Prigioni I, Casella C
Boll Soc Ital Biol Sper. 1984 Feb 28;60(2):363-8.
ACh (5.10(-4) M), when applied to isolated ganglion preparations elicited an apparently antidromic discharge in the cervical sympathetic trunk. The intensity of this back-firing was found to be about 10 times lower than that of the postganglionic discharge evoked by ACh in the internal carotid nerve. Both responses however displayed a similar time course consisting mainly of an early and a late component. In the back-firing the early component died out in few seconds, while the late one lasted 20-30 seconds. The two components were cancelled by d-tubocurarine (5.10(-6) M) and atropine (10(-6) M) respectively, suggesting that both nicotinic and muscarinic cholinoceptive sites are involved. In chronically decentralized preparations ACh evoked a clear back-firing response not substantially different from that elicited in normal ganglia. Therefore it is likely that the back-firing phenomenon is not due to antidromic activation of preganglionic fibers. The back-firing observed in the rat superior cervical ganglion was interpreted as being due to activation of sympathetic neurons, known to give rise to recurrent axons in the cervical sympathetic cord.
将乙酰胆碱（5×10⁻⁴ M）应用于离体神经节标本时，可在颈交感干引发明显的逆向放电。发现这种逆向放电的强度比乙酰胆碱在内颈动脉神经中引发的节后放电强度低约10倍。然而，两种反应都呈现出相似的时间进程，主要由早期成分和晚期成分组成。在逆向放电中，早期成分在几秒钟内消失，而晚期成分持续20 - 30秒。这两个成分分别被筒箭毒碱（5×10⁻⁶ M）和阿托品（10⁻⁶ M）消除，表明烟碱样和毒蕈碱样胆碱能感受位点均参与其中。在慢性去中枢神经的标本中，乙酰胆碱引发的逆向放电反应与正常神经节中引发的反应没有实质性差异。因此，逆向放电现象可能不是由于节前纤维的逆向激活所致。在大鼠颈上神经节中观察到的逆向放电被解释为是由于交感神经元的激活，已知这些神经元会在颈交感索中产生折返轴突。
