VIP and autonomic neurotransmission

Increased Vasoactive Intestinal Peptide (VIP) in polycystic ovary syndrome patients undergoing IVF

Introduction

Polycystic ovary syndrome (PCOS) is a common multifactorial and polygenic disorder of the endocrine system, affecting up to 20% of women in reproductive age with a still unknown etiology. Follicular fluid (FF) represents an environment for the normal development of follicles rich in metabolites, hormones and neurotransmitters, but in some instances of PCOS the composition can be different. Vasoactive intestinal peptide (VIP) is an endogenous autonomic neuropeptide involved in follicular atresia, granulosa cell physiology and steroidogenesis.

Methods

ELISA assays were performed to measure VIP and estradiol levels in human follicular fluids, while AMH, FSH, LH, estradiol and progesterone in the plasma were quantified by chemiluminescence. UHPLC/QTOF was used to perform the untargeted metabolomic analysis.

Results

Our ELISA and metabolomic results show: i) an increased concentration of VIP in follicular fluid of PCOS patients (n=9) of about 30% with respect to control group (n=10) (132 ± 28 pg/ml versus 103 ± 26 pg/ml, p=0,03) in women undergoing in vitro fertilization (IVF), ii) a linear positive correlation (p=0.05, r=0.45) between VIP concentration and serum Anti-Müllerian Hormone (AMH) concentration and iii) a linear negative correlation between VIP and noradrenaline metabolism. No correlation between VIP and estradiol (E2) concentration in follicular fluid was found. A negative correlation was found between VIP and noradrenaline metabolite 3,4-dihydroxyphenylglycolaldehyde (DOPGAL) in follicular fluids.

Conclusion

VIP concentration in follicular fluids was increased in PCOS patients and a correlation was found with noradrenaline metabolism indicating a possible dysregulation of the sympathetic reflex in the ovarian follicles. The functional role of VIP as noradrenergic modulator in ovarian physiology and PCOS pathophysiology was discussed.

The role of sensory and sympathetic nerves in craniofacial bone regeneration

Multiple factors regulate the regeneration of craniofacial bone defects. The nervous system is recognized as one of the critical regulators of bone mass, thereby suggesting a role for neuronal pathways in bone regeneration. However, in the context of craniofacial bone regeneration, little is known about the interplay between the nervous system and craniofacial bone. Sensory and sympathetic nerves interact with the bone through their neuropeptides, neurotransmitters, proteins, peptides, and amino acid derivates. The neuron-derived factors, such as semaphorin 3A (SEMA3A), substance P (SP), calcitonin gene-related peptide (CGRP), neuropeptide Y (NPY), and vasoactive intestinal peptide (VIP), possess a remarkable role in craniofacial regeneration. This review summarizes the roles of these factors and recently published factors such as secretoneurin (SN) and spexin (SPX) in the osteoblast and osteoclast differentiation, bone metabolism, growth, remodeling and discusses the novel application of nerve-based craniofacial bone regeneration. Moreover, the review will facilitate understanding the mechanism of action and provide potential treatment direction for the craniofacial bone defect.

Vagus nerve stimulation protects against ventricular fibrillation independent of muscarinic receptor activation

AIMS

The role of the vagus in the ventricle is controversial, although the vagus can protect against ventricular fibrillation (VF) via nitric oxide (NO). This study aims to determine whether the mechanisms involved are dependent on post-ganglionic release and muscarinic receptor activation. For this purpose, NO release and electrophysiological effects of vagus nerve stimulation (VNS) were evaluated in relation to acetylcholine and vasoactive intestinal peptide (VIP). In addition, the role of the coronary endothelium and afferent nerves was tested.

METHODS AND RESULTS

Using the isolated innervated rabbit heart, we measured ventricular NO release using 4,5-diaminofluorescein (DAF-2) fluorescence and ventricular fibrillation threshold (VFT) during VNS after muscarinic, ganglionic, and VIP inhibition [atropine, hexamethonium, and VIP (6-28), respectively] and after Triton-X endothelial functional dysfunction. The vagal-mediated increases in NO and VFT were not significantly affected (P> 0.05) during (i) atropine perfusion [increase in NO: 196.8 ± 35.2 mV (control) vs. 156.1 ± 20.3 mV (atropine) and VFT 3.1 ± 0.5 mA (control) vs. 2.7 ± 0.4 mA (atropine)], (ii) VIP inhibition-increase in NO: 243.0 ± 42.4 mV (control) vs. 203.9 ± 28.5 mV [VIP(6-28)] and VFT 3.3 ± 0.3 mA (control) vs. 3.9 ± 0.6 mA [VIP(6-28)], or (iii) after endothelial functional dysfunction [increase in NO: 127.7 ± 31.7 mV (control) vs. 172.1 ± 31.5 mV (Triton-X) and VFT 2.6 ± 0.4 mA (control) vs. 2.5 ± 0.5 mA (Triton-X)]. However, the vagal effects were inhibited during ganglionic blockade [increase in NO: 175.1 ± 38.1 mV (control) vs. 0.6 ± 25.3 mV (hexamethonium) and VFT 3.3 ± 0.5 mA (control) vs. -0.3 ± 0.3 mA (hexamethonium)].

