Perineural capsaicin induces the uptake and transganglionic transport of choleratoxin B subunit by nociceptive C-fiber primary afferent neurons

The distribution of spinal primary afferent terminals labeled transganglionically with the choleratoxin B subunit (CTB) or its conjugates changes profoundly after perineural treatment with capsaicin. Injection of CTB conjugated with horseradish peroxidase (HRP) into an intact nerve labels somatotopically related areas in the ipsilateral dorsal horn with the exceptions of the marginal zone and the substantia gelatinosa, whereas injection of this tracer into a capsaicin-pretreated nerve also results in massive labeling of these most superficial layers of the dorsal horn. The present study was initiated to clarify the role of C-fiber primary afferent neurons in this phenomenon. In L5 dorsal root ganglia, analysis of the size frequency distribution of neurons labeled after injection of CTB-HRP into the ipsilateral sciatic nerve treated previously with capsaicin or resiniferatoxin revealed a significant increase in the proportion of small neurons. In the spinal dorsal horn, capsaicin or resiniferatoxin pretreatment resulted in intense CTB-HRP labeling of the marginal zone and the substantia gelatinosa. Electron microscopic histochemistry disclosed a dramatic, ∼10-fold increase in the proportion of CTB-HRP-labeled unmyelinated dorsal root axons following perineural capsaicin or resiniferatoxin. The present results indicate that CTB-HRP labeling of C-fiber dorsal root ganglion neurons and their central terminals after perineural treatment with vanilloid compounds may be explained by their phenotypic switch rather than a sprouting response of thick myelinated spinal afferents which, in an intact nerve, can be labeled selectively with CTB-HRP. The findings also suggest a role for GM1 ganglioside in the modulation of nociceptor function and pain.

Molecular and functional changes in glucokinase expression in the brainstem dorsal vagal complex in a murine model of type 1 diabetes

Glucose concentration changes in the nucleus tractus solitarius (NTS) affect visceral function and metabolism by influencing central vagal circuits, especially inhibitory, GABAergic NTS neurons. Acutely elevated glucose can alter NTS neuron activity, and prolonged hyperglycemia and hypoinsulemia in animal models of type 1 diabetes results in plasticity of neural responses in the NTS. NTS neurons contributing to metabolic regulation therefore act as central glucose sensors and are functionally altered in type 1 diabetes. Glucokinase (GCK) mediates cellular utilization of glucose, linking increased glucose concentration to excitability changes mediated by ATP-sensitive K(+) channels (KATP). Using quantitative reverse transcriptase-polymerase chain reaction (RT-PCR), Western blot, and in vitro electrophysiology, we tested the hypothesis that changes in GCK expression in the NTS accompany the development of diabetes symptoms in the streptozotocin (STZ)-treated mouse model of type 1 diabetes. After several days of hyperglycemia in STZ-treated mice, RNA expression of GCK, but not Kir6.2 or SUR1, was decreased versus controls in the dorsal vagal complex. Electrophysiological recordings in vitro indicated that neural responses to acute hyperglycemia, and synaptic responsiveness to blockade of GCK with glucosamine, were attenuated in GABAergic NTS neurons from STZ-treated mice, consistent with reduced molecular and functional expression of GCK in the vagal complex of hyperglycemic, STZ-treated mice. Altered autonomic responses to glucose in type 1 diabetes may therefore involve reduced functional GCK expression in the dorsal vagal complex.

The Effect of Pressure on the Hydrogen Bond Structure of Liquid Water

The results of molecular dynamics simulations of low and high pressure liquid water using a modified central force potential have been analyzed in order to study the effect of pressure on the hydrogen bond structure of water. The properties investigated and discussed include the hydrogen bond angle distribution, the O -O distance distribution between the neighbour molecules, the structure of the first coordination sphere in the high density liquid and the average number of hydrogen bonds.

The Dependence of the Internal Vibrational Frequencies of Liquid Water on Central Force Potentials

The differences in the liquid phase internal vibrational frequencies of water, obtained from molecular dynamics (MD) simulations, between the two versions of the central force model of Rahman and Stillinger (CF1 and CF2) are investigated by employing the theory of Buckingham on solvent effects. It is found that the differences can be essentially accounted for by the different O-H stretching cubic anharmonic force constants of CF1 and CF2. A significantly improved agreement between the results of MD simulations and spectroscopically observed liuqid phase frequencies could be achieved by using a harmonic force field, supplemented by a cubic stretching force constant, for the intramolecular interactions of water, and the CF2 potential for the intermolecular interactions.

Molecular Dynamics Study of the Effect of Pressure on an Aqueous NaCl Solution

Molecular dynamics simulations of a 2.2 molal NaCI solution at room temperature and pressure of 1 bar and 10 kbar have been performed employing a modified version of the central-force model of water. The changes in the structural and dynamical properties of the solution resulting from the increase in pressure are reported. The effect of ions on the self-diffusion coefficients of hydration and bulk water and on the IR spectroscopical properties of the solution is also discussed and compared with the available experimental data.

Rapid genotyping of genetically modified laboratory animals from whole blood samples without DNA preparation

A new, rapid method is described which permits the genotyping of genetically modified animals from a microlitre volume of whole blood samples via one step polymerase chain reaction amplification. The major advantage of the presented method is the exclusion of a DNA preparation step, which significantly reduces the time expenditure and work load of the genetic testing. Pilot studies indicate, that this method is efficient and applicable also on tissue biopsies and larger amount of blood providing a rapid and reliable new technique over conventional genotyping approaches.

Ischaemic postconditioning reduces serum and tubular TNF-α expression in ischaemic-reperfused kidney in healthy rats

OBJECTIVE

We studied the protective effects of postconditioning (PS) in healthy and hypercholesterolemic rats after renal ischaemia-reperfusion (IR) injury. We aimed to examine cytokine expression and apoptosis in tissue damage after revascularisation (TNF-α levels in serum and tissue).

