Vasoactive Intestinal Polypeptide Antiserum Research Articles

Vasoactive Intestinal Polypeptide as Possible Mediator of Relaxation in the Rat Gastric Fundus

Relaxations were induced in longitudinal muscle strips of the rat gastric fundus by stimulation of non-adrenergic non-cholinergic (NANC) neurons and by administration of vasoactive intestinal polypeptide (VIP) or isoprenaline. The effect of antiserum against vasoactive intestinal polypeptide (VIP antiserum) and of control serum on these relaxations was investigated. Incubation with VIP antiserum (dilution 1/50) for 1 h almost completely prevented the relaxation by VIP. It partially prevented the relaxation evoked by electrical stimulation while the relaxation induced by isoprenaline was not influenced. Control serum decreased the VIP- and stimulation-induced relaxations much less than did VIP antiserum. In addition, the effect of the putative VIP antagonist (4Cl-D-Phe6, Leu17) VIP was studied on the relaxations induced by NANC neuron stimulation and by VIP. The VIP antagonist (3 x 10(-5) M, incubation time 10 min) had a relaxatory effect itself but had no influence on either VIP- or stimulation-induced relaxations. The results with VIP antiserum confirm the involvement of VIP in the inhibitory NANC neurotransmission of the rat gastric fundus.

Characterization of vagal pathways mediating gastric accommodation reflex in rats.

1. We investigated the vagal pathways mediating the gastric accommodation reflex in the rat stomach. 2. Gastric distension (6 ml) evoked an increase of 9.0 +/- 1.0 cmH2O of intragastric pressure in vivo. Pretreatment with tetrodotoxin (TTX) caused a significant pressure increase by gastric distension, reaching 17.0 +/- 1.7 cmH2O, suggesting mediation by neural pathways. 3. The pressure increase evoked by gastric distension was significantly enhanced in vivo by acute truncal vagotomy (TV), hexamethonium (C6), and NG-nitro-L-arginine methyl ester (L-NAME), but not by vasoactive intestinal polypeptide (VIP) antiserum, guanethidine, or splanchnicotomy. 4. Gastric distension (6 ml) evoked a much larger intragastric pressure in the denervated, vascularly isolated, perfused rat stomach in vitro. Intra-arterial application of TTX and L-NAME did not cause further pressure increases evoked by gastric distension. 5. The pressure increase evoked by gastric distension remained high 2 weeks after TV in vivo. However, the accommodation reflex was fully restored 4 weeks after TV in vivo. This reflex was antagonized by TTX, C6 and L-NAME, but not by VIP antiserum, guanethidine and splanchnicotomy. 6. Similar to in vivo studies, gastric distension caused a smaller increase in intragastric pressure in response to gastric distension in the denervated, vascularly isolated, perfused stomach obtained from rats 4 weeks after vagotomies in vitro. The pressure increase evoked by gastric distension was significantly enhanced by L-NAME, hexamethonium and TTX. 7. It is suggested that the vago-vagal reflex plays an important role in mediating the accommodation reflex. This involves a vagal efferent pathway that uses nitric oxide as a final neurotransmitter mediating gastric relaxation in intact rats. It is also suggested that the adaptive mechanism mediating the accommodation reflex following vagotomy occurs in the gastric myenteric plexus.

Localisation of VIP-and CGRP-like substances in the skin and sinus hair follicles of various mammalian species.

Using an ultrastructural postembedding immunogold technique, we demonstrated vasoactive intestinal polypeptide (VIP)- and calcitonin gene-related peptide (CGRP)-like immunoreactivity in the Merkel cell dense-cored granules of skin and sinus hair follicles of adult cat and dog. The VIP-like substance was located in cat Merkel cells while both VIP- and CGRP-like substances were colocalised in dog Merkel cells. In cat Merkel cells, the magnitude of labelling of VIP was qualitatively higher than in dog Merkel cells. In the dog Merkel cell, CGRP appeared as the most abundant peptide. Dense-cored granules were labelled for these peptides. In addition, mast cells encountered in the dermal region of dog skin were also found to be immunolabelled by VIP antiserum. The immunoreaction was found to be confined to the secretory granules of the cells. Furthermore, all non-myelinated nerve plexuses encountered in the dermal region of the skin and the sinus hair follicles of the various mammalian species studied were immunolabelled by CGRP antiserum. The specific location was again restricted to the dense-cored granules present in these nerves. As VIP and CGRP have potent vasodilatory effects, our observations suggest that Merkel cells may play a separate or synergistic role in regulatory functions of the skin neuroendocrine cell, exerting their influence by paracrine, endocrine and neurocrine pathways, or a combination of these. Different methodologies of double labelling with different sizes of gold particles are also discussed.