CONCLUSIONS

We show that the vagal anti-fibrillatory action in the rabbit ventricle occurs via post-ganglionic efferent nerve fibres, independent of muscarinic receptor activation, VIP, and the endothelium. Together with our previous publications, our data support the possibility of a novel ventricular nitrergic parasympathetic innervation and highlight potential for new therapeutic targets to treat ventricular dysrhythmias.

Prospect of vasoactive intestinal peptide therapy for COPD/PAH and asthma: a review

There is mounting evidence that pulmonary arterial hypertension (PAH), asthma and chronic obstructive pulmonary disease (COPD) share important pathological features, including inflammation, smooth muscle contraction and remodeling. No existing drug provides the combined potential advantages of reducing vascular- and bronchial-constriction, and anti-inflammation. Vasoactive intestinal peptide (VIP) is widely expressed throughout the cardiopulmonary system and exerts a variety of biological actions, including potent vascular and airway dilatory actions, potent anti-inflammatory actions, improving blood circulation to the heart and lung, and modulation of airway secretions. VIP has emerged as a promising drug candidate for the treatment of cardiopulmonary disorders such as PAH, asthma, and COPD. Clinical application of VIP has been limited in the past for a number of reasons, including its short plasma half-life and difficulty in administration routes. The development of long-acting VIP analogues, in combination with appropriate drug delivery systems, may provide clinically useful agents for the treatment of PAH, asthma, and COPD. This article reviews the physiological significance of VIP in cardiopulmonary system and the therapeutic potential of VIP-based agents in the treatment of pulmonary diseases.

Role of nitric oxide produced by constitutive and inducible nitric oxide synthases in the mouse gastric fundus

In the present study, the role of nitric oxide (NO) produced by constitutive and inducible nitric oxide synthases (cNOS and iNOS, resepctively) on the contraction and relaxation of fundus in normal and lipopolysaccharide (LPS)-treated mice was examined. A whole fundic ring isolated from mice pretreated with reserpine was mounted in an organ bath containing Krebs' solution with 0.001 mmol/L atropine. Rings were contracted initially by 5-hydroxytryptamine (5-HT; 0.03 mmol/L) before relaxation was induced using ATP (0.03 mmol/L), ADP (0.03 mmol/L), pentoxifylline (0.002 mmol/L), electrical field stimulation (EFS; 50 V, 1 msec, 50 Hz, 3 min) and L-arginine (0.05 mmol/L). All drugs and EFS induced significant relaxation of isolated rings. The relaxations induced were significantly inhibited by N(G)-nitro-L-arginine methyl ester (L-NAME; 1.0 mmol/L). However, the iNOS inhibitors L-N(6)-(1-iminoethyl) lysine hydrochloride (L-NIL; 1.0 mmol/L) and amino guanidine (AMG; 1.0 mmol/L) had no significant effect on tissue relaxation. Then, the relaxant effects of 0.03 mmol/L ATP were tested on precontracted isolated fundic rings taken from 10 mg/kg LPS-treated animals. The non-selective NOS inhibitor L-NAME (10 mg/kg), the iNOS inhibitors L-NIL (3 mg/kg) and AMG (20 mg/kg) and betamethasone (0.1 mg/kg) were used to examine the role of NO produced by iNOS in the relaxation responses. It was found that the level of contraction induced by 0.03 mmol/L 5-HT in rings isolated from LPS-treated animals was significantly (P < 0.5) less than that in rings from untreated mice. However, precontracted tissues from LPS-treated mice were significantly relaxed by ATP and the relaxation response to ATP was significantly inhibited by L-NIL, ANG and betamethasone, but not by L-NAME. We suggest that, in LPS-treated mice, the production of NO from iNOS produces a reduction in the contractile response, as well as a decrease in NO formation by cNOS, resulting in changes to smooth muscle cell function.

Involvement of endothelial NO in the dilator effect of VIP on rat isolated pulmonary artery

The endothelium and its interaction with smooth muscle play a central role in the local control of the pulmonary vasculature, and endothelial dysfunction is thought to contribute to pulmonary hypertension and chronic obstructive pulmonary disease. Vasoactive intestinal peptide (VIP), a 28-amino acid neuropeptide, relaxes the rat pulmonary artery, but there is controversy as to whether or not this action of VIP depends on the endothelium. The aim of this study, therefore, was to investigate the role of the endothelium and nitric oxide (NO), the major endothelium-derived relaxing factor, in the dilator action of VIP on the rat isolated pulmonary artery. Pulmonary artery preparations pre-contracted by the alpha(1)-adrenoceptor agonist L-phenylephrine were relaxed by VIP (0.003-1 microM) and acetylcholine (0.003-10 microM) in a concentration-dependent manner. Mechanical removal of the endothelium reduced the maximal response to VIP by about 50% and practically abolished the response to acetylcholine. Inhibition of NO synthesis by N(omega)-nitro-L-arginine methyl ester (0.5 mM) had a similar effect, abolishing the vasorelaxation caused by acetylcholine and attenuating the vasorelaxation caused by VIP by about 50%. From these data it is concluded that the relaxant action of VIP on the rat isolated pulmonary artery depends in part on the presence of the endothelium and that this part is mediated by endothelial NO.

