Structural organization and neuropeptide distributions in the equine enteric nervous system: an immunohistochemical study using whole-mount preparations from the small intestine

Abstract

The architecture and neurochemistry of the enteric nervous system was studied by use of whole-mount preparations obtained by microdissection of the horse jejunum. A myenteric plexus and two plexuses within the submucosa were identified. The external submucosal plexus lying in the outermost region of the submucosa had both neural and vascular connections with the inner submucosal plexus situated closer to the mucosa. Counts of neurones stained for NADH-diaphorase demonstrated the wide variation in size, shape and neurone content of individual ganglia in both the external and internal submucosal plexuses. The average number of cells/ganglion was similar in each plexus (about 25 cells). Immunoreactivities for galanin, vasoactive intestinal peptide and neuropeptide Y were observed in nerve cell bodies and fibres of each of the plexuses. Immunoreactivity for substance P was extensive and strong in nerve fibres of all plexuses but was weaker in cell bodies of the submucosal neurones and absent in the cell bodies of the myenteric plexus. Comparative quantitative analysis of immunoreactive cell populations with total cell numbers (enzyme staining) was indicative of neuropeptide colocalization in the external submucosal plexus.

The topography, architecture and structure of the enteric nervous system in the jejunum and ileum of cattle

“…While it is generally accepted that the boundary between ESP and ISP is the vascular arcades (Scheuermann et al 1987 a, b ;Brehmer et al 1994 ;Pearson, 1994 ;Balemba et al 1998), other authors have reported a third intermediate plexus in the submucous layer of the colon of the pig (Gunn, 1968), opposum (Christensen & Rick, 1987) and man (Hoyle & Burnstock, 1989). It is therefore not yet clear whether the ESP and ISP should be considered as 2 different plexuses.…”

“…However, in recent years it has been established that the submucous plexus comprises 2 different ganglionated plexuses, the internal submucous plexus (ISP) and the external submucous plexus (ESP) (Scheuermann et al 1987 b ;Messenger & Furness, 1990 ;Timmermans et al 1992 ;Pearson, 1994 ;Balemba et al 1998). The ISP is located adjacent to the mucosa and is proposed to be primarily Correspondence to Dr Vet.…”

“…Various techniques including routine histological staining, immunohistochemistry and scanning electron microscopy have been employed to study the organisation of the enteric plexuses of pig, man and horse (Mannl et al 1986 ;Scheuermann et al 1987 a, b ;Stach, 1989 ;Holy & Burnstock, 1989 ;Timmermans et al 1990 ;Brehmer et al 1994 ;Pearson, 1994 ;Balemba et al 1998), but the morphological descriptions of the submucous plexus are not fully concordant. While it is generally accepted that the boundary between ESP and ISP is the vascular arcades (Scheuermann et al 1987 a, b ;Brehmer et al 1994 ;Pearson, 1994 ;Balemba et al 1998), other authors have reported a third intermediate plexus in the submucous layer of the colon of the pig (Gunn, 1968), opposum (Christensen & Rick, 1987) and man (Hoyle & Burnstock, 1989).…”

“…It is therefore not yet clear whether the ESP and ISP should be considered as 2 different plexuses. In addition, their appropriate nomenclature has yet to be agreed upon (Scheuermann et al 1987 b ;Hoyle & Burnstock, 1989 ;Pearson, 1994 ;Balemba et al 1998). There are also contradictory reports on the organisation of the ESP and ISP in relation to the vascular arcades and the lymphoid follicles in the region of the gut with Peyer's patches (Krammer & Ku$ hnel, 1993 ;Lowden & Heath, 1994 ;Balemba et al 1998).…”

“…Wholemounts from the submucous layer are usually prepared by freeing the submucous layer from the underlying circular muscle without much damage to the ESP (Gunn, 1968 ;Stach, 1989 ;Messenger & Furness, 1990 ;Pearson, 1994 ;Balemba et al 1998). In this study, the microdissection of the jejunal and ileal submucous wholemounts was performed by teasing the submucous layer and inner circular muscle layer from the outer longitudinal muscle followed by careful removal of individual muscle fibres by using very fine forceps.…”