METHODS

Male Wistar rats (n = 32) were divided into four groups. The animals of normal feed groups (NF) were fed with normal rat chow and the cholesterol feed groups (CF) were fed with 1.5% cholesterol containing diet for 8 weeks. Anaesthetized rats underwent a 45-min cross-clamping in both kidney pedicles. Ischaemia was followed by 120-min reperfusion with or without PS protocol (group PS vs. IR). Postconditioning was induced by four intermittent periods of ischaemia-reperfusion of 15-s duration each. Serum cholesterol, triglyceride, urea and creatinine levels were determined. Proinflammation was characterized by the measurement of serum TNF-α. Tissue injury in kidney was determined by formaline-fixed, paraffin-embedded tissue sections. Tissue TNF-α levels were determined by immunohistochemistry.

RESULTS

Significant elevation was observed in serum TNF-α level after IR injury in normal feed groups, which was reduced by PS. In CF group neither the elevation nor the postconditioning induced reduction were as significant as in the NF groups. In normal feed group PS caused a significant reduction in tissue TNF-α level which was significantly higher in CF.

CONCLUSIONS

Ischaemic postconditioning proved to be an effective defense against IR in NF groups, but it was ineffective in CF groups in kidney tissue.

Effect of vitamin E on reperfusion injuries during reconstructive vascular operations on lower limbs

INTRODUCTION

The challenge against reperfusion injury and tissue oxidative stress, especially in vascular surgical interventions has an essential importance to reach the optimal clinical result. Numerous experimental attempts have proved the positive antioxidant effect of vitamin E in both chronic and acute phase models. In our study we monitored the effect of continuous preoperative treatment with vitamin E, on oxidative stress and tissue inflammation reactions developed after reconstructive operations.

PATIENTS AND METHODS

32 patients have been involved in a randomized, prospective study, all suffering from AFS occlusion proved by angiography, and all undergone supragenual reconstruction. Duration of ischemia and amount of tissues under vascular clamping were almost the same in all patients. In the group treated with E-vitamin, we administered 1 x 200 mg of vitamin E p/o from the preoperative day till the 7th post operative day. Patients of the second group did not receive vitamin E.

MATERIALS AND METHODS

Peripheral blood samples were collected immediately before operation and at the end of the second reperfusion hour (early reperfusion period). Late reperfusion period has been monitored by analyzing blood samples taken at 24th hour and 7th day next to the operative ischemia. Among oxidative stress parameters, direct measurement of reactive oxygen intermediator (ROI) and determination of antioxidant state (GSH, Total-SH group, SOD) have been performed. Malondialdehyde was chosen as marker for lipidperoxidation. Inflammation reactions were monitored up on expression of adhesion molecules (CD11a and CD18). We also controlled the oscillation of myeloperoxidase (MPO) activity.

RESULTS

Our study has proved that preoperative (from the preoperative day till the 7th post operative day) administration of 200 mg vitamin E could reduce the level of oxidative stress developed after ischemic-reperfusion insult (lipidproxidation, antioxidant enzymes). According to our results, the prooxidant-antioxidant imbalance also diminished in the group with E-vitamin treatment. We proved that elective administration of vitamin E could decrease the WBC activity (MPO activity, free radicals production, expression of adhesion molecules) and its consequential local inflammation process, during early reperfusion.

Pathology and diagnostic options of lower limb compartment syndrome

BACKGROUND

The indication of surgical treatment in lower limb compartment syndrome mostly depends on the clinical signs which can be often uncertain, resulting in delayed insufficient intervention.

AIM

The aim of the study was to evaluate the progression of compartment syndrome by measuring of intracompartmental pressure and monitoring of decreased tissular oxygenation, indicating an insufficient secondary microcirculation.

MATERIALS AND METHODS

16 patients were examined in our study (12 males, 4 females, mean age: 62.7+/-9.5 years), who underwent acute lower limb revascularization surgery for a critical (lasting more than 4 hours) limb ischemia. The indications were: 5 iliac artery embolizations and 11 femoral artery occlusions. After revascularization, on the second postoperative day, we detected significant lower limb edema and swelling of several grade. To monitor the elevated intracompartmental pressure (ICP) and to evaluate the extremital circulation, we used KODIAG pressure meter and the tissular oxygen saturation (StO2) was measured by near-infrared-spectroscopy.

RESULTS

In 12 cases the ICP exceeded the critical 40 mmHg. In these patients the average StO2 was 50-53%, in spite of complete recanalization. In these cases we made urgent, semi-open fasciotomy. In 4 cases, where the clinical aspect showed compartment syndrome, the measured parameters did not indicate a surgical intervention (ICP: 25-35 mmHg, StO2: around normal).

SUMMARY

A novel approach in our examination is that, besides empirical therapeutic guidelines generally applied in clinical practice, we established an objective, parameter-based ("evidence based medicine") surgical indication strategy for the lower limb compartment syndrome. Our parameter results produced by the above pressure and saturation measurements help the clinicians to decide between conservative and operative treatment of the disease.

