Pain management in hemophilia: expert recommendations

INTRODUCTION

As a typical consequence of bleeding into muscles and joints, patients with severe hemophilia suffer from acute and chronic pain. In spite of its high prevalence, pain in this patient group is not always sufficiently considered or treated in an effective manner.

AIM

The recommendations presented in this paper address possible improvements in pain management in hemophilia patients and particularities that have to be taken into account in this patient group.

METHOD

The manifold aspects of pain management in hemophilia patients were discussed within the framework of an expert meeting. Based on the available literature and the experts' clinical experience, the participants developed a set of recommendations presented in this paper.

RESULTS

Pain management in patients with hemophilia is often insufficient, a fact that not only influences the patients' quality of life but also implies the risk of difficult to manage chronic pain. Both the prevalent polypharmacy (due to comorbidities) as well as the underlying disease itself present special challenges to pain therapy in this patient group. The present review and recommendations are intended to support medical professionals in recognising the risks of pain chronicity, applying basic principles of multimodal pain therapy, including the options of psychological intervention and modalities of physical medicine in therapy concepts, and reaching a comprehensive understanding of the range of analgesic options available.

Effect of CB1 Ligands on Neurogenic and Myogenic Contractile Responses in the Guinea-Pig Ileum

This study aimed at investigating whether the synthetic cannabinoid receptor agonist (+)-WIN 55212-2 has neurogenic and myogenic relaxant effects on the longitudinal muscle-myenteric plexus (LMMP) strip of the guinea-pig ileum. (+)-WIN 55212-2, 1–1,000 nmol/L, concentration-dependently inhibited both the electrical stimulation-induced cholinergic twitch responses as well as the myogenic smooth muscle contractions in the LMMP preparation. SR-141716A (rimonabant) 1–1,000 nmol/L, the cannabinoid CB1 receptor antagonist, being without effect on its own, antagonized the (+)-WIN 55212-2-induced effects. The allyl isothiocyanate (mustard oil, 100 µmol/L) induced a relaxant effect in the guinea-pig ileum, which can be regarded as neurogenic and myogenic, was augmented by (+)-WIN 55212-2, and inhibited by SR-141716A. (+)-WIN 55212-2 only moderately modified the 60 mmol/L KCl-evoked contractions. These results provide functional evidence that the CB1 agonist (+)-WIN 55212-2-induced inhibitory effects in the guinea-pig ileum are exerted both at the neuronal as well as at the intestinal smooth muscle cell level.

Effects of Allyl Isothiocyanate, Acetaminophen, and Dipyrone in the Guinea-Pig Ileum

Allyl isothiocyanate (AITC, mustard oil, 50-200 µmol/l), depending on specific dosages, inhibited the cholinergic twitch response in the longitudinal muscle-myenteric plexus (LMMP) strip of the guinea-pig ileum. AITC also induced short-lasting contractile responses, and decreases of the basal tone of the LMMP strip at low concentrations and increases at high concentrations. Hexamethonium, a blocker of nicotinic ganglionic transmission, was able to prevent the AITC-evoked inhibitory effect, an effect that was also observed with the opioid antagonist naloxone. The P2 purinoceptor antagonist pyridoxalphosphate-6-azophenyl-2'-4'-disulphonic acid and guanethidine had no significant influence on the inhibitory effect of AITC. Since AITC also reduced the electrical stimulation-induced myogenic smooth muscle contractions in the LMMP preparation, its contractile and relaxant actions can be regarded as neurogenic and myogenic in nature. The analgesics, acetaminophen (paracetamol, 100-500 µmol/l) and dipyrone (metamizole, 100-500 µmol/l), reduced both the cholinergic twitch and the myogenic contractions in the LMMP strip to the same extent; therefore, their action in the intestinal smooth muscle can be regarded as myogenic spasmolytic in nature.

Interaction of αβ-Methylene ATP with the Cholinergic Twitch Response in the Guinea-Pig Ileum

In this study, direct effects of the P2X purinoceptor agonist αβ-methylene ATP (αβ-meATP) and effects on the cholinergic twitch response of the electrically stimulated longitudinal muscle-myenteric plexus (LMMP) strip of the guinea-pig ileum, were investigated. αβ-meATP (1, 3, and 10 µmol/l) induced short-lasting contractions on its own, followed by an inhibition of the twitch response during its presence in the organ bath. The inhibitor of small conductance Ca2+-activated K+ (SK) channels, apamin (100 nmol/l), prevented the inhibitory effect of αβ-meATP on the twitch response, whereas tetraethylammonium (300 µmol/l), a blocker of voltage-gated K+ channels and an inhibitor at nicotinic acetylcholine receptors, augmented the inhibitory effect of αβ-meATP on the twitch response. It is concluded, that there is a functional interaction between P2X receptors and nicotinic receptors in the LMMP strip, and that a major part of the excitatory input to the cholinergic motor neuron evoking the twitch response is purinergic and not nicotinergic.

Nicotine-Induced Modulation of the Cholinergic Twitch Response in the Ileum of Guinea Pig

In the present study, the direct drug effects of nicotine and its effects on the cholinergic twitch responses of the electrically stimulated longitudinal muscle-myenteric plexus strip from the ileum of guinea pig were investigated. Nicotine dose-dependently (0.3-10 µmol/l) evoked the well-known contractile responses on its own. Whereas the interposed twitch responses remained present without a change in height at 1 µmol/l nicotine, a nicotine concentration of 3 µmol/l slightly and a concentration of 10 µmol/l markedly diminished the twitch during their presence. After the washout of 1-10 µmol/l nicotine, the height of the twitch response was also temporarily and significantly reduced by 30-77%. The P2X purinoceptor agonist αβ-methylene ATP (1-10 µmol/l) dose-dependently induced contractions on its own and reduced the twitch response during its presence in the organ bath; however, it did not diminish the twitch responses after washout of the drug as nicotine did. The P2X antagonist pyridoxalphosphate-6-azophenyl-2'-4'-disulphonic acid, the NMDA channel blocker MK-801 and the inhibitor of small conductance Ca(2+)-activated K(+) (SK) channels apamin reduced the contractile effect of 1 µmol/l nicotine. Apamin also significantly prevented the 'post-nicotine inhibition of the twitch' following the washout of 1-3 µmol/l nicotine. As a conclusion, we provide evidence for a functional interaction between nicotinic receptors and the P2X receptors in the ileum of the guinea pig. The 'post-nicotine inhibition of the twitch' is not due to nicotinic acetylcholine receptor desensitization or transmitter depletion, but most probably the secondary effects of nicotine on SK channels determine the reduced cholinergic motor neuron excitability.

Drug fever due to a single dose of pantoprazole

Although proton pump inhibitors (PPI) are generally well tolerated, with most adverse effects being minor and self-limiting, there are singular reports on hypersensitivity immune reactions triggered by a PPI or its metabolites. Here we report a case of acute drug-induced fever with leukocytosis and a transient increase in CRP due to pantoprazole. This was apparently an idiosyncratic reaction (inflammatory fever), showing no cross-sensitivity towards esomeprazole.

Amphotericin B transfer to CSF following intravenous administration of liposomal amphotericin B

OBJECTIVES

Although amphotericin B (AmB) and its lipid formulations are used for the treatment of fungal infections of the CNS, the kinetics of AmB in the CSF after intravenous administration of liposomal amphotericin B (LAmB) are not well characterized.

PATIENTS AND METHODS

From 14 paediatric haemato-oncological patients (aged 0.4-19.5 years, median 7.6 years), we obtained 30 CSF samples by means of routine punctures (performed for intrathecal treatment of the underlying diseases) at different timepoints after the prophylactic intravenous infusion of LAmB (AmBisome, 3 mg/kg/day). Concurrent serum samples were obtained to calculate the transfer rates. An HPLC method was used for AmB detection.

