Ontogeny of the VIP system in the gastro-intestinal tract of the Axolotl, Ambystoma mexicanum: successive appearance of co-existing PACAP and NOS

Abstract

Evidence for the presence and potential co-existence of vasoactive intestinal polypeptide (VIP), pituitary adenylate cyclase-activating polypeptide (PACAP) and nitric oxide synthase (NOS) in gastro-intestinal endocrine cells and/or nerve fibers is conflicting and very few results exist on development. This immunofluorescence study aims to clarify the appearance and localization of VIP, PACAP and NOS in the gastro-intestinal tract of the Axolotl, Ambystoma mexicanum, during ontogeny. VIP-immunoreactivity appeared in nerve fibers as early as on day 3 after hatching likely indicating a particular role, such as a trophic action, of VIP in very early development. PACAP-immunoreactivity was observed 3 days later within the VIP-immunoreactive (-IR) fibers. From this time on, VIP- and PACAP-immunoreactivity exhibited complete co-existence. VIP/PACAP-IR fibers were found throughout the gastro-intestinal tract. They were most prominent in the myenteric plexus and the muscle layers and less frequent in the submucosa. NOS-immunoreactivity appeared as late as at the 1st (64 days) juvenile stage in a subpopulation of the VIP/PACAP-IR fibers that contacted submucosal arteries. We found only very few VIP/PACAP-IR perikarya, indicating that part of the VIP/PACAP-IR fibers is of extrinsic origin. On day 12 and in the 1st and 2nd (104 days) juvenile stage, infrequent PACAP-IR entero-endocrine cells were noted, while neither VIP- nor NOS-immunoreactivity occurred in endocrine cells at any stage of development. The complete coexistence of neuronal PACAP- and VIP-immunoreactivities and their very early appearance in ontogeny may suggest important and coordinated roles of both peptides in the control of Axolotl gastro-intestinal activity, while the VIP/ PACAP/NOS-IR fibers may be involved in the regulation of submucosal blood flow.

The effects of endogenous and exogenous nitric oxide on gut motility in zebrafish Danio rerio embryos and larvae

“…The first observation of detectable levels of NOS in the present study correlates well with the occurrence of other putative neurotransmitters, both excitatory (NKA, acetylcholine) and inhibitory (PACAP), in zebrafish larvae (Holmberg et al, 2004). In addition, a variety of inhibitory and excitatory neurotransmitters have been observed in other vertebrate species including mammals, amphibians and teleosts before or around the onset of exogenous feeding (Gintzler et al, 1980;Rothman and Gershon, 1982;Saffrey et al, 1982;Epstein et al, 1985;Huang et al, 1986;Saffrey and Burnstock, 1988;Reinecke et al, 1997;Salvi et al, 1999;Holmberg et al, 2001;Maake et al, 2001;Badawy and Reinecke, 2003;Holmberg et al, 2004;Pederzoli et al, 2004).…”

“…A variety of neurotransmitters have been identified in the developing gut in mammals (Gintzler et al, 1980;Rothman and Gershon, 1982;Larsson et al, 1987;Timmermans et al, 1994;Brandt et al, 1996;van Ginneken et al, 1998), birds (Epstein et al, 1985;Rothman et al, 1986;Balaskas et al, 1995), amphibians (Holmberg et al, 2001;Maake et al, 2001;Badawy and Reinecke, 2003) and teleosts (Reinecke et al, 1997;Villani, 1999;Poon et al, 2003;Holmberg et al, 2004;Holmqvist et al, 2004;Pederzoli et al, 2004). In the zebrafish, enteric neurons are present in the gut before the onset of exogenous feeding (Raible et al, 1992;Bisgrove et al, 1997;Holmberg et al, 2003).…”

Ontogeny of the gut motility control system in zebrafishDanio rerioembryos and larvae

“…In the turbot Scophthalmus maximus (Reinecke et al, 1997), the axolotl Ambystoma mexicanum (Maake et al, 2001;Badawy and Reinecke, 2003) and chicken (Epstein et al, 1983;Epstein and Poulsen, 1991), vasoactive intestinal polypeptide (VIP)-containing nerve fibres have been observed before or around the time of onset of feeding. In the axolotl, PACAP coexisted with VIP and was found in gut neurons at an early stage (Badawy and Reinecke, 2003). In Xenopus laevis larvae, several transmitters, including PACAP and NKA, have been detected by immunohistochemistry in neurons before the onset of feeding (Holmberg et al, 2001).…”

Pituitary Adenylate Cyclase-Activating Polypeptide and Its Receptors: 20 Years after the Discovery

“…Although PACAP is able to exert an indirect hypertensive action mediated through the release of catecholamines (Ishizuka et al, 1992;Minkes et al, 1992a), this peptide, in very much the same way as VIP, is mainly considered as a highly potent vasorelaxant factor (Hirata et al, 1985;Ross-Ascuitto et al, 1993;Tong et al, 1993;Ascuitto et al, 1996). This vasodilatory activity, which can be ascribed at least in part to its activity on arterial smooth muscle cells Naruse et al, 1993;Steenstrup et al, 1996;Bruch et al, 1997), is well documented in various organs, including the brain (Tong et al, 1993;Anzai et al, 1995), the eye (Nilsson, 1994;Elsås and White, 1997;Dorner et al, 1998), the pulmonary vascular bed (Minkes et al, 1992b;Cheng et al, 1993;Foda et al, 1995), the mesentery (Wilson and Warren, 1993), the pancreas (Bertrand et al, 1996;Ito et al, 1998), the testis (Lissbrant et al, 1999), the ovary (Steenstrup et al, 1994;Yao et al, 1996), the vagina (Steenstrup et al, 1994;Giraldi et al, 2002;Aughton et al, 2008), the kidney (Gardiner et al, 1994), the gastrointestinal tract (Portbury et al, 1995;Badawy and Reinecke, 2003), and the skin (Wallengren, 1997).…”