The distribution and significance of the VIPergic system in man and other mammals

The effects of PACAP and VIP on guinea pig tracheal smooth muscle in vitro

Neither pituitary adenylate cyclase activating polypeptide-38 (PACAP) nor its homologue, vasoactive intestinal polypeptide (VIP), contracted guinea pig isolated trachea (GPT), but on preparations contracted with KCl (40 mM), both caused concentration-related relaxation (3 nM-3 microM, VIP IC50 = 72 nM, PACAP IC50 = 224 nM). Relaxant curves to PACAP were slower in reaching a maximum than those to VIP (approximately 150 and 50 min, respectively). The protease inhibitors, phosphoramidon (1 microM), leupeptin (50 microM), bestatin (100 microM), soya bean trypsin inhibitor (1 microM), and aprotinin (5 microM), together caused a small enhancement of relaxations to VIP, but not to PACAP. The VIP antagonist, [4-Cl-D-Phe6, Leu17]VIP (1-10 microM), did not inhibit the relaxation to either peptide, but did cause large contractions, which were enhanced by protease inhibition. These findings demonstrate that PACAP relaxes GPT in a similar manner to VIP.

Enteric nerves in diabetic rats: increase in vasoactive intestinal polypeptide but not substance P

The distribution of vasoactive intestinal polypeptide (VIP) and substance P-like immunoreactivities was studied by immunohistochemistry in the myenteric plexus and circular muscle layer of the ileum and proximal colon of rats 8 wk after induction of diabetes with streptozotocin. A consistent increase was observed in fluorescence intensity of VIP-like immunoreactivity in the nerve fibers, and intensely stained cell bodies were significantly more frequent in the myenteric plexus of the ileum (p less than 0.001) from diabetic animals. Some varicosities of VIP-like immunoreactive fibers in the myenteric plexus appeared to be enlarged. Vasoactive intestinal polypeptide-like immunoreactivity was increased and VIP-like immunoreactive nerves appeared thicker in the circular muscle layer of both diabetic ileum and proximal colon. The VIP levels were measured biochemically in tissue consisting of the smooth muscle layers and myenteric plexus. A significant increase in the VIP content per centimeter of intestine was found in both the ileum (p less than and proximal colon (p less than 0.01) from diabetic rats. In contrast, no apparent change in substance P innervation was observed immunohistochemically in the myenteric plexus and circular muscle layer of either diabetic ileum or proximal colon when compared with controls. The results are discussed in relation to the symptoms of autonomic neuropathy of the gut in diabetes.

Hypermotility induced by vasoactive intestinal peptide in the rat: its reciprocal action to cholecystokinin octapeptide

Intracerebroventricular administration of vasoactive intestinal peptide (VIP) shortened the duration of pentobarbital-induced sleep and produced significant hypermotility in the rat. Although hypermotility induced by methamphetamine was not potentiated by central administration of VIP, L-DOPA-induced hypermotility in pargyline-pretreated rats was markedly enhanced by VIP and this hypermotility was suppressed by simultaneous administration of cholecystokinin octapeptide (CCK-8) in a dose-related manner. Apomorphine-induced hypermotility was also potentiated by VIP. These results suggest that VIP may stimulate postsynaptic dopaminergic receptor, causing an increase in motility, and that a possible reciprocal interaction exists between VIP and CCK-8.

Studies on the trigeminal antidromic vasodilatation and plasma extravasation in the rat

Antidromic stimulation of sensory peripheral branches of the trigeminal system (mental nerve) led to cutaneous vasodilatation and increased vascular permeability in rats anaesthetized with urethane. The antidromic vasodilatation observed in intact animals was not altered by decentralization or sympathectomy. Both antidromic vasodilatation and neurogenic plasma extravasation remained unaffected by pre-treatment with cimetidine, indomethacin, baclofen, guanethidine plus phentolamine and propranolol, but were significantly reduced by cimetidine plus mepyramine and atropine, suggesting that cholinergic and histaminergic components might be involved in the sensory neurogenic responses. Methysergide reduced only the extravasation, suggesting that probably serotonin liberated by mast cells upon sensory stimulation can contribute to the neurogenic responses. In tests using substance P (SP) antagonists (D-pro4, D- trp 7, 9, 10)-SP (4-11) and (D-pro2, D-trp 7, 9)-SP it was found that they are more active in reducing the neurogenic extravasation than the vasodilatation. In addition it was observed that (D-pro 4, D-trp 7, 9, 10)-SP (4-11) was the most potent substance P antagonist in reducing the plasma extravasation and antidromic vasodilatation resulting from sensory stimulation.

Peptidergic innervation irregularities in Hirschsprung's disease. Immunohistochemistry--radioimmunoassay

The distribution of vasoactive intestinal polypeptide (VIP)-containing nerves and the contents of both VIP and substance P (S-P) in the intestines from 12 children with Hirschsprung's disease were examined using immunohistochemical methods and radioimmunoassay. VIP-containing nerve fibers were markedly decreased in number in the true muscle coats of aganglionic segments, while extrinsic hypertrophic nerve bundles in these segments showed positive VIP-immunoreactivities. This finding suggests the existence of extrinsic origins of VIP-containing nerves in the human gut. The contents of VIP were 44.5 +/- 8.2 in aganglionic segments and 130 +/- 17.1 pg/mg wet tissue weight in normoganglionic segments. The contents of S-P were 0.42 +/- 0.18 in aganglionic segments and 6.38 +/- 2.3 pg/mg wet tissue weight in normoganglionic segments. Both VIP and S-P contents in aganglionic segments were significantly reduced as assessed by the use of radioimmunoassay (p less than 0.001 and p less than 0.05). These abnormal peptidergic patterns of innervation might relate to the non-peristaltic state in Hirschsprung's disease.

Vasoactive intestinal polypeptide is more potent than prostaglandin E2 as a vasodilator and oedema potentiator in rabbit skin

1 The 28 amino acid polypeptide, vasoactive intestinal polypeptide (VIP) induced increased local blood flow when injected intradermally in the rabbit. 2 VIP was found to be even more potent than prostaglandin E2 (PGE2) in increasing blood flow; VIP induced a significant effect at a 1 pmol dose. 3 VIP was shown to be poor in increasing microvascular permeability but very potent in enhancing local oedema induced by two substances which increase permeability, bradykinin and C5a des Arg. VIP was more potent than PGE2 as an oedema potentiator. 4 Indomethacin had no effect on oedema potentiation induced by VIP, suggesting that a release of endogenous prostaglandins was not involved. 5 These results support our hypothesis for the regulation of oedema formation by arteriolar vasodilators, although the observations do not exclude the possibility of additional regulation by agonist interaction in the region of the venule. 6 VIP may be involved in the physiological control of normal blood flow and in hyperaemia in some types of inflammatory reactions.

Vipergic nerves in the penis

High concentrations of vasoactive intestinal polypeptide (VIP) were detected by immunocytochemistry and radioimmunoassay in thirty surgical specimens of male external genitalia. VIP was found exclusively in fine autonomic nerves. VIPergic nerves were most densely concentrated in the penis around the pudendal arteries and in the erectile tissue of the corpus cavernosum. Considerable numbers of VIP nerve fibres were also seen in the vas deferens and epididymis. VIP is known to exert regulatory actions on blood-flow, secretion, and muscle tone. Its presence in considerable amounts in the male genital tract suggests that this newly discovered peptide neurotransmitter may be important in the nervous control of male external genitalia.