RESULTS

CSF levels of AmB 1-100 h after the intravenous infusion of LAmB were between 10 and 120 ng/mL, except in one case with a level of 529 ng/mL. Concurrent serum levels were about 1000-fold higher, ranging between 3 and 75 μg/mL. CSF levels did not show a clear time-dependent concentration profile, but remained at a steady-state for longer than 48 h after infusion. The transfer rate ranged from 0.02% to 0.92% (median 0.13%) and correlated significantly (r=0.801, P<0.001) with increasing time after infusion.

CONCLUSIONS

After the intravenous administration of LAmB, AmB CSF levels were low, confirming published animal data. CSF levels remained at a steady-state level for longer than 48 h. As indicated by published post mortem data, higher levels in brain tissue, which would be necessary for the successful treatment of CNS infections, might be possible.

Phosphorylation of ERK1/2 in dorsal root ganglia following sequential mustard oil and thermal stimulation of the rat hind paw

The effect of a sequential stimulation by mustard oil and noxious heat or cold on the phosphorylation of ERK1/2 in sensory afferents was investigated. The stimuli were applied to the rat hind paw and phospho-ERK1/2 (p-ERK1/2) was measured by fluorescence-immunohistochemistry in the lumbar dorsal root ganglia (DRGs) neurons. All stimuli lead to a significant increase in the number of small size DRG cells displaying cytoplasmic staining for p-ERK1/2. The combination of mustard oil with cold significantly increased the number of cells with cytoplasmic staining above the level obtained with cold stimulus alone, however this was not observed with the combination of mustard oil and heat. Nuclear staining was weak and was found increased by mustard oil combined with cold stimulation. Mustard oil is known to activate TRPA1 and TRPV1 channels, heat TRPV1, and cold TRPA1 and TRPM8. The present findings shed new light on the DRG cell populations reacting with cytoplasmic and nuclear staining for p-ERK1/2 following sequential irritant chemical and thermal stimuli to the skin.

A fluorescence-immunohistochemical study on phosphorylation of ERK1/2, p38, and STAT3 in rat dorsal root ganglia following noxious stimulation of hind paw sensory neurons

A fluorescence-immunohistochemical investigation was performed in lumbar dorsal root ganglia (DRGs) neurons of the rat with regard to ERK1/2-, p38- and STAT3-phosphorylation in response to nociceptor activation in the rat. The stimuli applied were perineural capsaicin treatment of the sciatic nerve, mustard oil application to the hind paw and heat or cold stimulation of the hind paw. The time points of investigations were 15 min/30 min after perineural capsaicin, 30 min/2 h/4 h for mustard oil, 10 min/4 h for cold and 30 min/2 h/8 h for the heat stimulus. All four stimuli lead to a time-dependent, significant 2-3 fold increase in the number of small and medium size DRG cells displaying cytoplasmic staining for p-ERK1/2, but to no activation of satellite cells. Phosphorylated p38 immunoreactivity was increased in the cytoplasma of DRG cells at 2 h after the mustard oil treatment of the hind paw and 30 min after the perineural capsaicin application to the sciatic nerve axons, but not following heat or cold stimuli to the hind paws. Phospho-STAT3 staining was characteristically observed as nuclear and cytoplasmic staining. It was found increased after the perineural capsaicin application to the sciatic nerve axons, however, no marked increase was found with the other 3 noxious stimuli. The present results show that sensory neurons respond with a selective long-lasting increase in p-ERK1/2 in small and medium-size DRG cells, when their axons or axon terminals are stimulated by capsaicin, mustard oil, noxious heat or noxious cold.

Antidepressants: clinically relevant drug interactions to be considered

Drug interactions in clinical practice are common and have developed into an increasing challenge for the medical profession. Specifically antidepressant drugs (ADs), which are among the 5 most frequently prescribed drugs, are predestined for adverse drug interactions because of their multiple mechanisms of action and/or their influence on drug-metabolizing cytochrome P450 (CYP) enzymes. Although selective serotonin reuptake inhibitors (SSRIs) and other new-generation ADs have an overall improved safety profile, their potential for drug interactions is to be considered. A review of the current literature has been performed, and selected examples of clinically relevant interactions with ADs have been chosen. With regard to pharmacodynamic interactions, the serotonin syndrome, the risk of bleeding under SSRI therapy, and the corrected Q-T interval prolongation are discussed in this review. The inhibitory effects of new-generation ADs on CYP enzymes show great variability and might be relevant for prescription recommendations in elderly patients and in patients with polypharmacy. The CYP-enzyme-inducing effect of St. John's wort, a popular over-the-counter herbal drug, may lead to decreased plasma levels of CYP substrates. When comparing prescription data and observed adverse drug events, there is fortunately a safety gap between the number of potential drug-drug interactions and the number of clinically observed side effects due to drug-drug interactions.

Seminal fluid ribavirin level and functional semen parameters in patients with chronic hepatitis C on antiviral combination therapy

BACKGROUND & AIMS

Due to the possible teratogenic effect of ribavirin, effective contraception is mandatory during antiviral therapy in patients with chronic hepatitis C (CHC). The aim of this study was to evaluate seminal parameters and ribavirin and HCV-RNA concentrations in seminal fluid and serum prior to and during antiviral treatment.

PATIENTS AND METHODS

Fifteen male patients (age: 42+/-9 (years+/-SD)) with CHC treated with pegylated interferon-alpha-2a and ribavirin were investigated. Seminal fluid (sperm concentration, motility, and morphology) was analysed morphologically. HCV-RNA and ribavirin concentration were determined by quantitative PCR and HPLC, respectively. Examinations were carried out at baseline, week 4, and week 12.

RESULTS

Ribavirin concentration was higher in seminal fluid than in serum (week 4: 5.2+/-2.5 vs. 2.1+/-0.3; week 12: 4.4+/-1.8 vs. 2.0+/-0.3 (microg/ml, mean+/-SD; p<0.001)). Semen abnormalities were common at baseline (asthenoteratozoospermia: n=6; asthenozoospermia: n=3; teratozoospermia: n=3). Sperm density (BL: 67+/-33x10(6)/ml; week 4: 42+/-25 (p<0.05); week 12: 49+/-33 (n.s.)), percentage of sperm with progressive motility (BL: 40+/-26%; week 4: 27+/-25; week 12: 31+/-20 (n.s.)), and percentage of sperm with normal morphology (BL: 25+/-15; week 4: 20+/-11; week 12: 16+/-9; p<0.05 for both) further decreased during antiviral therapy. HCV-RNA was detectable in the seminal fluid of only two patients prior to antiviral therapy and was undetectable in all patients during combination therapy.

CONCLUSION

Semen abnormalities were common in CHC patients, with further impairment during antiviral therapy. Ribavirin concentration was elevated twofold in seminal fluid compared to serum levels, which reinforces the need for contraception during antiviral combination therapy.

Dorsal root ganglion neurons respond with prolonged extracellular signal-regulated protein kinase phosphorylation following noxious heat and cold stimulation

In the present study the time course of extracellular signal-regulated protein kinase phosphorylation (pERK1/2 appearance) in lumbar sensory dorsal root ganglia (DRG) was determined following a 5-min noxious heat or a noxious cold stimulus to the hind paw of the rat. The thermal stimuli were chosen to activate transient receptor potential (TRP) channels, but not to induce tissue damage. A quantitative analysis of phospho-ERK1/2 was performed by protein extraction and Western blot analysis. Western blot analysis showed that following the heat stimulus, phosphorylation of ERK1/2 increased 2-3-fold between 10 and 30min in the DRG on the ipsilateral side. High levels were maintained from 30min up to 16h. Following the cold stimulus to the paw, pERK1/2 immediately increased 2-fold within 2min in the DRG on the ipsilateral side, it declined within 2h and reached a second peak at 4h. In the DRGs on the contralateral side of the paw's heat or cold immersion the pERK1/2 remained low at all time points investigated. Fluorescence immunohistochemistry of the DRG following the thermal stimuli revealed an increased cytoplasmic staining for pERK1/2 in neurons. The present results show that following a 5-min nociceptive thermal stimulus sensory neurons respond with a characteristic long-lasting phosphorylation of ERK1/2.

