Skin vascular reactivity to the neuropeptide substance P in rats with peripheral mononeuropathy

Topical combinations aimed at treating microvascular dysfunction reduce allodynia in rat models of CRPS-I and neuropathic pain

Growing evidence indicates that various chronic pain syndromes exhibit tissue abnormalities caused by microvasculature dysfunction in the blood vessels of skin, muscle, or nerve. We tested whether topical combinations aimed at improving microvascular function would relieve allodynia in animal models of complex regional pain syndrome type I (CRPS-I) and neuropathic pain. We hypothesized that topical administration of either α(2)-adrenergic (α(2)A) receptor agonists or nitric oxide (NO) donors combined with either phosphodiesterase (PDE) or phosphatidic acid (PA) inhibitors would effectively reduce allodynia in these animal models of chronic pain. Single topical agents produced significant dose-dependent antiallodynic effects in rats with chronic postischemia pain, and the antiallodynic dose-response curves of PDE and PA inhibitors were shifted 2.5- to 10-fold leftward when combined with nonanalgesic doses of α(2)A receptor agonists or NO donors. Topical combinations also produced significant antiallodynic effects in rats with sciatic nerve injury, painful diabetic neuropathy, and chemotherapy-induced painful neuropathy. These effects were shown to be produced by a local action, lasted up to 6 hours after acute treatment, and did not produce tolerance over 15 days of chronic daily dosing. The present results support the hypothesis that allodynia in animal models of CRPS-I and neuropathic pain is effectively relieved by topical combinations of α(2)A or NO donors with PDE or PA inhibitors. This suggests that topical treatments aimed at improving microvascular function may reduce allodynia in patients with CRPS-I and neuropathic pain.

PERSPECTIVE

This article presents the synergistic antiallodynic effects of combinations of α(2)A or NO donors with PDE or PA inhibitors in animal models of CRPS-I and neuropathic pain. The data suggest that effective clinical treatment of chronic neuropathic pain may be achieved by therapies that alleviate microvascular dysfunction in affected areas.

Effects of removal of dietary polyunsaturated fatty acids on plasma extravasation and mechanical allodynia in a trigeminal neuropathic pain model

Background

Neuropathic pain (NP) is partially mediated by neuroinflammatory mechanisms, and also modulates local neurogenic inflammation. Dietary lipids, in particular the total amount and relative proportions of polyunsaturated fatty acids (PUFAs) of the ω-3 and ω-6 families, have been reported to modify the threshold for thermal and mechanical allodynia in the partial sciatic nerve ligation model of NP in rats. The effects of dietary lipids on other popular NP models, such as the chronic constriction injury (CCI), have not yet been examined. It is also unknown whether dietary PUFAs exert any effect on the capsaicin (CAP)-induced neurogenic inflammation under control or NP conditions. In this study we investigated these interrelated phenomena in the trigeminal territory, which has been much less explored, and for which not all data derived from limb nerves can be directly applied.

Results

We studied the effects of a CCI of the infraorbital nerve (IoN) on the development of mechanical allodynia and CAP-induced plasma extravasation in rats fed either a regular diet (RD), or a modified diet (MD) with much lower total content and ω-3:ω-6 ratio of PUFAs. In rats kept on MD, mechanical allodynia following CCI-IoN was more pronounced and developed earlier. Extravasation was substantially increased in naive rats fed MD, and displayed differential diet-depending changes one and four weeks after CCI-IoN. When compared with basal levels (in naive and/or sham cases), the net effect of CCI-IoN on ipsilateral extravasation was a reduction in the MD group, but an increase in the RD group, effectively neutralizing the original intergroup differences.

Conclusion

In summary, PUFA intake reduces CAP-induced neurogenic plasma extravasation in the trigeminal territory, and their removal significantly alters the mechanical allodynia and the plasma extravasation that result from a unilateral CCI-IoN. It is likely that this "protective" effect of dietary lipids is temporary. Also, the presence of contralateral effects of CCI-IoN precludes using the contralateral side as control.