Dynamics of Prolactin Secretion from Diethylstilbestrol-Induced Rat Prolactinoma Tissue In Vitro

Experiments were performed to determine whether PRL secretion in the rat diethylstilbestrol (DES)-induced prolactinoma model is affected by the addition of thyrotropin-releasing hormone (TRH) and/or immunoneutralization of intrapituitary vasoactive intestinal polypeptide (VIP) in vitro. Male Fischer 344 rats were implanted with either a 10 mg DES or placebo pellet 30 days prior to obtaining the anterior pituitary glands for perifusion. The anterior pituitaries were quartered and used in three different perifusion experiments. In Experiment I, placebo-treated tissue channels were perifused for 2 baseline hr followed consecutively by a 30-min exposure to 1:100 nonimmune rabbit serum (NRS), a 30-min wash, and a final 30-min exposure to 10(-5) M TRH. Additional placebo channels were run as above except 1:100 VIP antiserum (AVIP) was substituted for NRS and AVIP was added to the TRH. In Experiment II, the same perifusion protocol was used as in Experiment I, except DES-induced tumor tissue was used instead of placebo tissue. Results from Experiment I and II reveal that AVIP significantly decreased PRL secretory rate in both DES and placebo groups. In the tumor group, both TRH alone and in the presence of AVIP significantly increased the PRL secretory rate. In Experiment III DES-induced tumor tissue channels were perifused with a similar protocol, except the concentrations of NRS and AVIP were increased to 1:10. Both NRS and AVIP significantly decreased PRL secretory rate; however, AVIP had a significantly greater effect than NRS. In this experiment, 1:10 AVIP overcame the stimulatory effect of TRH. In conclusion, AVIP decreases and TRH increases, even in the presence of AVIP, PRL release in DES-induced prolactinoma tissue in vitro. Increasing the AVIP concentration 10-fold diminished the PRL-releasing action of TRH in the tumor tissue. These data suggested that PRL secretion is not autonomous in these prolactinomas and can be affected by exogenous TRH and partial immunoneutralization of endogenous VIP.

Endogenous neurotensin antagonizes methamphetamine-enhanced dopaminergic activity

Neurotensin (NT) has been proposed to be an endogenous neuroleptic based on observations that i.c.v. administration of this peptide antagonizes dopamine-mediated behavior. Because NT influences dopamine activity, this peptide may contribute to the pathogenesis of psychotic disorders such as schizophrenia; however, the precise physiological effects of NT remain speculative. In order to elucidate the function of endogenous NT, a selective NT antiserum (NTAS) was administered i.c.v. through a push-pull cannula in unanesthetized, freely moving rats in combination with dopamine activation caused by methamphetamine (METH). Locomotor and rearing activities induced by a low dose of METH (0.5 mg/kg) were substantially enhanced (4–5-fold) in rats receiving NTAS compared to control animals receiving METH alone. Similarly raised antiserum to vasoactive intestinal polypeptide (VIP) did not alter METH-induced effects. To determine a possible mechanism for these observations, perfusate delivered into the cerebral ventricular space was collected by push-pull cannulae and assayed for dopamine release. METH-induced dopamine release was enhanced 4–5-fold by co-administration of NTAS but not VIP antiserum. To verify these observations, and to identify the site of dopamine release, this experiment was repeated utilizing microdialysis and the recently described NT antagonist, SR-48692. Results from this experiment were similar to those found using NTAS. Like NTAS, co-administration of the NT antagonist enhanced the behavioral responses to a low dose of METH. These studies with SR-48692 also revealed that blockade of NT receptors increased METH-induced release of dopamine from the nucleus accumbens. These findings are the first to demonstrate directly that endogenous NT antagonizes stimulated dopamine pathways and its inactivation substantially enhances METH-induced DA release and related behaviors.

