Systemic injections of gastro-intestinal peptides alter behavior in rats

Twenty-four male albino rats were given daily intraperitoneal injections of vasoactive intestinal polypeptide (VIP), motilin, human gastrin I (1–17) or the diluent control vehicle at a dose of 100 μg/kg for four consecutive days and food intake, water intake, body weight, and running wheel activity were determined every 24 hours. Animals injected with motilin or human gastrin I (1–17) exhibited decreased food intake relative to those injected with VIP or diluent, which did not differ from each other, although food intake increased reliably over days. The mean water consumption followed the same pattern as that of food intake. As expected from the above results, VIP produced weight gains as compared with rats injected with motilin or gastrin but not reliably more than after diluent. A reliable effect of trials for weight gain was the greatest on day three. Running wheel activity was not affected by injections of human gastrin I (1–17), motilin, or diluent but was reliably decreased by VIP. No significant differences existed across days. Although the results indicate that GI peptides may affect behavior when injected systemically and that like other peptides they have multiple effects, caution is urged in the interpretation of behavioral results at this time.     

Interaction of a bovine thymic peptide extract with vasoactive intestinal peptide (VIP) receptors

Bovine t hymic peptide extract (1–100 g/ml) is shown to completely inhibit the binding of [¹²⁵I]VIP to rat blood mononuclear cells, lymphoid cells of spleen, and liver plasma membranes. In the three models, the bovine thymic peptide extract inhibits [¹²⁵I]VIP binding with a potency that is 4000–7000 times lower than that of the native VIP, on a weight basis. In rat liver plasma membranes, the bovine thymic peptide extract stimulates adenylate cyclase with a maximal efficiency that is similar to that of VIP. At maximal doses, VIP and thymic peptide extract do not exert an additive effect on adenylate cyclase, suggesting that the activation of the enzyme by the bovine thymic peptide extract occurs through VIP receptors. Finally, no VIP-like immunoreactivity was detected in the thymic peptide extract using an antiserum raised against mammalian VIP. All these data suggest the presence in the bovine thymic peptide extract of a new substance which behaves as a VIP agonist in rat.     

Further evidence that peptide histidine isoleucine (PHI) may function as a prolactin releasing factor in rats

Intraventricular administration of peptide histidine isoleucine (PHI) (200 ng, 1, 5 and 10 micrograms/rat) resulted in a significant and dose-related increase in plasma prolactin (PRL) levels in urethane-anesthetized rats and in conscious rats with intraatrial and intraventricular catheters. Intravenous injection of PHI (10 micrograms/rat) also raised plasma PRL levels in these animals. In in vitro studies, PRL release from superfused rat anterior pituitary cells was stimulated by PHI (10(-9), 10(-8) and 10(-7) M) in a dose-related manner. The stimulating effect of PHI (10(-7)M) on PRL release in vitro was as potent as that of vasoactive intestinal polypeptide (VIP) (10(-7) M) and was observed even in the presence of dopamine (10(-7) M). These results suggest that PHI plays a stimulating role in regulating PRL secretion by acting, at least in part, directly on the pituitary in the rat.     

The effect of VIP on guinea pig taenia coli requires the whole sequence

Truncated sequences of VIP_1–28 i.e., VIP_1–6, VIP_15–28 and VIP_18–28, were synthesized. The biological activity of the peptides was tested on the isolated taenia coli from guinea-pig. Unlike VIP_1–28, the truncated peptides had no effect alone or in combination. We also synthesized two peptides where VIP_1–6 or VIP_1–9 were joined with VIP_20–28 or VIP_21–28, respectively, with omission of the mid portion of VIP_1–28. These peptides had no detectable biological activity. Finally, we synthesized Gly^17,18,19-VIP, and tested it in the above mentioned system. It had a greatly reduced bioactivity compared with native VIP.     

Immunohistochemical localization and vascular effects of vasoactive intestinal polypeptide in skeletal muscle of the cat

Summary Scattered vasoactive intestinal polypeptide (VIP) — immunoreactive nerves were found in the striated muscle of the hind limb of the cat, where they usually were associated with small blood vessels. VIP-immunoreactive nerves were also demonstrated in the sciatic nerve; after nerve ligation an abundance of intensely immunoreactive VIP fibres were seen proximal to the ligation. Intraarterial infusion of VIP into the isolated hind limb of the cat had dramatic effects on different sections of the vascular bed. Thus, VIP dilated the resistance vessels leading to a marked increment in muscle blood flow. VIP also relaxed the capacitance vessels causing regional pooling of blood; it increased the capillary surface area available for fluid exchange. Infusions of VIP at a dose of 8 g/min significantly inhibited the vasoconstriction induced by electrical stimulation of the regional sympathetic nerves. It is suggested that local nervous release of VIP may act as a modulator of vascular tone in skeletal muscle.     

