Electrical maturation of spinal neurons in the human fetus: comparison of ventral and dorsal horn.
The spinal cord is critical for modifying and relaying sensory information to, and motor commands from, higher centers in the central nervous system to initiate and maintain contextually relevant locomotor responses. Our understanding of how spinal sensorimotor circuits are established during in utero development is based largely on studies in rodents. In contrast, there is little functional data on the development of sensory and motor systems in humans. Here, we use patch-clamp electrophysiology to examine the development of neuronal excitability in human fetal spinal cords (10-18 wk gestation; WG). Transverse spinal cord slices (300 μm thick) were prepared, and recordings were made, from visualized neurons in either the ventral (VH) or dorsal horn (DH) at 32°C. Action potentials (APs) could be elicited in VH neurons throughout the period examined, but only after 16 WG in DH neurons. At this age, VH neurons discharged multiple APs, whereas most DH neurons discharged single APs. In addition, at 16-18 WG, VH neurons also displayed larger AP and after-hyperpolarization amplitudes than DH neurons. Between 10 and 18 WG, the intrinsic properties of VH neurons changed markedly, with input resistance decreasing and AP and after-hyperpolarization amplitudes increasing. These findings are consistent with the hypothesis that VH motor circuitry matures more rapidly than the DH circuits that are involved in processing tactile and nociceptive information.
School of Biomedical Sciences & Pharmacy, Faculty of Health and Medicine, Hunter Medical Research Institute, The University of Newcastle, Callaghan, New South Wales, Australia; and.
M A
MA
Tadros
School of Biomedical Sciences & Pharmacy, Faculty of Health and Medicine, Hunter Medical Research Institute, The University of Newcastle, Callaghan, New South Wales, Australia; and.
R
R
Lim
Spinal Cord Research Group, Institute of Neuroscience and Psychology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom.
D I
DI
Hughes
School of Biomedical Sciences & Pharmacy, Faculty of Health and Medicine, Hunter Medical Research Institute, The University of Newcastle, Callaghan, New South Wales, Australia; and.
A M
AM
Brichta
School of Biomedical Sciences & Pharmacy, Faculty of Health and Medicine, Hunter Medical Research Institute, The University of Newcastle, Callaghan, New South Wales, Australia; and robert.callister@newcastle.edu.au.
R J
RJ
Callister
D000200:Action Potentials; D000870:Anterior Horn Cells / Q000502:physiology*; D005333:Fetus / Q000502:physiology*; D006801:Humans; D020671:Posterior Horn Cells / Q000502:physiology*; D066148:Spinal Cord Dorsal Horn / Q000196:embryology* / Q000502:physiology; D066151:Spinal Cord Ventral Horn / Q000196:embryology* / Q000502:physiology
action potential; excitability; motoneuron; pain