Neuropeptídeos na pele

Há evidências crescentes de que a inervação cutânea é capaz de modular uma variedade de fenômenos cutâneos agudos e crônicos, interagindo com as células da pele e seus componentes imunes. Essa forma de sinalização local entre tecido nervoso e tecido cutâneo ocorre especialmente por meio dos neuropeptídeos, uma numerosa família de neurotransmissores de natureza química comum e nomenclatura heterogênea presentes em todo o sistema nervoso e secretados pelas fibras nervosas cutâneas. São alvo desta revisão os neuropeptídeos substância P (SP), o peptídeo relacionado ao gene da calcitonina (CGRP), o peptídeo vasoativo intestinal (VIP), o peptídeo ativador da adenilato-ciclase pituitária (PACAP), o neuropeptídeo Y (NPY) e a somatostatina (SOM). Serão discutidas suas ações sobre as células da pele e sistema imune, bem como estudos recentes que sugerem a participação dos neuropeptídeos nas respostas inflamatórias cutâneas, nas reações de hipersensibilidade e em dermatoses humanas, notadamente na psoríase, dermatite atópica, hanseníase e alopecia.

Gut/brain peptides in the genital tract: VIP and PACAP

The two structurally related gut/brain peptides vasoactive intestinal polypeptide (VIP) and pituitary adenylate cyclase activating polypeptide (PACAP) are pleiotropic peptides with a wide-spread occurrence. Besides their presence and functions in the gut and the brain VIP and PACAP have distinct physiological roles in the genital tract. VIP seems to be involved in the nervous control of ovum transportation, sexual arousal in women and penile erection in men. Dysfunction of the VIP nerves can lead to erectile failure and VIP in combination with phentolamine can be successfully used as self-injection therapy of impotence. PACAP could be a co-transmitter with VIP in a number of functions involving nervous control of blood flow and motility, but in addition PACAP is a sensory neurotransmitter. The most fascinating role for PACAP is, however, its auto- or paracrine function in the peri- and postovulatory events involving acute progesterone production and subsequent luteinization in periovulatory granulosa/lutein cells.

The developmental expression of vasoactive intestinal peptide (VIP) in cholinergic sympathetic neurons depends on cytokines signaling through LIFRβ-containing receptors

Sympathetic ganglia are composed of noradrenergic and cholinergic neurons. Cholinergic sympathetic neurons are characterized by the expression of choline acetyl transferase (ChAT), vesicular acetylcholine transporter (VAChT) and the vasoactive intestinal peptide (VIP). To investigate the role of cytokine growth factor family members in the development of cholinergic sympathetic neurons, we interfered in vivo with the function of the subclass of cytokine receptors that contains LIFRβ as essential receptor subunit. Expression of LIFRβ antisense RNA interfered with LIFRβ expression and strongly reduced the developmental induction of VIP expression. By contrast, ganglion size and the number of ChAT-positive cells were not reduced. These results demonstrate a physiological role of cytokines acting through LIFRβ-containing receptors in the control of VIP expression in sympathetic neurons.

A robust method for evaluation of NANC transmission in human sigmoid colon muscle in vitro

INTRODUCTION

Human tissues are notoriously difficult to work with, giving results that are quantitatively variable within and between studies. Hence, previous investigations of nonadrenergic, noncholinergic (NANC) relaxation in human colon muscle report both partial and complete inhibitions of the NANC response by specific competitive inhibitors of nitric oxide (NO) production. We have established a robust and reproducible model to examine the contribution of NO during NANC relaxation assay in human sigmoid colon muscle strips.

METHODS

Complete control curves to long-train, stepwise, frequency-dependent, continuous electrical field stimulation (EFS) relaxation using vertical platinum electrodes connected to a biphasic pulse train stimulator generated NANC responses in fresh human sigmoid colon circular muscle strips set up in Bennett baths. A second complete curve was generated on the same strip in the presence of specific drugs to determine the contribution of NO to NANC relaxation. Responses to NO were also generated in muscle strips. Results were fitted to the Hill equation.

RESULTS

The first and second frequency-response curves without test drugs could be fitted to the Hill equation, resulting in similar midpoint locations ([f](50)), maximal asymptotes (alpha), and midpoint slope (n) parameters. L-N(G)-nitro-arginine (L-NOARG), TTX, and haemoglobin produced a tonic contraction in the muscle strips. NANC relaxations to EFS were inhibited by L-NOARG (30-37%), TTX (56-62%), and haemoglobin (48-90%). NO relaxations were concentration dependently inhibited by haemoglobin. Haemoglobin was equipotent in mediating tonic contraction and inhibiting NO relaxation.

DISCUSSION

We established reproducible assays for human colon muscle strips by the generation of two complete dose-response curves to long-train EFS, thus enabling a "within-preparations" study. The results suggest that NO contributes but is not the sole mediator of relaxations to long-train EFS in human sigmoid colon muscle. Moreover, a basal production of NO may serve to regulate tone of human colonic muscle.