Stimulus-evoked opioid inhibition in guinea-pig longitudinal muscle-myenteric plexus strip is modulated by NMDA receptors

Longitudinal muscle-myenteric plexus (LMMP) strips of the guinea-pig ileum were used to investigate the stimulus-evoked endogenous opioid inhibition and its modulation by ionotropic glutamate receptors. Regular cholinergic twitch responses evoked by a short 3-s-field stimulation in intervals of 80s were found reduced after an interposed period of prolonged 40-s-field stimulation. In the presence of a peptidase-inhibitor-cocktail, the cholinergic twitch response following the period of prolonged stimulation was even further reduced as compared to normal Tyrode solution without peptidase inhibitors. In both instances, the impairment of the cholinergic twitch response was completely abolished by naloxone thus demonstrating its opioidergic nature. This endogenous inhibitory opioid effect was significantly mitigated by the NMDA-receptor antagonist MK-801, but not by the AMPA/kainate receptor antagonist CNQX. These results demonstrate by functional experiments that there is a significant opioid-mediated inhibition in guinea-pig LMMP preparations evoked by a prolonged electrical stimulation, and that an NMDA antagonist can mitigate the opioid inhibition.

The NK1 Receptor Antagonist SR140333 Inhibits Capsaicin-Induced ERK Phosphorylation in Sensory Neurons

Primary sensory neurons respond to a vigorous excitation via the capsaicin receptor/TRPV1 cation channel by a phosphorylation of the Jak/STAT pathway as measured by phospho-STAT3, and of the Ras/Raf-MAPK pathway as measured by phospho-MAPK/ERK1/2. In the present investigation a possible involvement of NK1 receptors in the capsaicin-induced activation of these signal transduction pathways was investigated by protein extraction and Western immunoblotting. Phospho-MAPK/ERK1/2 and phospho-STAT3 were determined in the dorsal root ganglia (DRG) and in the sciatic nerve of rats at 3 and 6 h following a systemic capsaicin treatment without or with the pretreatment of the selective NK1 receptor antagonist SR140333 (1 mg/kg s.c.; 3 h before capsaicin). Capsaicin evoked a threefold increase in phospho-ERK in the sciatic nerve and a two- to threefold increase in the DRG at 3 h and 6 h after the treatment. SR140333 markedly attenuated the capsaicin-induced increase in phosphorylated ERK. In the sciatic nerve the difference was significant at each individual time point (3 and 6 h, p < 0.001). In the DRG the difference was significant when the data at 3 h and 6 h were combined (p < 0.05), but not when individual time points were considered. Capsaicin evoked a four- to fivefold increase in phospho-STAT3 in the sciatic nerve and a twofold increase in the DRG at 3 and 6 h after the treatment. SR140333 less markedly attenuated the capsaicin-induced increase in phosphorylated STAT3: whereas in the sciatic nerve the difference was significant when the data at 3 h and 6 h were combined (p < 0.05), no such treatment effect of SR140333 was observed in the DRG. The expression of TRPV1 mRNA, a specific marker of capsaicin-sensitive small sensory neurons, was investigated by RT-PCR 4 days after the capsaicin treatment. Treatment of rats with SR140333 had no influence on the long-term downregulation of TRPV1 mRNA by capsaicin. Based on the present results and previous findings it can be postulated that the capsaicin-induced ERK phosphorylation in sensory neurons is not a direct effect by capsaicin, but that rather substance P release from the stimulated sensory neurons with an NK1-mediated nerve growth factor (NGF) production is involved.

Ribavirin Levels and Haemoglobin Decline in Early Virological Responders and Non-Responders to Hepatitis C Virus Combination Therapy

Therapeutic drug monitoring of ribavirin has been claimed to predict virological response and/or haematological side effects in patients with chronic hepatitis C undergoing peginterferon/ribavirin combination treatment. In the present study, steady-state ribavirin levels were retrospectively analyzed in serum samples from patients at week 12 of combination therapy with peginterferon alpha-2a or alpha-2b and ribavirin. Patients were classified as early virological responders on the basis of undetectable HCV-RNA or HCV-RNA drop >or=2 log from baseline at week 12. The mean ribavirin level was not different between early virological responders (2.3 +/- 0.1 microg/ml, n = 45) and early virological non-responders (2.0 +/- 0.2 microg/ml, n = 10). There was no correlation between ribavirin levels at week 12 and early virological response. In patients with early virological response, haemoglobin (Hb) levels were found to be decreased by 18% on average from the basal values; however, in only 2 patients Hb levels declined below 100 g/l. There was a moderate negative correlation between ribavirin levels and Hb levels at week 12 (R = -0.50, p < 0.001); however, ribavirin levels did not correlate with relative or absolute decline in Hb as compared to basal levels or with ribavirin dose per kilogram body weight. In addition, a significant negative correlation between ribavirin levels and glomerular filtration rate was found (R = -0.31, p < 0.05). Based on our results, monitoring of ribavirin serum levels at week 12 of HCV combination therapy does not appear to predict early virological response or reductions in Hb levels. Further research is needed to assess their diagnostic value at other time points of peginterferon/ribavirin combination treatment and/or in patients with renal insufficiency.

ERK and STAT3 phosphorylation in sensory neurons during capsaicin-induced impairment and nerve growth factor treatment

Distinct signal transduction pathways have been shown to regulate injury responses and regeneration in peripheral nerves. In the present investigation, the time courses of the induction of phospho-MAPK/ERK1/2 and of phospho-STAT3 were investigated in the dorsal root ganglia (DRG) and in the sciatic nerve of rats following a systemic capsaicin treatment without or with concomitant intraplantar NGF injections. Western blots were probed with polyclonal antibodies that specifically detect phosphorylated ERK 1/2 and STAT3. Phosphorylation of ERK clearly peaked in the sciatic nerve and in the lumbar DRGs at 6 and 10 h after the capsaicin treatment. In the following 8 days phospho-ERK decreased to very low levels and was found recovered to basal values at the time point 16 days. An additional intraplantar nerve growth factor (NGF) injection at time points 20, 44 and 92 h after the capsaicin treatment, and collection of tissues 4 h later, markedly increased the level of phospho-ERK in the sciatic nerve as well as in the DRG, as compared to the samples taken from rats at the same time points with a capsaicin treatment only. Posphorylated STAT3, which was almost non-detectable in the control sciatic nerve, clearly peaked at 6 h after the capsaicin treatment and decreased again during the following days to almost undetectable levels. The intraplantar NGF injections slightly stimulated phosho-STAT3 in the sciatic nerve. A basal level of phosphorylated STAT3 was present in DRGs of control animals, it remained at a high level up to 6 h after the capsaicin treatment, then markedly decreased and recovered on day 8 and day 16. NGF increased STAT3 phosphorylation in DRG on day 1 and day 2 above the level observed in samples taken from rats at the same time points with a capsaicin treatment only. The present study demonstrates that a capsaicin impairment of small diameter primary sensory neurons followed by an NGF treatment evokes a characteristic pattern of ERK and STAT3 activation indicative of neuronal degeneration and regeneration.

