Neurogenic mechanism for symmetrical arthritis.
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Arthritis, Rheumatoid↗
Biomedical subjects
A I Basbaum
Publications and source records attributed to A I Basbaum.
Deafferentation in the rat increases mechanical nociceptive threshold in the innervated limbs.
In this study in the rat, we evaluated the effect of unilateral, multiple cervical dorsal rhizotomy (C5-T1) on nociceptive thresholds in the unoperated limbs. This was tested by measuring the vocalization threshold to paw pressure. We report that deafferentation by dorsal rhizotomy results in a delayed, but transient increase in mechanical nociceptive thresholds in the 3 innervated limbs.
Afferent Pathways↗
Neural influences on synovial mast cell density in rat.
The mast cell, an immunocompetent cell that contributes to neurogenic inflammation in a variety of tissues, including synovium, is found in close proximity to peripheral terminals of unmyelinated primary afferents and sympathetic postganglionic nerve terminals. In this study we evaluated the hypothesis that the density of mast cells in synovial tissue is dependent on the neural innervation. In normal rats, we found that the density of mast cells in the ankle joint capsule, which is heavily innervated, is greater than in the capsule of the knee, which is less densely innervated. Selective lesions of unmyelinated primary afferents with capsaicin, or of sympathetic postganglionic neurons with guanethidine, produced a significant decrease in mast cells; surgical removal of the parasympathetic ganglia did not significantly affect mast cell density. Finally, the number of mast cells in the synovial joint of spontaneously hypertensive rats, which have increased sympathetic activity, was significantly greater than in normotensive control rats. These observations support the hypothesis that the innervation in the synovial joint of the rat, by unmyelinated afferents and sympathetic efferents, exerts a trophic effect on mast cell density.
Animals↗
Epinephrine exacerbates arthritis by an action at presynaptic B2-adrenoceptors.
Sympathetic efferents contribute to the severity of joint injury in experimental arthritis in the rat, [Levine J. D. et al. (1986) J. Neurosci. 6, 3423-3429] and beta 2-adrenergic receptor antagonists suppress the disease [Levine J. D. et al. (1988) Proc. natn. Acad. Sci. U.S.A. 85, 4553-4556]. The present study was directed at determining the endogenous ligand for, and target of, the beta 2-receptor contribution to arthritis. We report that adrenal medullectomy significantly reduced joint injury in experimental arthritis, but that severe joint injury was re-established in adrenal medullectomized rats chronically treated with epinephrine or the beta 2-agonist, salbutamol. The ability of these two drugs to enhance joint injury in adrenal medullectomized rats was blocked by sympathectomy. These data suggest that adrenal medulla-derived epinephrine acts at beta 2-adrenoceptors on sympathetic efferent nerve terminals, to contribute to the severity of experimental arthritis.
Adrenal Medulla↗
The 15-lipoxygenase product, 8R,15S-diHETE, stereospecifically sensitizes C-fiber mechanoheat nociceptors in hairy skin of rat.
1. This study examined the effects of the 15-lipoxygenase product of arachidonic acid metabolism, (8R,15S)-dihydroxyicosa-(5E-9,11,13Z)tetraenoic acid (8R,15S-diHETE), on mechanical thresholds and thermal responses of saphenous nerve cutaneous C-fiber nociceptors that innervate the hairy skin of the rat hindpaw. Single C-fiber mechanoheat nociceptors (C-MH) that had von Frey hair (VFH) thresholds greater than 5 g and were activated by a noxious heat stimulus were chosen for study. We also studied the effects of prostaglandin E2 (PGE2), a cyclooxygenase product of arachidonic acid metabolism, on these nociceptors. 2. The 63 C-MHs studied had a conduction velocity of 0.82 +/- 0.03 m/s (mean +/- SE) and a mechanical threshold of 13.4 +/- 2.4 g. In a subgroup of these (n = 24), the thermal threshold was measured as (44 +/- 1 degree C) (mean +/- SE). 3. 8R,15S-diHETE produced a significant decrease in mechanical threshold of C-MHs (n = 33). The 8R,15S-diHETE-induced sensitization of C-MHs to mechanical stimuli was completely antagonized by coadministration with a stereoisomer, 8S,15S-diHETE (n = 10). 4. The mechanical threshold of C-MHs (n = 10), previously injected with the combination of 8R,15S-diHETE and 8S,15S-diHETE, was significantly reduced by a subsequent injection of PGE2. In a separate group of C-MHs (n = 7), PGE2 was co-injected with 8S,15S-diHETE, which failed to antagonize the sensitizing effect of PGE2 on mechanical threshold. 5. 8R,15S-diHETE also sensitized C-MHs (n = 9) to a thermal stimulus consisting of 37 degrees C for 5 min.(ABSTRACT TRUNCATED AT 250 WORDS)
Action Potentials↗
Systemic morphine suppresses noxious stimulus-evoked Fos protein-like immunoreactivity in the rat spinal cord.