Immunohistochemical studies on the distribution of nerve fibers in the human prostate with special reference to the anterior fibromuscular stroma

BACKGROUND

Although the anterior fibromuscular stroma (AFMS) comprises up to one third of the total bulk of the prostate, its physiological function remains unknown. We recently reported the possible contribution of the AFMS to micturition. The aim of this study is to reveal the differences in the distribution of innervation between the AFMS and the other regions of the prostate.

METHODS

We performed immunohistochemical stainings using antibodies such as protein gene product (PGP) 9.5, tyrosine hydroxylase(TH), neuropeptide Y (NPY), and vasoactive intestinal peptide (VIP). Morphometric analysis was made to examine the density of peripheral nerve fibers containing PGP 9.5, TH, NPY, and VIP by using a computer-assisted imaging system.

RESULTS

The number of PGP 9.5-immunoreactive (IR) nerve fibers and the smooth muscle in the AFMS decreased from the base to the apex of the prostate. TH-IR nerve fibers were more abundant in the AFMS than in the transition zone. NPY- and VIP-IR nerve fibers were less numerous in the AFMS than in the peripheral zone.

CONCLUSIONS

This study is the first to demonstrate that the AFMS has peculiar neuronal innervation. We observed significantly different innervation in the AFMS compared with the other regions of the prostate.

Role of PAC(1) receptor in adrenal catecholamine secretion induced by PACAP and VIP in vivo

The present study was conducted to investigate the functional implication of the pituitary adenylate cyclase-activating polypeptide (PACAP) type I (PAC(1)) receptor in the adrenal catecholamine (CA) secretion induced by either PACAP-27 or vasoactive intestinal polypeptide (VIP) in anesthetized dogs. PACAP-27, VIP, and their respective antagonists were locally infused to the left adrenal gland via the left adrenolumbar artery. Plasma CA concentrations in adrenal venous and aortic blood were determined by means of a high-performance liquid chromatograph coupled with an electrochemical detector. Adrenal venous blood flow was measured by gravimetry. The administration of PACAP-27 (50 ng) resulted in a significant increase in adrenal CA output. VIP (5 microg) also increased the basal CA secretion to an extent comparable to that observed with PACAP-27. In the presence of PACAP partial sequence 6--27 [PACAP-(6--27); a PAC(1) receptor antagonist] at the doses of 7.5 and 15 microg, the CA response to PACAP-27 was attenuated by approximately 50 and approximately 95%, respectively. Although the CA secretagogue effect of VIP was blocked by approximately 85% in the presence of PACAP-(6--27) (15 microg), it remained unaffected by VIP partial sequence 10--28 [VIP-(10--28); a VIP receptor antagonist] at the dose of 15 microg. Furthermore, the CA response to PACAP-27 did not change in the presence of the same dose of VIP--(10--28). The results indicate that PACAP-(6--27) diminished, in a dose-dependent manner, the increase in adrenal CA secretion induced by PACAP-27. The results also indicate that the CA response to either PACAP-27 or VIP was selectively inhibited by PACAP-(6--27) but not by VIP-(10--28). It is concluded that PAC(1) receptor is primarily involved in the CA secretion induced by both PACAP-27 and VIP in the canine adrenal medulla in vivo.

Role of nitric oxide- and vasoactive intestinal polypeptide-containing neurones in human gastric fundus strip relaxations

The morphological pattern and motor correlates of nitric oxide (NO) and vasoactive intestinal polypeptide (VIP) innervation in the human isolated gastric fundus was explored. By using the nicotinamide adenine dinucleotide phosphate hydrogen (NADPH)-diaphorase and specific rabbit polyclonal NO-synthase (NOS) and VIP antisera, NOS- and VIP-containing varicose nerve fibres were identified throughout the muscle layer or wrapping ganglion cell bodies of the myenteric plexus. NOS-immunoreactive (IR) neural cell bodies were more abundant than those positive for VIP-IR. The majority of myenteric neurones containing VIP coexpressed NADPH-diaphorase. Electrical stimulation of fundus strips caused frequency-dependent NANC relaxations. N(G)-nitro-L-arginine (L-NOARG: 300 microM) enhanced the basal tone, abolished relaxations to 0.3 - 3 Hz (5 s) and those to 1 Hz (5 min), markedly reduced ( approximately 50%) those elicited by 10 - 50 Hz, and unmasked or potentiated excitatory cholinergic responses at frequencies > or =1 Hz. L-NOARG-resistant relaxations were virtually abolished by VIP (100 nM) desensitization at all frequencies. Relaxations to graded low mechanical distension (< or =1 g) were insensitive to tetrodotoxin (TTX: 1 microM) and L-NOARG (300 microM), while those to higher distensions (2 g) were slightly inhibited by both agents to the same extent ( approximately 25%). In the human gastric fundus, NOS- and VIP immunoreactivities are colocalized in the majority of myenteric neurones. NO and VIP mediate electrically evoked relaxations: low frequency stimulation, irrespective of the duration, caused NO release only, whereas shortlasting stimulation at high frequencies induced NO and VIP release. Relaxations to graded mechanical distension were mostly due to passive viscoelastic properties, with a slight NO-mediated neurogenic component at 2 g distension. The difference between NO and VIP release suggests that in human fundus accommodation is initiated by NO. British Journal of Pharmacology (2000) 129, 12 - 20