Nociceptive transmitter release in the dorsal spinal cord by capsaicin-sensitive fibers after noxious gastric stimulation

Little is known about transmitters that encode noxious gastric stimuli in the spinal cord. The release of glutamate, substance P, and CGRP from the spinal cord was therefore investigated in response to acid injury of the gastric mucosa. Dorsal halves of the caudal thoracic spinal cord (T7-T13) were removed 6 h after oral application of 0.5 M HCl or saline, transferred to a superfusion chamber, and the basal and capsaicin-stimulated (3.3 microM) transmitter release was determined. After acid injury, basal glutamate release increased 134% as compared to saline-treated animals. Capsaicin-stimulated release of CGRP and SP was 48% and 58% lower in acid- than in saline-treated animals, indicating that capsaicin-sensitive fibers in the dorsal spinal cord were already partially depleted by acid treatment. Capsaicin denervation reduced basal glutamate release by 33% after acid injury as compared to non-denervated acid-treated animals. Gastric origin and capsaicin sensitivity of glutamatergic, CGRP- and SP-containing primary afferents in thoracic dorsal root ganglia were then determined by retrograde tracing with True Blue and immunohistochemical labeling with the vanilloid receptor TRPV1. About 65% of True Blue-labeled cells were glutamatergic and more than 73% of this population expressed the TRPV1 receptor. Nearly all True Blue/CGRP (85%)- and True Blue/SP-positive cells (97%) coexpressed TRPV1. We conclude that noxious gastric stimulation with acid induces release of glutamate, SP, and CGRP from capsaicin-sensitive sensory afferents in the dorsal horn of the spinal cord where they may play an important role in gastric nociception and hyperalgesia.

Differential regulation of 3-beta-hydroxysteroid dehydrogenase and vanilloid receptor TRPV1 mRNA in sensory neurons by capsaicin and NGF

It was the aim of the present study to investigate by RT-PCR the regulation of the mRNA of the neurosteroid-synthesizing enzyme 3beta-hydroxysteroid dehydrogenase (3beta-HSD) and of the vanilloid receptor TRPV1 in dorsal root ganglia (DRGs) of rats during the process of capsaicin denervation of primary sensory neurons and the following regeneration. The expression of 3beta-HSD in DRG was increased 3 days after the capsaicin treatment, and it remained at that level during a 22 day observation period. The expression of TRPV1, a specific marker of capsaicin-sensitive small sensory neurons connected to C- and Adelta-fibers, was markedly reduced 3 days after the capsaicin treatment. It slowly recovered during the 22 days observation period reaching almost control levels on day 22. When the capsaicin-treated rats received 5 intraplantar injections of nerve growth factor (NGF), the prototypical neurotrophin for capsaicin-sensitive neurons, on day 1, 2, 3, 5 and 6, both the 3beta-HSD and the TRPV1 mRNA had returned to control levels at the time point 8 days after capsaicin. The present results demonstrate that both 3beta-HSD and TRPV1 are markers for neurodegeneration and neuroregeneration in capsaicin-sensitive primary afferent neurons, and that NGF is an effective tool to induce recovery after peripheral nerve injury.

Therapeutic Drug Monitoring of the HIV/AIDS Drugs Abacavir, Zidovudine, Efavirenz, Nevirapine, Indinavir, Lopinavir, and Nelfinavir

Combination therapy with antiretroviral drugs is used for the treatment of patients infected with the human immunodeficiency virus. To achieve optimal drug concentrations for viral suppression and avoidance of drug toxicity, monitoring of drug levels has been considered essential. We set up an analytical procedure for monitoring the plasma concentrations of a total of seven drugs: abacavir, zidovudine, efavirenz, nevirapine, indinavir, lopinavir, and nelfinavir. The plasma samples were liquid/liquid extracted and subjected to high-performance liquid chromatography (HPLC) analysis. The compounds were monitored by ultraviolet detection: indinavir, lopinavir, and nelfinavir at 215 nm; efavirenz at 254 nm, and abacavir, zidovudine, and nevirapine at 266 nm. Two different extraction procedures and two different HPLC eluents on a C(8) reversed-phase HPLC column were used to monitor all seven compounds. Under steady state conditions, the plasma concentrations of antiviral drugs in 175 patients were correlated with the time after the last dosing to define the peak or trough levels. Due to the short plasma elimination half-life of abacavir and zidovudine, only peak levels could be determined for these compounds, whereas both peak and trough levels could be assessed for the other compounds because of a longer plasma elimination half-life. The mean peak concentrations (microg/ml) were 0.69 for abacavir and 0.57 for zidovudine; the mean peak/trough concentrations (microg/ml) were 2.07/1.32 for efavirenz, 2.43/2.23 for nevirapine, 5.48/1.08 for indinavir, 4.69/3.51 for lopinavir, and 3.54/1.45 for nelfinavir. The described analytical method offers a broad-spectrum monitoring of plasma levels of antiretroviral drugs.

Regeneration of primary sensory neurons

Primary sensory neurons have an inherent capacity for regeneration of their cut, crushed, or chemically lesioned axons. This capacity is displayed to a much greater extent after lesions of the peripheral axons than after lesions of their centrally directed axons. Additionally, the surrounding tissue determines to a significant extent the degree of recovery: whereas the peripheral nerve tissue provides neurotrophic support and a favorable environment for axonal growth, the central terminals of primary sensory neurons face a non-permissive and inhibitory glial tissue. Mechanical lesions of the peripheral axons of dorsal root ganglion (DRG) sensory neurons can be repaired by the intrinsic regenerative capacity of the neuron itself, when outgrowing axons from the proximal stump are able to transverse the tissue scar and reach the distal stump of the nerve. Bridging the gap with an autologous nerve graft or a short artificial graft filled with nerve growth factor (NGF) can improve recovery. Neurotoxic lesions of the axon terminals are effectively recovered by intermittent local or systemic NGF injections. A recovery from a diabetic sensory neuropathy probably requires the continuous delivery of NGF or additional neurotrophic factors. A recovery from a dorsal rhizotomy or from a dorsal column lesion can possibly be achieved by the concomitant transgene-mediated overexpression of neurotrophins, the transformation of the DRG neuron cells to a competence for regrowth, and the counteraction of the growth-inhibitory nature of the central nervous system tissue.

Severe hypoxia inhibits prostaglandin I(2) biosynthesis and vasodilatory responses induced by ionophore A23187 in the isolated rabbit ear

The present study was designed to test the hypothesis that lack of oxygen in severely hypoxic tissue may inhibit arachidonic acid oxygenation and thereby result in an inhibition of eicosanoid synthesis. Hypoxia was induced in the isolated rabbit ear, and arachidonate metabolism and peripheral resistance of the preparation were monitored simultaneously. Severe hypoxia completely inhibited the biosynthesis of prostaglandin I(2) induced by ionophore A23187 and converted the vasodilatory response observed under normoxia into vasoconstriction. The cyclooxygenase 1 inhibitor SC560 (1 micromol/l) effectively inhibited the normoxic prostaglandin I(2) biosynthesis, while the cyclooxygenase 2 inhibitor DFU (1 micromol/l) did not. Neither SC560 nor DFU affected normoxic vasodilatory responses, indicating no involvement of prostanoids. The nitric oxide (synthase inhibitor Nomega-nitro-L-arginine methyl ester (100 micromol/l) converted the vasodilation into vasoconstriction, similar to what was observed under hypoxia, suggesting that the hypoxia-mediated conversion might occur due to the inhibition of nitric oxide.

