Introduction: Cocaine- and amphetamine-regulated transcript (CART), neuropeptide Y (NPY) and galanin (GAL) act as neurotransmitters and neuromodulators in both the central and peripheral nervous systems. Their presence has been found in different taxonomic groups, in particular in mammals. However, only few investigators have studied these neuropeptides in the class Aves (birds). The aim of the present study was to describe the distribution of CART, NPY and GAL in the pterygopalatine ganglion (PPG) of the domestic duck (Anas platyrhynchos f. domestica).
Material and methods: The experiment was conducted on 16 one-year-old domestic ducks of the Pekin breed of both sexes (8 males and 8 females). Frozen sections of the PPG were subjected to immunofluorescence staining using primary mouse monoclonal antibodies directed against CART and GAL and rabbit polyclonal antibody directed against NPY. Secondary antibodies were conjugated with Cy3 and FITC fluorochromes.
Results: CART, NPY, and GAL were present in the PPG of the domestic duck. The highest immunoreactivity (IR) in the ganglionic cells was found for CART in the majority (83-85%) of neurons of both superior (SPPG) and inferior (IPPG) PPG. CART-IR was also found in small aggregations of neurons on the medial surface of the Harderian gland, and on the course of the palatine branch of the facial nerve. CART-IR was also observed in the nerve fibers of these neurons' aggregations; however, it was low in comparison to the immunoreactivity of the perikarya. Immunoreactivity of NPY was found in ganglionic neurons, but above all in numerous fibers of the SPPG and IPPG and within aggregations on the surface of the Harderian gland. NPY-IR cells were distributed irregularly over the cross-sections of the tested aggregations, and constituted from 36% to 43% of the SPPG and from 37% to 40% of the IPPG of all cross-sectioned neurons. GAL-immunoreactive perikarya, distributed irregularly across the sections, were observed in the SPPG, where they constituted 61-65%, and in the IPPG, where they made up 50-57% of all neurons. All immunoreactive neurons were characterized by immunopositive neuroplasm and immunonegative cell nuclei.
Conclusions: The presence of CART, NPY, and GAL in the PPG of the domestic duck suggests that these peptides may contribute to the secretory innervation of the glands of the mucosa of the palate and nasal cavity, the Harderian gland, and the lacrimal gland.
Keywords: CART; GAL; NPY; domestic duck; immunoreactivity; pterygopalatine ganglion.