Interaction between Vasoactive Intestinal Polypeptide (VIP) and Neuropeptide Y (NPY) in the Isolated Rat Lacrimal Gland

Abstract

Lacrimal protein output and fluid secretion are regulated by the autonomic nerves that innervate the acini, duct, and blood vessels. The known putative neurotransmitters released by the autonomic nerves include acetylcholine (ACh), noradrenaline (NA), and vasoactive intestinal polypeptide (VIP).^1–3 Moreover, exogenous applications of ACh, NA, and VIP can elicit protein secretion from the rat lacrimal gland.^2,3 Recently, several studies have shown that neuropeptide Y (NPY) is widely distributed in the body and to co-exist with VIP in nerves.^4,5 However, the presence of NPY-immunoreactive nerves in the lacrimal gland, and more so its ability to stimulate protein secretion and to interact with VIP, has not yet been fully established. This study employs the technique of electrical field stimulation (FS) and exogenous agonists and antagonists to investigate the involvement of VIP and NPY in the control of lacrimal protein secretion. The technique of immunohistochemistry was used to demonstrate the distribution of the two neuropeptides in the lacrimal gland.