Transcranial imaging of somatotopic map plasticity after tail cut in mice

Peripheral afferent denervation induces reorganization of somatotopic maps in the primary somatosensory cortex (S1). In the present study, we investigated somatotopic map plasticity after tail cut. Neonatal mice at postnatal days (P) 2-3 and adult mice at eight weeks of age were anesthetized with ether, and approximately two thirds of the tail was cut from the tip. Both groups of mice were anesthetized with urethane (1.7g/kg, i.p.) at 10weeks of age, and transcranial flavoprotein fluorescence imaging was performed in the S1. Neural activities in the S1 were elicited by vibratory stimulation applied to the contralateral hindpaw or the tail in control mice. The cortical areas activated by hindpaw, tail base, and tail tip stimuli were placed in this order according to the medial and posterior direction. In mice with tail cut, the tail base area moved to the more medial and posterior area corresponding to the tail tip in control mice. The shift of the tail base area was observed in both neonatal and adult tail cut mice, indicating the absence of a critical period before eight weeks. Medial and posterior shift of the tail base area with regard to the bregma was confirmed in tail cut mice. These data suggest that transcranial flavoprotein fluorescence imaging is a useful technique for investigating somatosensory map plasticity in mice.