Development of differential preganglionic projections to pre- and paravertebral sympathetic ganglia

Abstract

Sympathetic preganglionic axons project to spatially distinct targets in the periphery. A precise topographic pattern exists within the thoracic preganglionic cell column relative to the direction of axonal projections within the sympathetic chain. In this study, the time course and pattern of axonal outgrowth from different populations of preganglionic neurons in the chicken embryo is examined in detail to clarify the origin of the topography in this system. Projections to prevertebral targets are established by development of the splanchnic nerves by stage 25, well after the earliest somatic motor projections at stage 19 but at least two stages before the reported onset of paravertebral projections. Further, preganglionic axons that project rostrally into the sympathetic chain may do so earlier than those that project caudally in the chain. The separation of preganglionic axons into prevertebral, rostral paravertebral or caudal paravertebral directions occurs at a common site in the ventral mesenchyme, established by the initial ventromedial projection of the splanchnic nerves. Analysis of the axonal trajectories of rostrally and caudally projecting cells reveals that preganglionic axons are not selectively fasciculated before their point of separation at the sympathetic chain. The patterning of the preganglionic cell column is specified before the establishment of functional connections within the chain, indicating that target contact is not a determinant of the segmental pattern. We suggest that the differential outgrowth of preganglionic axons to peripheral targets is determined by the unique identities of underlying subpopulations of preganglionic axons.

Ontogeny of galanin-immunoreactive elements in chicken embryo autonomic nervous system

“…Our data fully agree with the findings of Cornbrooks et al (1997), who showed the first connection between pregangliar axons and primary chain at E4.5 and the development of secondary, paravertebral, chain and preaortic plexus between E4.5 and E5.5 using GAP43 immunohistochemistry, retrograde and ortograde labeling with dextran amines, and acetylcholinesterase histochemistry. In the spinal cord, GAL‐immunoreactive cells lying medially in the motor column and then in the intermediate zone, could belong to the visceral motor cell population that between E5.5 and E6.5 migrates dorsomedially to the intermediate gray matter (Prasad and Hollyday, 1991; Cornbrooks et al, 1997). At E6, celiac, hypogastric and pelvic plexuses branch from the aortic plexus; three nerves originate from the celiac plexus toward stomach‐duodenum, pancreas and small intestine; and the hypogastric plexus gives rise to the Remak ganglion (Romanoff, 1960).…”

“…Somatostatin‐IR elements were described at E4.5 at sacral level (New and Mudge, 1986) and NPY from E5–6 (García Arrarás et al, 1992). The development of the primary chain has also been studied using other markers: in the quail, immunoreactivity for TH has been observed from E3.5 (Vogel and Weston, 1990); in the chick, acetylcholinesterase was shown from E4 (Cornbrooks et al, 1997); and, at thoracic level, TH from E2.5 and choline acetyltransferase from E6 (Ernsberger and Rohrer, 1996; Ernsberger et al, 1997).…”

MicroRNA miR-9 Modifies Motor Neuron Columns by a Tuning Regulation of FoxP1 Levels in Developing Spinal Cords

“…LMC neurons occur only in the brachial and lumbar regions in spinal cords, which are aligned with the forelimbs and hindlimbs respectively in mammals, and wings and legs in birds. In the chick, preganglionic autonomic motor neurons, termed Column of Terni (CT) neurons, are positioned in the dorsomedial spinal cord at thoracic levels and project axons to sympathetic targets (Prasad and Hollyday, 1991; Gutman et al, 1993; Cornbrooks et al, 1997). …”

Functional organization of peripheral vasomotor pathways

“…It has been assumed, but never tested definitively, that all the final motor neurones in a neural unit are functionally similar in some way. Nevertheless, developmental studies imply that pre-ganglionic neurones are somehow pre-determined to make correct contacts with the appropriate sets of final motor neurones (Cornbrooks et al 1997, Anderson et al 2002, further reinforcing the idea of functional Ôneural unitsÕ. Figure 2 Simplified circuit diagram of the guinea-pig coeliac ganglion.…”