Neurobiology Program and Department of Zoology and Physiology, University of Wyoming, 1000 E Univ. Ave., Dept. 3166, Laramie, WY 82071, USA.
J Neurosci Methods. 2011 Aug 15;199(2):175-82. doi: 10.1016/j.jneumeth.2011.02.019. Epub 2011 Mar 2.
The anterior pituitary gland regulates physiological processes via the secretion of hormones, which are under the control of factors produced either in the hypothalamus or the pituitary gland itself. Studies investigating how the pituitary gland functions have employed both in vitro and in vivo approaches. Although in vitro analysis has the advantage that it is pituitary specific, the results may be incomplete because the tissue is isolated from other physiological inputs that could affect function under natural conditions. Without vascular input, such studies are inherently of short duration. Conversely, in vivo experiments that rely upon systemic hormone injections require high doses, are non-target specific and the precise hormone concentrations reaching the pituitary gland are difficult to control. Intracerebroventricular hormone infusions are reliant on assumptions that factors are transported to the pituitary gland from the cerebrospinal fluid and are without cerebral effects. Here we describe an innovative method to investigate anterior pituitary function in conscious sheep by direct infusion of peptides into the pituitary tissue surrounding the hypophyseal portal blood vessels. This approach is an adaptation of the hypophyseal portal cannulation technique whereby an indwelling cannula provides direct access to the rostral aspect of the adenohypophysis. Peptide infusions were achieved by insertion of a needle through the implanted cannula such that it penetrated the pituitary. Using this technique, infusion of TRH (17 ng/1 μl/min for up to 6h) induced a sustained rise in systemic prolactin levels that lasted for the duration of the infusion.
垂体前叶通过激素的分泌来调节生理过程,这些激素受下丘脑或垂体自身产生的因素控制。研究垂体功能的方法既有体外方法,也有体内方法。虽然体外分析具有垂体特异性的优势,但结果可能不完整,因为组织与其他可能影响自然条件下功能的生理输入相分离。没有血管输入,这样的研究本质上是短暂的。相反,依赖于全身激素注射的体内实验需要高剂量,非靶向特异性,并且到达垂体的精确激素浓度难以控制。脑室内激素输注依赖于这样的假设,即因子从脑脊液中被运送到垂体,并对大脑没有影响。在这里,我们描述了一种通过直接将肽注入围绕垂体门脉血管的垂体组织来研究清醒绵羊前叶功能的创新方法。这种方法是垂体门脉插管技术的一种改编,其中留置的插管提供了对腺垂体前叶的直接进入。通过将针穿过植入的插管插入来实现肽输注,使得针穿透垂体。使用这种技术,TRH(17ng/1μl/min,持续 6h)的输注诱导了全身催乳素水平的持续升高,持续时间与输注时间相同。