Vasoactive Intestinal Polypeptide Antiserum Affects Rat Prolactin mRNA in 40-Day but Not 110-Day Diethylstilbestrol-Induced Prolactinoma Tissue

Experiments were designed to examine whether vasoactive intestinal polypeptide (VIP), a known stimulator of basal prolactin (PRL) secretion, regulates PRL gene expression in the rat diethylstilbestrol (DES)-induced prolactinoma model. The VIP-induced increase in PRL release could result from increased PRL synthesis and/or decreased PRL degradation. Male Fischer 344 rats were implanted with 10 mg DES pellets 40 or 110 days prior to obtaining the anterior pituitary glands for cell dispersal. Cells were incubated in 1:10 normal rabbit serum or VIP antiserum (AVIP). After incubation, cells were pelleted, washed, and pooled for total nucleic acid extraction. The rat PRL (rPRL) mRNA abundance was quantitated using a solution hybridization/ribonuclease protection assay. Supernatant was collected and analyzed for PRL content using radioimmunoassay. Results from this experiment reveal partial immunoneutralization of intrapituitary VIP significantly decreased PRL secretory rate by rapid reduction in rPRL mRNA in the 40-day tumors. However, in the 110-day tumors the rPRL mRNA steady-state levels were unchanged but the basal release of PRL continued to be decreased by AVIP. These results indicate VIP exerts its effects on PRL secretion through at least two mechanisms.

Co-localization of peptides in the Brockmann bodies of the cod (Gadus morhua) and the rainbow trout (Oncorhynchus mykiss)

Endocrine cells exhibiting immunoreactivity to FMRFamide-like, LPLRFamide-like, neuropeptide Y(NPY)-like and peptide YY(PYY)-like peptides were found in the periphery of the Brockmann bodies of the cod, Gadus morhua, and rainbow trout, Oncorhynchus mykiss. No immunoreactivity or very weak labelling was found with antisera to pancreatic polypeptide (PP). Vasoactive intestinal polypeptide (VIP)-like immunoreactivity was found in nerve fibres, whereas labelling with VIP antiserum in endocrine cells disappeared after preincubation with nonimmune serum. There were always more immunoreactive cells in the rainbow trout than in the cod. No immunoreactivity could be seen with antisera to gastrin/cholecystokinin (CCK) or enkephalin. Double-labelling studies were performed to study the colocalization of the peptides in peripheral endocrine cells. Cells immunoreactive to NPY were also labelled with antisera to FMRFamide, LPLRFamide and PYY. The co-localization pattern of NPY varied; in some Brockmann bodies, a population of the immunoreactive cells showed co-localization and others contained NPY-like immunoreactivity only, whereas in other Brockmann bodies, all NPY-labelled cells also contained FMRFamide-like, LPLRFamide-like and PYY-like immunoreactivity. Cells immunoreactive to PYY similarly contained FMRFamide-like, LPLRFamide-like and NPY-like immunoreactivity, comparable to the patterns observed with NPY. Glucagon-like immunoreactivity was found at the periphery of the Brockmann bodies. A subpopulation of the glucagon-containing cells contained NPY-like immunoreactivity. PYY-like immunoreactivity was also found co-localized with glucagon-like immunoreactivity, as were FMRFamide-like and LPLRFamide-like immunoreactivity. Therefore, either NPY-like and PYY-like immunoreactivity together with FMRFamide-like and LPLRFamide-like immunoreactivity occur in the same endocrine cells of the Brockmann body of the cod and rainbow trout, or a hybrid NPY/PYY-like peptide recognized by both NPY and PYY antisera is present in the Brockmann body.