Effect of FK506 on neurotransmitter content and expression of GAP-43 in neurotoxin-lesioned peripheral sensory and sympathetic neurons

It has previously been shown that the capsaicin-lesioned peptidergic sensory neurons and the 6-hydroxydopamine (6-OHDA)-lesioned sympathetic noradrenergic neurons represent a useful model to study neurotrophin-induced nerve regeneration in the adult rat. The present study was aimed at investigating if the immunosuppressant drug FK506 (tacrolimus) has neuroregeneratory properties in these capsaicin- or 6-OHDA-lesioned peripheral nerves. FK506 was injected in a dose of 0.5 mg/kg/day for 10 days or in a dose of 1.5 mg/kg/day for 7 days. One day after the last FK506 injection neurotransmitter content was investigated in selected tissues. The content of the sensory neuron marker peptide calcitonin gene-related peptide (CGRP) was reduced after the capsaicin treatment in the hind paw skin by 35-40% and in the dorsal lumbar spinal cord by 48%. The treatment with FK506 did not induce a recovery of the CGRP content. Following the 6-OHDA treatment the noradrenaline content was reduced by 50-62% in the hind paw skin and by 73% in the heart atrium. FK506 alone did not increase the noradrenaline levels, whereas an additional local intraplantar treatment with nerve growth factor recovered noradrenaline levels almost completely. The expression of a marker protein for growth processes in cells of sympathetic or sensory ganglia, growth-associated protein-43, was significantly increased by the FK506 treatment. This study demonstrated that despite a stimulatory effect of FK506 on the expression of a growth-associated protein a recovery of the transmitter content is not evident in peripheral small diameter sensory or postganglionic sympathetic neurons of the adult rat.

Nerve growth factor stimulates synthesis of calcitonin gene-related peptide in dorsal root ganglion cells during sensory regeneration in capsaicin-treated rats

Administration of human recombinant nerve growth factor (rhNGF) into one hindpaw of capsaicin-treated rats can locally facilitate the regeneration of calcitonin gene-related peptide (CGRP)-containing primary sensory neurons (Schicho, R., Skofitsch, G., Donnerer, J., 1999. Brain Res. 815, 60-69). In this study we used in situ hybridization histochemistry (ISH) to determine synthesis of CGRP mRNA in lumbar L4 dorsal root ganglion (DRG) cells during NGF-induced regeneration. Whereas 8 days after the capsaicin treatment alone (50 mg/kg s.c.) CGRP mRNA expression in DRG cells was reduced to 40-60% of control levels, the additional intraplantar injections of rhNGF (5 x 4 microg) during this time period were able to raise CGRP mRNA expression again. The increase in CGRP expression was seen ipsi- and contralaterally and it was more pronounced in small- and medium-sized (about 110% of control levels), than in large-sized CGRP-producing cells (70% of controls). The percentage of the CGRP-expressing neurons in capsaicinized and in capsaicin + NGF-treated animals stayed unaltered. In conclusion, the present results demonstrate that NGF-induced regeneration of capsaicin-lesioned sensory afferents is accompanied by an elevated production of CGRPmRNA mainly in small- and medium-sized DRG cells.

Increased expression of GAP-43 in small sensory neurons after stimulation by NGF indicative of neuroregeneration in capsaicin-treated rats

Intraplantar injections of human recombinant nerve growth factor (rhNGF-beta) into the hind paw of capsaicin-treated adult rats are known to lead to a recovery of depleted peptide transmitter substances, to the immunohistochemical reappearance of peptidergic innervation in the skin and in the dorsal horn of the spinal cord, as well as to a recovery of the function of capsaicin-lesioned neurons. In the present study a marker peptide for neuronal regeneration and outgrowth, growth associated protein 43 (GAP-43), was investigated in lumbar dorsal root ganglia (DRGs) and in the hindpaw skin, in order to differentiate which population of the sensory neurons responds with a neuroregenerative behaviour. In situ hybridization histochemistry (ISH) revealed that at day 8 after the capsaicin treatment GAP-43 expression was significantly increased in small DRG cells as compared to control animals, and treatment with NGF in capsaicinized rats lead to an even more pronounced increase of GAP-43 expression in the small-sized cell population. Intraepidermal labelling of GAP-43 peptide was observed in the skin of control animals, but was markedly reduced in the animals that were treated with capsaicin alone. However, intraepidermal GAP-43 immunoreactive (GAP-43-IR) fibres nearly fully recovered in the capsaicin + NGF-treated group. These results indicate that the population of small DRG cells shows spontaneous regenerative activity after a capsaicin lesion which does not lead to a successful recovery of nerve terminals in the skin. Only after an additional NGF treatment small DRG cells show an even stronger regenerative response which now also involves structural reorganization of neuron membranes and axogenesis in the periphery.

Regenerative effect of human recombinant NGF on capsaicin-lesioned sensory neurons in the adult rat

Nerve growth factor (NGF) has the ability to increase the content of peptide transmitter in intact primary sensory afferents of the adult rat. We have previously shown that NGF can also induce a refill of peptide transmitters in capsaicin-depleted peptidergic nerve terminals of the rat paw skin upon intraplantar injection. The present study was aimed at investigating the neurochemical, immunohistochemical and functional recovery of peripheral and central terminals of capsaicin-lesioned afferents following administration of recombinant human NGF-beta (rhNGF-beta). The systemic capsaicin treatment in adult rats by 50 mg/kg s.c. (day 0) was followed by intraplantar rhNGF-beta injections (4 micrograms each) into one hind paw on days 1, 2, 3, 5, 6 and by the analysis on day 8. The content of the marker peptide calcitonin gene-related peptide (CGRP) showed a 100% NGF-induced recovery in the peripheral (sciatic nerve) and central axons (lumbar dorsal roots) on the side of the NGF treatment and also in the contralateral sciatic nerve and lumbar dorsal roots. In the terminals of the hind paw skin, the recovery of the CGRP content, as measured by radioimmunoassay, was 100% in the plantar and 80% in the dorsal skin ipsilaterally, and 55% in the dorsal and plantar hind paw skin contralaterally. In the lumbar dorsal spinal cord, CGRP content recovered by 85% bilaterally. The morphological appearance of the sensory nerve terminals was visualized by CGRP-immunohistochemistry. In the paw skin, the CGRP-immunoreactive (CGRP-IR) nerve endings were restricted to a fragmentary subepidermal plexus after the capsaicin treatment, whereas the subsequent NGF treatment caused a bilateral recovery of the subepidermal plexus and an intact reinnervation of the epidermis and blood vessels with free nerve terminals. The capsaicin-induced fragmentation of the CGRP terminal plexus in laminae I and II of the lumbar spinal dorsal horn was also markedly repaired on both sides by the intraplantar NGF injections. The NGF treatment caused the CGRP nerve terminals in the spinal cord to regain their ability of releasing transmitter upon capsaicin stimulation as shown in tissue slice superfusion experiments. These results show that within one week, rhNGF-beta can induce a complete reinnervation of skin and spinal cord with intact CGRP-IR nerve terminals after an acute capsaicin lesion.

Evidence for a neurotransmitter role of glutamate in guinea pig myenteric plexus neurons

Longitudinal muscle-myenteric plexus strips of the guinea pig ileum were used to investigate a possible transmitter role of glutamate (Glu) in the enteric nervous system. Glu was released from this nerve muscle preparation by high K(+)-depolarization in a Ca2(+)-dependent manner, by electrical field stimulation and by the ganglionic stimulant dimethylphenylpiperazinium which indicates its neural origin. Contractions of the longitudinal muscle evoked by electrical stimulation of the myenteric nerves or by Glu, were significantly reduced by the N-methyl-D-aspartate (NMDA)-receptor antagonist FR115427 (9 and 18 microM), whereas contractions induced by histamine were unaffected. The results show that the amino acid Glu is likely to play an excitatory neurotransmitter role via NMDA receptors in the myenteric plexus of the guinea pig.

