抄録
The cortical areas of primates are structurally and functionally highly specialized compared with their rodent counterpart. To study the molecular basis of cortical differentiation in primates, we searched for genes that are specifically expressed in restricted areas of macaque monkeys and found the striking enrichment of serotonin (5-HT)1B receptor mRNA in the primary visual area (V1). In situ hybridization (ISH) analyses revealed that 5-HT2A but no other 5-HT receptors are also enriched in V1. 5-HT1B and 5-HT2A receptor mRNA expression in V1 was upregulated in geniculorecipient layers 4A and 4C during early postnatal periods to achieve their area and lamina specificity in adults. In adults, the expression of these mRNAs were dependent on retinal activity. These observations strongly suggest the central role of visual activity in sculpting the cortical expression of these 5-HT receptors. We also show evidence that 5-HT1B and 2A receptors are functional in monkey V1. The pharmacological study suggested that these receptors have opposite modulatory effects on the firing of V1 neurons. Interestingly, the modulatory effects were dependent on the firing rate of the recorded neurons. So far, the enriched expression of 5-HT1B and 2A receptor mRNAs in V1 is observed only in primates. The potential role of these serotonin receptors in visual function of primates will be discussed. [J Physiol Sci. 2007;57 Suppl:S37]