Previous experiments have shown that noxious stimulation increases expression of the c-fos proto-oncogene in subpopulations of spinal cord neurons. c-fos expression was assessed by immunostaining for Fos, the nuclear phosphoprotein product of the c-fos gene. In this study, we examined the effect of systemic morphine on Fos-like immunoreactivity (FLI) evoked in the formalin test, a widely used model of persistent pain. Awake rats received a subcutaneous 150 microliters injection of 5% formalin into the plantar aspect of the right hindpaw. The pattern of nuclear FLI was consistent with the known nociceptive primary afferent input from the hindpaw. Dense labeling was recorded in the superficial dorsal horn (laminae I and IIo) and in the neck of the dorsal horn (laminae V and VI), areas that contain large populations of nociceptive neurons. Sparse labeling was noted in lamina IIi and in the nucleus proprius (laminae III and IV), generally considered to be nonnociceptive areas of the cord. Fos immunoreactivity was also evoked in the ventromedial gray, including laminae VII, VIII, and X. There was no labeling in lamina IX of the ventral horn. Since FLI was time dependent and distributed over several spinal segments, we focused our analysis where maximal staining was found (L3-L5) and at the earliest time point of the peak Fos immunoreactivity (2 hr). Twenty minutes prior to the formalin injection, the rats received morphine (1.0, 2.5, 5.0, or 10 mg/kg, s.c.) or saline vehicle. Two hours later, the rats were killed, their spinal cords removed, and 50 microns transverse sections of the lumbar enlargement were immunostained with a rabbit polyclonal antiserum directed against Fos. Prior treatment with morphine sulfate profoundly suppressed formalin-evoked FLI in a dose-dependent and naloxone-reversible manner. The dose-response relationship of morphine-induced suppression of FLI varied in different laminae. To quantify the effect of morphine on FLI, labeled neurons in sections taken from the L4/5 level of each rat were plotted with a camera lucida and counted. Staining in the neck of the dorsal horn (laminae V and VI) and in more ventral laminae VII, VIII, and X, was profoundly suppressed by doses of morphine which also suppress formalin-evoked behavior. Although the labeling was also significantly reduced in laminae I and II, at the highest doses of morphine there was substantial residual labeling in the superficial dorsal horn. These data indicate that analgesia from systemic opiates involves differential regulation of nociceptive processing in subpopulations of spinal nociceptive neurons.
Animals↗
Expression of c-fos protein in interneurons and projection neurons of the rat spinal cord in response to noxious somatic, articular, and visceral stimulation.
This study used immunocytochemistry to examine the pattern of noxious-stimulus evoked expression of the proto-oncogene c-fos in the spinal cord of the rat. Both noxious somatic and joint stimulation in awake rats evoked the expression of c-fos protein in similar areas of the lumbar spinal cord. C-fos-immunoreactive neurons were found in laminae I and outer II, in the lateral part of the neck of the dorsal horn, and in laminae VII, VIII, and X. All of the labelled neurons were located ipsilateral to the injured hindpaw, except for lamina VIII where bilateral labelling was recorded. The c-fos-immunoreactive neurons in lamina I extended from the L3 segment to the rostral sacral cord; staining in outer lamina II was only found at the L4 segment. The more deeply located cells, of the dorsal and medioventral horns, had the most extensive rostrocaudal spread; they were found from L1 through the rostral sacral segments. The pattern of c-fos-immunoreactivity produced by visceral stimulation, in anesthetized rats, differed in several ways from that produced by somatic stimulation. First, there was considerable bilateral, symmetrical labelling of cells. Second, there was a much more extensive rostrocaudal spread of the labelling, from cervical through sacral cord. Third, the greatest rostrocaudal spread was found for neurons in the superficial dorsal horn; labelled cells in the neck of the dorsal horn and in lamina X were restricted to segments at the thoracolumbar junction, which is also where the superficial dorsal horn cells were most concentrated. Fourth, there were very few labelled neurons in the outer part of the substantia gelatinosa. To determine whether any neurons that express the c-fos protein in response to noxious stimulation project to supraspinal sites, we combined the immunocytochemical localization of c-fos with the localization of a retrogradely transported protein-gold complex that was injected into the thalamic and brainstem targets of the major ascending spinal pathways. In rats that received the somatic noxious stimulus, 90% of all of the c-fos projection neurons were recorded in four major areas of the cord: lamina I (37%), the lateral part of the neck of the dorsal horn (24%), laminae VIII (9%), and X (29%). The remainder were scattered throughout the spinal gray. With the exception of lamina VIII, which contained c-fos projection neurons contralateral to the inflamed paw, all of the c-fos projection neurons were located ipsilateral to the injured paw.(ABSTRACT TRUNCATED AT 400 WORDS)
Animals↗
Effect of deafferentation on the levels of uric acid in the spinal cord of the rat.
