Biagioni S, Tata A M, Agrati C, Cianfarani F, Augusti-Tocco G
Dipartimento di Biologia Cellulare e dello Sviluppo, Università "La Sapienza," Rome, Italy.
J Neurosci Res. 2000 Nov 15;62(4):591-9. doi: 10.1002/1097-4547(20001115)62:4<591::AID-JNR14>3.0.CO;2-S.
The presence of cholinergic markers in sensory ganglia has suggested a possible functional role of acetylcholine both as a cofactor of morphogenesis in embryonic life and in sensory transduction during adult life. Acetylcholine, in fact, is able to excite cutaneous nociceptors and to modulate noxious stimuli. Nerve growth factor (NGF) overexpression induces the survival of nociceptive neurons, the expression of their specific markers, and hyperalgesia. On the other hand, NGF modulate the levels of cholinergic markers in several area of nervous system. Considering these observations, the present work aims to investigate whether NGF is able also to control the expression of cholinergic markers in chick sensory neurons in culture. We selected three developmental stages (E8, E12, and E18) representative of different phases of chick embryo development and performed observations on culture in which NGF was omitted at the plating time, withdrawn after the initial 24 hr of culture or maintained for 48 hr. In the experimental protocol devised, NGF did not significantly affect cell survival. At E12 a 48 hr treatment with NGF causes a significant but limited increase in acetylcholinesterase activity; activity increase was not observed when NGF was removed after 24 hr. No changes in acetylcholinesterase activity were observed at E8 and E18 stages. NGF appears to be more effective in the modulation of choline acetyltransferase activity. At E12, in fact, about a doubling of enzyme activity was measured after 24 or 48 hr of treatment with NGF. A response was also found at E18, when a 50% increase in choline acetyltransferase activity was observed just after 24 hr treatment. The behavior of muscarinic receptors in response to NGF differs compared to the two cholinergic enzymes. At E8 and E12 a profound increase in muscarinic receptor expression was observed. Conversely, at E18 NGF produces a 50% reduction of receptors. Considering these observations and the demonstrated role of muscarinic receptors in the desensitization of nociceptors, the reduction of muscarinic receptors in DRG after NGF treatment is in agreement with the proposed algogenic action of NGF in the skin.
感觉神经节中胆碱能标志物的存在表明，乙酰胆碱在胚胎期作为形态发生的辅助因子以及在成年期的感觉转导过程中可能具有功能性作用。事实上，乙酰胆碱能够刺激皮肤伤害感受器并调节有害刺激。神经生长因子（NGF）的过度表达可诱导伤害性神经元的存活、其特异性标志物的表达以及痛觉过敏。另一方面，NGF可调节神经系统多个区域中胆碱能标志物的水平。考虑到这些观察结果，本研究旨在探讨NGF是否也能够控制培养的鸡感觉神经元中胆碱能标志物的表达。我们选择了代表鸡胚胎发育不同阶段的三个发育时期（E8、E12和E18），并对在接种时省略NGF、培养最初24小时后撤除NGF或维持48小时的培养物进行观察。在设计的实验方案中，NGF对细胞存活没有显著影响。在E12时，用NGF处理48小时会导致乙酰胆碱酯酶活性显著但有限地增加；当NGF在24小时后撤除时未观察到活性增加。在E8和E18阶段未观察到乙酰胆碱酯酶活性的变化。NGF在调节胆碱乙酰转移酶活性方面似乎更有效。事实上，在E12时，用NGF处理24或48小时后，酶活性测定约增加一倍。在E18时也发现了反应，在处理24小时后胆碱乙酰转移酶活性增加了50%。毒蕈碱受体对NGF的反应行为与两种胆碱能酶不同。在E8和E12时观察到毒蕈碱受体表达显著增加。相反，在E18时NGF使受体减少50%。考虑到这些观察结果以及毒蕈碱受体在伤害感受器脱敏中的已证实作用，NGF处理后背根神经节中毒蕈碱受体的减少与NGF在皮肤中提出的致痛作用一致。
