodine diet but not in a separate group of rats fed a high iodine diet. However, these treatments had no effect on VIP or NPY concentrations in thyroid venous plasma or in thyroid ganglia. Thus, our results indicate that VIP and NPY, which are present in the thyroid nerves, may not be directly involved in the regulation of thyroid function.
在本研究中，我们验证了这样一个假设：甲状腺神经中存在的神经肽，即血管活性肠肽（VIP）和神经肽Y（NPY），作为参与调节甲状腺激素分泌和甲状腺血流的生理神经递质发挥作用。具体而言，我们研究了这些神经肽是否可通过电刺激甲状腺主要神经而释放到甲状腺血管中，或者其表达是否会因碘摄入量的变化而改变。本研究使用了Sprague-Dawley大鼠。在麻醉的大鼠中，用双极电极刺激颈交感干或喉上神经。在神经刺激期间，从甲状腺静脉采集血样。通过激光多普勒血流仪监测甲状腺血流。交感神经刺激导致甲状腺血流显著减少，这与去甲肾上腺素释放的显著增加相关。然而，这些效应并未伴随着NPY释放到甲状腺静脉中的任何变化。刺激喉上神经与甲状腺血流或VIP释放到甲状腺静脉中的变化无关。在另一项实验中，给大鼠喂食含低、高或正常碘浓度的饮食。喂食低碘饮食的大鼠甲状腺静脉血浆中的三碘甲状腺原氨酸（T3）和甲状腺素（T4）水平显著降低，但喂食高碘饮食的另一组大鼠则未降低。然而，这些处理对甲状腺静脉血浆或甲状腺神经节中的VIP或NPY浓度没有影响。因此，我们的结果表明，甲状腺神经中存在的VIP和NPY可能不直接参与甲状腺功能的调节。
