Acetylcholine turnover in an autoactive molluscan neuron.
Acetylcholine turnover in an autoactive molluscan neuron.
复制标题
自动活动软体动物神经元中的乙酰胆碱周转。
DOI：
10.1007/bf00710939
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发表时间：
1984
影响因子：
4
通讯作者：
Gelperin,A
中科院分区：
文献类型：
--
作者：
Barry,SR;Gelperin,A
1.研究了陆生软体动物Limax maximus的唾液爆发器（SB）和唾液管肌细胞（SD）之间胆碱能突触的乙酰胆碱（ACh）转换。SB是一种自发性神经元，每分钟可发出1 ~ 12个动作电位脉冲，在持续的脉冲放电过程中，即使在没有外源性胆碱的情况下，SB也能维持18小时的递质释放。SB引起的JPs的大小在18小时的活动期间没有变化。如果胆碱摄取阻断剂，半胆碱-3（HC-3; 20µM），存在于盐水中，在14小时的活动后，递质释放和JP大小被抑制约30%。4.在高钾（9.45 mM）生理盐水中，SB以两倍于其平均峰频率的频率进行紧张性放电。JP振幅最初增加，然后下降到初始水平的60%的振幅。在高钾盐水中加入20µMHC-3后，30 min内JP的大小减少了75%~ 100%。因此，在高频紧张性放电过程中，SB主要依赖于胆碱的再摄取来合成和释放ACh。SB恢复了爆发式的活动。因此，HC-3的高频放电并没有耗尽SB的全部内源性胆碱或乙酰胆碱。6.如果突触在含有HC-3的高K+盐水中疲劳，然后放入富含300μ M胆碱的盐水中，JP大小在几分钟内增加。因此，胆碱的合成和释放可能是一个更快的过程比动员内源性递质库。7.最后，SB-SD突触疲劳在高K+盐水含有HC-3。然后从盐水中取出HC-3。SB保持高频强直活动。我们的结论是SB具有两个可释放的ACh库，一个是“易释放的”，一个是“储备的”递质库。易释放池由从盐水中摄取的胆碱新合成的ACh组成。在高频发射期间，SB从该存储器中释放所有ACh。在正常的爆发活动期间，SB可以从容易释放的和储备的发射器池中释放ACh。从每个池中释放的ACh的比例可以随着SB神经元的总递质储存和尖峰活动而变化。
1.We have studied acetylcholine (ACh) turnover at the cholinergic synapse between an identified motoneuron, the salivary burster (SB), and the muscle cells of the salivary duct (SD) in the terrestrial molluskLimax maximus.2.Electrophysiological recordings were made of the SB action potentials and the SB-elicited junction potentials (JPs) on the SD. The amplitude of the JP was used as a measure of ACh release by the SB.3.The SB is an autoactive neuron that discharges 1 to 12 bursts of action potentials per min. During sustained bursting activity, the SB is able to maintain transmitter release for 18 hr even in the absence of exogenous choline. The size of SB-elicited JPs does not vary during 18 hr of activity. If the choline uptake blocker, hemicholinium-3 (HC-3; 20µM), is present in the saline, transmitter release and JP size are depressed by about 30% after 14 hr of activity. Thus, the SB is partially dependent upon choline reuptake for maintained ACh synthesis and release.4.In high (9.45 mM)-potassium (K+) saline, the SB fired tonically at twice its average spike frequency. JP amplitude initially increased, then declined to an amplitude which was 60% of the initial level. The addition of 20µMHC-3 to the high-K+saline caused a 75 to 100% decrease in JP size within 30 min. Thus, during high-frequency tonic firing, the SB was primarily dependent on choline reuptake for ACh synthesis and release.5.After JP size had been reduced in high-K+saline containing HC-3, the SB-SD synapse was returned to normal choline-free saline. The SB resumed bursting activity. JP amplitude gradually increased over the next 30 min. Thus, high-frequency firing in HC-3 had not depleted the SB of its entire endogenous store of choline or ACh.6.If the synapse was fatigued in high-K+saline containing HC-3 and then placed in saline enriched with 300µMcholine, JP size increased within minutes. Thus, uptake of choline for ACh synthesis and release may be a more rapid process than mobilization of an endogenous transmitter store.7.Finally, the SB-SD synapse was fatigued in high-K+saline containing HC-3. HC-3 was then removed from the saline. The SB maintained high-frequency tonic activity. JP size did not increase unless choline was added to the saline.8.We conclude that the SB possesses two releasable pools of ACh, a “readily releasable” and a “reserve” transmitter store. The readily releasable pool is made up of ACh newly synthesized from choline taken up from the saline. During high-frequency firing, the SB discharges all ACh from this store. During normal bursting activity, the SB may discharge ACh from both the readily releasable and the reserve transmitter pool. The proportion of ACh released from each pool may vary with the total transmitter stores and the spiking activity of the SB neuron.