Involvement of vasoactive intestinal polypeptide in gastric reflex relaxation

We have previously presented evidence for a non-adrenergic, vagally mediated colono-gastric inhibitory reflex induced by distension of the colon. We also found that pain stimulation by putting pressure on a testicle induced a pronounced gastric relaxation mediated by both adrenergic and vagal non-adrenergic fibers in anesthetized rats. Previous in vitro studies by other workers have strongly indicated that vasoactive intestinal polypeptide (VIP) is a neural mediator of gastric relaxation. The aim of the present in vivo study was to investigate, in anesthetized rats, whether VIP is involved in the gastric reflex relaxation induced by colonic distension and pain stimulation. A volumetric method was used to monitor changes in gastric volume. Gastric reflex relaxation following colonic distension was significantly and markedly inhibited by VIP antiserum as compared to the control relaxation before administration of the antiserum. Non-immunized control serum did not significantly influence gastric relaxation caused by colonic distension. Pain-induced gastric relaxation was moderately but significantly reduced after the administration of VIP antiserum but not after control serum. The selective β 2-adrenoceptor agonist, salbutamol, induced a pronounced gastric relaxation of the same magnitude before and after the administration of VIPantiserum. VIP antiserum changed the pattern of gastric motility by inducing a specific type of gastric contraction appearing spontaneously or in response to colonic distension. A close intra-arterial injection of VIP induced gastric relaxation and inhibition of phasic gastric contractions. The present results in the rat suggest that VIP or a VIP-like peptide is involved in gastric reflex relaxation induced by colonic distension and pain stimulation.

Modulation of cholinergic neurotransmission by the peptide VIP, VIP antiserum and VIP antagonists in dog and cat trachea.

1. Comparative studies on the effects of vasoactive intestinal polypeptide (VIP), commercially available VIP antiserum or VIP antagonists [Ac-Tyr1, D-Phe2]-GRF(1-29)-NH2 and [4-Cl-D-Phe6, Leu17]-VIP on excitatory neuroeffector transmission in the dog and cat trachea were performed with microelectrode, double sucrose-gap, and tension recording methods. 2. VIP (10(-11)-10(-9) M) had no effect on the resting membrane potential or on the input resistance of the smooth muscle cells of dog and cat trachea. However, with increased concentrations (greater than 10(-8) M) VIP hyperpolarized the membrane and decreased the input resistance of the membrane in both tissues. 3. VIP (10(-10)-10(-7) M) dose-dependently reduced the amplitude of the contractions evoked through the nervous structure excited by field stimulation in the combined presence of indomethacin (10(-5) M) and guanethidine (10(-6) M) in the dog, and in the presence of guanethidine (10(-6) M) in cat trachea. In parallel with actions on twitch contractions, VIP (10(-11)-10(-7) M) reduced the amplitude of the excitatory junction potentials (EJPs) evoked through the nervous structure excited by single pulse field stimulation in both tissues. 4. VIP (10(-9) M) had no effect on the post-junctional response of smooth muscle cells to exogenous acetylcholine (ACh) (10(-9)-10(-5) M). 5. During repetitive field stimulation at the stimulus frequency of 0.033-0.1 Hz, the amplitude of the EJPs was gradually reduced, and VIP (10(-9) M) enhanced this depression phenomenon in the dog and cat trachea. 6. EJPs also showed summation when repetitive field stimulation was applied at high frequency (20 Hz) in the dog trachea. The slope of the relationship between the relative amplitude of the EJP and number of stimuli at 20 Hz was 2.2 +/- 0.4 mV/stimulation (n = 4) in the dog trachea. However, in the cat trachea, summation of EJPs was not prominent, giving a mean slope of 0.6 +/- 0.2 mV/stimulation (n = 6) measured by the microelectrode method. VIP (10(-9) M) shifted downward the relationship between the relative amplitude of the EJP and the number of stimuli at 20 Hz in both tissues. 7. Overnight incubation with VIP antiserum (10(-6) g/ml) had little effect on the depression of the EJP in the dog and cat trachea, or the summation of the EJP observed in the dog trachea.(ABSTRACT TRUNCATED AT 400 WORDS)

