Selective innervation of target regions within fetal mouse spinal cord and medulla explants by isolated dorsal root ganglia in organotypic co-cultures.
Correlative electrophysiologic and cytologic analyses demonstrate that a significant group of neurons in isolated (NGF-enhanced) fetal mouse dorsal root ganglia (DRGs) can grow across a collagen substrate and selectively innervate specific dorsal horn and dorsal column nuclei regions in co-cultured explants of deafferented spinal cord and medulla. Neurites from this group of DRG cells from connections in CNS target zones that generate characteristic primary afferent network responses to sensory stimuli, as observed in cultures of spinal cord with attached DRGs. Systematic microelectrode stimulus-mapping tests revealed that many DRG neurites were preferentially distributed in sensory target zones of co-cultured cord and medulla explants and that few collaterals of these DRG neurons were present in neighboring inappropriate regions, especially in the ventral cord. Another group of DRG neurons appears to be responsible for the less prominent, but clear-cut, innervation that developed in some of the co-cultured ventral cord explants. Fetal DRGs were also able to establish characteristic primary afferent dorsal horn or dorsal column nuclei networks when introduced into cultures of deafferented spinal cord and medulla that had been explanted alone for 1-3 weeks prior to introduction of the DRGs. These experiments demonstrate that CNS target neurons remain receptive to DRG innervation even after 1-3 weeks of maturation in vitro. Our electrophysiologic and cytologic analyses of DRG and CNS explants in organotypic co-cultures provide the first systematic attempt to establish conditions under which preferential neuritic growth to and functional innervation of specific CNS target tissues can occur in vitro. This model system should facilitate analyses of mechanisms underlying development, as well as regeneration, of specific synaptic connections in the CNS.
D000344:Afferent Pathways / Q000502:physiology; D000818:Animals; D004553:Electric Conductivity; D005260:Female; D005333:Fetus; D005727:Ganglia, Spinal / Q000502:physiology*; D008526:Medulla Oblongata / Q000502:physiology*; D051379:Mice; D009474:Neurons / Q000502:physiology; D009924:Organ Culture Techniques; D011247:Pregnancy; D013116:Spinal Cord / Q000502:physiology*; D013569:Synapses / Q000502:physiology*