VIP (Vasoactive Intestinal Polypeptide) — immunoreactive innervation of the portal vein

Summary Nerve fibres displaying immunoreactivity for vasoactive intestinal polypeptide (VIP) were found in the wall of the portal vein in cats, guinea pigs, rats and mice. In whole-mount preparations a sparse network of VIP fibres was seen in the vessel wall. Electrical field stimulation of the rat portal vein in vitro caused a significant release of VIP. The results suggest that VIP ergic nerve fibres play a role in the regulation of portal blood flow.     

Vasoactive intestinal polypeptide immunoreactivity in the spinal cord of the guinea pig

Summary The distribution of vasoactive intestinal polypeptide-immunoreactive (VIP-IR) neurons in the lower medulla oblongata and the spinal cord has been analyzed in guinea pigs. This study includes results obtained by colchicine treatment and transection experiments. In the spinal cord, numerous VIP-IR varicosities were observed in the substantia gelatinosa of the columna dorsalis; some were also found in the substantia intermedia and the columna anterior. The spinal VIP-IR nerve fibers were mainly of intraspinal origin and oriented segmentally. VIP-IR nuclei in the spinal cord extended dorsally into corresponding regions of the caudal medulla oblongata, namely from the substantia intermedia medialis and lateralis into the vagus-solitarius complex and from the nucleus spinalis lateralis into the area of the nucleus reticularis lateralis. Additional VIP-IR perikarya were observed in the pars caudalis of the nucleus spinalis nervi trigemini. The VIP-IR nuclei within the caudal medulla oblongata probably form a continuous system with those localized within the spinal cord. They may be involved functionally in the modulation of cardiovascular and respiratory regulation in the guinea pig.Supported by the DFG, Carvas SFB 90     

Cellular localization and ontogeny of immunoreactive Vasoactive intestinal polypeptide (VIP) in the chicken gut

Summary Vasoactive intestinal polypeptide (VIP)-immunoreactive nerves were abundant along the entire digestive tract of the chicken. In the proventriculus, gizzard and small intestine VIP nerves were numerous around glands and less numerous in the smooth muscle. Submucosal blood vessels were often encircled by VIP nerves. VIP nerves were also seen in the submucosal and myenteric plexus. In the large intestines the VIP innervation of the smooth muscle was more predominant, while there was a rather sparse supply of VIP nerves around the base of the crypts. This innervation pattern was a consistent finding with four different VIP antisera. VIP-immunoreactive cells, however, were demonstrated with only three of the antisera. They were found scattered in the epithelium of the proventriculus and small and large intestines. The failure of one of the antisera to demonstrate endocrine cells suggests that the VIP-immunoreactive material in these cells differs from that in nerves. Conceivably, the material present in nerves represents VIP, while that in endocrine cells represents cross-reacting peptides or other molecular forms of VIP.VIP nerves appeared comparatively early in embryonic development. They appeared in the upper part of the digestive tract at 13 days of incubation and in the colon a few days before hatching; at this stage, only smooth muscle received VIP nerves. The adult pattern of innervation was established about two to four weeks after hatching. VIP-immunoreactive endocrine cells appeared in the intestines a few days before hatching. The adult frequency of occurrence was established about one week after hatching.     

Immunohistochemical localization of vasoactive intestinal polypeptide(VIP)-containing neurons in the hypothalamus of the Japanese quail,Coturnix coturnix

Summary The localization of vasoactive intestinal polypeptide (VIP) in the hypothalamus of the quail has been studied by means of light- and electron-microscopic immunohistochemistry. Numerous VIP-immunoreactive perikarya are distributed in the caudal portion of the nucleus infundibularis (n. tuberis) and nucleus mamillaris lateralis, and sparse in the preoptic area, nucleus supraopticus and nucleus paraventricularis. Dense localization of immunoreactive-VIP fibers is observed in the external layer of the median eminence, in close contact with the primary portal capillaries. The main origins of these fiber terminals are VIP-immunoreactive perikarya of the nucleus infundibularis. These neurons are spindle or bipolar and extend one process to the ventricular surface and another to the external layer of median eminence. They are CSF-contacting neurons and apparently constitute the tubero-hypophysial tract that links the third ventricle and the hypophysial portal circulation. VIP-reactive neurons in the nucleus mamillaris lateralis also project axons to the external layer of the median eminence, constituting the posterior bundle of the tuberohypophysial tract. Numerous VIP-immunoreactive perikarya occur also in the nucleus accumbens/pars posterior close to the lateral ventricle. They are also CSF-contacting neurons extending a process to the lateral ventricle. There are moderate distributions of VIP-reactive fibers in the area ventralis and in the area septalis.Ultrastructurally, the immunoreactive products against VIP are found in the elementary granules, 75–115 nm in diameter, within the nerve fibers in the median eminence.This investigation was supported by Scientific Research Grants No. 00556196, No. 56360027 and No. 56760183 from the Ministry of Education of Japan to Professor Mikami and Mr. Yamada     

