The acetylcholinesterase histochemistry is used to identify the cholinergic nerves in tissue sections. Little is known on localization of cholinergic nerves in the oviduct of laying hens. We have used this technique to localize and compare the acetylcholinergic neurons in different regions through the oviduct in laying hens. The cholinergic neurons were seen as single cells, pairs or three cells arranged together. The cytoplasm and the processes of positive neurons showed strong reaction, with an eccentric nucleus. Morphologically, the neurons were rounded and oval cells of unipolar, bipolar and multipolar shapes. Similar features were seen in the whole mounts. Varicose nerve fibers were present. Cholinergic neurons were commonly seen in the muscularis; the fibers ran along the muscularis, occasionally showed a bifurcation to enter the lamina propria, reaching the secondary and tertiary mucosal folds; the fibers also targeted the blood vessels in the intermuscular region. The regional distribution of cholinergic neurons was highest seen in the infundibulum; medium in the magnum, isthmus and uterus (shell gland), while vagina had significantly lower (P<0.05) number; i.e. 8.00±1.00, 5.33±0.33, 4.67±0.67; 5.67±0.33; and 3.67±0.33, respectively. The local comparison of cholinergic neurons in muscularis and lamina propria showed significantly higher (P<0.05) number in muscularis than lamina propria of the isthmus. It was concluded that acetylcholinesterase positive (cholinergic) nerves may have a role in the regulation of the smooth muscle functions and blood supply in the oviduct of chicken.

Key words: AChE histochemistry, Cholinergic innervation, Laying hen, Oviduct