Involvement of capsaicin-sensitive afferent nerves in the proteinase-activated receptor 2-mediated vasodilatation in the rat dura mater

Neurogenic inflammation of the dura mater encephali has been suggested to contribute to the mechanisms of meningeal nociception and blood flow regulation. Recent findings demonstrated that the rat dura mater is innervated by trigeminal capsaicin-sensitive peptidergic nociceptive afferent nerves which mediate meningeal vascular responses through activation of the transient receptor potential vanilloid type 1 (TRPV1) receptor. The present work explored the functional significance of the capsaicin-sensitive subpopulation of dural afferent nerves via their contribution to the meningeal vascular responses evoked through activation of the proteinase-activated receptor 2 (PAR-2). The vascular responses of the dura mater were studied by laser Doppler flowmetry in a rat open cranial window preparation. Topical applications of trypsin, a PAR-2-activator, or Ser-Leu-Ile-Gly-Arg-Leu-amide (SLIGRL-NH(2)), a selective PAR-2 agonist peptide, resulted in dose-dependent increases in meningeal blood flow. The SLIGRL-NH(2)-induced vasodilatation was significantly reduced following capsaicin-sensitive afferent nerve defunctionalization by prior systemic capsaicin treatment and by pretreatment of the dura mater with the calcitonin gene-related peptide (CGRP) receptor antagonist CGRP(8-37). Nomega-nitro-L-arginine methyl ester hydrochloride (L-NAME) an unspecific inhibitor of nitric oxide (NO) production, but not 1-(2-trifluoromethylphenyl) imidazole (TRIM), a neuronal NO synthase inhibitor, also inhibited the vasodilator response to SLIGRL-NH(2). The vasodilator responses elicited by very low concentrations of capsaicin (10 nM) were significantly enhanced by prior application of SLIGRL-NH(2). The present findings demonstrate that activation of the PAR-2 localized on capsaicin-sensitive trigeminal nociceptive afferent nerves induces vasodilatation in the dural vascular bed by mechanisms involving NO and CGRP release. The results indicate that the PAR-2-mediated activation and sensitization of meningeal capsaicin-sensitive C-fiber nociceptors may be significantly implicated in the pathophysiology of headaches.

Distribution of substance P in brain and periphery and its possible role as a co-transmitter

Substance P is widely distributed in the nervous system. In brain and spinal cord it may act as a transmitter, for example at the central branches of primary sensory neurons. It may also be released from the sensory nerve endings and is thought to be involved in antidromic vasodilatation and in synaptic transmission in autonomic ganglia. In some central neurons substance P is stored together with 5-hydroxytryptamine and thyrotropin-releasing hormone. These neurons project to the ventral horn of the spinal cord, amongst other places. In another system substance P coexists with a cholecystokinin-like peptide. These neurons are localized in the periaqueductal central grey matter and also project to the spinal cord. Finally, injection of a substance P antagonist into the ventral mesencephalon causes marked morphological changes in neurons that contain dopamine, substance P and gamma-aminobutyric acid (GABA).

Reperfusion injury and inflammatory responses following acute lower limb revascularization surgery

After revascularization of an acute arterial occlusion the development of a serious ischaemic-reperfusion injury is a menacing challenge and a hard task in peripheral vascular surgery. A whale of evidences point to oxidative stress, as an important trigger, in the complex chain of events leading to reperfusion injury. In the present study authors aimed to examine oxidative stress parameters, antioxidant-prooxidant state and leukocyte adhesion molecules (CD11a and CD18) expression following acute revascularization surgery of lower limb.10 patients were examined in the prospective randomized study. Peripheral blood sample was collected in ischaemic period, and after reperfusion in the 2nd and 24th hours, and on 7th day. Superoxide-dismutase activity, reduced glutathion concentration and leukocytes free radical production were measured. The degree of lipidperoxidation was marked with the quantity of malondialdehyde. The expressions of adhesion molecules were measured with flowcytometry.The speed and rate of free radical production significantly increased in the early reperfusion (p<0.05). The level of antioxidant enzymes decreased after revascularization. The CD11a and CD18 expression of the granulocytes significantly (p<0.05) decreased right after the revascularization, but with a gradual elevation until the 7th day they exceed the ischaemic value. Our results showed a time specific turnover of the sensitive antioxidant-prooxidant balance after revascularization operation.

Ischaemic postconditioning reduces peroxide formation, cytokine expression and leukocyte activation in reperfusion injury after abdominal aortic surgery in rat model

OBJECTIVE

We studied the protective effects of ischaemic postconditioning (PS) on ischemia-reperfusion injury of the lower extremities in a rat model of abdominal aortic intervention. We aimed to examine the evoked oxidative stress, cytokine expression and leukocyte activation after revascularisation surgery.

METHODS

Anesthetized animals (48 Whistar rats) underwent a 60 min infrarenal aorta cross-clamping. After the ischaemic period, an intermittent 4 times 15 s reperfusion--15 seconds ischaemic episodes--were applied (ischaemic postconditioning: group PS). Then we started a 120 min reperfusion in the aorta. In untreated group animals underwent a long ischaemia (60 min) and the following reperfusion (group IR). Peripherial blood samples were collected before operation, and in early (5, 10, 15, 30, 60 and 120 min) reperfusion periods. Serum peroxide level, TNF-alpha concentration, myeloperoxidase (MPO) activity and PMA-induced leukocyte ROS production were measured.

RESULTS

In PS group, plasma peroxide level elevation was significantly lower in very early reperfusion (5-30 min) comparing to non-conditioned IR group (10.04+/-1.9 microM/l vs. 16.91+/-3.67 microM/l, p<0.05). PS also reduced serum TNF-alpha concentration (167.41+/-31.26 microg/ml vs. 116.55+/-12.04 microg/ml, p<0.05), MPO activity (1.759+/-0.239 microM/ml vs. 1.22+/-0.126 microM/ml, p<0.05) and leukocyte activation detected by PMA-induced leukocyte ROS production (5.7+/-0.96 AU/10(3) cells vs. 4.63+/-0.69 AU/10(3) cells).

CONCLUSIONS

Ischaemic postconditioning could reduce ROI production after IR in early reperfusion period, thus limiting ROI mediated tissue lesion, cytokine-leukocyte activation and inflammatory responses. PS seems to be an effective tool in vascular surgery to reduce reperfusion injuries after revascularization interventions.