Septal afferents to the area dentata terminate on vasoactive intestinal polypeptide (VIP)-like immunoreactive,non-pyramidal neurons

Summary Thermic lesions in the medial septum of adult rats result in dark degeneration of terminal boutons in the stratum moleculare and hilus of the area dentata. While most of the degenerating terminals are in synaptic contact with non-reactive cells, part of them end on dendrites of VIP-like immunoreactive neurons.     

Innervation of arteriovenous anastomoses in the brood patch of the domestic fowl

Summary The innervation of blood vessels in the brood patch (thoracic skin) of the domestic fowl was studied by use of the catecholamine fluorescence technique, acetylcholinesterase staining, and the immunoperoxidase technique for demonstration of vasoactive intestinal polypeptide (VIP). Large arteries and veins were sparsely innervated, whereas arteriovenous anastomoses (AVAs) were densely innervated by adrenergic, acetylcholinesterase-positive, and VIP-immunoreactive nerve fibres. The rich supply of different vasomotor nerves to AVAs emphasizes the importance of these vascular shunts in regulating blood flow and, in turn, the transport of heat to the brood patch. Furthermore, the presence of VIP-immunoreactive nerve fibres in the vasculature of the brood patch suggests that VIP might be the mediator of the previously reported cold-induced vasodilatation.     

Selective effect of castration on the anterior pituitary VIP receptor of male rats

We investigated the effect of surgical castration of male rats on the binding of [Tyr(¹²⁵I)¹⁰]VIP to receptors on the anterior pituitary gland, superior mesenteric artery, brain, liver, and prostate gland. In anterior pituitary membranes the maximum number of VIP binding sites was increased whereas binding affinity was decreased 24 hours following castration. In particular, the high affinity equilibrium dissociation constant (K_D) increased from 0.13±0.02 nM (mean±SEM) to 0.67±0.07 nM and the maximum number of high affinity binding sites (B_max) increased from 71±9 to 470±112 fmol/mg protein. No significant change was observed in the other tissues. Anesthesia or sham operation did not alter the anterior pituitary VIP receptor binding parameters. The changes in the VIP receptor 24 hours after castration were prevented by prior injection of testosterone. These findings demonstrate tissue-selective alterations to the anterior pituitary VIP receptor by castration that are likely mediated by withdrawal of testosterone.     

Distribution of vasoactive intestinal peptide-like and neurophysin-like immunoreactive neurons and acetylcholinesterase staining in the ring dove hypothalamus with emphasis on the question of an avian suprachiasmatic nucleus

Summary Two nuclei, termed here the medial hypothalamic nucleus and the lateral hypothalamic retinorecipient nucleus, are possible homologs of the mammalian suprachiasmatic nucleus. As the mammalian suprachiasmatic nucleus is characterized by a dense concentration of vasoactive intestinal peptide (VIP)-and neurophysin (NP)-immunoreactive neurons and an absence of acetylcholinesterase (AChE) staining, we decided to examine these factors in the ring dove hypothalamus. Neither the medial hypothalamic nucleus nor the lateral hypothalamic retinorecipient nucleus contained either VIP-or NP-like immunoreactive neurons. The lateral hypothalamic retinorecipient nucleus stained darkly for AChE. Although there was some overlap in the distribution of VIP-and NP-like immunoreactive neurons, a clustering of both types into a well defined nucleus was not observed. Therefore, an avian homolog to the mammalian suprachiasmatic nucleus must differ in its chemoarchitecture from that of mammalian species described to date.     

