Enriched expression of serotonin 1B and 2A receptor genes in macaque visual cortex and their bidirectional modulatory effects on neuronal responses.
To study the molecular mechanism how cortical areas are specialized in adult primates, we searched for area-specific genes in macaque monkeys and found striking enrichment of serotonin (5-hydroxytryptamine, 5-HT) 1B receptor mRNA, and to a lesser extent, of 5-HT2A receptor mRNA, in the primary visual area (V1). In situ hybridization analyses revealed that both mRNA species were highly concentrated in the geniculorecipient layers IVA and IVC, where they were coexpressed in the same neurons. Monocular inactivation by tetrodotoxin injection resulted in a strong and rapid (<3 h) downregulation of these mRNAs, suggesting the retinal activity dependency of their expression. Consistent with the high expression level in V1, clear modulatory effects of 5-HT1B and 5-HT2A receptor agonists on the responses of V1 neurons were observed in in vivo electrophysiological experiments. The modulatory effect of the 5-HT1B agonist was dependent on the firing rate of the recorded neurons: The effect tended to be facilitative for neurons with a high firing rate, and suppressive for those with a low firing rate. The 5-HT2A agonist showed opposite effects. These results suggest that this serotonergic system controls the visual response in V1 for optimization of information processing toward the incoming visual inputs.
Watakabe
Akiya
A
Division of Brain Biology, National Institute for Basic Biology, 38 Nishigonaka Myodaiji, Okazaki 444-8585, Japan.
Komatsu
Yusuke
Y
Sadakane
Osamu
O
Shimegi
Satoshi
S
Takahata
Toru
T
Higo
Noriyuki
N
Tochitani
Shiro
S
Hashikawa
Tsutomu
T
Naito
Tomoyuki
T
Osaki
Hironobu
H
Sakamoto
Hiroshi
H
Okamoto
Masahiro
M
Ishikawa
Ayako
A
Hara
Shin-ichiro
S
Akasaki
Takafumi
T
Sato
Hiromichi
H
Yamamori
Tetsuo
T
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D002522:Chlorocebus aethiops; D004594:Electrophysiology; D015870:Gene Expression; D017403:In Situ Hybridization; D008251:Macaca; D009474:Neurons / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D010775:Photic Stimulation; D044302:Receptor, Serotonin, 5-HT1B / Q000378:metabolism* / Q000502:physiology; D044402:Receptor, Serotonin, 5-HT2A / Q000378:metabolism* / Q000502:physiology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017366:Serotonin Receptor Agonists / Q000378:metabolism / Q000494:pharmacology; D014793:Visual Cortex / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology
D044302:Receptor, Serotonin, 5-HT1B; D044402:Receptor, Serotonin, 5-HT2A; D017366:Serotonin Receptor Agonists