Abstract
Lampreys, a representative of the most primitive living vertebrates, have a definite preopticohypophysial neurosecretory system in their diencephalon comparable to that of higher vertebrates (Sterba, 1972). As was shown in previous papers (Öztan and Gorbman, 1960; Tsuneki and Gorbman, 1975a; Nakai et al., 1979; Yui and Honma, 1979), the preoptic nucleus of lampreys contains so-called cerebrospinal fluid (CSF)-contacting neurons which project their dendritic process into the ventricular cavity. During the course of our anatomical studies on the brainventricular system of the arctic lamprey, Lampetra japonica (Chiba et al., 1981; Chiba and Honma, 1986a), the preoptic neurosecretory cells, which should be better-called intraventricular perikarya according to Vigh-Teichmann and Vigh (1983), were encountered. In spite of extensive studies on the periventricular structures of the brain of the arctic lamprey (Honma, 1969; Honma and Honma, 1970; Ochi and Hosoya, 1974; Tsuneki, 1974; Tsuneki et al., 1975; Shioda et al., 1977; Nakai et al., 1979; Yui and Honma, 1979; Chiba et al., 1981; Yamamoto et al., 1983; Chiba and Honma, 1986a; Ushiki et al., 1986), no cytological details of such intraventricular perikarya have been described.
In this short communication, we report ultrastructural features of the intraventricular neurosecretory perikarya in the lamprey brain, along with a brief discussion on a possible role of the cells in neuroendocrine integration.
