ABSTRACT
This chapter attempts to summarize own results on the distribution of peptides and 5-hydroxytryptamine (5-HT) in the mesenteric circulation, obtained with indirect immunofluorescence or peroxidase antiperoxidase techniques, and discusses the physiological effects of the substances on mesenteric blood flow. It focuses on substances where information on both morphology and physiology is available, but also peptides, for which no physiological data are available. Studies on nonadrenergic, noncholinergic innervation of gastrointestinal vessels must include both morphological observations and physiological experiments. The effects of 5-HT on the gastrointestinal circulation have been studied in vitro and in vivo using various techniques. Vasoactive intestinal polypeptide has been proposed to participate as a neurotransmitter in the control of blood flow in all segments of the gastrointestinal tract. Neuropeptide-Y (NPY)-like immunoreactivity (NPY-LI) partly coexists with noradrenaline in sympathetic nerves, and therefore the localization of NPY-LI in many cases coincides with the distribution of adrenergic neurons.