In previous studies we reported that the rat spinal cord contains relatively high levels of uric acid and that the levels in a rat model of bilateral chronic pain, experimental adjuvant arthritis. In this report we evaluate the changes in UA in the unilaterally deafferented rat, a preparation which has also been used to study chronic pain. Uric acid was measured by high-pressure liquid chromatography with electrochemical detection in the spinal cord of rats that underwent unilateral, multiple cervical dorsal rhizotomy. Compared to control and sham-operated rats, there was a significant increase in the level of uric acid in the dorsal quadrant of the spinal cord ipsilateral to the dorsal rhizotomy. This increase was present at 1 and 4 weeks after surgery. At 1 week, we also observed a small but statistically insignificant increase in uric acid levels in the dorsal quadrant contralateral to the deafferentation and in sham-operated rats. Four weeks after surgery the levels of UA in all regions except for the deafferented dorsal quadrant returned to normal. The possibility was raised that the changes in uric acid reflect an increase in purinergic metabolism in the spinal cord secondary to the increased activity of the dorsal horn neurons that occurs with deafferentation.
Afferent Pathways↗
Ultrastructural analysis of dynorphin B-immunoreactive cells and terminals in the superficial dorsal horn of the deafferented spinal cord of the rat.
Light microscopic studies have demonstrated important differences in the distribution of enkephalin and dynorphin cells and terminals in the dorsal horn. Most importantly, dynorphin neurons are located in regions almost exclusively associated with the transmission and/or control of nociceptive messages (laminae I, IIo, and V); enkephalin neurons, although located in the same regions, are also found in areas involved in the transmission of nonnociceptive messages, e.g., laminae IIi and III. To determine whether there are also differences in the synaptic organization of the two opioid peptides, we have examined the distribution of dynorphin B immunoreactivity at the ultrastructural level. The studies were performed in colchicine-treated rats that underwent dorsal rhizotomy so that the relationship of dynorphin terminals and cells to primary afferent terminals could be established. Dynorphin B-immunoreactive cell bodies and dendrites in laminae I and IIo receive convergent primary and nonprimary afferent input, which suggests that dynorphin neurons receive a small-diameter, nociceptive input. Dynorphin terminals predominantly contain round, agranular vesicles; some terminals also contain a few dense core vesicles. Most dynorphin terminals are presynaptic to unlabelled dendrites; both asymmetric and symmetrical axonal contacts were noted. Dynorphin-immunoreactive boutons are also presynaptic to unlabelled cell bodies and spines. Twenty-nine percent of dynorphin terminals were associated with axonal profiles, including degenerating primary afferent terminals; only rarely could a synaptic density be detected. Although some degenerating primary afferent terminals were clearly presynaptic to dynorphin-immunoreactive terminals, in most cases, the polarity of the relationship between primary afferents and dynorphin terminals could not be established. These data indicate that synaptic interactions made by and with dynorphin-immunoreactive cells and terminals in the superficial dorsal horn are not very different from those that were previously reported for enkephalin cells and terminals. Thus, it is unlikely that dynorphin terminals provide a significant presynaptic input to primary afferent fibers. On the other hand, the presence of a primary afferent input to dynorphin cell bodies and dendrites in the superficial dorsal horn suggests that dynorphin cells receive a direct input from small-diameter, nociceptive primary afferents. That connection might contribute to the increased levels of dynorphin message and peptide that have been reported in rats experiencing a chronic inflammatory condition.(ABSTRACT TRUNCATED AT 400 WORDS)
Afferent Pathways↗
Arborization of single axons of the spinal dorsolateral funiculus to the contralateral superficial dorsal horn.