Analyzing of segregation in mixtures of 3-methylpyridine and heavy water by dynamic neutron radiography

The closed-loop phase diagram of 3-methylpyridine-heavy water mixture was studied, to our best knowledge, for the first time with dynamic neutron radiography (DNR) at the 10MW VVR-SM Research Reactor in Budapest (Hungary). Visualized were the (i) lower temperature non-segregated states (below 38 degrees C), (ii) transition (40-43 degrees C), (iii) segregated states (46-128 degrees C), (iv) higher temperature transition (110-128 degrees C) and (v) higher temperature non-segregated states. The non-segregated state belonging to 141 degrees C, was found to be definitely dissimilar from the lower temperature state. Existence of a solid-like structure at the liquid-liquid interface was indicated.

Transganglionic transport of choleragenoid by capsaicin-sensitive C-fibre afferents to the substantia gelatinosa of the spinal dorsal horn after peripheral nerve section

Choleratoxin B subunit-binding thick myelinated, A-fibre and unmyelinated, capsaicin-sensitive nociceptive C-fibre primary afferent fibres terminate in a strict topographic and somatotopic manner in the spinal cord dorsal horn. Injection of choleratoxin B subunit-horseradish peroxidase conjugate into injured but not intact peripheral nerves produced transganglionic labelling of primary afferents not only in the deeper layers (Rexed's laminae III-IV), but also in the substantia gelatinosa (Rexed's laminae II) of the spinal dorsal horn. This was interpreted in terms of a sprouting response of the Abeta-myelinated afferents and suggested a contribution to the pathogenesis of neuropathic pain [Nature 355 (1992) 75; J Comp Neurol 360 (1995) 121]. By utilising the selective neurotoxic effect of capsaicin, we examined the role of C-fibre sensory ganglion neurons in the mechanism of this phenomenon. Elimination of these particular, capsaicin-sensitive C-fibre afferents by prior intrathecal or systemic capsaicin treatment inhibited transganglionic labelling by the choleratoxin B subunit-horseradish peroxidase conjugate of the substantia gelatinosa evoked by chronic sciatic nerve section. More importantly, prior perineural capsaicin treatment of the transected nerve proximal to the anticipated site of injection of choleragenoid 12 hours later prevented the labelling of the substantia gelatinosa, but not that of the deeper layers. Electron microscopic examination of the dorsal roots revealed no significant difference in the proportion of labelled myelinated fibres relating to the intact (54.4+/-5.5%) and the transected (62.4+/-5.4%) sciatic nerves. In contrast, the proportion of labelled unmyelinated dorsal root axons relating to the transected, but not the intact nerves showed a significant, six-fold increase after sciatic nerve transection (intact: 4.9+/-1.3%; transected: 35+/-6.7%). These observations indicate that peripheral nerve lesion-induced transganglionic labelling of the substantia gelatinosa by choleratoxin B subunit-horseradish peroxidase may be primarily accounted for by the uptake and transganglionic transport of choleragenoid by injured capsaicin-sensitive C-fibre afferents rather than a sprouting response of A-fibre afferents. The present findings suggest an essential role of capsaicin-sensitive primary sensory neurons in lesion-induced spinal neuroplastic changes and provide further support for C-fibre nociceptor neurons being promising targets for the development of new strategies in pain management.

Peripheral nerve lesion-induced uptake and transport of choleragenoid by capsaicin-sensitive c-fibre spinal ganglion neurons

In the present experiments the effect of systemic capsaicin treatment on the retrograde labelling of sensory ganglion cells was studied following the injection of choleratoxin B subunit-horseradish peroxidase conjugate (CTX-HRP) into intact and chronically transected peripheral nerves. In the control rats CTX-HRP injected into intact sciatic nerves labelled medium and large neurons with a mean cross-sectional area of 1,041 +/- 39 gm2. However, after injection of the conjugate into chronically transected sciatic nerves of the control rats, many small cells were also labelled, shifting the mean cross-sectional area of the labelled cells to 632 +/- 118 microm2. Capsaicin pretreatment per se induced a moderate but significant decrease in the mean cross-sectional area of the labelled neurons (879 +/- 79 microm2). More importantly, systemic pretreatment with capsaicin prevented the peripheral nerve lesion-induced labelling of small cells. Thus, the mean cross-sectional areas of labelled neurons relating to the intact and transected sciatic nerves, respectively, did not differ significantly. These findings provide direct evidence for a phenotypic switch of capsaicin-sensitive nociceptive neurons after peripheral nerve injury, and suggest that lesion-induced morphological changes in the spinal cord may be related to specific alterations in the chemistry of C-fibre afferent neurons rather than to a sprouting response of A-fibre afferents.

Capsaicin stimulation of the cochlea and electric stimulation of the trigeminal ganglion mediate vascular permeability in cochlear and vertebro-basilar arteries: a potential cause of inner ear dysfunction in headache

Trigeminal neurogenic inflammation is one explanation for the development of vascular migraine. The triggers for this inflammation and pain are not well understood, but are probably vasoactive components acting on the blood vessel wall. Migraine-related inner ear symptoms like phonophobia, tinnitus, fluctuation in hearing perception and increased noise sensitivity provide indirect evidence that cochlear blood vessels are also affected by basilar artery migraine. The purpose of this investigation was to determine if a functional connection exists between the cochlea and the basilar artery. Neuronally mediated permeability changes in the cochlea and basilar artery were measured by colloidal silver and Evans Blue extravasation, following orthodromic and antidromic stimulation of the trigeminal ganglion innervating the cochlea. Capsaicin and electrical stimulation induced both dose- and time-dependent plasma extravasation of colloidal silver and Evans Blue from the basilar artery and anterior inferior cerebellar artery. Both orthodromic and antidromic activation of trigeminal sensory fibers also induced cochlear vascular permeability changes and significant quantitative differences between the treated and control groups in spectrophotometric assays. These results characterize a vasoactive connection between the cochlea and vertebro-basilar system through the trigeminal sensory neurons. We propose that vertigo, tinnitus and hearing deficits associated with basilar migraine could arise by excitation of the trigeminal nerve fibers in the cochlea, resulting in local plasma extravasation. In addition, cochlear "dysfunction" may also trigger basilar and cluster headache by afferent input to the trigeminal system.

