Bulbar catecholaminergic neurons projecting to the thoracic spinal cord of the chicken

Abstract

This study was undertaken to map the location of cell groups in the chicken brain stem that project to the thoracic spinal cord by retrogradely transported Evans Blue (EB). The majority of EB-labeled neurons are located in an area between the nucleus vagus motorius (NVMD) and hypoglossus ventralis dorsomedialis, the nucleus raphis, the nucleus vestibularis ventrolateralis, the nucleus tegmentalis dorsalis (NTD) and the reticular formation. However, this procedure demonstrates that no cell bodies within the nucleus tractus solitarii project to the spinal cord, unlike those of mammals. It is possible that this difference may be involved in the existence of the diaphragma. Additionally, catecholamine (CA)-containing cells in the brain stem projecting to the thoracic spinal cord were investigated with the aid of a technique demonstrating both CA and EB fluorescence in the same neuron. The doubly labeled cells are constantly found to be located within such areas as the lateral reticular formation at the level of the NVMD, the ventrolateral reticular formation at the level of the nucleus abducens major, the NTD and the ventrolateral reticular formation at the level of the NTD. The doubly labeled neurons are most numerous in the medial part of the NTD in transverse section, reflecting a similar tendency in the mammalian locus coeruleus.

Descending supraspinal pathways in amphibians. II. Distribution and origin of the catecholaminergic innervation of the spinal cord

“…Nevertheless, on the basis of retrograde tracing studies and immunohistochemical data, it is conceivable that the supraspinal CA inputs to the spinal cord in reptiles and birds are comparable to those in mammals. Preliminary results in birds support this notion (Chikasawa et al, 1983). The same may hold for amphibians, where recently a noradrenergic projection from the locus coeruleus to the spinal cord was demonstrated by double-labeling techniques (Marín et al, 1996).…”

“…Nevertheless, on the basis of retrograde tracing studies and immunohistochemical data, it is conceivable that the supraspinal CA inputs to the spinal cord in reptiles and birds are essentially the same. Preliminary results in birds support this notion (Chikasawa et al, 1983;Coote, 1985). Furthermore, the distribution of catecholaminergic cell bodies in cartilaginous fish (Meredith and Smeets, 1987;Stuesse et al, 1994) and cells projecting to the spinal cord (Smeets and Timerick, 1981;Timerick et al, 1992) point in the same direction.…”