AM404, an anandamide transport inhibitor, reduces plasma extravasation in a model of neuropathic pain in rat: role for cannabinoid receptors

Neuropathic pain consequent to peripheral nerve injury has been associated with local inflammation. Following noxious stimulation afferent fibres release substance P (SP) and calcitonin-gene related peptide (CGRP), which are closely related to oedema formation and plasma leakage. The effect of the anandamide transport blocker AM404 has been studied on plasma extravasation after chronic constriction injury (CCI) which consists in a unilateral loose ligation of the rat sciatic nerve (Bennett and Xie, 1988). AM404 (1-3-10 mg kg(-1)) reduced plasma extravasation in the legated paw, measured as mug of Evans Blue per gram of fresh tissue. A strong effect on vascular permeability was also produced by the synthetic cannabinoid agonist WIN 55,212-2 (0.1-0.3-1 mg kg(-1)). Using specific antagonists or enzyme inhibitors, we demonstrate that cannabinoids act at several levels: data on the 3rd day suggest a strong involvement of substance P (SP) and calcitonin gene-related peptide (CGRP) in the control of vascular tone, whereas at the 7th and 14th days the major role seems to be played by prostaglandins (PGs) and nitric oxide (NO). Capsaicin injection in ligated paws of AM404- or WIN 55,212-2-treated rats resulted in an increase of Evans Blue extravasation, suggesting the involvement of the cannabinergic system in the protective effect of C fibres of ligated paws. Taken together, these data demonstrate the efficacy of cannabinoids in controlling pain behaviour through the modulation of several pain mediators and markers of vascular reactivity, such as SP, CGRP, PGs and NO.

Alteration in sensitivity of ionotropic glutamate receptors and tachykinin receptors in spinal cord contribute to development and maintenance of nerve injury-evoked neuropathic pain

Allodynia or hyperalgesia induced by peripheral nerve injury may be involved in changes in the sensitivity of neurotransmitters at the spinal cord level. In order to clarify the functional role of neurotransmitters in peripheral nerve injury, we used rats with nerve injury induced by chronic constriction of the sciatic nerve (CCI rat model) and estimated the effects of the intrathecal injection of drugs known to affect glutamate and tachykinin receptors. In sham-operated rats, the NMDA receptor agonist NMDA and AMPA-kinate receptor agonist RS-(5)-bromowillardin reduced withdrawal latency. The non-competitive NMDA receptor antagonist MK-801, competitive NMDA receptor antagonist AP-5 and AMPA-kinate receptor antagonist NBQX increased withdrawal latency. Substance P (SP) increased the withdrawal latency but only transitorily. The NK1 receptor antagonist RP67580 increased withdrawal latency, but the NK2 receptor antagonist SR48968 did not show an effect. In CCI rats, RS-(5)-bromowillardin reduced withdrawal latency, but NMDA did not show an effect. NBQX increased withdrawal latency, while MK-801 and AP-5 showed little or no effect. SP reduced withdrawal latency, and both RP67580 and SR48968 increased it. These results indicate that the alteration in sensitivity of ionotropic glutamate receptors and tachykinin receptors in the spinal cord contribute to development and maintenance of nerve injury-evoked neuropathic pain.

Modulation of peripheral inflammation by the substance P N-terminal metabolite substance P1-7

The N-terminal metabolite of the undecapeptide substance P (SP), substance P1-7 (SP1-7), is known to modulate nociception in the central nervous system (CNS) and often has opposite effects from SP. This study investigated the ability of SP(1-7) to modulate the vasodilatation response to SP in anaesthetized rats under different injury conditions using a blister model of inflammation on the hind footpad. The results indicated that SP1-7 inhibited the vascular response to SP in a dose-dependent manner. The putative antagonists naloxone and D-Pro2-D-Phe7-SP1-7 (D-SP1-7) reversed the effect of SP1-7. D-SP1-7 improved the responsiveness to SP under chronic nerve injury, which suggests a role for endogenous SP1-7 in this model. SP1-7 did not inhibit the response to electrical stimulation of the sciatic nerve, which indicates that the heptapeptide interacts at a post-terminal binding site. The current results suggest that SP1-7 may have inhibitory properties in inflammation, analogous to its antinociceptive role in the central nervous system.