This study provides an anatomical basis for the observation that a unilateral lesion of the spinal dorsolateral funiculus (DLF) can reduce the inhibitory effect of electrical stimulation of the nucleus raphe magnus (NRM) on dorsal horn nociceptive neurons located caudal and contralateral to the lesion. We injected the anterograde tracer Phaseolus vulgaris leucoagglutinin (PHA-L) into the NRM and traced the arborization of single DLF axons in the spinal gray matter. Although the majority of DLF axons arborized in the dorsal horn ipsilaterally, we found some axons which entered the spinal gray matter, traversed the gray matter to the central canal and then abruptly changed direction and coursed to the contralateral superficial dorsal horn. Very few branches were given off en route. These data indicate that some raphe-spinal axons may selectively influence the firing of neurons of the superficial dorsal horn, contralateral to the DLF in which they descend the spinal cord.
Animals↗
Neural control of vascular permeability: interactions between primary afferents, mast cells, and sympathetic efferents.
1. This study addressed the contribution of primary afferents, mast cells, and sympathetic efferents to the control of vascular permeability in synovial joints. Extravasation of Evans blue dye into the synovial space was measured by perfusion of the knee joint in the adult rat. Plasma extravasation (PE) was evoked by pharmacologic activation of either unmyelinated primary afferents, mast cells, or sympathetic postganglionic nerve (SPGN) terminals with acute injection of either capsaicin, compound 48/80, or 6-hydroxydopamine (6-OHDA), respectively. In otherwise untreated control rats, acute infusion of capsaicin or compound 48/80 produced a brief increase in vascular permeability; infusion of 6-OHDA produced a larger and more prolonged increase. 2. To evaluate the contribution of an interaction of different cellular elements in the joint to PE, we repeated these experiments in rats pretreated with capsaicin, compound 48/80, or 6-OHDA; administered quercetin; or surgically sympathectomized by excision of the lumbar sympathetic chain. Eliminating unmyelinated afferent nerve terminals by neonatal treatment with capsaicin only reduced the increase in PE produced by acute infusion of capsaicin. Degranulating mast cells by pretreatment with compound 48/80, or preventing the degranulation of mast cells by treatment with quercetin, reduced the increase in PE evoked by infusion of either capsaicin or compound 48/80. Finally, sympathectomy, produced by excision of the lumbar sympathetic chain or by pretreatment with 6-OHDA, significantly reduced PE elicited by acute infusion of capsaicin, compound 48/80, or 6-OHDA. 3. Neither infusing substances normally localized to sympathetic efferents nor inducing changes in blood pressure could mimic the profound increase in PE evoked by activation of sympathetic postganglionic neurons with acute infusion of 6-OHDA. Thus norepinephrine produced a significant decrease in PE, adenosine triphosphate produced only a brief increase, neuropeptide Y had no effect, and manipulating blood pressure (either up or down) had no effect on either base-line or 6-OHDA-induced PE. 4. Indomethacin treatment significantly reduced the increase in PE produced by 6-OHDA. This effect of indomethacin was reversed by the addition of prostaglandin E2 (PGE2) to the 6-OHDA in the perfusion fluid. This finding implicates prostaglandins (i.e., cyclooxygenase products of arachidonic acid metabolism) in SPGN-dependent generation of PE.(ABSTRACT TRUNCATED AT 400 WORDS)
Afferent Pathways↗
A rapid and simple silver enhancement procedure for ultrastructural localization of the retrograde tracer WGAapoHRP-Au and its use in double-label studies with post-embedding immunocytochemistry.
WGAapoHRP-Au is a colloidal gold conjugate of wheat germ agglutinin (WGA) coupled to enzymatically inactive (apo) horseradish peroxidase (HRP). This protein-gold complex has proven very useful for retrograde tracing studies in the nervous system (Basbaum and Menétrey: J Comp Neurol 261:306, 1987). To identify retrogradely labeled cells, the colloidal gold is made visible by silver intensification. As the tracer has no HRP enzymatic activity, it can be combined with HRP-based procedures (or with fluorescent methods) in a variety of multiple-label studies. Standard silver intensification procedures, however, are run at low pH and therefore are incompatible with good EM preservation; moreover, osmication of the tissue oxidizes the silver product, which is then lost in subsequent dehydration steps. This report describes a rapid and simple commercially available silver intensification procedure. The procedure is run at neutral pH and can be performed after osmication. The tracer is readily detected at the EM level and tissue preservation is excellent. This report also demonstrates how sections containing retrogradely labeled neurons can be stained with a post-embedding immunocytochemical method so that the transmitter content of synaptic inputs to these neurons can be identified.
