就像蒲公英定时释放种子一样，海马突触中神经递质的释放也有特定的释放几率。尽管释放几率是衡量突触效能的基础指标，但是，突触是如何控制神经递质的释放目前还不为人们所知。
在8月14日的《神经元》（Neuron）杂志上，Branco等人通过研究连接一对海马神经元的突触前终末，发现同一树突分支的相邻突触有着相似的神经递质释放几率，该释放几率与树突分支上的突触数目呈负相关。
该项研究成果表明，树突的活性决定了突触释放神经递质的几率，树突的这种负反馈作用可能具有调节突触与树突的作用距离的功能。（生物谷Bioon.com）
生物谷推荐原始出处：
Neuron，Vol 59, 475-485, 14 August 2008，Tiago Branco, Yukiko Goda
Local Dendritic Activity Sets Release Probability at Hippocampal Synapses
Tiago Branco,1,2, Kevin Staras,1,3 Kevin J. Darcy,1 and Yukiko Goda1,2
The arrival of an action potential at a synapse triggers neurotransmitter release with a limited probability, pr. Althoughpr is a fundamental parameter in defining synaptic efficacy, it is not uniform across all synapses, and the mechanisms by which a given synapse sets its basal release probability are unknown. By measuring pr at single presynaptic terminals in connected pairs of hippocampal neurons, we show that neighboring synapses on the same dendritic branch have very similar release probabilities, and pr is negatively correlated with the number of synapses on the branch. Increasing dendritic depolarization elicits a homeostatic decrease in pr, and equalizing activity in the dendrite significantly reduces its variability. Our results indicate that local dendritic activity is the major determinant of basal release probability, and we suggest that this feedback regulation might be required to maintain synapses in their operational range.