Nitric oxide and its modulators in chronic constriction injury-induced neuropathic pain in rats

This study was conducted to examine the role of nitric oxide (NO) in peripheral neuropathy induced by chronic constriction injury of sciatic nerve of rats by using NO precursor, NO donors and nitric oxide synthase (NOS) inhibitors. Chronic constriction injury of sciatic nerve of rats resulted in peripheral neuropathy as confirmed by nociceptive behavioural tests using mechanical, thermal and cold allodynia. NO precursor, L-arginine and NO donors sodium nitroprusside, S-nitroso-N-acetylpenicillamine potentiated the hyperalgesia and allodynia significantly suggesting proalgesic effect in neuropathic rats. Intracerebroventricular (i.c.v.) administration of rats with NOS inhibitors such as L-N(G)-nitroarginine methyl ester, N-iminoethyl lysine and 7-nitroindazole did not show any effect but i.p. administration of NOS inhibitors aminoguanidine, L-N(G)-nitroarginine methyl ester and 7-nitroindazole caused alleviation of pain. The study confirms the involvement of endogenously synthesized and exogenously administered NO in chronic constriction injury-induced neuropathy in rats. Significant increase in the levels of nitrate and nitrite in ligated sciatic nerve suggest that local up regulation of NO in the production and maintenance of neuropathic pain. In conclusion, initial attempt to manipulate L-arginine: NO pathway is indicative of therapeutic potential of these interventions in the management of neuropathic pain.

Alpha-conotoxin Vc1.1 alleviates neuropathic pain and accelerates functional recovery of injured neurones

This paper demonstrates the capacity of the neuronal nicotinic acetylcholine receptor (nAChR) antagonist alpha-conotoxin Vc1.1 to inhibit pain responses in vivo. Vc1.1 suppressed pain behaviors when tested in two models of peripheral neuropathy of the rat sciatic nerve, the chronic constriction injury (CCI) and partial nerve ligation (PNL) models. Mechanical hyperalgesia was assessed using an Ugo Basile Analgesymeter. Vc1.1 was administered by intramuscular bolus injection near the site of injury at doses of 0.036 microg, 0.36 microg and 3.6 microg in CCI rats and at a dose of 0.36 microg in PNL rats. Vc1.1 was also administered contralaterally in CCI rats at doses of 0.36 microg and 3.6 microg. Treatment started after the development of hyperalgesia and continued for 7 days. Vc1.1 significantly attenuated mechanical hyperalgesia in both CCI and PNL rats for up to a week following cessation of treatment. Vc1.1 also accelerated functional recovery of injured neurones. A blister was raised over the footpad innervated by the peripheral terminals of the injured nerve. The ability of these terminals to mount an inflammatory vascular response upon perfusion of the blister base with substance P provided a measure of functional recovery. This study shows that alpha-conotoxin Vc1.1, a neuronal nAChR antagonist, suppressed mechanical pain responses associated with peripheral neuropathy in rats in vivo and accelerated functional recovery of the injured neurones. A role for neuronal nAChRs in the analgesic activity of Vc1.1 is proposed.

Skin reactivity to aeroallergens is reduced in human T-lymphotropic virus type I-infected healthy blood-donors (asymptomatic carriers)

BACKGROUND

A type 2 immune response, characterized by high levels of interleukin-4 and immunoglobulin E synthesis is a hallmark of respiratory allergic diseases. Individuals infected with human T-lymphotropic virus type I (HTLV-I) virus have spontaneous T-cell proliferation and increased interferon gamma production, which are immunological functions associated with a type 1 immune response.