Immunocytochemical analysis of calcitonin gene-related peptide and vasoactive intestinal polypeptide in Merkel cells and cutaneous free nerve endings of cats

Summary Calcitonin gene-related peptide (CGRP)-and vasoactive intestinal polypeptide (VIP)-immunoreactivity were observed to coexist in Merkel cells of cats. No differences in peptide content were found between Merkel cells located in epithelia of the hard palate, in hairy and glabrous skin of the upper lip, and in vibrissae follicles. CGRP-and VIP-immunoreactive nerve fibres were also found near CGRP/VIP-immunoreactive Merkel cells. In the vibrissae follicles some CGRP-and VIP-immunoreactive nerve terminals end abutting on the glassy membrane. Other CGRP immunoreactive nerve fibres penetrate the epithelium of the skin and end within it. Electron microscopy of vibrissae follicles revealed that Merkel cell neuntes are not immunostained and that immunostained nerve fibres form unmyelinated bundles before ending freely. Thus, CGRP-and VIP immunoreactive nerve fibres in cat skin do not end as Merkel cell neuntes but as different kinds of free nerve endings.     

Vasoactive intestinal polypeptide-like immunoreactivity in nerves of the pancreatic islet of the teleost fish,Gillichthys mirabilis

Summary In the teleost fish, Gillichthys mirabilis, vasoactive intestinal polypeptide (VIP)-like immunoreactivity is present in some nerve fibres of the principal pancreatic islet and surrounding tissues, the vagus and splanchnic nerves, the coeliac ganglion and the wall of the intestine. The nerves of the pancreatic islet that contain VIP-like immunoreactivity probably correspond to one of the two types of non-cholinergic, non-adrenergic (peptidergic) nerve previously described in this fish. Similarities in the localisation of hormonal peptides in fish and mammals suggest that the regulation of gastroenteropancreatic physiology in fish may resemble that of mammals.This work was supported by grants from the Medical Research Council of Great Britain and the National Institutes of Health, USA (Grant No. AM 17161)     

Localization of VIP-immunoreactive nerves in airways and pulmonary vessels of dogs,cats, and human subjects

Summary VIP-containing neurons were localized in lungs from dogs, cats, and human subjects by means of the indirect immunofluorescence technique. Nerve fibers and terminals were observed in the smooth muscle layer and glands of airways, and within the walls of pulmonary and bronchial vessels, especially at the medial-adventitial junction. VIP-positive nerve cell bodies were identified in ganglia located in the walls of bronchi. These findings provide an anatomic basis for the possible modulation of airway and pulmonary vascular function by this neuropeptide.Supported by National Research Service Award HL 5914 and by Lung Center Award HL 14187 from NHLBI, USPHS     

Substance P- and vasoactive intestinal polypeptide (VIP)-immunoreactive nerve fibers in relation to ovarian postganglionic perikarya in para- and prevertebral ganglia: Evidence from combined retrograde tracing and immunocytochemistry

Summary Retrograde neuronal tracing with the fluorescent dye True Blue and immunocytochemistry were utilized to examine postganglionic sympathetic neurons in para- and prevertebral ganglia projecting to the rat ovary. Perikarya in both ganglia were labeled with True Blue after application of the tracer to either the superior ovarian or ovarian plexus nerve. After application of True Blue to the superior ovarian nerve, 17% of the labeled cells in paravertebral ganglia were immunoreactive for vasoactive intestinal polypeptide. In contrast, after application of True Blue to the ovarian plexus nerve, approximately 1 % of the labeled cells in paravertebral ganglia were immunoreactive for the same polypeptide. Some vasoactive intestinal polypeptide-immunoreactive perikarya in paravertebral ganglia were not labeled with True Blue. In some cases, substance P- and vasoactive intestinal polypeptide-immunoreactive fibers were closely apposed to True Blue-labeled perikarya in para-and prevertebral ganglia. Paravertebral vasoactive intestinal polypeptide-immunoreactive perikarya projecting to the ovary presumably participate directly in the control of various ovarian functions. Substance P- and vasoactive intestinal polypeptide-immunoreactive fibers closely apposed to perikarya projecting to the ovary may participate indirectly in the control of various ovarian functions by affecting the activity of ovarian postganglionic neurons.     

Co-existence of peptide HI (PHI) and VIP in nerves regulating blood flow and bronchial smooth muscle tone in various mammals including man

