The Development of Cutaneous Afferent Pathways in Fetal Sheep: A Structural and Functional Study

This study examined the development of cutaneous afferent pathways in fetal sheep hindlimbs from 67 to 143 days of gestation. Functional responses to cutaneous stimulation began at 75 days, with most cells responding to light touch and fewer to intense stimuli. Noxious heat responses were first observed at 107 days. Structural studies showed initial skin innervation at 75 days, with increasing complexity and wool/hair follicle innervation by 100-106 days. By 134 days, advanced nerve structures were present around follicles. Afferent fibres entered the dorsal horn at 56 days, with significant growth and synaptic maturation occurring between 87-128 days. Activation of dorsal horn cells by cutaneous stimulation started by mid-gestation, coinciding with peripheral nerve skin innervation.