OBJECTIVE

To determine the frequency of asthma and rhinitis symptoms and immediate skin reactivity to aeroallergens in HTLV-I infected individuals, compared with noninfected subjects.

METHODS

Cross sectional study of 101 HTLV-I infected and 101 control uninfected blood donors, assessed by enzyme-linked immunosorbent assay and Western blot assays. The subjects were age and sex-matched, identified as presenting allergy history by questionnaire, which was complemented by a complete clinical examination and skin prick tests for aeroallergens.

RESULTS

The frequency of atopy was lower in infected than uninfected subjects, 14.9 and 29.7% (P = 0.017), respectively. Skin reactivity to Dermatophagoides pteronissynus, Dermatophagoides farinae and Blomia tropicalis were the most frequently observed among all the tested antigens in both groups. Skin reactivity to histamine was also reduced in the infected individuals compared with uninfected subjects (medians 4.0 vs 5.0, respectively; P < 0.0001). Infection by HTLV-I was found to be a factor of protection to atopy (RP 0.44; P = 0.005).

CONCLUSIONS

The HTLV-I infection reduces the frequency of respiratory allergy and skin reactivity to aeroallergens.

Influence of capsaicin cream in rats with peripheral neuropathy

We investigated the effect of topical application of capsaicin cream on withdrawal latency in the hind foot of rat in response to radiant heat in an experimental model of neuropathic pain. A neuropathic state was induced by loose ligation of the sciatic nerve with chromic gut suture. A marked thermal hyperalgesia was observed in response to heat stimulus applied to the operated side from 3 days through 2 weeks, followed by a gradual return to the control level by 35 days after surgery. Capsaicin cream applied to both the bilateral hind instep and sole once a day for a continuous period of 2 weeks or 4 weeks alleviated thermal hyperalgesia in a dose-dependent manner. A remarkable effect was observed 2 weeks after the start of the application and this effect proved to be reversible. On the other hand, in sham-operated animals when capsaicin cream was applied once daily from day 7 after the sham operation, from 1 day through 3 weeks following capsaicin application, withdrawal latency of the sham-operated paws of the capsaicin-treated group was significantly increased as compared to that of the vehicle cream-treated group. The effects of antagonists of glutamate receptor and tachykinin receptors were investigated 7 days post surgery. Pretreatment with MK-801 (0.5 mg kg(-1), i.p.), but not with CNQX (0.5 mg kg(-1), i.p.), reversed the thermal hyperalgesia following nerve injury. Neither of RP67580 (1--10 mg kg(-1), i.p.) nor SR48968 (1--10 mg kg(-1), i.p.) had any effect on the withdrawal latency in the injured and non-injured hind paw. These results suggest that although the manifestation of effectiveness may be delayed by changes in networks of neurotransmitters related to the nociceptive pathways following nerve injury, longer-term repetitive application of capsaicin cream has a significant therapeutic effect on subjects with painful peripheral neuropathy.

Influence of painful chronic neuropathy on neurogenic inflammation

The effect of topical application of capsaicin cream on neurogenic inflammation was investigated in a neuropathic pain model in rat. The neuropathic state was induced by loose ligation of the sciatic nerve with a chromic gut suture. A marked thermal hyperalgesia was observed in response to heat stimulation applied to the operated side from 3 days through 2 weeks, followed by a gradual return to the control level 35 days after surgery. In sham-operated animals, topical application of capsaicin cream to both sides of the hind paw, the instep and sole, as well as antidromic stimulation of the sciatic nerve led to a significant increase in the amounts of Evans blue and substance P (SP) released into the perfusates. This stimulus-induced extravasation was significantly suppressed by pretreatment with RP67580, an NK1 antagonist. On day 7 after ligation, capsaicin- and antidromic stimulation-induced extravasation were significantly reduced. At this time, both amount of SP released immediately after application of capsaicin and during antidromic stimulation were almost similar to that in sham-operated rats, whereas the basal amount of SP release significantly increased in ligated animals. In particular a major release of SP was detected immediately after the start of the perfusion compared with that in sham-operated rats. Plasma extravasation evoked by SP (10(-4) M) applied to the subcutaneous perfusate was significantly less in ligated than in sham-operated rats. These results suggest that nerve injury with chronic pain may produce increase in basal SP release into the peripheral tissues, and then such enhanced SP release cause reduction of SP-induced extravasation.