Inhibitory neurogenic modulation of histamine-induced cutaneous plasma extravasation in the pigeon

The neurohumoral modulation of the permeability increasing effect of histamine was studied in pigeon skin. Substances were administered through plasmapheresis capillaries inserted into the dorsal wing skin and the protein contents of the perfusates were determined by a quantitative method. The vascular labelling technique was also utilized to histologically identify leaky blood vessels. In the innervated skin histamine evoked a significant, dose-dependent plasma extravasation which was markedly augmented by the coadministration of a specific galanin receptor antagonist, galanin-1-16-bradykinin-2-9-amide (M35). Chronic cutaneous denervation per se resulted in a significant elevation of the permeability-enhancing effect of histamine. In the denervated skin this response was not affected by M35 but was significantly inhibited by galanin. It is concluded that in the normally innervated skin endogenous galanin may exert a neurogenic tonic inhibitory effect on histamine-induced plasma leakage. It is suggested that sensory nerves possess not only pro-inflammatory, but also anti-inflammatory (inhibitory) sensory-efferent functions.

Capsaicin-sensitive mechanisms are involved in cortical spreading depression-associated cerebral blood flow changes in rats

We tested the hypothesis that capsaicin-sensitive mechanisms play a role in the cortical spreading depression (CSD)-related changes in cortical blood flow (CBF). CBF was measured with laser Doppler flowmetry in anesthetized rats. The animals were treated with capsaicin before (48 h-2 weeks) or during the experiments. This agent is thought to stimulate small-diameter sensory nerve fibers selectively and to deplete stored peptides. In the vehicle-treated group (n=8), the peak value of the CSD-associated hyperperfusion was 257+/-12% above the baseline (mean+/-SEM, P<0.05). In the groups treated with 20 and 40 microg/kg or 20 mg/kg capsaicin, there were only small decreases in CBF. In the groups treated with 100 mg/kg capsaicin, the CSD-associated hyperemia was reduced at 48 h (158+/-7%, P<0.05). However, at 96 h a transient hyperresponsiveness (390+/-38%, P<0.05) was observed, which had disappeared by 2 weeks. These results indicate that the manipulation of sensory neuropeptide stores results in a biphasic effect on CSD-induced CBF responses.

Galanin mediated inhibitory nervous modulation of cutaneous vascular reactions

Noxious stimulation induces local inflammatory responses in a variety of mammals but these reactions are only faint in avian species. The possibility that endogenous galanin inhibits neurogenic vascular responses in avians was tested in the wing skin of anaesthetized pigeons. Intraarterial infusion of nanomolar concentrations of the specific galanin antagonist M35 dose dependently enhanced the small mustard oil induced increase of skin blood flow measured by means of a Laser Doppler Imager. Similarly, the small transient vasodilatation following electrical stimulation of a cutaneous nerve was also enhanced by M35. The effect of M35 was not observed after chronic denervation. Coperfusion of M35 dose dependently augmented the histamine and bradykinin induced plasma extravasation revealed by skin microdialyses, but this effect was abolished in the chronically denervated skin. However, chronic denervation per se enhanced the plasma extravasation induced by histamine but not by bradykinin and this effect was diminished by coperfusion of galanin. The results suggest an inhibitory modulation of cutaneous neurogenic inflammatory reactions by endogenous galanin in the pigeon.

Inhibitory modulation of cutaneous vascular responses by endogenous galanin in the pigeon

The possible role of endogenous galanin in modulation of cutaneous vascular responses was studied in pigeons. Chemically induced plasma extravasation and regional skin blood flow changes were measured simultaneously with a capillary perfusion technique and a laser Doppler imager, respectively. Perfusion with both histamine and bradykinin increased plasma protein extravasation which was dose-dependently and significantly augmented by co-administration of M35, a specific galanin antagonist. This effect of M35 was abolished after chronic cutaneous denervation. In intact but not denervated skin, M35 increased the vasodilatatory effect of histamine, too. It is suggested that galanin-containing nerves may play an inhibitory efferent role in the modulation of cutaneous inflammatory responses.

Changes in fibre populations of the rat hairy skin following selective chemodenervation by capsaicin

Perineural application of capsaicin results in a selective and permanent reduction in the sensitivity to noxious chemical and heat stimuli and elimination of the neurogenic inflammatory response. The present quantitative immunohistochemical study has been undertaken to reveal the populations of cutaneous afferent nerves that are affected by perineural capsaicin treatment. Areas of intact and chemodenervated skin were determined with the aid of the vascular labelling technique. In sections taken from intact skin areas, staining with antibodies against protein gene product 9.5 revealed a rich epidermal innervation. Fibres immunoreactive for growth-associated protein 43 were also abundant; nerve fibres immunoreactive for substance P and calcitonin gene-related peptide were less numerous. Somatostatin- and RT97-immunoreactive fibres were seen only in the subepidermal layer. In sections taken from skin areas supplied by the sciatic nerve treated with capsaicin 3 days previously, the number of epidermal nerve fibres immunoreactive to protein gene product 9.5, growth-associated protein 43, substance P and calcitonin gene-related peptide was reduced by 90%, 95%, 97% and 66%, respectively. These changes persisted for at least 42 days. The findings reveal that the majority of epidermal axons are capsaicin-sensitive and comprise a chemically heterogeneous population. Reductions in cutaneous fibre populations following perineural capsaicin treatment may result from both the degeneration of sensory axons and the depletion of neuron-specific macromolecules. In addition, most cutaneous nociceptive axons may not use the major sensory neuropeptides substance P and calcitonin gene-related peptide as afferent neurotransmitters.