Medical treatment of erectile dysfunction

Erectile dysfunction (ED) is defined as the consistent inability to obtain or maintain an erection for satisfactory sexual relations. Data from the Massachusetts Male Aging Study have indicated that the prevalence of erectile dysfunction of any degree is 39% in 40-year old men, and 67% in those aged 70 years. Effective therapy has been available for some time, but it has commonly involved surgery, external devices or penile self-injection. For many men, these represent unacceptable barriers to seeking therapy. Recently, however, an effective oral medication has become available. This article reviews the physiology and pharmacology of ED. The literature currently available on the effectiveness and safety of various drugs used for ED is summarized, with particular attention to newly available oral agents. Guidelines for work-up and drug treatment of patients with ED are given. Detailed history and physical examination are crucial to the safe and effective treatment of men with erectile impotence. An extensive review of the literature shows that based on safety, effectiveness and ease of use, oral sildenafil citrate is an excellent choice for first-line therapy. Patients who use organic nitrates of any kind in any capacity should not be offered sildenafil. Based solely on effectiveness intracavernosal injection therapy remains the golden standard and should also be offered as an option for first-line therapy for the appropriate patients. Many alternatives are available for men who cannot use sildenafil or injection therapy. A thorough knowledge of existing medications is essential for proper treatment of ED.

Pituitary adenylate cyclase-activating polypeptide modulates gastric enterochromaffin-like cell proliferation in rats

BACKGROUND & AIMS

Gastric carcinoids (types I and II) involve the transformation of naive enterochromaffin-like (ECL) cells to the neoplastic state and are associated primarily with hypergastrinemia. In this study, we evaluated the effects of two related neuropeptides, pituitary adenylate cyclase-activating polypeptide (PACAP) and vasoactive intestinal polypeptide (VIP), on ECL cell proliferation and characterized the receptor subtype(s) and signal transduction pathways that mediate this effect.

METHODS

Purified rat ECL cells were analyzed in culture for DNA synthesis as measured by 24-hour 5-bromo-2-deoxyuridine (BrdU) uptake. Reverse-transcription polymerase chain reaction (RT-PCR) with gene-specific oligonucleotide primers was performed to characterize the PACAP/VIP receptor subtype(s).

RESULTS

PACAP/VIP neuropeptide-stimulated BrdU uptake was significantly greater (3.4-3.8-fold greater than control) than that at the maximal dose of gastrin (2.2-fold greater than control). PACAP-stimulated ECL cell proliferation (EC50, approximately 3 x 10(-)14 mol/L) was approximately 100-fold more potent than VIP (EC50, approximately 3x 10(-)12 mol/L). The stimulated BrdU uptake by both PACAP and VIP was competitively inhibited by PACAP-receptor antagonist (IC50, 10(-)9 mol/L, 3 x 10(-)9 mol/L, respectively) and VIP-receptor antagonist (IC50, 3 x 10(-)7 mol/L, 5 x 10(-)7 mol/L, respectively). RT-PCR identified the presence of the PACAP-specific but not PACAP/VIP receptor subtypes. The PACAP-stimulated BrdU uptake was inhibited (70%-80%) by inhibitors of adenosine 3',5'-cyclic monophosphate, phosphatidylinositol 3 kinase, and protein tyrosine kinase as well as mitogen-activated protein kinase.

CONCLUSIONS

PACAP/VIP-related peptides are more potent modulators of ECL cell proliferation than gastrin, and their effect is mediated by a PACAP-specific receptor whose activation is transduced by multiple intracellular messenger systems.

Treating men with predominantly nonpsychogenic erectile dysfunction with intracavernosal vasoactive intestinal polypeptide and phentolamine mesylate in a novel auto-injector system: a multicentre double-blind placebo-controlled study

OBJECTIVE

To study the effect of intracorporeal injection (IC) of vasoactive intestinal polypeptide (VIP) and phentolamine mesylate (PM) on men with erectile dysfunction (ED) of nonpsychogenic aetiology.

PATIENTS AND METHODS

The study comprised 236 men with primarily nonpsychogenic ED attending sexual dysfunction clinics at eight institutions. In an initial dose-assessment phase, the men were given IC injections of 25 micrograms VIP combined with PM 1.0 mg (VIP/P-1) or 2.0 mg (VIP/P-2) in a prefilled, single-use auto-injector. The main aetiologies of ED were arteriogenic (38), diabetes mellitus (DM) (39), neurogenic (35), mixed (90), and venous leakage (30). In a placebo-controlled phase, 171 patients were subsequently treated and self-administered up to 12 injections over a 6-month interval.