Mechanical hyperalgesia after an L5 spinal nerve lesion in the rat is not dependent on input from injured nerve fibers

An injury to a peripheral nerve in animals often leads to signs of neuropathic pain including hyperalgesia to heat, cold and mechanical stimuli. The role of injured and intact nerve fibers in mechanical hyperalgesia was evaluated in rats subjected to an L5 spinal nerve ligation-and-cut ('modified SNL lesion'). To assess the contribution of injured afferents, an L5 dorsal rhizotomy was performed immediately before, or 7 days after the modified SNL lesion. To study the role of adjacent intact spinal nerves, an L4 dorsal rhizotomy was performed 7 days after the modified SNL lesion. The up-down method of Dixon (Dixon WJ, Annu Rev Pharmacol Toxicol 1980;20:441-462) was used to measure the paw withdrawal threshold to mechanical stimuli at three sites on the rat hindpaw corresponding to the L3, L4, and L5 dermatomes. We found that the modified SNL lesion produced a significant, lasting (20 days) decrease of the mechanical withdrawal threshold. The severity and duration of mechanical hyperalgesia varied across testing sites. The L5 and L4 dermatome test sites developed the most severe and lasting mechanical hyperalgesia. In contrast, the L3 testing site developed significantly less severe and shorter lasting mechanical hyperalgesia. L5 dorsal rhizotomy, by itself, produced a transient decrease in mechanical withdrawal thresholds. L5 dorsal rhizotomy performed before, or 7 days after, the modified SNL lesion did not prevent or resolve the observed decrease in mechanical withdrawal thresholds. L4 dorsal rhizotomy performed 7 days after the modified SNL lesion resulted in an immediate reversal of mechanical withdrawal thresholds back to baseline values. These results suggest that, after L5 spinal nerve ligation-and-cut, mechanical hyperalgesia develops and persists independent of input from injured afferents. We propose that the Wallerian degeneration that develops after a nerve injury leads to interactions between the degenerating fibers of the injured spinal nerve and the intact fibers of adjacent spinal nerves. This leads to changes in the intact fibers that play a critical role for both initiation and maintenance of mechanical hyperalgesia.

Reflex sympathetic dystrophy: facts and hypotheses

Reflex sympathetic dystrophy (RSD) syndrome has been recognized clinically for many years. It is most often initiated by trauma to a nerve, neural plexus, or soft tissue. Diagnostic criteria are the presence of regional pain and other sensory changes following a noxious event. The pain is associated with changes in skin colour, skin temperature, abnormal sweating, oedema, and sometimes motor abnormalities. The clinical course is commonly divided into three stages: first (acute or hyperaemic), second (dystrophic or ischaemic), and third (atrophic) stage. The diagnosis is primarily clinical, but roentgenography, scintigraphy, thermography, electromyography and assessment of nerve conduction velocity can help to confirm the diagnosis. Although a wide variety of treatments have been recommended, the only therapies found to be effective in large studies aim at interfering with the activity of the sympathetic nervous system. To this end, efferent sympathetic nerve activity can be interrupted surgically or chemically. Alternatively, adrenoceptor blockers may be used to relieve pain. Numerous theories have been proposed to explain the pathophysiology. Sympathetic dysfunction, which often has been purported to play a pivotal role in RSD, has been suggested to consist of an increased rate of efferent sympathetic nerve impulses towards the involved extremity induced by increased afferent activity. However, the results of several experimental studies suggest that sympathetic dysfunction consists of supersensitivity to catecholamines induced by (partial) autonomic denervation. Besides, it has been suggested that excitation of sensory nerve fibres at axonal level causes release of neuropeptides at the peripheral endings of these fibres. These neuropeptides may induce vasodilation, increase vascular permeability, and excite surrounding sensory nerve fibres -- a phenomenon referred to as neurogenic inflammation. At the level of the central nervous system, it has been suggested that the increased input from peripheral nociceptors alters the central processing mechanisms.