VIP and acetylcholine: neurotransmitters in esophageal circular smooth muscle

Vasoactive intestinal polypeptide (VIP) and acetylcholine were evaluated as possible inhibitory and excitatory neurotransmitters in the cat esophageal circular smooth muscle. Circular muscle strips 2 mm in thickness were obtained from 1 to 3.4 cm above the lower esophageal sphincter and tested in vitro. Muscle strips contracted with bethanechol (10(-5) M) were relaxed by electrical stimulation (0.5-5 Hz) and by VIP (10(-8)-10(-6) M). Relaxation induced by electrical stimulation was blocked by tetrodotoxin, whereas VIP-induced relaxation was not affected. Highly specific VIP antiserum (5%) antagonized both VIP and electrically induced relaxation, and the antagonism was eliminated when the antiserum was neutralized with VIP (10(-6.5) M). Dopamine (10(-4) M) reduced the relaxation induced both by exogenous VIP and by electrical stimulation but did not affect the relaxation caused by sodium nitroprusside (10(-8)-10(-5) M). In untreated strips, physostigmine (10(-10)-10(-8) M) enhanced the off contraction in response to electrical stimulation, whereas atropine caused a dose-dependent reduction with complete abolition at 10(-4) M. These data suggest that in the esophagus inhibition and excitation are mediated by distinct mechanisms: VIP mediates inhibition and acetylcholine is responsible for the off contraction in response to electrical stimulation.

Similarities between the relaxations induced by vasoactive intestinal peptide and by stimulation of the non-adrenergic non-cholinergic neurons in the rat stomach

The characteristics of the non-adrenergic, non-cholinergic inhibitory response of the rat stomach fundus to transmural nerve stimulation were compared with the relaxation induced by vasoactive intestinal polypeptide (VIP). Treatment with alpha-chymotrypsin (5 U/ml) or VIP antiserum (1:200) significantly reduced the relaxation induced by transmural nerve stimulation at 30 Hz, indicating that the possible transmitter in the non-adrenergic, non-cholinergic nerves is a peptide and may be VIP or a closely related peptide. VIP was able to relax, fully and dose-dependently, the stomach fundus that had previously been constricted by treatment with 10(-6) M serotonin, and the IC50 value for VIP was 2.4 X 10(-9) M. VIP elevated levels of cyclic AMP in a dose-dependent manner and the EC50 value was 2.8 X 10(-9) M in the presence of 10(-6) M atropine and 10(-6) M guanethidine. The stomach fundus was relaxed by transmural nerve stimulation (30 Hz, 50 mA) and transmural nerve stimulation also caused production of cyclic AMP in the rat stomach in the presence of atropine and guanethidine. The basal level of cyclic AMP in the stomach was 8.7 +/- 0.26 pmole/mg protein. When transmural nerve stimulation was applied for 5 min, the contraction of the stomach, induced by 10(-6) M serotonin, was inhibited by 54% in the presence of atropine and guanethidine and the level of cyclic AMP was increased to 13.0 +/- 0.73 pmol/mg protein. Apamin inhibited the transmural nerve stimulation-induced relaxation and shifted the dose-response curve for VIP to the right.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of the effect of vasoactive intestinal polypeptide and non-adrenergic non-cholinergic neurone stimulation in the cat gastric fundus

The possible involvement of vasoactive intestinal polypeptide (VIP) in the non-adrenergic non-cholinergic (NANC) relaxation of the cat gastric fundus was studied in circular and longitudinal muscle strips. Cumulative transmural stimulation induced a frequency-dependent relaxation, while cumulative administration of VIP induced a concentration-dependent relaxation. Tetrodotoxin almost completely antagonized the relaxation induced by transmural stimulation (1 Hz), but did not influence the relaxation induced by VIP (10 −7 M); the latter was not influenced by hexamethonium or propranolol plus phentolamine. Trypsin (30 min incubation) and VIP antiserum (1 h incubation) prevented the relaxation induced by VIP and reduced that induced by transmural stimulation, but did not influence the relaxation induced by isopropylnoradrenaline. Two putative VIP receptor antagonists, [AcTyr 1]hGRF-(1–40)OH and [4Cl-D-Phe 6,Leu 17]VIP, did not influence the relaxation induced by VIP or transmural stimulation. These results are compatible with the hypothesis that VIP is involved in the NANC relaxation of the cat gastric fundus, although participation of a non-VIP component cannot be excluded.

