Histamine compartments of the Drosophila brain with an estimate of the quantum content at the photoreceptor synapse
Histamine compartments of the Drosophila brain with an estimate of the quantum content at the photoreceptor synapse
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DOI：
10.1152/jn.00894.2004
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发表时间：
2005-03-01
影响因子：
2.5
通讯作者：
Meinertzhagen, IA
中科院分区：
文献类型：
--
作者：
Borycz, JA;Borycz, J;Meinertzhagen, IA
组胺能神经元的量子尺寸的可靠估计是不可用的。我们利用果蝇（Drosophila melanogaster）视觉系统中的两个不寻常的机会，对组胺能光感受器突触进行了这样的测定：1）从丙酮中冷冻干燥的整个果蝇头部连续显微解剖的可能性：复眼：第一个视神经柱，或层，以及大脑的其余部分; 2）光感受器R1-R6的层突触末端的均匀束。我们用这个组织来计数仔细的30 nm突触囊泡的数量从电子显微照片的R1-R6配置文件，并从显微解剖，我们确定了组胺的区域含量的复眼，板。和中央大脑头部组胺总量平均为1.98 ng，其中9%在丙酮中冷冻干燥后丢失，另外28%在大脑显微解剖后丢失。其余71%位于眼和椎板。假设组胺从组织中的损失主要是通过均匀分布在所有区域中的扩散发生的，则解剖前头部的总层含量为0.1935 ng。从公布的值的体积的大脑的隔间，计算的区域浓度的组胺是最高的薄层（4.35毫米），因为终端的R1-R6。视网膜中的浓度与板层中的浓度相似，为13%，表明大多数组胺是泡状的。每个末端有大约43，500 +/-7，400（SD）个突触小泡。如果所有组胺在这些细胞中平均分配，那么在大约670 mM的浓度下，囊泡的含量将为858 +/-304 × 10（-21）摩尔或近似于5.000 +/-1800（SD）分子。
Reliable estimates of the quantum size in histaminergic neurons are not available. We have exploited two unusual opportunities in the fly's (Drosophila melanogaster) Visual system to make such determinations for histaminergic photoreceptor synapses: 1) the possibility to microdissect successively from whole fly heads freeze-dried in acetone: the compound eyes: the first optic neuropils, or lamina-, and the rest of the brain; and 2) the uniform sheaves of lamina synaptic terminals of photoreceptors R1-R6. We used this organization to count scrupulously the numbers of 30-nm synaptic vesicles from electron micrographs of R1-R6 profiles, and from microdissections we determined the regional contents of histamine in the compound eye, lamina. and central brain. Total head histamine averages 1.98 ng of which 9% was lost after freeze-drying in acetone and a further 28% after the brain was microdissected. Of the remainder, 71% was in the eye and lamina. Assuming that histamine loss from the tissue occurred mostly by diffusion evenly distributed among all regions, the overall lamina content of the head would be 0.1935 ng before dissection. From published values for the volumes of the brain's compartments, the computed regional concentrations of histamine are highest in the lamina (4.35 mM) because of the terminals of R1-R6. The concentration in the retina is similar to13% that in the lamina, suggesting that most histamine is vesicular. There are similar to43,500 +/- 7,400 (SD) synaptic vesicles per terminal and. if all histamine is allocated equally and exclusively among these, the vesicle contents would be 858 +/- 304 X 10(-21) moles or similar to5.000 +/- 1800 (SD) molecules at an approximate concentration of 670 mM. These values are compared with the vesicle contents at synapses using acetylcholine and catecholamines.