Antinociceptive effects of neurotropin in a rat model of painful peripheral mononeuropathy

A non-protein extract isolated from the inflamed skin of rabbits inoculated with vaccinia virus (Neurotropin, NTP), has been clinically used in Japan for the treatment of chronic painful conditions such as low back pain, osteoarthritis, postherpetic neuralgia, subacute myelo-opticoneuropathy, and so on. Recent studies have shown its efficacy on patients with complex regional pain syndrome (CRPS). The chronic constriction injury (CCI) model described by Bennett and Xie has been thought to show similar painful conditions to those seen in CRPS patients. Thus, the antinociceptive effects of NTP were tested in CCI model. In rats with mechanical hyperalgesia 2 weeks after nerve injury, i.p. injection of NTP (100 Neurotropin Unit, NU/kg) produced an analgesic effect that lasted for at least 50 min. An analgesic effect lasting up to 30 min. was observed in rats with heat hyperalgesia 2 weeks after nerve injury. Seven daily i.p. injections (50 NU/kg) of NTP commencing 1 week after surgery produced an early recovery from heat hyperalgesia. Prior studies suggest that NTP produces analgesia by activation of a descending pain inhibitory system. Thus, our findings suggest the possibility that the dysfunction of the descending pain inhibitory system could be related to the hyperalgesia in the nerve injury model, and perhaps also in people who suffer from painful peripheral neuropathies.

Influence of partial nerve injury in the rat on efferent function of sympathetic and antidromically acting sensory nerve fibers

OBJECTIVE

To investigate how partial injury of a large peripheral nerve affects efferent (vasomotor) function of sympathetic and antidromically acting sensory nerve fibers.

DESIGN

Randomized animal study.

MATERIALS AND METHODS

We assessed, by laser Doppler flowmetry, skin blood flow (SBF) in the hindpaw of male Lewis rats before partial injury of the ipsilateral sciatic nerve (through loose ligation) as well as at an early stage (day 4) and at a later stage (day 21) after this procedure. This procedure has been reported to induce signs and symptoms like those observed in patients with causalgia. At the two time points after nerve injury, SBF was assessed before and after (chemical) blockade of sensory and nonsensory (sympathetic) sciatic nerve fibers. Furthermore, at day 21 we measured the density of sympathetic nerve fibers in footpad arteries.

MEASUREMENTS AND MAIN RESULTS

At day 4, compared with preligation values, we observed an increase in SBF that was reduced by blockade of sensory nerve fibers. Subsequent blockade of nonsensory nerve fibers further reduced SBF. At day 21, SBF was decreased compared with preligation values. Blockade of sensory nerve fibers further reduced SBF, and subsequent blockade of nonsensory nerve fibers did so as well. The density of sympathetic nerve fibers was lower on the ligated side than on the nonligated side.

CONCLUSIONS

Partial injury of the rat sciatic nerve causes an ipsilateral increase in SBF at an early stage, which is followed by a decrease at a later stage. At both stages, antidromically acting sensory and orthodromically acting nonsensory (sympathetic) nerve fibers are involved in the vasodilator response. At a later stage, however, neurogenic vasodilator mechanisms are overruled by a nonneurogenic vasoconstrictor mechanism. The latter may consist of supersensitivity of skin microvessels to catecholamines consequent to reduced neurogenic disposition of catecholamines.