Bradykinin-evoked sensitization of neuropeptide release from afferent neurons in the guinea-pig lung

1. It has been shown that bradykinin (BK) causes sensitization of airway sensory neurons and an enhancement of the cough reflex in guinea-pigs. In the present study, the guinea-pig isolated perfused lung was used to investigate the possible enhancement by BK of histamine-evoked neuropeptide release from peripheral terminals of primary afferent neurons, and to determine the contribution of cyclooxygenase products of arachidonate metabolism to this effect. 2. The lung was perfused with oxygenated physiological salt solution containing peptidase inhibitors (thiorphan, bestatin and captopril, 1 microM each). BK and histamine were added to the perfusate for 10 and 5 min, respectively. 3. BK alone (0.1 microM) evoked the release of 10.35+/-2.4 fmol immunoreactive calcitonin gene-related peptide (CGRP), histamine alone (100 microM) evoked the release of 12.7+/-1.6 fmol CGRP. Stimulation with 100 microM histamine in the presence of 0.1 microM BK (added 5 min before histamine and present during histamine) evoked the release of 67.1+/-5.3 fmol CGRP. 4. Prostaglandin (PG) release was stimulated by BK (418+/-71 pmol 15-keto-13,14-dihydro-PGF2alpha and 345+/-59 pmol 6-keto-PGF1alpha), and, to a lesser extent, by histamine (36.1+/-7.4 pmol 15-keto-13,14-dihydro-PGF2alpha, and 24.6+/-3.9 pmol 6-keto-PGF1alpha). Prostaglandin release induced by histamine in the presence of BK was not significantly higher than with BK alone. 5. Indomethacin (5 microM) as well as the bradykinin B2 receptor antagonist HOE140 (icatibant, 1 microM) inhibited prostaglandin release following stimulation with histamine in combination with BK. CGRP release evoked by histamine in combination with BK was attenuated by indomethacin and HOE140 to 22.1+/-7.8 fmol and 16.4+/-3.8 fmol, respectively, significantly less than the value obtained in control experiments (67.1+/-5.3 fmol). 6. The results suggest that BK-induced stimulation of prostaglandin synthesis results in facilitation of histamine-evoked release of pro-inflammatory neuropeptides from afferent neurons, a mechanism that probably becomes relevant during inflammation, and that can be blocked by a bradykinin B2 receptor antagonist.

Involvement of NGF in the induction of increased noradrenergic innervation of the ureter in neonatally capsaicin-treated rats

Neonatal denervation of primary afferents with capsaicin leads to increased sympathetic innervation of the rat ureter. In the present study the development and the immunohistochemical characterization of this sympathetic hyperinnervation as well as the specific involvement of nerve growth factor (NGF) was investigated. Noradrenaline levels were found elevated in neonatally capsaicin-treated rats by 2 weeks of age and remained at that high level into adulthood. Injections of an anti-NGF antiserum during postnatal days (PN) PN 8-14, PN 13-19 or during PN 17-23 counteracted the capsaicin effect and reduced noradrenaline towards control levels. Immunohistochemical localization of tyrosine hydroxylase (TH), a marker for sympathetic nerve fibres, revealed that the capsaicin-induced hyperinnervation was mainly represented by fibres in deeper muscle layers and to a smaller extent by fibres in the submucosa. In control animals and in rats treated with capsaicin and anti-NGF antiserum fibres were mainly distributed in the adventitia and in the outer part of the smooth muscle layer. These results show that NGF is responsible for the development of an increased noradrenergic innervation in the rat ureter after neonatal capsaicin treatment.

Mediation by 5_hydroxytryptamine of the femoral vasoconstriction induced by acid challenge of the rat gastric mucosa

1. Gastric mucosal barrier disruption in the presence of luminal acid causes femoral vasoconstriction via a pathway that appears to be stimulated by messengers generated in the injured gastric mucosa. This study was undertaken to analyse the gastric factors that are responsible for the femoral vasoconstrictor response. 2. Gastric mucosal barrier disruption in the presence of luminal acid was induced by perfusing the stomach of urethane-anaesthetized rats with ethanol (15 %) in 0.01-0.15 M HCl. Blood flow in the left gastric and right femoral artery was estimated by the ultrasonic transit time shift technique. 3. Gastric perfusion of ethanol in HCl caused loss of H+ ions from the gastric lumen, decreased the HCO3- concentration in hepatic portal vein blood, induced macroscopic histological damage to the gastric mucosa, dilated the left gastric artery and constricted the femoral artery. These responses were related to the HCl concentration in the ethanol-containing perfusion medium. 4. The femoral vasoconstriction was also seen when, instead of ethanol, taurocholate (20 mM) was used to disrupt the gastric mucosal barrier in the presence of 0.15 M HCl. 5. The femoral vasoconstriction evoked by gastric perfusion of ethanol in HCl was left unaltered by pharmacological blockade of gastrin and histamine receptors. In contrast, the 5-hydroxytryptamine 5-HT1/2 receptor antagonist methiothepin, but not the 5-HT2A receptor antagonist ketanserin or the 5-HT3 receptor antagonist granisetron, inhibited the ability of both 5-hydroxytryptamine and gastric acid back-diffusion to constrict the femoral artery. 6. Gastric acid back-diffusion caused release of 5-hydroxytryptamine into the gastric lumen, which was related to the HCl concentration in the ethanol-containing perfusion medium. 7. These data show that femoral vasoconstriction evoked by gastric mucosal barrier disruption depends on back-diffusion of acid into the mucosa. The acid-induced damage results in release of 5-hydroxytryptamine from the gastric mucosa, and the pathway leading to constriction of the femoral artery involves 5-hydroxytryptamine acting via 5-HT1/2 receptors as a messenger molecule.

Release of calcitonin gene-related peptide in cardiac anaphylaxis

We have investigated the antigen-stimulated release of calcitonin gene-related peptide (CGRP) from ovalbumin-sensitized guinea-pig isolated hearts and the interaction with other mediators of anaphylaxis released concomitantly. It was found that antigen challenge caused a significant increase of CGRP release (from basal 31.2 +/- 2.9 to 51.6 +/- 4.9 fmol/5 min). Anaphylactic CGRP release was significantly attenuated in the presence of the cyclooxygenase inhibitor indomethacin while the 5-lipoxygenase inhibitor Bay-X1005 ((R)-2-[4-quinolin-2-yl-methoxy)phenyl]-2-cyclopentyl acetic acid) had no significant effect. Combined treatment with the histamine receptor (H1,H2) antagonists mepyramine and cimetidine also significantly attenuated anaphylactic release of CGRP. Under control conditions antigen injection increased release of cysteinyl-leukotrienes (LT), thromboxane (TXB2) and 6-keto-prostaglandin (PG)F1 alpha from basal values of 0.96 +/- 0.09, 2.7 +/- 0.7 and 3.4 +/- 0.28 ng/5 min respectively, to 5.9 +/- 0.9, 48.4 +/- 3.4 and 6.9 +/- 1.4 ng/5 min. Indomethacin abolished the release of cyclooxygenase products of arachidonate metabolism and simultaneously increased cysteinyl-LT release significantly (8.8 +/- 1.4 ng/5 min). Conversely Bay-X1005 completely abolished cysteinyl-LT release and had no significant effect on anaphylactic release of TXB2 and 6-keto-PGF1 alpha. Simultaneous blockade of H1 and H2 receptors abolished release of 6-keto-PGF1 alpha, while release of TXB2 and cysteinyl-LT was not significantly affected. The results indicate that CGRP is not a primary mediator of the immediate hypersensitivity reaction of the heart, but is in turn released by arachidonic acid metabolites of the cyclooxygenase pathway and histamine. In contrast, LT obviously do not contribute to anaphylactic CGRP release. CGRP is a potent coronary vasodilator and could act as endogenous functional antagonist of vasoconstrictor mediators also released during cardiac anaphylaxis such as cysteinyl-LT, platelet activating factor and TXA2.