RESULTS

In the dose-assessment phase there was an overall response rate of 82%, with responses by aetiology as follows: arteriogenic (82%), DM (85%), neurogenic (86%), mixed (80%), and venous leakage (77%). In a subgroup of 159 patients who withdrew from previous IC therapies for ED, 64% responded with an erection suitable for intercourse. Of the 171 patients treated in the placebo-controlled phase, 75% responded to VIP/P-1 and 12% to placebo (P<0.001); 66% responded to VIP/P-2 and 18% to placebo (P<0. 001), with a median duration of erection of 56 min. The principal adverse event was transient facial flushing accompanying 40% of 1711 injections. There was no pain after injection and one episode of priapism (0.06%); only seven patients withdrew because of adverse events. Over 88% and 92% of patients were satisfied with the drug and auto-injector, respectively. More than 85% of patients and 77% of partners reported an improved quality of life.

CONCLUSION

The combination of VIP and PM at the dose used is a safe and effective means of treating male ED of primarily nonpsychogenic aetiology.

Intracavernous pharmacotherapy

Intracavernous application of vasoactive substances not only has enhanced our understanding of penile hemodynamics, the physiology of penile erection, and the pathophysiology of erectile dysfunction but also has revolutionized the diagnosis and treatment of erectile dysfunction in the last 15 years. Virag was the first to report on the erectile effect of papaverine in humans, and Brindley later reported the effect of intracavernous application of alpha-receptor-blocking agents on cavernous tissue. These reports led to numerous basic and clinical investigations and ultimately established a new treatment alternative for patients with erectile dysfunction that is now considered to be the treatment of choice for most patients. Changes in penile hemodynamics include the relaxation of cavernous smooth musculature and arteries, which leads to an increase in arterial blood flow and a restriction of venous outflow through a compression of subtunical veins. These hemodynamic changes are the prerequisite for the induction and maintenance of penile erection. With the intracavernous application of vasoactive substances it was possible to influence penile hemodynamics at a local level and to induce an erection despite alterations in the nervous system, penile arterial blood flow, cavernous musculature, or neurotransmitter status. In addition, the local application of pharmacologically active substances directly to the end organ enabled the achievement of high local drug concentrations without severe systemic side effects. The commonly used substances are papaverine the combination of papaverine and phentolamine, and prostaglandin E1 (alprostadil). In addition to these established substances, several other regimens, such as linsidomine (SIN-1), calcitonin gene-related peptide (CGRP), moxisylyte, and various triple- or quadruple-drug mixtures have been described. In addition, several other compounds as well as different routes of administration are on the horizon and may prove to be effective in the future diagnosis and treatment of erectile dysfunction.

Patterns of neuronal colocalisation of tyrosine hydroxylase, neuropeptide Y, vasoactive intestinal polypeptide, calcitonin gene-related peptide and substance P in human ureter

The patterns of colocalisation of neuropeptides, tyrosine hydroxylase (TH), and protein gene product 9.5 (PGP), were studied in nerve fibres supplying the upper and lower human ureter using a double labelling immunofluorescence technique. The majority (85%-95%) of nerve fibres within the ureter contained neuropeptide Y-like immunoreactivity (NPY-LIR), in combination with other peptides. Approximately 52%-63% of the total ureteral innervation was made up of NPY-LIR fibres also expressing TH-LIR, while 21%-42% of fibres contained NPY-LIR in combination with vasoactive intestinal polypeptide (VIP)-LIR. These two immunochemically defined classes did not overlap, since TH- and VIP-LIR were never present within the same nerve fibre. Other minor populations of neurones included those containing calcitonin gene-related peptide (CGRP)-LIR in combination with substance P (SP)-LIR (4%-17%) and those without SP (5%). Rare coexistences were also noted between CGRP- and VIP-LIR (1%-2%), CGRP- and NPY-LIR (< or = 1%), and CGRP- and TH-LIR (< 1%). Regional differences in innervation were found. There were fewer of each class of nerve fibres in the upper ureter compared to the lower ureter. In addition, the proportion of VIP/NPY-LIR fibres of the total innervation was less in the upper ureter, where they were very sparse. Differences in the distribution to various tissue targets were also observed. In the lower ureter, TH/NPY-LIR fibres were localised predominantly to the outer muscle fascicles and adventitia, while VIP/NPY immunoreactive nerves supplied the submucosa and inner smooth muscle fascicles. Both of these populations were also found around blood vessels. A population of presumptive sensory fibres expressing CGRP/SP-LIR were typically present immediately beneath the urinary epithelium and around blood vessels, and only very rarely within muscle fascicles. The finding that TH/NPY- and VIP/NPY-LIR fibres innervate different layers of the ureter raises the possibility that the muscle layers of the ureter may be independently controlled.

Vasoactive intestinal polypeptide gene expression is characteristically higher in opossum gastrointestinal sphincters

BACKGROUND/AIMS

Vasoactive intestinal polypeptide (VIP) has been suggested to be an inhibitory neurotransmitter in the sphincteric and nonsphincteric smooth muscles of the gut. However, the relative gene expression of VIP in these functionally diverse regions is not known.