Increased delayed type hypersensitivity in rats subjected to unilateral mononeuropathy is mediated by neurokinin-1 receptors

An animal model or peripheral mononeuropathy was utilized in the present study to investigate the potential role of substance P (SP) in modifying immune responses associated with chronic pain conditions. Animals subjected to unilateral sciatic ligation and sham-operated animals were sensitized with keyhole limpet hemocyanin (KLH) and subsequently challenged in the ipsilateral or contralateral hind paw to produce a delayed-type hypersensitivity (DTH) response. Subcutaneous microdialysis and radioimmunoassay were used to measure interstitial fluid SP levels in the challenged tissue prior to and following immune challenge in control and neuropathic animals. Following immune challenge, there was a significant increase in the concentration of SP in tissue dialysate samples from the challenged paw of both sham-operated and neuropathic animals. However, tissue SP levels in neuropathic animals were more than two-fold higher than those obtained from sham-operated controls following challenge. SP concentration remained elevated for 2.5 h following immune challenge in neuropathic animals compared to 90 min in sham-operated animals. Compared with controls, neuropathic animals also exhibited an increased DTH response that was reversed, in a dose-related fashion, by the non-peptide NK-1 receptor blocker L-703,606. The same antagonist had no effect in sham-operated animals. These data suggest that the increased DTH response in animals subjected to unilateral mononeuropathy involves SP and NK-1 receptors present in the challenged tissue.

Chronic pain and immunity: mononeuropathy alters immune responses in rats

In order to investigate the possible relationship between chronic pain and the immune system, delayed-type hypersensitivity (DTH) and humoral immunity were assessed in Sprague-Dawley rats subjected to unilateral peripheral mononeuropathy induced by sciatic ligation. Paw withdrawal latency (PWL) time was measured twice during the experiment in animals subjected to sciatic nerve ligation or sham surgery. Sciatic nerve-ligated animals showed hyperalgesia in the leg subjected to neural ligation when compared to the contralateral leg. No differences in PWL times existed in sham-operated animals. In order to exclude possible alterations in immune response due to the surgical procedure or to the hyperalgesia testing, a group of control animals, not subjected to surgical procedures or hyperalgesia testing, was also included in the experiment. Three days post-sciatic ligation or sham surgery, both experimental and control animals were sensitized to keyhole limpet hemocyanin (KLH). A secondary sensitization followed 1 week after the initial immunization. Fourteen days after the initial sensitization, KLH was injected into the hind foot pad and vehicle into the contralateral foot pad in order to assess DTH. One group of rats subjected to sciatic nerve ligation was tested for DTH in the hind foot pad ipsilateral to the ligated nerve, while another group was tested in the contralateral foot pad. Twenty-four hours following foot pad injections, the thickness of both paws was measured and animals were bled to test for anti-KLH immunoglobulins. Animals in which mononeuropathy was induced, but not sham-operated or control animals, exhibited an enhanced DTH response to KLH.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of sympathectomy on the cutaneous temperature abnormalities in rats with chronic constriction injury of the sciatic nerve

Effects of surgical sympathectomy on the cutaneous temperature abnormalities of plantar surface evoked by the chronic constriction injury (CCI) of the sciatic nerve were investigated in the rat. In normal animals, there were very small temperature differences between both plantar surfaces. There were also very small temperature differences in plantar surfaces following the sympathectomy prior to CCI. In rats with CCI, the cutaneous temperature of the nerve-injured plantar surface was significantly higher (warmer) than that of the contralateral plantar surface during the first week following CCI, and then became lower (cooler). Surgical sympathectomy prior to and just after CCI significant suppressed the temperature abnormalities during the first week, but no effect was observed after 2 weeks following CCI. These observations indicate that sympathetic vasoconstriction may contribute to the cutaneous temperature abnormalities evoked by CCI during the early stage, but does not affect the abnormalities at later stages.