By immunohistochemistry it was found that PHI- and VIP-like immunoreactivity (-IR) occurred in the same autonomic neurons in the upper respiratory tract, tongue and salivary glands with associated ganglia in rat, guinea-pig, cat, pig and man. VIP- and PHI-like immunoreactivity was also found in similar locations in the human heart. The N-terminally directed, but not the C-terminally directed, PHI antiserum or the VIP antiserum stained endocrine cells in the pig duodenum. This suggests the existence of an additional PHI-like peptide. Ligation of nerves acutely caused marked overlapping axonal accumulations of PHI- and VIP-IR central to the lesion. Two weeks after transection of the nerves, both types of immunoreactivities were still observed in accumulations both in the axons as well as in the corresponding cell bodies. The levels of PHI- and VIP-IR in normal tissues from the cat were around 10-50 pmol/g with a molar ratio of about 1 to 2. Systemic administrations of PHI and VIP induced hypotension, probably due to peripheral vasodilation in both guinea-pig and cat. Furthermore, both PHI and VIP caused an inhibition of the vagally induced increase in respiratory insufflation pressure in guinea-pig. PHI and VIP relaxed the guinea-pig trachea in vitro, suggesting a direct action on tracheobronchial smooth muscle. VIP was about 5-10 times more potent than PHI with regard to hypotensive effects and 2-3-fold, considering respiratory smooth muscle-relaxant effects in the guinea-pig. PHI was about 50-fold less potent to induce hypotension in the cat than in the guinea-pig. Although species differences seem to exist as regards biological potency, PHI should also be considered when examining the role of VIP as an autonomic neurotransmitter.     

Origin and distribution of neuropeptide Y-, vasoactive intestinal polypeptide- and substance P-containing nerve fibers in the urinary bladder of the rat

Summary The origin and distribution in the urinary bladder of nerve fibers containing neuropeptide Y (NPY), vasoactive intestinal polypeptide (VIP) and substance P (SP) were investigated in rats. Experimental procedures comprised preganglionic decentralization or postganglionic denervation of the bladder and also chemical sympathectomy as well as capsaicin treatment of newborn rats.Nerve fibers containing NPY were richly distributed in the detrusor muscle and also in the pelvic ganglia. Numerous NPY-containing nerve cell bodies were found in pelvic ganglia. A rich occurrence of VIP fibers and a more sparse distribution of SP-containing fibers were also found in the bladder as well as a relatively rich representation of VIP- containing nerve cell bodies in the pelvic ganglia. After decentralization the intensity of VIP and NPY immunofluorescence increased in nerve cell bodies of the pelvic ganglia and in nerve fibers in the wall of the bladder. Postganglionic denervation, on the other hand, eliminated all peptides examined in the bladder wall. After postganglionic denervation the situation in the ganglia was approximately the same as after decentralization. Chemical sympathectomy (6-OHDA) did not seem to change significantly the frequency and distribution of VIP-, SP- and NPY-fibers in the muscle layer of the bladder or in the pelvic ganglia, while the NPY-containing nerve fibers in the submucosal layer and around blood vessels of the bladder disappeared. Adrenergic nerve fibers in the wall of the bladder (visualized by histofluorescence) were markedly reduced in number after administration of 6-OHDA. Capsaicin-treatment of newborn rats caused a loss of SP-fibers in the wall of the bladder, supporting the view that these fibers are sensory in nature in the urinary bladder. Although it cannot be entirely excluded that NPY-containing fibers in the wall of the bladder are adrenergic, the present results suggest that the NPY-fibers as well as the VIP-fibers of the bladder wall originate mainly in non-adrenergic cell bodies of the pelvic ganglia. However, perivascular NPY-containing nerve fibers are adrenergic in nature.     

Role of vasoactive intestinal polypeptide (VIP) in regulating the pituitary function in man

Intramuscular injection of synthetic VIP (200 micrograms) resulted in a rapid increase in plasma prolactin (PRL) concentrations in normal women, which was accompanied by the 4- to 7-fold increase in plasma VIP levels. Mean (+/- SE) peak values of plasma PRL obtained 15 min after the injection of VIP were higher than those of saline control (28.1 +/- 6.7 ng/ml vs. 11.4 +/- 1.6 ng/ml, p less than 0.05). Plasma growth hormone (GH) and cortisol levels were not affected by VIP in normal subjects. VIP injection raised plasma PRL levels (greater than 120% of the basal value) in all of 5 patients with prolactinoma. In 3 of 8 acromegalic patients, plasma GH was increased (greater than 150% of the basal value) by VIP injection. In the in vitro experiments, VIP (10(-8), 10(-7) and 10(-6) M) stimulated PRL release in a dose-related manner from the superfused pituitary adenoma cells obtained from two patients with prolactinoma. VIP-induced GH release from the superfused pituitary adenoma cells was also shown in 5 out of 6 acromegalic patients. VIP concentrations in the CSF were increased in most patients with hyperprolactinemia and a few cases with acromegaly. These findings indicate that VIP may play a role in regulating PRL secretion in man and may affect GH secretion from pituitary adenoma in acromegaly.