METHODS

The gastrointestinal smooth muscle sphincters of opossums were excised from the adjoining nonsphincteric smooth muscles. RNAs were isolated and subjected to blot hybridizations with VIP complementary DNA probe. Relative expression of VIP gene was quantitated using the densitometric scanning of the VIP messenger RNA (mRNA) transcripts. The cellular specificity of VIP gene expression was investigated in cultures of neuroblastoma cells and myenteric plexuses and compared with those of the smooth muscle cells.

RESULTS

The data showed higher levels of VIP mRNA in the sphincteric than the adjoining nonsphincteric tissues. VIP mRNA were found in significantly higher amounts in the myenteric neurons and neuroblastoma cells than in the smooth muscle cells.

CONCLUSIONS

VIP gene expression was significantly higher in the sphincteric smooth muscle regions than in the nonsphincteric regions of the gut. The studies provide further evidence for the role of VIP in neurotransmission of the gut.

Location of PHM/VIP mRNA in human gastrointestinal tract detected by in situ hybridization

The expression of the gene for vasoactive intestinal polypeptide (VIP) and peptide histidine methionine (PHM) in the human gastrointestinal tract was studied by in situ hybridization and Northern blotting for PHM/VIP mRNA and immunocytochemistry using specific antisera against the bioactive peptides PHM and VIP. In the colon sigmoideum, antisera against all five putative processing products of the VIP precursor (prepro-VIP) were used, namely prepro-VIP 22-79, PHM, prepro-VIP 111-122, VIP and prepro-VIP 156-170. Furthermore, RNA extracted from various regions of the gastrointestinal tract was examined by Northern blots and hybridization to a VIP-cDNA probe. Throughout the gastrointestinal tract, PHM/VIP mRNA was found in neurons only. Using single- or double-staining methods, we demonstrated both PHM/VIP mRNA and the corresponding peptides PHM and VIP in the neurons. In the sigmoideum, the single-staining methods were extended to investigate whether the neurons simultaneously contained PHM/VIP mRNA and each of the five prepro-VIP-derived peptides. Only one major band of PHM/VIP mRNA (1.9 kb) was found by Northern blotting in the tissue of the gastrointestinal tract.

Structure-activity relationships for relaxation of smooth muscle by VIP

Utilizing VIP and five VIP analogues, concentration-response curves for relaxation of rat mesenteric artery and rat gastric longitudinal muscle were determined for comparison with our previously published radioligand binding data on rat smooth muscle and other tissues. The biological potency of the VIP analogues in the present study compared more closely with their potency for VIP receptor binding in smooth muscle tissue (arteries) vs. other tissues (pituitary, brain, liver).

An immunohistochemical study of the innervation of the large intestine of the toad (Bufo marinus)

The distribution of intrinsic enteric neurons and extrinsic autonomic and sensory neurons in the large intestine of the toad, Bufo marinus, was examined using immunohistochemistry and glyoxylic acid-induced fluorescence. Three populations of extrinsic nerves were found: unipolar neurons with morphology and location typical of parasympathetic postganglionic neurons containing immunoreactivity to galanin, somatostatin and 5-hydroxytryptamine were present in longitudinally running nerve trunks in the posterior large intestine and projected to the muscle layers and myenteric plexus throughout the large intestine. Sympathetic adrenergic fibres supplied a dense innervation to the circular muscle layer, myenteric plexus and blood vessels. Axons containing colocalized calcitonin gene-related peptide immunoreactivity and substance P immunoreactivity distributed to all layers of the large intestine and are thought to be axons of primary afferent neurons. Five populations of enteric neurons were found. These contained immunoreactivity to vasoactive intestinal peptide, which distributed to all layers of the large intestine; galanin/vasoactive intestinal peptide, which projected to the submucosa and mucosa; calcitonin gene-related peptide/vasoactive intestinal peptide, which supplied the circular muscle, submucosa and mucosa; galanin, which projected to the submucosa and mucosa; and enkephalin, which supplied the circular muscle layer.

Nitric oxide pathway in rectoanal inhibitory reflex of opossum internal anal sphincter

The role of nitric oxide in relaxation of the internal anal sphincter (IAS) in response to the rectoanal reflex was studied in the opossum. Resting pressures in the IAS (IASP) were monitored using low-compliance continuously perfused catheters. The NO-synthase inhibitor L-NG-nitro-arginine (L-NNA) caused significant and dose-dependent suppression of the decrease in IASP in response to the reflex mimicked by the rectal balloon distention. NO-synthase inhibitor blocked IAS relaxation in response not only to rectoanal reflex but also to other neural stimuli such as sacral nerve stimulation, local intramural stimulation, and the nicotinic ganglionic stimulant 1,1-dimethyl-4-phenylpiperazinium. Suppression of the neurally mediated IAS relaxation by L-NNA was stereoselective; D-NNA had no effect on the relaxation. The suppression of the rectoanal reflex-induced IAS relaxation by L-NNA was completely reversed by NO precursor L-arginine stereoselectively as D-arginine failed to reverse the suppressed IAS relaxation. Sodium nitroprusside caused a decrease in IASP that was modified neither by the neurotoxin tetrodotoxin nor by L-NNA. Furthermore, the decrease in IASP by the direct-acting beta-adrenoceptor agonist isoproterenol was also not modified by the inhibitor of NO synthase. It is concluded that NO or an NO-like substance is an important mediator of IAS relaxation in response to noradrenergic, noncholinergic nerve stimulation.

