발생중인 흰쥐 뇌에서 γ-aminobutyric acid (GABA) 생성에 관여하는 효소의 발현

Abstract

Gamma-aminobutyric acid (GABA) is known to be the major inhibitory neurotransmitter in the mammalian central nervous system. GABA is produced mainly through enzymatic decarboxylation of glutamic acid by glutamic acid decarboxylase (GAD), and it is also synthesized by the degradation of putrescine. These studies were performed to elucidate GABA metabolism and regulation by comparing the distribution of GABA and its synthesizing enzymes GAD and γ-amino-butyraldehyde dehydrogenase (γ -ABALDH). GABA-immunoreactive cells first appeared in gestation 15th day, and in gestation 17th day the number of GABA-immunoreactive cells increased and the cells were stained deeply. However, immunoreactivies against GABAdecreased in first day after birth and third day, and then recovered slightly in postnatal 10th day. GAD-immunoreactive structures were shown first in cardiac muscles in 12th day of gestation. In gestation 13th day, GAD-immunoreactive fibers were observed in mesenchymal tissues around the brain vesicle. GAD-immunoreactive cells were distributed widely in the brain in gestation 15th day, and GAD-immunoreactivities were increased gradually. In postnatal 10th day, GAD-immunoreactive cells were distributed evenly in the brain similar to the distribution pattern of adult rat ; however, numbers of immunoreactive cells were decreased and nerve fibers were stained strongly. On the other hand, γ-ABALDH appeared first in the 13th day of gestation, the earlist period in the brain vesicle and in 15th and 17th day of gestation, various regions show strong immunoreactivity. In the 19th day of gestation, the immunoreactivity was decreased and it was recovered in 3 days after birth and those phenomenon were observed not only in the γ-ABALDH-immunoreactive neurons but also in the neuroglia. The distribution of γ-ABALDH was similar to that of the GABA from the period of 15th day of gestation to after birth and even in the adult period. In this study, we investigated the distribution of GABA and its synthesizing enzymes, GAD and γ-ABALDH, and it was confirmed that γ-ABALDH is another enzyme related to GABA synthesis. γ -ABALDH may play an important role in GABA synthesis, especially in early developmental stages.