Serotonergic regulation of somatosensory cortical development: Lessons from genetic mouse models

Monoaminergic neurotransmitter systems appear early during embryogenesis, suggesting that they could play important roles in brain development. Accumulated evidence indicates that serotonin (5-hydroxytryptamine, 5-HT) regulates neural as well as nonneural development, including early aspects of embryonic development, differentiation of neuronal progenitors, and morphogenesis of the craniofacial region, heart and limb. Recent studies using monoamine oxidase-A (MAO-A), 5-HT transporter, vesicular monoamine transporter-2 (VMAT2) and 5-HT_1B receptor single, double and triple knockout mice have provided evidence that the serotonergic system plays important roles in barrel field formation in the developing somatosensory cortex. Here we review evidence from these genetic mouse models and, based on the accumulated evidence, propose a testable model for future studies of mechanisms underlying serotonergic regulation of cortical development.