Beta-amyloid (1-42) peptide impairs blood-brain barrier function after intracarotid infusion in rats

The effects of intracarotid infusions of beta-amyloid (1-42) peptide was studied on the permeability of brain vessels. Using a quantitative Evans blue method a dose-dependent increase of brain tissue albumin content was established following intracarotid injections of the peptide. Cerebral vessels of increased permeability were also demonstrated with a vital 'staining' technique. Lectin histochemistry revealed an almost complete abolition of specific lectin binding sites of affected endothelial cells. The findings indicate a significant deterioration by beta-amyloid (1-42) peptide of blood-brain barrier function and suggest that this may result from endothelial damage. It is assumed that altered permeability of cerebral vessels may be involved in the development of brain pathologies associated with Alzheimer's disease.

Evidence for an inhibition by endogenous galanin of neurogenic cutaneous vasodilatation in the pigeon

The effect of high affinity galanin antagonist M35 on neurogenic cutaneous vasodilatation has been studied in the pigeon using a Laser Doppler Imager. Cutaneous application of mustard oil or antidromic electrical stimulation of a cutaneous nerve produced a small increase in skin blood flow. Close arterial injection of M35 prior to chemical or electrical stimulation resulted in a marked augmentation of the vasodilatory response. This effect was abolished by chronic denervation. The results suggest a nerve-mediated inhibitory effect of endogenous galanin on neurogenic cutaneous vasodilatation in the pigeon skin and provide the first experimental evidence for an inhibitory local regulatory function of cutaneous sensory nerves at least in the avian skin.

Capsaicin-sensitive local sensory innervation is involved in pacing-induced preconditioning in rat hearts: role of nitric oxide and CGRP?

Among several mediators, nitric oxide (NO) and calcitonin gene-related peptide (CGRP) were suggested to be involved in the mechanism of preconditioning. We examined the possible role of the cardiac capsaicin-sensitive sensory innervation in pacing-induced preconditioning, as well as in the cardiac NO and CGRP content. Wistar rats were treated subcutaneously with capsaicin or its solvent in the sequence of 10, 30, and 50 mg/kg increasing single daily doses for 3 days to deplete neurotransmitters of the sensory innervation. Isolated hearts from both groups were then subjected to either preconditioning induced by three consecutive periods of pacing at 600 beats per minute for 5 min with 5 min interpacing periods, or time-matched non-preconditioning perfusion, followed by a 10-min coronary occlusion. NO content of left ventricular tissue samples was assayed by electron-spin resonance, and CGRP release was determined by radioimmunoassay. CGRP immunohistochemistry was also performed. In the non-preconditioned, solvent-treated group, coronary occlusion decreased cardiac output (CO) from 68.1 to 32.1 mL/min, increased left ventricular end-diastolic pressure (LVEDP) from 0.58 to 1.90 kPa, and resulted in 200 mU/min/g LDH release. Preconditioning significantly increased ischaemic CO to 42.9 mL/min (P < 0.05), decreased ischaemic LVEDP to 1.26 kPa (P < 0.05) and decreased LDH release to 47 mU/min/g (P < 0.05) in the solvent-treated group. Preconditioning did not confer protection in the capsaicin-pretreated group (ischaemic CO: 35.6 mL/min; LVEDP: 1.76 kPa; LDH 156 mU/min/g). Capsaicin-treatment markedly decreased cardiac NO content, CGRP release, and CGRP-immunoreactivity.

CONCLUSIONS

(i) The presence of an intact local sensory innervation is a prerequisite to elicit pacing-induced preconditioning in the rat heart. (ii) A significant portion of cardiac basal NO content may be of neural origin. (iii) Release of NO and CGRP from capsaicin-sensitive nerves may be involved in the mechanism of pacing-induced preconditioning.

Trigeminal ganglion innervation of the cochlea--a retrograde transport study

Innervation patterns of sensory nerves from the trigeminal ganglion to the cochlear blood vessels were studied using retrograde transport of wheat germ agglutinin conjugated to horseradish peroxidase. Guinea-pigs (n=7) were unilaterally implanted with an osmotic pump and a cannula for cochlear delivery of 2% or 20% wheat germ agglutinin horseradish peroxidase (Group 1), 2% wheat germ agglutinin-horseradish peroxidase followed by 100 micromol capsaicin (Group 2), or vehicle alone. Histological sections of the trigeminal ganglia, the C1 and C2 dorsal ganglia, the superior and inferior ganglia of the glossopharyngeal nerve bilaterally, the midbrain and the brainstem were obtained after 48 h of infusion. In Group 1, a large number of labeled nerve cell bodies were observed in the anteromedial portion of the trigeminal ganglion and at the origin of the ophthalmic nerve. Some labeled cells were also found on the lateral side of the ophthalmic nerve, as well as on the medial side of the maxillary nerve root. Capsaicin pretreatment significantly reduced the density of labeled neurons in the trigeminal ganglion. A few labeled neurons were also found in the trigeminal brainstem nucleus complex and in certain auditory brainstem nuclei. No wheat germ agglutinin horseradish peroxidase-positive cells were observed in the spinal C1 or C2 cervical ganglia or in the superior or inferior glossopharyngeal ganglia. In contrast, wheat germ agglutinin-horseradish peroxidase application to the middle ear resulted in labeled cells in the middle posterolateral portion of the trigeminal ganglia and in the superior ganglia of the glossopharyngeal nerve. These results provide the first direct evidence that the trigeminal ganglion sends projections to the cochlea.

