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The development of descending projections from the brainstem to the spinal cord in the fetal sheep.

Stockx EM, Anderson CR, Murphy SM, Cooke IR, Berger PJ - BMC Neurosci (2007)

Bottom Line: At G140, CTB labelled cells were found within and around nuclei in the reticular formation of the medulla and pons, within the vestibular nucleus, raphe complex, red nucleus, and the nucleus of the solitary tract.The distribution of CTB labelled neurons in the G55 fetus was similar to that of the G140 fetus.All projections present in the mature fetus at G140 have already arrived at the spinal cord by approximately one third of the way through gestation.

View Article: PubMed Central - HTML - PubMed

Affiliation: Ritchie Centre for Baby Health Research, Monash Institute of Medical Research, Monash University, Clayton, Victoria, Australia. elaine.stockx@med.monash.edu.au

ABSTRACT

Background: Although the fetal sheep is a favoured model for studying the ontogeny of physiological control systems, there are no descriptions of the timing of arrival of the projections of supraspinal origin that regulate somatic and visceral function. In the early development of birds and mammals, spontaneous motor activity is generated within spinal circuits, but as development proceeds, a distinct change occurs in spontaneous motor patterns that is dependent on the presence of intact, descending inputs to the spinal cord. In the fetal sheep, this change occurs at approximately 65 days gestation (G65), so we therefore hypothesised that spinally-projecting axons from the neurons responsible for transforming fetal behaviour must arrive at the spinal cord level shortly before G65. Accordingly we aimed to identify the brainstem neurons that send projections to the spinal cord in the mature sheep fetus at G140 (term = G147) with retrograde tracing, and thus to establish whether any projections from the brainstem were absent from the spinal cord at G55, an age prior to the marked change in fetal motor activity has occurred.

Results: At G140, CTB labelled cells were found within and around nuclei in the reticular formation of the medulla and pons, within the vestibular nucleus, raphe complex, red nucleus, and the nucleus of the solitary tract. This pattern of labelling is similar to that previously reported in other species. The distribution of CTB labelled neurons in the G55 fetus was similar to that of the G140 fetus.

Conclusion: The brainstem nuclei that contain neurons which project axons to the spinal cord in the fetal sheep are the same as in other mammalian species. All projections present in the mature fetus at G140 have already arrived at the spinal cord by approximately one third of the way through gestation. The demonstration that the neurons responsible for transforming fetal behaviour in early ontogeny have already reached the spinal cord by G55, an age well before the change in motor behaviour occurs, suggests that the projections do not become fully functional until well after their arrival at the spinal cord.

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Medulla (G140). In the medulla of the G140 fetal sheep, CTB labelled cells were present in the raphe magnus (RMg), gigantocellular reticular (Gi), and vestibular (Ve) nuclei, in the nucleus of the solitary tract (Nsol), spinal trigeminal (Sp5), lateral reticular (LRt), paramedian reticular (PMn), dorsal paragigantocellular (DPGi) nuclei and along the ventral edge of the brainstem section. Both sides of the figure are ipsilateral labelling (see methods).
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Figure 5: Medulla (G140). In the medulla of the G140 fetal sheep, CTB labelled cells were present in the raphe magnus (RMg), gigantocellular reticular (Gi), and vestibular (Ve) nuclei, in the nucleus of the solitary tract (Nsol), spinal trigeminal (Sp5), lateral reticular (LRt), paramedian reticular (PMn), dorsal paragigantocellular (DPGi) nuclei and along the ventral edge of the brainstem section. Both sides of the figure are ipsilateral labelling (see methods).

Mentions: At the level of the mid-medulla, CTB labelled cells were present in the gigantocellular reticular nucleus (Fig. 5) bilaterally. The cells were present at a much higher density ipsilateral to the side of the CTB injection. Just ventral to the gigantocellular reticular nucleus there was a large number of labelled cells within the raphe magnus nucleus. Labelled cells continued to be found in the nucleus of the solitary tract, the lateral reticular nucleus and along the ventral edge of the brainstem sections. There was a small number of CTB labelled cells in the spinal trigeminal nucleus, restricted to its ventral part. Labelled cells were observed in the caudal pole of the vestibular nucleus and in the dorsal paragigantocellular reticular nucleus.