Improved neurochemical recovery of 6-hydroxydopamine-lesioned postganglionic sympathetic neurons by nerve growth factor in the adult rat

Intraplantar injections of nerve growth factor (NGF; five injections of 4 micrograms each in 30 h intervals) were able to locally improve the recovery of the noradrenaline content in 6-hydroxydopamine (6-OHDA)-lesioned sympathetic nerves in adult rats. Whereas 8 days after the 6-OHDA treatment the noradrenaline content in the paw skin was still less than 10% of control, it reached up to 40% of control levels in NGF injected paws. Intraplantar NGF also significantly improved the recovery of the noradrenaline content in the innervating sciatic nerve, but not in distant tissues. The NGF-induced recovery of noradrenergic nerves was independent of the presence of sensory peptidergic afferents and it could not be mimicked by a local inflammatory response known to raise endogenous NGF production. These results show that rather low doses of exogenous NGF were able to locally restore peripheral noradrenergic nerves after an acute neurotoxin lesion.

Complete recovery by nerve growth factor of neuropeptide content and function in capsaicin-impaired sensory neurons

In the present study the ability of nerve growth factor (NGF) to facilitate the recovery of peptidergic primary sensory C-fibers after an acute capsaicin treatment (50 mg/kg s.c.) was investigated in adult rats. NGF (4 micrograms 1/day for 3 days) was injected into the plantar of one hind paw starting 24 h after the capsaicin treatment. Without NGF, there was a significant reduction of calcitonin gene-related peptide (CGRP) and substance P content of the paw skin and the sciatic nerve. CGRP and substance P levels were completely replenished in the NGF-treated paw skin and in the innervating sciatic nerve they even increased over control levels as determined 40 h after the last injection of NGF. CGRP levels also recovered in the contralateral paw and sciatic nerve, but no recovery was observed in other tissues such as the front paw, the auricle, or the urinary bladder. Mustard oil-induced neurogenic plasma extravasation, taken as a functional parameter for peptidergic primary sensory C-fibers, was significantly decreased after the capsaicin treatment and showed a complete recovery by NGF in the injected paw as well as in the contralateral paw skin. These results show that NGF not only was able to reverse the decrease of transmitter content caused by capsaicin but also restored the peripheral function of primary afferent neurons.

Intraplantar injection of nerve growth factor into the rat hind paw: local edema and effects on thermal nociceptive threshold

Nerve growth factor (NGF) is known to produce hyperalgesia as well as to stimulate synthesis of neuropeptides in dorsal root ganglia (DRG). In the present study, we wanted to determine the effects of local NGF administration and assess to which extent mast cell-dependent factors are mediating NGF responses. Rats received 1 daily unilateral intraplantar injection for 3 days. Local edema (days 1-3), changes in thermal nociceptive threshold (days 1-4), and the content of calcitonin gene-related peptide (CGRP) and substance P (SP) in the sciatic nerve (day 4), were determined. NGF injection caused edema which was absent in rats pretreated with compound 48/80 as well as in rats treated neonatally with capsaicin ('capsaicin denervation'). NGF-induced edema was not reduced by the neurokinin-1 receptor antagonist SR140333, but attenuated by the CGRP receptor antagonist CGRP[8-37]. On each day, NGF injection caused a decrease in thermal nociceptive threshold which lasted for less than 3 h. Capsaicin denervation, but not treatment with indomethacin, abolished NGF-induced thermal hyperalgesia. Treatment with compound 48/80 attenuated hyperalgesia produced by the first, but not by subsequent, NGF injections. On day 4, 24 h after the last of 3 NGF injections, thermal nociceptive threshold was not different from control values, but at that time, CGRP and SP were elevated in the sciatic nerve. We suggest therefore that NGF-induced local edema was caused by mast cell-derived vasoactive compounds which act together with afferent neuron-derived CGRP to increase vascular permeability. NGF-induced thermal hyperalgesia most likely was caused by an increased sensitivity of peripheral endings of capsaicin sensitive afferents. This effect of NGF was not mediated by products of the cyclooxygenase pathway, and was also observed in mast cell-depleted rats.

Stimulation by nerve growth factor of neuropeptide synthesis in the adult rat in vivo: bilateral response to unilateral intraplantar injections

Unilateral intraplantar injections (1/day for 3 days) of 4 mu g nerve growth factor (NGF) into the rat hindpaw increased the expression of prepro-tachykinin (PPT)- and prepro-calcitonin gene-related peptide (ppCGRP)-mRNA in bilateral L5 dorsal root ganglia (DRGs). This was accompanied by an increase of CGRP-like immunoreactivity in the ipsi- and contralateral sciatic nerve but by no detectable change of CGRP-IR in other afferents. NGF injections into the skin of one ear or into the plantar side of one forepaw increased CGRP-IR in the respective afferents (trigeminal ganglion, or nerves arising from the brachial plexus, respectively), but had no effect on sciatic CGRP-IR. This suggests that the NGF-induced symmetrical increase of CGRP synthesis in L5 DRGs was not caused by systemic action of NGF, which, therefore, may be a useful tool to further investigate mechanisms which are responsible for contralateral effects of unilateral inflammation.

The non-peptide NK1 receptor antagonist SR140333 produces long-lasting inhibition of neurogenic inflammation, but does not influence acute chemo- or thermonociception in rats

In anaesthetized rats, the neurokinin (NK)1 receptor antagonist SR140333 (10-1000 micrograms/kg) stereo-selectively inhibited mustard oil-induced plasma protein extravasation in the dorsal skin of the hind paw. After s.c. administration of SR140333, inhibition of plasma protein extravasation was maximal 3 h after injection. A dose of 0.1 mg/kg i.v. or 1.0 mg/kg s.c. produced long-lasting inhibition which was still significant 24 h after treatment. Since systemic administration of SR140333 has been shown to inhibit nociceptive responses in anaesthetized rats, we wanted to evaluate a possible effect of SR140333 on chemo- and thermonociception in conscious rats. SR140333 (100 micrograms/kg s.c.) did not reduce the behavioral response of rats to the irritant effect of capsaicin in the wiping test, nor did it affect the thermal nociceptive threshold in the plantar test. Furthermore, the decrease in thermal nociceptive threshold which was produced by intraplanter injection of PGE2, and which has been shown to be entirely dependent on capsaicin-sensitive afferents, was not affected by treatment with this NK1 receptor antagonist. These results show that systemic administration of SR140333, at doses which cause inhibition of neurogenic inflammation, has no detectable effect on acute chemo- or thermonociception in conscious rats.

Neuroantibodies: ectopic expression of a recombinant anti-substance P antibody in the central nervous system of transgenic mice

Recombinant antibodies are efficiently secreted by cells of the nervous system. Thus, their local expression in the CNS of transgenic mice could be used to perturb the function of the corresponding antigen. As a first application of this approach, we have generated transgenic mice that express antibodies against the neuropeptide substance P, under the transcriptional control of the promoter of the neuronal gene vgf. The transgenic antibodies are expressed in a tissue-specific and developmentally regulated manner and are effective in competing with the endogenous substance P, as demonstrated by a marked inhibition of neurogenic inflammation and by motor deficits. This phenotypic knockout approach may provide a complementary alternative to gene knockout by homologous recombination.