Capsaicin-sensitive mechanisms in the modulation of rat colonic vascular permeability under physiological and pathological conditions

Inflammatory bowel disease (IBD) causes a prolonged life-quality reduction of patients and high costs for health services. The aim of this study was to explore the possible involvement of peptidergic capsaicin-sensitive afferent nerves (CSN) in the pathogenesis of IBD. For the defunctionalization of colonic CSN, the lower part of the colon (1-4 cm from the anus) was exposed through a midline laparotomy and small pieces of gelfoam moistened with a solution of capsaicin (1%, 100 microL) was applied onto the serosal surface for 30 min in male Wistar rats. Colonic vascular permeability was assessed by measuring the extravasation of [125I] human serum albumin (2 microCi/kg, i.v., 2 h prior to killing). Two months after capsaicin treatment a significant increase in albumin extravasation was found in the lower (P < 0.005), but not in the upper (5-8 cm from the anus) part of the colon as compared to the sham-operated control. Intrarectal (8 cm from anus) administration of trinitrobenzene-sulphonic acid (TNBS; 30 mg/rat) induced similar plasma leakage in the lower and upper colon of control (CSN-intact) rats (P < 0.001) 1 week later. TNBS + ethanol (50%) produced further extravasation throughout the colon (P < 0.001) of CSN-intact animals. In the lower colon of capsaicin-pretreated rats TNBS-alone provoked an increase in plasma extravasation (P < 0.001) similar to that caused by TNBS + ethanol in CSN-intact rats. In the upper colon there was no difference in the effect of TNBS-alone on plasma leakage between control (CSN-intact) and CSN-depleted rats. The results suggest that capsaicin-sensitive nerves may play a significant protective/anti-inflammatory role in the colon under normal and pathological conditions.

Neurogenic inflammation in the gastrointestinal tract of the rat

In contrast to the skin and some visceral organs the capability of capsaicin-sensitive sensory nerves of evoking an inflammatory response in the gastrointestinal tract is equivocal. We have therefore investigated the neurogenic plasma extravasation induced by local application of capsaicin to the stomach, duodenum, jejunum, ileum and colon of the rat. Permeable vessels were visualised histologically with the vascular labelling technique using colloidal silver. In the smooth muscle layer of the small intestine, capsaicin elicited a 3-fold increase in the density of labelled blood vessels (diameter, 7-35 microns). Significant capsaicin-evoked plasma extravasation was also observed in the submucosa of the jejunum and ileum, and in the basal layer of the jejunal mucosa. Capsaicin-induced extravasation was not noted in the stomach and the colon. The data suggest the involvement of capsaicin-sensitive afferents in inflammatory processes in the rat small intestine.

Inhibition of the neurogenic inflammatory response by lidocaine in rat skin

Axon reflex vasodilatation and neurogenic plasma extravasation are characteristic cutaneous vascular responses mediated by neuropeptides released from stimulated capsaicin-sensitive sensory nerve endings. Intracutaneous injections of local anaesthetics inhibit the axon-reflex flare elicited by chemical irritants in human skin. Results of earlier reports on the effects of local anaesthetics on neurogenic plasma extravasation are controversial. The aim of the present study, therefore, was to re-examine the effect of the local anaesthetic lidocaine on the neurogenic inflammatory response of rat skin. The effects of lidocaine on cutaneous inflammatory reactions were measured quantitatively by means of the Evans blue technique. Intracutaneous injection of lidocaine resulted in a dose-dependent inhibition of the neurogenic inflammation elicited by mustard oil and of the dye leakage response to compound 48/80 or histamine. It is suggested that the site of this inhibition is beyond the sensory nerve terminal, presumably at the level of the vascular endothelium.

In vitro capsaicin-induced cytological changes and alteration in calcium distribution in giant serotonergic neurons of the snail Helix pomatia: a light- and electron-microscopic study

Morphological changes induced by capsaicin were studied in the serotonergic metacerebral giant neurons of the cerebral ganglia of Helix pomatia under in vitro conditions. Capsaicin at a concentration of 10(-4)M caused characteristic structural alterations in the giant serotonergic neurons but did not significantly influence serotonin immunoreactivity in the neurons. At the light-microscopic level, the most conspiciuous structural alterations were swelling of the cell bodies, which contained a swollen pale nucleus. Under the electron microscope, the nuclei, mitochondria and the cisternae of the endoplasmic reticulum were swollen in the capsaicin-affected metacerebral giant neurons. Electron-microscopic cytochemical techniques for calcium demonstration revealed electron-dense deposits in the swollen mitochondria and in the cisternae of the endoplasmic reticulum, suggesting an increased Ca2+ influx. The serotonergic metacerebral giant neurons could be labelled by cobalt (1mM) in the presence of capsaicin (10(-4)M) suggesting that capsaicin opens the cation chanels of the capsaicin-sensitive neuronal membrane. The morphological and cytochemical alterations induced by capsaicin in the serotonergic metacerebral giant neurons of Helix pomatia closely resemble those induced in sensory neurons of mammalian dorsal root ganglion.

RT97: a marker for capsaicin-insensitive sensory endings in the rat skin

The mouse monoclonal antibody RT97, which recognises the 200-kDa neurofilament subunit in its phosphorylated form, selectively labels the somata of sensory A-fibres (large light cells) in the dorsal root ganglion of the rat. We have tested the hypothesis that this antibody also visualises large diameter sensory fibres and their end structures in peripheral tissue, in particular in the skin. RT97 immunoreactivity is found in endings that are known to be served by myelinated afferent fibres, including Meissner-like endings, Merkel discs, hair follicle receptors, Pacinian corpuscles and free nerve endings. RT97 immunoreactivity has not, however, been observed in endings of presumably unmyelinated sensory fibres (intraepidermal fibres immunoreactive for substance P and calcitonin gene-related peptide) or in sympathetic fibres innervating sweat glands and blood vessels. In addition, neither systemic (100-150 mg/kg as adults) nor perineural capsaicin pre-treatment affects RT97 immunoreactivity in the skin. The data indicate that RT97 is a useful marker in the study of the capsaicin-insensitive sensory innervation of the skin and possibly other peripheral organs.

