고양이 중간뇌 중심회색질에서 신경화학물질의 삼중 면역형광 표지

Abstract

The midbrain periaqueductal gray(PAG) comprises several longitudinal columns that have different neuroanatomical and functional properties. The present study aimed at characterizing the chemoarchitecture of the cat PAG and investigated the patterns of distirbution in the PAG of eleven neurochemical markers. Triple immunofluorescent labeling for calbindin-D28K (CB), calretinin (CR), parvalbumin (PV), nitric oxide synthase (NOS) somatostatin (SST), enkephalin (Enk) substance P (SubP), and tryptophan hydroxylase (TPH) were selectively carried out in midbrain slices. Histochemistry for NADPH-diaphorase (NADPHd), cytochrome oxidase (COx), and acetylcholinesterase (AChE) were additionally performed. Each neurochemical marker showed a distinct topographical distribution in the PAG. CB-immunoreactive (CB-ir) perikarya were found in the lateral (L) and ventrolateral columns (VL) and supraoculomotor cap nucleus (Su3C). A cluster of CB-ir perykarya marked an innominate nueuroanatomical nucleus at the rostral level of the PAG. CR-ir perikarya were observed in dorsolateral (DL) column and Su3C, whereras no PV-ir perikarya was found within the PAG. NOS-ir or NADPHd-positive perikarya and fibers were densely distributed in the DL and laterodorsal tegmental nucleus (LDTg) and marked Su3C with their low density. COx rectivity was found high in L and VL and very low in DL, wheras AChE reactivity was found high in VL and the outer halves of L and DL. SubP-, SST-, and Enk-ir axons and nerve endings were altogether densely distributed in middle one-third of VL(VLm). Clusters of CB-ir perikarya and SST-ir fibers marked dorsal (VLd) and ventral (VLv) compartments of VL. The medial half of L could be divided into two compartments; dorsal L(Ld) marked only with rich SubP-ir nerve endings and ventral L(Lv) marked with CB-ir perikarya and SubP-, SST-, and Enk-ir endings. Localized clusters of Enk-ir nerve terminals were also found in DL and in the subregion along the midline of dorsomedial column(DM). These findings suggest that neurons in a columnar region of the PAG are neurochemically heterogenous and that the conceptual PAG columns could be further compartmentalized into subnuclei based on the distribution of neurochemical markers.