Presence and regional variation in peptide-containing nerves in the human ureter

The occurrence, distribution and regional variation of neurones immunoreactive for the neuropeptides, vasoactive intestinal polypeptide (VIP), neuropeptide Y (NPY), enkephalin (ENK), calcitonin gene-related peptide (CGRP), and substance P (SP) were investigated in human ureters by indirect immunohistochemistry. In addition, immunoreactivities to tyrosine hydroxylase (TH), a marker of noradrenergic neurones and to protein gene product (PGP) 9.5, a general marker of neurones, were also studied. Neurones displaying PGP-, NPY-, VIP- and TH-like immunoreactivity (-LIR) provided a rich innervation to the smooth muscle and blood vessels of the ureter, where they formed dense muscular and perivascular nerve plexuses. In contrast, there was only a moderate to sparse innervation by SP and CGRP-LIR neurones, most of which were distributed to blood vessels and to the sub mucosal layer, and only rarely to smooth muscle bundles. No ENK-LIR was detected in this study. Nerve fibre bundle densities were estimated for each of the localized neurochemicals according to a method described. NPY-LIR nerve fibre bundles were found to account for 80% of the total nerve fibre bundles (i.e. PGP-LIR) in the ureter. On the other hand, TH-LIR and VIP-LIR nerve fibre bundles each accounted for 50% of the total ureteral innervation, whereas SP- and CGRP-LIR nerve fibre bundles each comprised 20% of the total innervation. The abundance and pattern of tissues innervated by these immunoreactive neurones is consistent with the view that some of these neuropeptide substances co-exist with other peptide substances and/or with other known neurotransmitters, such as noradrenaline or acetylcholine. A gradient of innervation was found to exist for all the neurochemicals demonstrated in the ureter, whereby the lower ureter receives a greater density of innervation than the upper ureter. This finding suggests the human ureter is primarily innervated by fibres arising from or via the lower pelvis, i.e. the pelvic plexus. It also supports the view that the lower ureter may perform an important physiological role, such as coordinating the tone of this region during bladder filling and emptying.

The autonomic innervation of the large intestine of the toad (Bufo marinus)

1. A study was made of the pelvic and the splanchnic nerve supplies to the toad large intestine. 2. Stimulation of pelvic nerve fibres in the 9th and 10th spinal nerves caused a series of contractions of the circular muscle, only the first of which was abolished by hyoscine. The entire response was blocked by d-tubocurarine. The response was not affected by capsaicin treatment. 3. Stimulation of the splanchnic nerves caused a rapid contraction followed by a prolonged relaxation. The relaxation was abolished by bretylium. The contraction was selectively antagonised by prolonged exposure to capsaicin. Splanchnic nerve stimulation also caused a slow, prolonged excitation that was abolished by bretylium. 4. Application of adrenaline caused relaxation of circularly cut strips of large intestinal wall, whereas substance P, acetylcholine, 5-hydroxytryptamine, somatostatin and galanin caused contraction. 5. The results suggest that stimulation of the pelvic nerves releases acetylcholine and a non-cholinergic co-transmitter from peripheral postganglionic neurons. Both the inhibitory response to splanchnic nerve stimulation and the subsequent slow excitation appear to be mediated by adrenergic nerves. The rapid capsaicin-sensitive excitation is likely to be due to release of substance P from antidromically activated afferent nerve fibres in the splanchnic outflow.

Expression of preproVIP-derived peptides in the human gastrointestinal tract: a biochemical and immunocytochemical study

In order to study biosynthetic processing of the precursor for vasoactive intestinal peptide (preproVIP) in the human gut we have developed antisera against the five functional domains of the precursor molecule: preproVIP 22-79, peptide histidine methionine (PHM), preproVIP 111-122, VIP and preproVIP 156-170. The antisera were used to quantify and characterize VIP-precursor peptides by radioimmunoassay (RIA) together with high-pressure liquid Uchromatography (HPLC) and to examine their cellular localization and colocalization by immunocytochemistry. All five peptides were expressed but not in equimolar amounts as expected from the amino acid sequence of the precursor. However, the ratios between them were fairly constant throughout the gastrointestinal tract. The only exceptions were the lower concentrations of PHM and preproVIP 111-122 in the gastric antrum which could be explained by the presence of PHV (the C-terminally extended form of PHM which includes preproVIP 111-122) in large concentrations in this region. It was also found that the C-terminal lysine residue of preproVIP is not removed during processing. Immunocytochemically all preproVIP-derived peptides were shown in neuronal elements. They had a similar distribution throughout the gut suggesting coexistence, a finding which was supported by doublestaining. The findings indicate that differences in the posttranslational processing of preproVIP exist in subpopulations of neurons in the human gut.