Gitler M S, Barraclough C A
Department of Physiology, School of Medicine, University of Maryland, Baltimore 21201.
Brain Res. 1988 May 3;447(2):205-14. doi: 10.1016/0006-8993(88)91121-3.
Recently we reported that locus coeruleus (LC) electrical stimulation (ES) amplifies the quantity of LH released after prior medial preoptic nucleus (MPN)-electrochemical stimulation (ECS). In these studies we also observed that amplification of LH release occurred only when we activated those LC neurons whose cell bodies reside contralateral to the site of MPN-ECS. Seemingly, stimulatory LC axons decussate to reach contralateral hypothalamic regions which contain LH-RH neurons. The purpose of the present study was to identify the site(s) at which such decussation(s) occur. To accomplish this we used a special knife blade to make gross transsections in hypothalamic regions previously described by others as regions where LC decussations occur. Transection 1 (T1) interrupted axons coursing through the medial forebrain bundle (MFB) in the region of the posterior lateral hypothalamus. This transection was placed ipsilateral to the side of LC-ES and it had no effect on LH patterns or concentrations which were released by MPN-ECS. However, T1 completely blocked the amplifying effects of LC stimulation on LH secretion after MPN-ECS. Transection 2 (T2) was placed in the region of the MPN, parallel to the superior sagittal sinus. The knife blade was lowered in midline to the top of the 3rd ventricle and transected all fibers which cross midline within and around the anterior commissure. LH release following MPN-ECS was not appreciably affected in these rats nor did T2 alter the amplifying effects of LC-ES on LH. However, while plasma LH peaked between 60 and 75 min and then declined towards baseline in MPN + LC-stimulated rats, it remained significantly elevated throughout the remainder of the blood collection periods (180 min) in rats receiving combined MPN + LC and T2. Transection 3 (T3) also was placed in the MPN region and differed from T2 only in that we lowered the knife to the base of the sphenoid bone. Thus, T3 disrupted all fibers which cross midline in the AC region and dorsal to the optic chiasm (dorsal supraoptic decussation of LC axons). This transection did not affect LH release evoked by MPN-ECS but completely eliminated the amplifying effects of LC stimulation after MPN-ECS on LH secretion. These data indicate that stimulatory LC axons which affect LH-RH neuronal activity enter the hypothalamus ipsilateral to the site of LC-ES and then project rostrally in the MFB to the lateral preoptic area.(ABSTRACT TRUNCATED AT 400 WORDS)
最近我们报道，蓝斑（LC）电刺激（ES）可增强先前内侧视前核（MPN）电化学刺激（ECS）后释放的促黄体激素（LH）的量。在这些研究中我们还观察到，仅当我们激活那些胞体位于与MPN-ECS部位对侧的LC神经元时，LH释放才会增强。显然，刺激性LC轴突交叉至对侧下丘脑区域，该区域含有促性腺激素释放激素（LH-RH）神经元。本研究的目的是确定这种交叉发生的部位。为实现这一目的，我们使用一种特殊刀片在其他人先前描述为LC交叉发生区域的下丘脑区域进行大体横切。横切1（T1）中断了在后外侧下丘脑区域穿过内侧前脑束（MFB）的轴突。该横切位于LC-ES一侧的同侧，对MPN-ECS释放的LH模式或浓度没有影响。然而，T1完全阻断了LC刺激对MPN-ECS后LH分泌的增强作用。横切2（T2）置于MPN区域，与上矢状窦平行。刀片在中线降至第三脑室顶部，横切在前连合内及周围穿过中线的所有纤维。在这些大鼠中，MPN-ECS后的LH释放没有受到明显影响，T2也没有改变LC-ES对LH的增强作用。然而，在MPN + LC刺激的大鼠中，血浆LH在60至75分钟之间达到峰值，然后降至基线，而在接受MPN + LC和T2联合处理的大鼠中，在采血期剩余时间（180分钟）内LH仍显著升高。横切3（T3）也置于MPN区域，与T2的不同之处仅在于我们将刀片降至蝶骨底部。因此，T3破坏了在AC区域和视交叉背侧（LC轴突的背侧视上交叉）穿过中线的所有纤维。该横切不影响MPN-ECS诱发的LH释放，但完全消除了MPN-ECS后LC刺激对LH分泌的增强作用。这些数据表明，影响LH-RH神经元活动的刺激性LC轴突进入与LC-ES部位同侧的下丘脑，然后在MFB中向嘴侧投射至外侧视前区。（摘要截短至400字）
