Van Bockstaele E J, Aston-Jones G, Pieribone V A, Ennis M, Shipley M T
Department of Mental Health Sciences, Hahnemann University, Philadelphia, Pennsylvania 19102-1192.
J Comp Neurol. 1991 Jul 15;309(3):305-27. doi: 10.1002/cne.903090303.
Previous anatomical and physiological studies have revealed a substantial projection from the periaqueductal gray (PAG) to the nucleus paragigantocellularis (PGi). In addition, physiological studies have indicated that the PAG is composed of functionally distinct subregions. However, projections from PAG subregions to PGi have not been comprehensively examined. In the present study, we sought to examine possible topographic specificity for projections from subregions of the PAG to PGi. Pressure or iontophoretic injections of wheat germ agglutinin-conjugated horseradish peroxidase, or of Fluoro-Gold, placed into the PGi of the rat retrogradely labeled a substantial number of neurons in the PAG from the level of the Edinger-Westphal nucleus to the caudal midbrain. Retrogradely labeled neurons were preferentially aggregated in distinct subregions of the PAG. Rostrally, at the level of the oculomotor nucleus, labeled neurons were i) compactly aggregated in the ventromedial portion of the PAG corresponding closely to the supraoculomotor nucleus of the central gray, ii) in the lateral and ventrolateral PAG, and iii) in medial dorsal PAG. More caudally, retrogradely labeled neurons became less numerous in the dorsomedial PAG but were more widely scattered throughout the lateral and ventrolateral parts of the PAG. Only few retrogradely labeled neurons were found in the ventromedial part of the PAG at caudal levels. Injections of retrograde tracers restricted to subregions of the PGi suggested topography for afferents from the PAG. Injections into the lateral portion of the PGi yielded the greatest number of labeled neurons within the rostral ventromedial PAG. Medially placed injections yielded numerous retrogradely labeled neurons in the lateral and ventrolateral PAG. Injections placed in the rostral pole of the PGi (medial to the facial nucleus) produced the greatest number of retrogradely labeled neurons in the dorsal PAG. To examine the pathways taken by fibers projecting from PAG neurons to the medulla, and to further specify the topography for the terminations of these afferents in the PGi, the anterograde tracer Phaseolus vulgaris-leucoagglutinin was iontophoretically deposited into subregions of the PAG that contained retrogradely labeled neurons in the above experiments. These results revealed distinct fiber pathways to the rostral medulla that arise from the dorsal, lateral/ventrolateral, and ventromedial parts of the PAG. These injections also showed that there are differential but overlapping innervation patterns within the PGi. Consistent with the retrograde tracing results, injections into the rostral ventromedial PAG near the supraoculomotor nucleus yielded anterograde labeling immediately ventral to the nucleus ambiguus in the ventrolateral medulla, within the retrofacial portion of the PGi.(ABSTRACT TRUNCATED AT 400 WORDS)
以往的解剖学和生理学研究表明，导水管周围灰质（PAG）向巨细胞旁核（PGi）有大量投射。此外，生理学研究表明，PAG由功能不同的亚区组成。然而，PAG亚区向PGi的投射尚未得到全面研究。在本研究中，我们试图研究PAG亚区向PGi投射可能存在的拓扑特异性。向大鼠的PGi内进行压力注射或离子电渗法注射小麦胚芽凝集素结合辣根过氧化物酶或荧光金，可逆行标记从动眼神经核水平到中脑尾部的PAG中大量神经元。逆行标记的神经元优先聚集在PAG的不同亚区。在吻侧，在动眼神经核水平，标记的神经元：i）紧密聚集在PAG腹内侧部分，与中央灰质的动眼神经上核紧密对应；ii）在PAG的外侧和腹外侧；iii）在PAG背内侧。在更尾侧的部位，背内侧PAG中逆行标记的神经元数量减少，但在PAG的外侧和腹外侧部分分布更广泛。在尾侧水平的PAG腹内侧部分仅发现少数逆行标记的神经元。将逆行示踪剂注射限制在PGi的亚区内提示了来自PAG的传入纤维的拓扑结构。向PGi外侧部分注射产生了吻侧腹内侧PAG内最多数量的标记神经元。向内侧注射在PAG外侧和腹外侧产生了大量逆行标记的神经元。向PGi吻端（面神经核内侧）注射在背侧PAG中产生了最多数量的逆行标记神经元。为了研究从PAG神经元投射到延髓的纤维所走的路径，并进一步明确这些传入纤维在PGi内终末的拓扑结构，将顺行示踪剂菜豆凝集素离子电渗沉积到上述实验中含有逆行标记神经元的PAG亚区内。这些结果揭示了从PAG的背侧、外侧/腹外侧和腹内侧部分到吻侧延髓的不同纤维路径。这些注射还表明，PGi内存在不同但重叠的神经支配模式。与逆行追踪结果一致，向动眼神经上核附近的吻侧腹内侧PAG注射，在延髓腹外侧的疑核腹侧、PGi的面神经后部分内产生了顺行标记。（摘要截取自400字）