The electrophysiological effects of vasoactive intestinal polypeptide in the guinea-pig inferior mesenteric ganglion.

1. The effects of vasoactive intestinal polypeptide (VIP) on the inferior mesenteric ganglion of the guinea-pig were studied in vitro. 2. In 67% of the neurones tested, application of VIP (1-7.5 X 10(-5) M) by pressure ejection caused a depolarization of the membrane potential which averaged 8.6 +/- 0.4 mV. 3. In 52% of the cells that were responsive to VIP, the membrane depolarization was accompanied by a decrease in membrane input resistance. In another 48% of the cells tested, there was an increase in membrane input resistance. 4. Membrane depolarization caused by VIP enhanced the excitability of post-ganglionic neurones and converted subthreshold electrotonic and subthreshold synaptic potentials to action potentials. 5. The effects of VIP persisted during nicotinic and muscarinic synaptic blockade. The effects of VIP also persisted in a low-Ca2+, high-Mg2+ solution. Thus, the site of action of VIP was on the postsynaptic membrane. 6. Electrical stimulation of the lumbar colonic nerves evoked a slow noncholinergic depolarization of the membrane potential. 7. VIP appeared to be one of the transmitters involved in the electrically evoked e.p.s.p. because both prior desensitization with exogenous VIP and VIP antiserum reduced the amplitude of the slow, non-cholinergic e.p.s.p. 8. Radial distension of a segment of colon attached to the inferior mesenteric ganglion (i.m.g.) evoked a non-cholinergic depolarization of the membrane potential in neurones in the i.m.g. 9. The distension-induced non-cholinergic depolarization was reduced by VIP antiserum. 10. The data support the hypothesis that a population of the mechanosensory afferent nerves running between the colon and the i.m.g. utilize VIP or a VIP-like peptide as a transmitter to modulate reflex activity between the colon and the i.m.g.

Cortical vasodilatation produced by vasoactive intestinal polypeptide (VIP) and by physiological stimuli in the cat.

In chloralose-urethanized cats, vasoactive intestinal peptide (VIP), applied by superfusion in steady-state concentration (10(-10)-10(-6) M) onto cortical vessels in situ resulted in a rapid concentration-dependent vasodilatation in vessels that were mildly constricted by prostaglandin F2 alpha (PGF2 alpha) (5 X 10(-5) M) or hypocarbia (PaCO2 = 26). The maximum dilatation produced by VIP (10(-6) M) was about 60% over baseline in pial arteries and 40% in pial veins. Blockade of local neuronal activity with tetrodotoxin (TTX) (10(-5) M) had no effect on the VIP-evoked dilation of pial vessels. Activation of the cortex by either direct electrical stimulation or indirectly by stimulation of the mesencephalic reticular formation (MRF) resulted in a rapid dilatation of pial arterioles and venules. The vasodilatory effects of VIP and of cortical activation via direct cortical stimulation were not blocked by phentolamine (10(-4) M), propranolol (10(-4) M), atropine (10(-4) M), or naloxone (10(-4) M), indicating that the stimulated vasodilatation was not mediated by adrenergic, cholinergic, or opiate receptors. The dilatory effects of MRF, but not direct cortical stimulation, were not blocked by TTX. VIP antiserum (1:25) preincubated in cortical cups had no effect on resting vessel diameter, but resulted in a significant, though subtotal, reduction in the vasodilatation elicited by direct cortical and MRF stimulation. Normal rabbit sera or VIP antiserum preincubated with saturating amounts of VIP were ineffective. In similar experiments, pial arteriolar and venular dilation evoked by hypercarbia was not attenuated by cortically applied VIP antisera. These observations suggest that pial dilation evoked by local increases in neuronal activity may be mediated in part by the local release of VIP from intrinsic neurons. Such a substrate would define a close obligatory coupling between local neuronal activation and local perfusion, such that nutritive flow could be enhanced prior to the onset of any metabolic deficit.