Histamine-induced edema in the rat paw--effect of capsaicin denervation and a CGRP receptor antagonist

Histamine is known to cause edema and excitation of small-diameter primary afferent neurons. In the present study we wanted to investigate to which extent afferent neurons participate in histamine-induced edema and, subsequently, determine possible inhibitory effects of a tachykinin NK1 receptor and CGRP receptor antagonist on the histamine response. Intraplantar injection of histamine (0.5 mumol) into the rat hind paw caused a 34% increase of paw volume. In capsaicin-denervated rats, this effect of histamine was nearly abolished. The calcitonin gene-related peptide (CGRP) receptor antagonist CGRP-(8-37), but not the tachykinin NK1 receptor antagonist SR140333, caused significant inhibition of the edema response. Further indication that CGRP can promote the histamine action was obtained in capsaicin-denervated rats, where co-injection of CGRP (0.3 pmol) increased the edema response to intraplantar histamine. In additional experiments, plasma protein extravasation in the paw skin was evaluated after close arterial infusion of histamine. Also in these experiments CGRP-(8-37), but not SR140333, significantly reduced the histamine effect. The observation that in the rat hind paw a CGRP receptor antagonist, but not a tachykinin NK1 receptor antagonist, attenuates histamine-induced vascular leakage raises the possibility that in some tissues CGRP receptor antagonists may be superior to tachykinin NK1 receptor antagonists in reducing histamine-induced neurogenic inflammatory responses.

Stereoselective increase of plasma concentrations of the enantiomers of propranolol and atenolol during exercise

OBJECTIVE

In vitro studies have shown that, like catecholamines, both propranolol and atenolol are taken up by and released from adrenergic cells. We performed this study to investigate whether this may also play a role in humans and whether stereoselective aspects are important.

METHODS

This was a randomized, double-blind, placebo-controlled, crossover study of two groups of 12 healthy volunteers. Subjects received single oral doses of 80 mg (R,S)-, 40 mg (R)-, and 40 mg (S)-propranolol; 100 mg (R,S)-, 50 mg (R)-, and 50 mg (S)-atenolol; and placebo at intervals of 1 week. Exercise was performed at 4 and 9 hours after drug intake, and blood samples were taken before and at the end of each exercise period. The plasma concentrations of the (R)- and (S)-enantiomers of propranolol and atenolol, as well as those of epinephrine and norepinephrine, were determined by HPLC.

RESULTS

Effects of exercise on the plasma levels of the enantiomers of propranolol and atenolol were similar. When the optically pure enantiomers were administered, exercise caused a marked and significant increase of the plasma concentrations of the (S)- but not of the (R)-enantiomers. When the drugs were administered in the racemic form, the plasma levels of both the (R)- and (S)-enantiomers were elevated to the same extent. The increase of norepinephrine levels during exercise was more pronounced than that of epinephrine and paralleled that of the (S)-enantiomers of the beta-blockers.

CONCLUSION

Bearing the in vitro data in mind, we conclude that (S)-propranolol and (S)-atenolol are taken up into and released from adrenergic cells together with norepinephrine during exercise. The reason why the plasma concentrations of (R)-propranolol and (R)-atenolol are increased only during exercise in the presence of the corresponding (S)-enantiomers remains to be determined.

Neonatal capsaicin treatment does not prevent splanchnic vasodilatation in portal-hypertensive rats

It has been suggested that the peripheral sensory neurons are involved in the splanchnic hemodynamic changes of portal hypertension. Therefore the influence of permanent ablation of sensory neurons by neonatal capsaicin pretreatment (50 mg/kg, subcutaneously) on the development of the hyperdynamic splanchnic circulation in portal-hypertensive rats was studied. In adulthood, portal hypertension was induced with partial portal vein ligation. In study 1, systemic and splanchnic hemodynamics were measured by means of a radiolabeled-microsphere technique in portal-hypertensive rats, under ketamine anesthesia, pretreated with capsaicin or vehicle. Mean arterial pressure, heart rate, cardiac index, systemic and splanchnic vascular resistance, portal pressure, portal venous inflow, portal-collateral resistance and portal-systemic shunting were not significantly different between capsaicin-pretreated and vehicle-pretreated rats. In study 2, gastric mucosal blood flow, measured by means of hydrogen gas clearance, and the hemoglobin and oxygen content of the gastric mucosa, as assessed with reflectance spectrophotometry, were not significantly different in the two groups of anesthetized portal-hypertensive rats pretreated with capsaicin or vehicle. In study 3, we confirmed the effectiveness of neonatal capsaicin pretreatment by measuring calcitonin gene-related peptide content of the gastric corpus wall. Capsaicin pretreatment caused a depletion of calcitonin gene-related peptide by at least 98% compared with that in vehicle-pretreated rats. These results do not support a role of capsaicin-sensitive sensory neurons that innervate the gastrointestinal tract in the development of the splanchnic vasodilatation characteristically observed in chronic portal hypertension.

Human and rat primary C-fibre afferents store and release secretoneurin, a novel neuropeptide

Secretoneurin is a recently discovered neuropeptide derived from secretogranin II (SgII). Since this peptide could be detected in the dorsal horn of the spinal cord we studied whether it is localized in and released from primary afferent neurons. Secretoneurin was investigated with immunocytochemistry and radioimmunoassay in spinal cord, dorsal root ganglia and peripheral organs. SgII mRNA was determined in dorsal root ganglia. Normal rats and rats pre-treated neonatally with capsaicin to destroy selectively polymodal nociceptive (C-) fibres were used. Slices of dorsal spinal cord were perfused in vitro for release experiments. Immunocytochemistry showed a distinct distribution of secretoneurin-immunoreactivity (IR) in the spinal cord and, lower brainstem. A particularly high density of fibres was found in lamina I and outer lamina II of the caudal trigeminal nucleus and of the spinal cord. This distribution was qualitatively identical in rat and human post-mortem tissue. Numerous small diameter and some large dorsal root ganglia neurons were found to contain SgII mRNA. Capsaicin treatment led to a marked depletion of secretoneurin-IR in the substantia gelatinosa, but not in other immunopositive areas of the spinal cord and to a substantial loss of small (< 25 microns) SgII-mRNA-containing dorsal root ganglia neurons. Radioimmunoassay revealed a significant decrease of secretoneurin-IR in the dorsal spinal cord, the trachea, heart and urinary bladder of capsaicin-treated rats. Perfusion of spinal cord slices with capsaicin as well as with 60 mM potassium led to a release of secretoneurin-IR. In conclusion, secretoneurin is a neuropeptide which is stored in and released from capsaicin-sensitive, primary afferent (C-fibre) neurons.(ABSTRACT TRUNCATED AT 250 WORDS)

Bradykinin-induced sensitization of afferent neurons in the rat paw

Determination of the thermal nociceptive threshold in the rat hind paw was used to investigate the participation of postganglionic sympathetic neurons and of capsaicin-sensitive afferent neurons to bradykinin-induced thermal hyperaesthesia. Intraplantar injection of 0.5 microgram bradykinin or of 0.3 microgram prostaglandin E2 significantly lowered paw withdrawal latencies, whereas injection of [des-Arg9]bradykinin was ineffective. The B-2 receptor antagonist HOE 140 (0.1 mg/kg) prevented bradykinin- but not prostaglandin E2-induced thermal hyperaesthesia. While morphine (1 mg/kg) antagonized the effect of bradykinin and prostaglandin E2, indomethacin (10 mg/kg) reduced only bradykinin-induced sensitization. Although this can be taken as indication that bradykinin-induced sensitization of heat-sensitive fibres is mainly mediated via local prostanoid formation, we failed to obtain evidence for an involvement of sympathetic postganglionic fibres in this process: chemical sympathectomy, which lowered the tissue concentration of noradrenaline by more than 90%, did not influence the ability of bradykinin to induce a decrease in thermal nociceptive threshold. The target of bradykinin/prostaglandin E2 action seemed to be capsaicin-sensitive afferents, since in rats which had been treated with capsaicin to destroy this group of afferents, both substances were completely ineffective in producing sensitization. We suggest therefore that in the rat paw, bradykinin, independently from sympathetic postganglionic neurons, lowers the thermal nociceptive threshold mainly via B-2 receptor-mediated formation of cyclo-oxygenase products which, in turn, act exclusively on capsaicin-sensitive afferent neurons.