Hoover Donald B, Ganote Charles E, Ferguson Shawn M, Blakely Randy D, Parsons Rodney L
Department of Pharmacology, James H. Quillen College of Medicine, East Tennessee State University, Johnson City, TN 37614, USA.
Cardiovasc Res. 2004 Apr 1;62(1):112-21. doi: 10.1016/j.cardiores.2004.01.012.
Previous studies have used acetylcholinesterase (AChE) histochemistry to identify cholinergic nerves in the heart, but this enzyme is not a selective marker for cholinergic neurons. This study maps cholinergic innervation of guinea pig heart using a new antibody to the human high-affinity choline transporter (CHT), which is present only in cholinergic nerves.
Immunohistochemistry was used to localize CHTs in frozen and paraffin sections of heart and whole mount preparations of atrial ganglionated nerve plexus. AChE-positive nerve fibers were identified in sections from separate hearts for comparison.
Control experiments established that the antibody to human CHT selectively labeled cholinergic neurons in the guinea pig. CHT-immunoreactive nerve fibers and AChE-positive nerves were very abundant in the sinus and AV nodes, bundle of His, and bundle branches. Both markers also delineated a distinct nerve tract in the posterior wall of the right atrium. AChE-positive nerve fibers were more abundant than CHT-immunoreactive nerves in working atrial and ventricular myocardium. CHT-immunoreactive nerves were rarely observed in left ventricular free wall. Both markers were associated with numerous parasympathetic ganglia that were distributed along the posterior atrial walls and within the interatrial septum, including the region of the AV node.
Comparison of labeling patterns for CHT and AChE suggests that AChE histochemistry overestimates the density of cholinergic innervation in the heart. The distribution of CHT-immunoreactive nerve fibers and parasympathetic ganglia in the guinea pig heart suggests that heart rate, conduction velocity, and automaticity are precisely regulated by cholinergic innervation. In contrast, the paucity of CHT-immunoreactive nerve fibers in left ventricular myocardium implies that vagal efferent input has little or no direct influence on ventricular contractile function in the guinea pig.
以往研究利用乙酰胆碱酯酶（AChE）组织化学方法来识别心脏中的胆碱能神经，但该酶并非胆碱能神经元的选择性标志物。本研究使用一种针对人类高亲和力胆碱转运体（CHT）的新型抗体，绘制豚鼠心脏胆碱能神经支配图谱，该转运体仅存在于胆碱能神经中。
采用免疫组织化学方法，在心脏的冰冻切片和石蜡切片以及心房神经节丛整装标本中定位CHT。在取自不同心脏的切片中识别AChE阳性神经纤维以作比较。
对照实验证实，针对人类CHT的抗体可选择性标记豚鼠体内的胆碱能神经元。CHT免疫反应性神经纤维和AChE阳性神经在窦房结、房室结、希氏束和束支中非常丰富。两种标志物还勾勒出右心房后壁的一条独特神经束。在工作中的心房和心室心肌中，AChE阳性神经纤维比CHT免疫反应性神经更为丰富。在左心室游离壁很少观察到CHT免疫反应性神经。两种标志物均与众多副交感神经节相关，这些神经节沿心房后壁分布并位于房间隔内，包括房室结区域。
CHT和AChE标记模式的比较表明，AChE组织化学高估了心脏中胆碱能神经支配的密度。豚鼠心脏中CHT免疫反应性神经纤维和副交感神经节的分布表明，心率、传导速度和自律性受胆碱能神经支配精确调节。相比之下，左心室心肌中CHT免疫反应性神经纤维的稀少意味着迷走神经传出输入对豚鼠心室收缩功能几乎没有直接影响。
