Distribution of nitric oxide synthase (NOS) immunoreactivity in the chicken stomach

NOS-immunoactive nerve structures were studied in the domestic hen (Gallus domesticus) stomach using single-labelling immunofluorescence. The examined tissues were collected from 10-12 months old laying hens (n=11), Isabrown and Zielononózka races. The distribution and number of the nerve fibres was examined considering differences between the proventriculus and gizzard, and also between particular layers of the stomach wall. Large or moderate numbers of nerve fibres showing NOS-immunoreactivity (NOS-IR) were found in all major layers of both parts of the stomach. In the muscular layer of the gizzard, NOS-positive nerve cell bodies were also observed. Small or moderate numbers of nerve terminals were distributed around blood vessels. NOS-IR nerve fibres associated with blood vessels were slightly more numerous in the gizzard than in the proventriculus. The widespread occurrence of NOS in both parts of the hen stomach can prove its important role in the control of digestive processes. It seems that there is a reasonable necessity of further, more detailed studies on morphological characteristics of the nitrergic nerve structures the bird alimentary tract, their functional significance and plasticity in different physiological and pathological conditions.