Distribution of Vasoactive Intestinal Polypeptide-Immunoreactive Structures in the Opossum Esophagus

Physiologic evidence that vasoactive intestinal polypeptide (VIP) regulates esophageal smooth muscle in the opossum has been gathered without knowledge of the distribution of VIP in that organ. We examined planar sections stained for VIP by the avidin-biotin complex method, measured VIP content in mucosa and muscularis propria by radioimmunoassay, and compared neural structures reactive to VIP antiserum with those revealed by osmication in the presence of zinc iodide. Immunoreactive terminal nerves interlaced smooth muscle bundles in all layers in all smooth muscle regions, formed loose tangled knots about widely dispersed muscle cells in striated muscle, and supplied vessels and submucosal glands. Bipolar interstitial cells in the circular muscle layer stained by osmication were not VIP-immunoreactive. Perikarya in both submucous and myenteric plexuses were VIP-immunoreactive. Vasoactive intestinal polypeptide-immunoreactive oval cells with round unstained nuclei and a faintly granular cytoplasm were scattered in the muscle in all regions and were concentrated in the planes of the plexuses. Vasoactive intestinal polypeptide content of muscularis propria in the smooth muscle esophageal body exceeded (p less than or equal to 0.05) that in the striated muscle esophageal body and the sphincter region, but contents in the latter two regions did not differ (p greater than or equal to 0.05). Mucosal content exceeded that of muscularis propria. The broad distribution and diversity of immunoreactive structures suggest that VIP may have functions in this organ besides the regulation of smooth muscle.

Is Vasoactive Intestinal Polypeptide the Principal Transmitter Involved in Human Penile Erection?

Previous work from this laboratory reported on the effects of several autacoids and other agents on strips of human corpus cavernosum (cc) muscle. These investigations indicated the presence in the cc muscle of a) atropine-sensitive cholinoceptors, b) alpha- and beta-adrenoceptors and c) a non-adrenergic non-cholinergic mechanism.Several recent publications have presented evidence in support of the possibility that vasoactive intestinal polypeptide (VIP) is an important, or the chief, transmitter in human penile erection. This paper describes the actions of VIP and other compounds on the cc muscle and the effect of intracavernous injection of VIP in volunteers. Among the agents tested, VIP was the most potent relaxant of the cc muscle. This effect, which was seen at a dose as low as 0.03nM, was suppressed by VIP antiserum. The response of the isolated penile vasculature to VIP was similar. VIP antiserum had no effect on the relaxation of the cc muscle produced by field stimulation. In five of the seven subjects given intracavernous VIP (1.0μg) some degree of penile enlargement was evident, but none had an erection.It is suggested that local release of VIP, withdrawal of the alpha-adrenoceptor mediated tonic supply to the penis and the activation of the latter’s beta-adrenoceptors are all probably involved in penile erection in man.

Cytochemical relationships in the paracervical ganglion (Frankenhäuser) of rat studied by immunocytochemistry

Vasoactive intestinal polypeptide (VIP), neuropeptide Y (NPY) and calcitonin gene-related peptide (CGRP) immunoreactivities have been demonstrated in the paracervical ganglion of the rat using immunocytochemistry. Dopamine β-hydroxylase (DβH) and neurofilament protein triplet immunoreactivities have also been demonstrated in this region. The VIP, NPY, DβH and neurofilament immunoreactivities were located in ganglion cells and nerve fibres, while CGRP immunoreactivity was localized only in nerve fibres. Many cells immunoreactive with DβH antiserum were also immunoreactive with NPY antiserum. A small number of cells immunoreactive with VIP antiserum were also immunoreactive with NPY antiserum. CGRP-immunoreactive nerve fibres were distributed in certain regions of the ganglion only.

