Neurochemical Features of Neuropeptide Y-ergic Enteric Submucosal Neurons in the Rat Small Intestine during Postnatal Ontogenesis

Neuropeptide Y (NPY) performs varied functions in the nervous system, including the regulation of vascular tone and gastrointestinal secretion. Specifically, it exerts a direct inhibitory effect on intestinal motility and secretion. Colocalization of NPY with choline acetyltransferase (ChAT), the enzyme catalyzing acetylcholine synthesis, as well as neuronal NO synthase (nNOS), vasoactive intestinal peptide (VIP) and calcium-binding protein calbindin (CB), was studied in enteric neurons of the submucosal plexus of the rat small intestine at different ages (from the moment of birth until old age) using double immunolabeling and fluorescence microscopy. From the moment of birth, all NPY-ergic neurons colocalize ChAT, while most of them also contain VIP and CB. In aged rats, the percentage of NPY-ergic neurons colocalizing CB, VIP and ChAT decreases. Both in juvenile (since birth until 20 days of age) and aged rats, NPY-ergic neurons were found to express nNOS. Thus, at early stages of ontogeny and in senescence, the rat enteric metasympathetic NPY-ergic submucosal neurons contain a wider range of neurotransmitters compared to adult animals.