功能性神经造影利用脑部血流量的变化来绘制的大脑活动谱图，然而神经突触前和突触后活动的作用目前还是未知的领域，它可能是潜在的细胞途径。
在6月26日的《神经元》（Neuron）杂志上，Petzold等人利用作用于活体的多光子显微镜，测量了小鼠的神经突触前的活动，突触后神经元和星形胶质细胞钙的反应，以及在气味刺激下红细胞的速度和嗅觉纤维球的流量等数据。
结果表明，气味诱发的纤维球毛细血管中的功能性充血与谷氨酸的释放高度相关，却不需要神经突触后活动。气味的刺激会诱导星形胶质细胞后段的钙瞬变和相关上行动脉的扩张。而星形胶质细胞中功能性充血的钙含量升高依赖于星形胶质细胞代谢型谷氨酸受体5和环氧合酶的激活。星形胶质细胞谷氨酸转运体也通过独立于钙上升和环氧合酶激活的机制来帮助功能性充血。
这些由谷氨酸启动的途径对神经突触活动和功能性充血纤维球的联结起到至关重要的作用。（生物谷Bioon.com）
生物谷推荐原始出处：
Neuron，Vol 58, 897-910, 26 June 2008，Gabor C. Petzold, Venkatesh N. Murthy
Coupling of Neural Activity to Blood Flow in Olfactory Glomeruli Is Mediated by Astrocytic Pathways
Gabor C. Petzold,1,2 Dinu F. Albeanu,1,2 Tomokazu F. Sato,1,2 and Venkatesh N. Murthy1,2,
1 Department of Molecular and Cellular Biology, Harvard University, 16 Divinity Avenue, Cambridge, MA 02138, USA
2 Center for Brain Science, Harvard University, 16 Divinity Avenue, Cambridge, MA 02138, USA
Corresponding author
Venkatesh N. Murthy
vnmurthy@fas.harvard.edu
Summary
Functional neuroimaging uses activity-dependent changes in cerebral blood flow to map brain activity, but the contributions of presynaptic and postsynaptic activity are incompletely understood, as are the underlying cellular pathways. Using intravital multiphoton microscopy, we measured presynaptic activity, postsynaptic neuronal and astrocytic calcium responses, and erythrocyte velocity and flux in olfactory glomeruli during odor stimulation in mice. Odor-evoked functional hyperemia in glomerular capillaries was highly correlated with glutamate release, but did not require local postsynaptic activity. Odor stimulation induced calcium transients in astrocyte endfeet and an associated dilation of upstream arterioles. Calcium elevations in astrocytes and functional hyperemia depended on astrocytic metabotropic glutamate receptor 5 and cyclooxygenase activation. Astrocytic glutamate transporters also contributed to functional hyperemia through mechanisms independent of calcium rises and cyclooxygenase activation. These local pathways initiated by glutamate account for a large part of the coupling between synaptic activity and functional hyperemia in the olfactory bulb.