Peptide-containing nerves in human urinary bladder

Nerves containing immunoreactive vasoactive intestinal polypeptide (VIP), substance P and two newly discovered peptides, neuropeptide tyrosine (NPY) and PHI (peptide having N-terminal histidine and C-terminal isoleucine), have been found in the human urinary bladder by immunocytochemistry and radioimmunoassay. Somatostatin immunoreactivity was detected by radio-immunoassay. The VIP-immunoreactive nerves were widely distributed in all regions, but were particularly dense beneath the epithelium and in the muscle layer. Scattered intramural ganglia were found to be reactive to VIP antiserum. Higher concentrations of extractable VIP were detected in the trigone than in the dome. VIP- and PHI-immunoreactive nerves were similarly distributed, the latter being less numerous. NPY immunoreactive nerves were seen mainly in the muscle layer, particularly in the trigonal area. The distribution patterns of VIP- and NPY-immunoreactive nerves resembled those of the previously reported cholinergic and adrenergic nerves, respectively. Many blood vessels were found to be innervated by both types of immunoreactive nerves. Scattered substance P-immunoreactive fibers were occasionally seen, being present in the submucosa and around the detrusor muscles. The significance of these nerves remains to be elucidated.

Coexistence of substance P- and methionine 5-enkephalin-like immunoreactivity in nerve cells of the myenteric ganglia in the cat ileum

Intramural ganglia of colchicine-injected cat ileum were examined immunohistochemically using antisera to substance P (SP), vasoactive intestinal polypeptide (VIP) and methionine5-enkephalin (ENK). SP- and ENK-like immunoreactive nerve cells were preferentially located in the myenteric ganglia, whereas VIP-like immunoreactive nerve cells were distributed in both myenteric and submucous ganglia. A small number of nerve cells in the myenteric ganglia showed immunoreactivities to both ENK and SP antisera, but not to VIP antiserum. These findings provide supportive evidence for the coexistence of SP and ENK in a small population of neurones in the cat myenteric plexus.

Vasoactive intestinal polypeptide. A neurotransmitter for lower esophageal sphincter relaxation.

The effect of rabbit vasoactive intestinal polypeptide (VIP) antiserum on in vitro relaxation of the lower esophageal sphincter (LES) was studied in 10 cats. The stomach and esophagus were opened along the lesser curvature of the stomach and stripped of mucosa. Consecutive strips were cut and mounted in a 2.5-ml muscle chamber. They were perfused with Tyrode's solution and oxygenated continuously. After equilibration for 1 h, perfusion was stopped and one strip from the lower esophageal sphincter region was incubated in solution that contained 12-25 parts of VIP antiserum per 1,000 to Tyrode's solution, while a second strip was incubated in a solution of normal rabbit serum at the same concentration. A third strip was maintained in Tyrode's solution for the duration of the experiment. After a 1-h incubation, the strips were stimulated with 6-s square wave trains of 0.1-, 0.2-, 0.4-, and 0.8-ms pulses at 1, 2, and 5 Hz. These stimulation parameters produced LES relaxation that was completely blocked by tetrodotoxin but not by atropine or phentolamine. The strips incubated in Tyrode's solution or in normal serum relaxed reliably and consistently at all levels of stimulation. In the antiserum-treated strips, LES relaxation in response to all stimuli was significantly inhibited. Strips treated with normal serum were relaxed in a dose-dependent fashion by 10(-7) and 10(-6) M VIP, whereas the antiserum inhibited the relaxation induced by 10(-7) M, but not by 10(-6) M, VIP. Stimulation with two successive 15-min trains of electrical pulses (2 ms, 5 Hz) separated by 30 min of rest released increasing amounts of VIP into the bathing solution. VIP released during the second train of electrical stimulation was significantly (P less than 0.05) greater than in control conditions. In the cat LES, VIP antiserum inhibits the relaxation induced by exogenous VIP or by electric stimulation of nonadrenergic, noncholinergic inhibitory nerves at a level that causes the release of VIP. These findings are consistent with the hypothesis that VIP may be an inhibitory neurotransmitter responsible for LES relaxation.