Carrow G M, Calabrese R L, Williams C M
J Neurosci. 1984 Apr;4(4):1034-44. doi: 10.1523/JNEUROSCI.04-04-01034.1984.
The architecture of neurosecretory cells (NSCs) from each of two bilaterally symmetrical clusters of somata in the brain of the moth, Manduca sexta, was determined by intracellular injection of Lucifer Yellow and horseradish peroxidase. Furthermore, the ionic basis of the action potential in these cells was examined. NSC somata were visualized in the desheathed pupal protocerebrum by their reflective opalescence under direct fiberoptic illumination. Intracellular staining revealed at least six morphological classes of monopolar neurons distinguishable by the size and position of their somata as well as the patterns of their dendritic fields, axonal pathways, and terminal projections. The number of morphological classes of NSCs is in accord with the estimated number of brain neurohormones--a finding that suggests a different neuroendocrine function for each class. The observed overlap of dendritic fields is consistent with synaptic interaction among NSCs or the sharing of common inputs. Finally, the demonstration of terminal ramifications and varicosities in the corpora cardiaca and corpora allata confirms that these are the neurohemal organs for cerebral NSCs. Intracellular recordings revealed that the NSC somata had resting membrane potentials of 35 to 45 mV and were electrically excitable; they showed broad (10 to 20 msec) overshooting action potentials, long hyperpolarizing afterpotentials, and postsynaptic potentials. Impulse amplitude was maintained in the absence of external sodium or in the presence of 10(-5)M tetrodotoxin, but impulses were completely and reversibly blocked by 10 mM cobalt. Postsynaptic potentials were blocked by all three conditions. These results indicate that impulses in the somata are generated primarily by calcium inward currents. Cations, tetrodotoxin, and horseradish peroxidase in the bathing medium did not readily exchange with the extracellular space of the desheathed brain. However, light protease treatment of the brain facilitated ion exchange. These findings provide evidence for the persistence of a blood-brain barrier even in desheathed ganglia.
通过向烟草天蛾大脑中两个双侧对称的躯体簇中的每一个的神经分泌细胞（NSCs）内注射路西法黄和辣根过氧化物酶，确定了其结构。此外，还研究了这些细胞动作电位的离子基础。在直接光纤照明下，通过其反射的乳光，在去鞘蛹原脑的NSC躯体可以被看到。细胞内染色揭示了至少六种形态学类型的单极神经元，可通过其躯体的大小和位置以及树突野、轴突通路和终末投射的模式来区分。NSCs的形态学类型数量与估计的脑神经激素数量一致——这一发现表明每个类型具有不同的神经内分泌功能。观察到的树突野重叠与NSCs之间的突触相互作用或共同输入的共享一致。最后，在心侧体和咽侧体中终末分支和膨体的证实表明，这些是大脑NSCs的神经血器官。细胞内记录显示，NSC躯体的静息膜电位为35至45 mV，并且具有电兴奋性；它们表现出宽（10至20毫秒）的超射动作电位、长的超极化后电位和突触后电位。在没有外部钠或存在10⁻⁵M河豚毒素的情况下，冲动幅度得以维持，但冲动被10 mM钴完全且可逆地阻断。突触后电位在所有三种情况下均被阻断。这些结果表明，躯体中的冲动主要由钙内向电流产生。浴液中的阳离子、河豚毒素和辣根过氧化物酶不容易与去鞘大脑的细胞外空间交换。然而，对大脑进行轻度蛋白酶处理促进了离子交换。这些发现为即使在去鞘神经节中血脑屏障的持续存在提供了证据。
