Circadian rhythm of aromatic L-amino acid decarboxylase in the rat suprachiasmatic nucleus: gene expression and decarboxylating activity in clock oscillating cells.
BACKGROUND
Aromatic L-amino acid decarboxylase (AADC) is the enzyme responsible for the decarboxylation step in both the catecholamine and indoleamine synthetic pathways. In the brain, however, a group of AADC containing neurones is found outside the classical monoaminergic cell groups. Since such non-monoaminergic AADC is expressed abundantly in the suprachiasmatic nucleus (SCN), the mammalian circadian centre, we characterized the role of AADC in circadian oscillation.


RESULTS
AADC gene expression was observed in neurones of the dorsomedial subdivision of the SCN and its dorsal continuant in the anterior hypothalamic area. These AADC neurones could uptake exogenously applied L-DOPA and formed dopamine. AADC was co-expressed with vasopressin and the clock gene Per1 in the neurones of the SCN. Circadian gene expression of AADC was observed with a peak at subjective day and a trough at subjective night. The circadian rhythm of AADC enzyme activity in the SCN reflects the expression of the gene.


CONCLUSIONS
Non-monoaminergic AADC in the SCN is expressed in clock oscillating cells, and the decarboxylating activity of master clock cells are under the control of the circadian rhythm.
Ishida
Yoshiki
Y
Division of Molecular Brain Science, Department of Brain Sciences, Kobe University Graduate School of Medicine, Chuo-ku, Kobe 650-0017, Japan.
Yokoyama
Chihiro
C
Inatomi
Tsutomu
T
Yagita
Kazuhiro
K
Dong
Xin
X
Yan
Lily
L
Yamaguchi
Shun
S
Nagatsu
Ikuko
I
Komori
Takahide
T
Kitahama
Kunio
K
Okamura
Hitoshi
H
D000818:Animals; D001142:Aromatic-L-Amino-Acid Decarboxylases / Q000235:genetics / Q000378:metabolism*; D001683:Biological Clocks; D018797:Cell Cycle Proteins; D002940:Circadian Rhythm; D003653:Decarboxylation; D015971:Gene Expression Regulation, Enzymologic; D007150:Immunohistochemistry; D007980:Levodopa / Q000378:metabolism; D008297:Male; D009474:Neurons / Q000201:enzymology; D009687:Nuclear Proteins / Q000096:biosynthesis; D056950:Period Circadian Proteins; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013493:Suprachiasmatic Nucleus / Q000166:cytology / Q000201:enzymology* / Q000502:physiology
D018797:Cell Cycle Proteins; D009687:Nuclear Proteins; C539024:Per1 protein, rat; D056950:Period Circadian Proteins; D012333:RNA, Messenger; D007980:Levodopa; D001142:Aromatic-L-Amino-Acid Decarboxylases