The development of descending projections from the brainstem to the spinal cord in the fetal sheep.

Stockx EM, Anderson CR, Murphy SM, Cooke IR, Berger PJ - BMC Neurosci (2007)

Medulla (G140). In the medulla of the G140 fetal sheep, CTB labelled cells were present in the raphe magnus (RMg), gigantocellular reticular (Gi), and vestibular (Ve) nuclei, in the nucleus of the solitary tract (Nsol), spinal trigeminal (Sp5), lateral reticular (LRt), paramedian reticular (PMn), dorsal paragigantocellular (DPGi) nuclei and along the ventral edge of the brainstem section. Both sides of the figure are ipsilateral labelling (see methods).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC1919385&req=5

Figure 5: Medulla (G140). In the medulla of the G140 fetal sheep, CTB labelled cells were present in the raphe magnus (RMg), gigantocellular reticular (Gi), and vestibular (Ve) nuclei, in the nucleus of the solitary tract (Nsol), spinal trigeminal (Sp5), lateral reticular (LRt), paramedian reticular (PMn), dorsal paragigantocellular (DPGi) nuclei and along the ventral edge of the brainstem section. Both sides of the figure are ipsilateral labelling (see methods).
Mentions: At the level of the mid-medulla, CTB labelled cells were present in the gigantocellular reticular nucleus (Fig. 5) bilaterally. The cells were present at a much higher density ipsilateral to the side of the CTB injection. Just ventral to the gigantocellular reticular nucleus there was a large number of labelled cells within the raphe magnus nucleus. Labelled cells continued to be found in the nucleus of the solitary tract, the lateral reticular nucleus and along the ventral edge of the brainstem sections. There was a small number of CTB labelled cells in the spinal trigeminal nucleus, restricted to its ventral part. Labelled cells were observed in the caudal pole of the vestibular nucleus and in the dorsal paragigantocellular reticular nucleus.

Bottom Line: At G140, CTB labelled cells were found within and around nuclei in the reticular formation of the medulla and pons, within the vestibular nucleus, raphe complex, red nucleus, and the nucleus of the solitary tract.The distribution of CTB labelled neurons in the G55 fetus was similar to that of the G140 fetus.All projections present in the mature fetus at G140 have already arrived at the spinal cord by approximately one third of the way through gestation.

View Article: PubMed Central - HTML - PubMed

Affiliation: Ritchie Centre for Baby Health Research, Monash Institute of Medical Research, Monash University, Clayton, Victoria, Australia. elaine.stockx@med.monash.edu.au

ABSTRACT

Background: Although the fetal sheep is a favoured model for studying the ontogeny of physiological control systems, there are no descriptions of the timing of arrival of the projections of supraspinal origin that regulate somatic and visceral function. In the early development of birds and mammals, spontaneous motor activity is generated within spinal circuits, but as development proceeds, a distinct change occurs in spontaneous motor patterns that is dependent on the presence of intact, descending inputs to the spinal cord. In the fetal sheep, this change occurs at approximately 65 days gestation (G65), so we therefore hypothesised that spinally-projecting axons from the neurons responsible for transforming fetal behaviour must arrive at the spinal cord level shortly before G65. Accordingly we aimed to identify the brainstem neurons that send projections to the spinal cord in the mature sheep fetus at G140 (term = G147) with retrograde tracing, and thus to establish whether any projections from the brainstem were absent from the spinal cord at G55, an age prior to the marked change in fetal motor activity has occurred.

Results: At G140, CTB labelled cells were found within and around nuclei in the reticular formation of the medulla and pons, within the vestibular nucleus, raphe complex, red nucleus, and the nucleus of the solitary tract. This pattern of labelling is similar to that previously reported in other species. The distribution of CTB labelled neurons in the G55 fetus was similar to that of the G140 fetus.

Conclusion: The brainstem nuclei that contain neurons which project axons to the spinal cord in the fetal sheep are the same as in other mammalian species. All projections present in the mature fetus at G140 have already arrived at the spinal cord by approximately one third of the way through gestation. The demonstration that the neurons responsible for transforming fetal behaviour in early ontogeny have already reached the spinal cord by G55, an age well before the change in motor behaviour occurs, suggests that the projections do not become fully functional until well after their arrival at the spinal cord.

Show MeSH
Related in: MedlinePlus