Neuronal activity is required for the circadian rhythm of vasopressin gene transcription in the suprachiasmatic nucleus in vitro.
Arginine vasopressin (AVP) is synthesized in and secreted by the suprachiasmatic nucleus (SCN) in a circadian pattern. Transcription of the AVP gene in organotypic cultures of rat SCN was studied by using an intronic in situ hybridization. AVP gene transcription in the cultured SCN maintained a daily rhythm with a peak in the daytime. Inhibition of spontaneous activity by the sodium channel blocker, tetrodotoxin (TTX), dramatically decreased AVP heteronuclear RNA levels and suppressed rhythmicity, indicating that ongoing neural activity was required for the AVP gene transcription. In the presence of TTX, the adenylate cyclase stimulator, forskolin, increased AVP transcription in the SCN. In contrast, the protein kinase C activator, phorbol 12-myristate 13-acetate, greatly increased AVP transcription in the absence of TTX, but this effect was blocked by TTX, indicating that the phorbol 12-myristate 13-acetate acted indirectly via synaptic input. Neither protein kinase A nor protein kinase C pathways appear to be involved in the rhythmicity of AVP transcription in the SCN because selective inhibitors of these protein kinases were without effect. In contrast, the MAPK pathway inhibitor, PD98059, profoundly decreased AVP transcription and abolished its daily rhythm. Hence, a functional MAPK signaling pathway appears to be critical for AVP gene expression in the SCN.
Arima
Hiroshi
H
Developmental Endocrinology Brach, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA. arima105@med.nagoya-u.ac.jp
House
Shirley B
SB
Gainer
Harold
H
Aguilera
Greti
G
D000818:Animals; D001127:Arginine Vasopressin / Q000235:genetics*; D002940:Circadian Rhythm; D005576:Colforsin / Q000494:pharmacology; D015870:Gene Expression / Q000187:drug effects; D017403:In Situ Hybridization; D009474:Neurons / Q000502:physiology*; D009924:Organ Culture Techniques; D012332:RNA, Heterogeneous Nuclear / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D026941:Sodium Channel Blockers / Q000494:pharmacology; D013493:Suprachiasmatic Nucleus / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013779:Tetrodotoxin / Q000494:pharmacology; D014158:Transcription, Genetic
D012332:RNA, Heterogeneous Nuclear; D012333:RNA, Messenger; D026941:Sodium Channel Blockers; D001127:Arginine Vasopressin; D005576:Colforsin; D013779:Tetrodotoxin; D013755:Tetradecanoylphorbol Acetate