Capsaicin treatment induces selective sensory degeneration and increased sympathetic innervation in the rat ureter

Quantitative immunohistochemistry was used to study the innervation of the ureter in adult rats pretreated with capsaicin as neonates (50 mg/kg) or as adults (100-150 mg/kg, 10-22 days prior to being killed) using antibodies against protein gene-product 9.5, neuron-specific enolase, substance P, calcitonin gene-related peptide, neuropeptide Y, dopamine-beta-hydroxylase and vasoactive intestinal polypeptide. The number of calcitonin gene-related peptide- and substance P-containing fibres was reduced in the subepithelial plexus (adult capsaicin treatment < 1%, neonatal treatment < 5% of control), the submucosa (adult treatment < 11%; neonatal treatment < 51%) and in the smooth muscle layer and adventitia (adult treatment < 11%; neonatal treatment < 58%). Fibres immunoreactive for protein gene-product 9.5, a general neuronal marker, were reduced to 11% (adult treatment) or 0.5% (neonatal treatment) in the subepithelial plexus, but unchanged in the other layers, indicating a selective regional degeneration. In the smooth muscle layer the number of neuropeptide Y- and vasoactive intestinal polypeptide-containing nerve fibres was not altered by capsaicin. The number of neuropeptide Y fibres in the subepithelial plexus, however, was significantly increased after adult treatment (174% of control). After neonatal capsaicin treatment the intensity of the neuropeptide Y immunoreactivity was increased, more neuropeptide Y-positive nerve bundles were found and immunoreactive cell bodies were observed regularly in the adventitia of the ureter. The data indicate that capsaicin produces a selective degeneration of most afferent fibres in the subepithelial plexus of the rat ureter. This loss of capsaicin-sensitive afferent nerves evokes neuroplastic changes resulting in a hyperinnervation by neuropeptide Y-immunoreactive, presumably sympathetic fibres. The results suggest a mutual regulation of the pattern and density of innervation of peripheral target tissues by sensory and sympathetic neurons.

Reduction of substance P binding sites in the spinal dorsal horn after perineural capsaicin treatment in the rat

The long-term effect of perineural capsaicin treatment on the distribution of substance P (SP) binding sites was studied in the rat spinal dorsal horn using 125I-labelled Bolton-Hunter-SP. Three months after local application of capsaicin onto the sciatic nerve quantitative evaluation of the autoradiograms revealed a significant decrease in the density of SP binding sites of up to 48% in regions of laminae I and II of the spinal dorsal horn somatotopically related to the capsaicin treated sciatic nerve. It is suggested that reduction in SP binding may result from transganglionic and transsynaptic degenerative changes affecting postsynaptic structures. Changes in the distribution of SP binding sites may significantly contribute to functional alterations observed after perineural treatment with capsaicin.

A new technique for the direct demonstration of overlapping cutaneous innervation territories of peptidergic C-fibre afferents of rat hindlimb nerves

A new technique based on the phenomenon of vascular labelling has been devised for the direct visualisation of overlapping innervation territories of cutaneous nerves. The saphenous, peroneal and sural nerves on one side in anaesthetised rats were exposed, cut centrally and successively stimulated antidromically to induce a neurogenic inflammatory response after an intravenous injection of either a 1% colloidal silver solution or a suspension of 3% Monastral Blue B. Light microscopic examination of transparent preparations of the dorsal hindpaw skin revealed labelled blood vessels of different colours which represented cutaneous territories served by different nerves. Blood vessels labelled with both substances were regarded as areas of overlapping innervation. Such areas were typically localised along the border of adjacent innervation territories. In addition, distinct areas exhibiting double-labelled blood vessels were regularly encountered in regions separate from this border zone. Areas of interest were drawn with the aid of a camera lucida and measured by means of a computerised system. The results indicate a significant, although topographically variable, degree of overlap of these cutaneous innervation areas. This new technique offers a possibility to explore the importance of normally existing overlap in the reinnervation of a denervated skin area by collateral nerve sprouting.

Ruthenium red antagonism of capsaicin-induced vascular changes in the rat nasal mucosa

Mechanisms of capsaicin-induced vascular changes were examined in the nasal mucosa of anesthetized adult rats. Intra-arterial infusions of capsaicin at doses of 20-100 pmol/min into the external carotid artery resulted in a dose-dependent increase in nasal blood flow as assessed by laser-Doppler flowmetry. Intra-arterial infusion of ruthenium red (RR, 2.5-10 mumol) prior to the administration of capsaicin significantly inhibited the capsaicin-evoked response. The technique of vascular labelling was used to examine nasal mucosal vascular permeability. Intravenous administration of colloidal silver solution prior to capsaicin infusion resulted in accumulation of colloid in the walls of small blood vessels, indicative of enhanced vascular permeability. Vascular labelling was largely abolished after RR pretreatment. These findings suggest that neuropeptides released from trigeminal sensory nerve endings play a significant role in the local vascular and inflammatory reactions of the nasal mucosa. The experimental approach utilized in this study provides a promising model for defining the roles of capsaicin-sensitive afferent nerves in the mechanisms of allergic and/or inflammatory diseases affecting the nasal mucosa.

[Functional study of the regeneration of nerve fibers after keratinocyte transplantation]

The functional regeneration of sensory nerves was investigated in 5 patients with skin defects (caused by leg ulcers, a burn or fasciitis necrotisans) after transplantation with a keratinocyte suspension. In this area, first the pain sense and soon after wards the cold and heat sense returned, followed finally by the flare reaction caused by the mustard oil test. No sweat production could be observed during the study, because sweat glands were not found after the keratinocyte transplantation. The reinnervation course is roughly the same for skin defects covered with split skin graft or with a keratinocyte suspension.