Elsevier

Developmental Biology

Volume 166, Issue 2, December 1994, Pages 502-508
Developmental Biology

Full Papers
Embryonic Expression of Motoneuron Topography in the Rat Diaphragm Muscle

https://doi.org/10.1006/dbio.1994.1333Get rights and content

Abstract

The phrenic motoneuron pool of the rat projects onto the diaphragm muscle with a distinct rostrocaudal bias. This bias is detectable at birth and is reestablished following denervation. In an effort to define the mechanisms underlying this topographic bias, we asked whether growing phrenic motoneurons select their muscle contacts initially upon first contact or whether the initial neuromuscular distribution is random, to be specified later through synaptic rearrangement. The onset of neurotransmission in embryonic diaphragm muscles aged E-14 to E-18 was studied using focal extracellular microelectrodes. Two important phenomena were observed. First, motoneurons from all three cervical ventral roots (C4, C5, and C6) establish functional innervation at the same time. Second, already at E-15, when the earliest synaptic potentials could be recorded, a distinct rostrocaudal bias was detected. This bias was amplified as innervation progressed to rostral and caudal sectors during E-16 to E-18. These results suggest that growing phrenic motoneurons make topographic choices as they navigate toward their muscle targets. Moreover, the results indicate that further research into the mechanisms for topographic selectivity should focus on initial nerve-muscle contacts in the embryo, rather than secondary processes of error correction.

References (0)

Cited by (20)

  • Identification of the neural pathway underlying spontaneous crossed phrenic activity in neonatal rats

    2009, Neuroscience
    Citation Excerpt :

    Furthermore, the anatomy of the pathway at this time point is not the same as the early neonatal crossed phrenic pathway, but is closer to the adult neural pathway (Moreno et al., 1992; Boulenguez et al., 2007). The phrenic motor neuron pool establishes a rostrocaudal somatotopic organization on the diaphragm muscle (Greer et al., 1999; Laskowski and Owens, 1994; Laskowski and Sanes, 1987). Specifically, the rostral phrenic motor neurons tend to innervate the ventral part of the diaphragm while caudal phrenic motor neurons tend to innervate the dorsal part of the diaphragm.

  • Perinatal development of respiratory motoneurons

    2005, Respiratory Physiology and Neurobiology
View all citing articles on Scopus
View full text