Neurotransmitters regulating acid secretion in the proventriculus of the Houbara bustard (Chlamydotis undulata): A morphological viewpoint

Abstract

Endocrine cells containing somatostatin (Som), gastrin-releasing peptide (GRP), and neuronal nitric oxide synthase (nNOS) and nerve fibers containing choline acetyl transferase (ChAT), tyrosine hydroxylase (TH), galanin (Gal), substance P (SP), and vasoactive intestinal polypeptide (VIP) were immunolocalized in the proventriculus of the Houbara bustard, Chlamydotis undulata. While GRP-immunoreactive (GRP-IR) cells occur in the inner zone, somatostatin (Som-IR) and polyclonal nNOS (nNOS-IR) immunoreactive cells were localized mainly in the peripheral zone of submucosal glands. GRP-IR, Som-IR, and nNOS-IR cells were occasionally observed in the walls of the gastric glands. Endocrine cells are of the closed variety and usually possess apical processes extending along the basal surfaces of adjacent nonreactive cells. Ultrastructural features of these cells are typical. ChAT, Gal, SP, VIP, and TH were immunolocalized in nerve fibers and terminals in the walls of arterioles and capillaries at the periphery of submucosal glands. Immunoreactivity to monoclonal nNOS occurred mainly in neuronal cell bodies in ganglia located around the submucosal glands. ChAT and TH immunoreactive cell bodies were also occasionally seen around the submucosal glands in the peripheral region. Immunoreactivity to Gal, SP, and VIP, but not ChAT or TH, was discernible around the walls of gastric glands. It was concluded that the distribution of neurotransmitters in neuronal structures is similar, but that of the endocrine cells varies from that of some avian species. The roles of these neurotransmitters in the regulation of acid secretion are discussed.

Distribution and ontogeny of gastrin- and serotonin-immunoreactive cells in the proventriculus of developing chick, Gallus gallus domestica

“…The localization of endocrine cells in the gastrointestinal tract has been investigated using immunohistochemical methods [2,19], fluorescence methods [18,28] and electron microscopy [6,21]. Endocrine cells observed to be in contact with the lumen of the organ are classified as an, "open type" and cells not contacting the lumen are classified have been as "closed type" [26].…”

Topography and neurochemistry of the enteric ganglia in the proventriculus of the duck ( Anas platyrhynchos)

“…Up to now, however, the enteric nervous system in the avian proventriculus has been considered to be regularly formed by myenteric and submucous ganglionated plexuses and no presence of ganglia or single neurons has ever been described in the tunica mucosa Balaskas et al 1995;Martìnez et al 2000;Mensah-Brown and Lawrence 2001). The reason for this controversy may reside in the fact that the histological organization of the proventriculus has been given different interpretations.…”

“…In the proventriculus, the distribution and neurochemistry of enteric ganglia have been studied in a few species of birds. Immunopositivity to vasoactive intestinal peptide (VIP) and/or the enzyme NOS has been described in proventricular myenteric and submucous ganglion cells of the chicken (Balaskas et al 1995;Martìnez et al 2000), quail ) and raptor bird houbara bustard (Mensah-Brown and Lawrence 2001). However,, in the proventriculus of the duck, the majority of neuropeptide-containing enteric ganglion cells have been reported to be located in the tunica mucosa (Mirabella et al 2002).…”