기니픽 중간뇌의 중심회색질에 대한 신경화학적 구획

Abstract

Current concept of the longitudinally columnar organization of the midbrain periaqueductal gray (PAG), which was originally proposed in the functional studies, could not be readily convinced by the general histological investigations. Among five longitudinal cell columns (LCC) including dorsomedial(DM), dorsolateral (DL), lateral (L), ventrolateral (VL), and juxtaaqueductal columns, only the boundary for DL has been elucidated in most of neuroanatomical studies. This study aims at searching neurochemical basis suitable for the identification and further subdivision of each LCC region in the PAG. Histochemistry for acetylcholinesterase (AChE), NADPH-diaphorase(NADPHd), and cytochrome oxidase (CO) and immunohistochemistry for calbindin-D28K (CB), calretinin (CR), and parvalbumin(PV) were carried out in coronally- sectioned midbrain slices of the guinea pig. CB-immunoreactive (CB-ir) perikarya and plexus of fibers and endings were selectively distributed in DL, VL and ventromedial part of the L but absent from DM and the junctional part between DL and L. Distribution patterns of CB-ir and CR-ir perikarya and fibers appeared to be mostly similar on the judgement criteria of LCC regions, but they were complementary each other within the same LCC region. Clusters of CB-ir or CR-ir perikarya revealed themselves to form LCC structure within the PAG whose rostral and caudal endings were reliably displayed. Difference in the distribution patterns between CB and CR revealed two neuroanatomically innominate nuclei. One was the supratrochlear cluster of CR-ir perikarya, and the other was rostrodorsal nucleus marked with CB-ir perikarya and endings in the rostral DM. PV-immunoreactivity in the PAG were very low and almost neglectable. Distribution of CO activity revealed regional subdivisions only in the longitudinally intermediate portion of the PAG in a pattern of higher CO activity in subregions with poor distribution of CB-ir or CR-ir perikarya. Comparison the distribution patterns among CB, CR, PV, NADPHd, AChE, and CO revealed the neuroanatomy of the rostral end of the PAG and the relationship between these neuroanatomical markers. These data suggested that each LCC regions within the PAG could be neurochemically identified and further subdivided into specific sub- compartments, based mainly on the distribution patterns of CB- or CR-ir perikarya and fibers.