Stuesse S L, Cruce W L, Northcutt R G
Neurobiology Department, Northeastern Ohio Universities College of Medicine, Rootstown, Ohio 44272.
J Comp Neurol. 1991 Jun 8;308(2):277-92. doi: 10.1002/cne.903080211.
In previous studies on reptiles and elasmobranchs, we determined that some reticular groups are either absent or may be displaced compared to their locations in mammals. For example, nucleus raphe dorsalis, the largest serotoninergic cell group in mammals, is not present in rays, skates, or guitarfish. In the present study, we chose heterodontid sharks, a sister group to these batoids, for an out-group comparison of this and other characters. We identified cells in the brainstem of Heterodontus francisci by use of antibodies against tyrosine hydroxylase, serotonin, or leu-enkephalin and compared the distribution of these nuclei to descriptions in mammals and other elasmobranchs. The majority of tyrosine hydroxylase-positive cells were found in the midbrain tegmentum (A8-A10) and the hypothalamus. In addition, putative A1, A2, A5, A7 (noradrenergic) groups were found in the metencephalon and myelencephalon. Serotonin-positive cells were found in raphe nuclei and scattered lateral to the raphe. We identified probable homologues to raphe pallidus, raphe obscurus, raphe magnus, and raphe centralis superior (B8) cell groups, which have been described in mammals. A cluster of cells dorsomedial to the medial longitudinal fasciculus was identified as raphe dorsalis. The distributions of leu-enkephalin and serotonin immunoreactive cells were similar to each other, but the tyrosine-hydroxylase immunoreactive cells rarely intermingle with the former two immunoreactive cell types. Other reticular groups that contained both serotonin- and leu-enkephalin-positive cells included reticularis (r.) ventralis, r. magnocellularis, r. paragigantocellularis lateralis, r. pontis caudalis, and r. pontis oralis medialis and lateralis. Thus, this shark contains many of the major brainstem raphe and catecholaminergic cell groups described for rats, but the relative distribution of the immunopositive cell groups differs in mammals and cartilaginous fish.
在之前对爬行动物和板鳃亚类的研究中，我们确定，与它们在哺乳动物中的位置相比，一些网状结构群要么不存在，要么可能发生了移位。例如，中缝背核是哺乳动物中最大的5-羟色胺能细胞群，在鳐鱼、鳐和犁头鳐中不存在。在本研究中，我们选择了异齿鲨（这些魟类的姐妹群）来对这一特征和其他特征进行外类群比较。我们通过使用抗酪氨酸羟化酶、5-羟色胺或亮脑啡肽的抗体，在弗朗氏异齿鲨的脑干中识别细胞，并将这些核的分布与哺乳动物和其他板鳃亚类中的描述进行比较。大多数酪氨酸羟化酶阳性细胞位于中脑被盖（A8 - A10）和下丘脑。此外，在脑桥和延髓中发现了假定的A1、A2、A5、A7（去甲肾上腺素能）群。5-羟色胺阳性细胞存在于中缝核中，并散布于中缝外侧。我们确定了可能与哺乳动物中描述的中缝苍白核、中缝隐核、中缝大核和中缝中央上核（B8）细胞群同源的结构。在内侧纵束背内侧的一群细胞被确定为中缝背核。亮脑啡肽和5-羟色胺免疫反应性细胞的分布彼此相似，但酪氨酸羟化酶免疫反应性细胞很少与前两种免疫反应性细胞类型混合。其他同时含有5-羟色胺和亮脑啡肽阳性细胞的网状结构群包括腹侧网状核、巨细胞网状核、外侧旁巨细胞网状核、尾侧脑桥网状核以及内侧和外侧口侧脑桥网状核。因此，这种鲨鱼包含许多在大鼠中描述的主要脑干中缝和儿茶酚胺能细胞群，但免疫阳性细胞群的相对分布在哺乳动物和软骨鱼类中有所不同。