Animals↗
Paradoxical analgesia produced by low doses of the opiate-antagonist naloxone is mediated by interaction at a site with characteristics of the delta opioid receptor.
This study addressed the opiate receptor subclass which underlies the paradoxical analgesic action of intrathecal administration of low doses of the stereospecific opiate receptor antagonist, naloxone. The analgesic effect of low dose naloxone was abolished in rats that had been pretreated 24 hr earlier with a large intrathecal dose of naloxone or 20 min previously with the delta receptor specific antagonist, ICI-174,864. A large intrathecal dose of naloxone administered 24 hr previously also abolished the analgesic effects of the delta-specific ligands [D-Pen2,5]-enkephalin and [D-Ser2]-Leu enkephalin-Thr but not those produced by mu-ligands Tyr-D-Ala-Gly-NMe-Phe-Gly-ol and beta-Casomorphin(1-4) amide or by the kappa-specific ligand, U50,488H. Furthermore, the analgesic action of low dose naloxone (on thermal and mechanical nociceptive threshold tests) persisted in rats made tolerant to mu-opioid receptor specific ligands. We conclude that the analgesic action of a low dose of naloxone is mediated via interaction with a stereospecific binding site with the characteristics of the delta-opioid receptor.
Analgesia↗
Distribution of glycine receptor immunoreactivity in the spinal cord of the rat: cytochemical evidence for a differential glycinergic control of lamina I and V nociceptive neurons.
In this study we characterized the distribution of glycine receptor immunoreactivity in the spinal cord of the rat by using monoclonal antisera directed against the purified glycine receptor. There was dense, punctate glycine receptor immunoreactive staining in all regions of the gray matter ventral to the substantia gelatinosa. The densest staining was found in laminae III and IV of the dorsal horn. There were also distinct, tributarylike bands of punctate staining that extended well into the white matter of the lateral and ventral funiculi. The only consistent cell body staining was found in small neurons of the ventral horn. The labelled neurons were distributed among larger, unlabelled motoneurons. In general, the pattern of glycine receptor immunoreactivity was similar at all levels of the spinal cord and was comparable to that seen with binding of a tritiated glycine receptor antagonist, strychnine, to sections of rat spinal cord (Zarbin et al.: J. Neurosci. 1:532-547, '81). Two important exceptions, however, were observed. In contrast to the high levels of strychnine binding reported in the substantia gelatinosa, we found almost no glycine receptor immunoreactivity in laminae I and II of the superficial dorsal horn of the spinal cord or of the trigeminal nucleus caudalis. There was also a notable absence of antibody staining in the intermediolateral cell column of the thoracic cord. The presence of dense glycine receptor immunoreactivity in the region of lamina V and its absence in the superficial dorsal horn are discussed in terms of a possible differential glycinergic control of nociceptive neurons of laminae I and V.
Animals↗
Use of serotonin immunocytochemistry as a marker of injury severity after experimental spinal trauma in rats.
In experimental models of spinal cord trauma there is often a relatively poor correlation between light microscopic histological changes and motor recovery. Previously it was shown that spinal cord levels of immunoreactive TRH and substance P, by radioimmunoassay, are significantly reduced caudal to the injury site. Since much of the substance P and TRH in the spinal cord derives from cells within the ventral medulla, many of which also contain serotonin, we examined changes in serotonin immunoreactivity within the spinal cord caudal to the injury site in rats subjected to varying degrees of impact trauma to the thoracic cord. Reductions in immunocytochemical staining of serotonin in ventral gray matter of the lumbar region at two weeks after trauma were significantly correlated with the degree of injury severity as reflected by motor impairment. Changes in the region of the central canal, but not dorsal horn, were also correlated with injury severity. These findings indicate that serotonin immunocytochemical analysis may permit better correlation between anatomical and functional outcome after spinal cord injury than generally utilized light microscopic methods.
Animals↗
The effect of gold, an antirheumatic therapy, on substance P levels in rat peripheral nerve.
Intramuscular injections of gold sodium thiomalate in the rat produce a significant depletion of the proinflammatory neuropeptide substance P (SP) from the sciatic nerve. The greatest reduction in SP content occurred during the first two months of treatment. The level of SP in the nerve, however, remained low, throughout an eight month administration of gold. These results, coupled with previous findings that gold produces a selective decrease in the number of unmyelinated axons in peripheral nerve, are consistent with the hypothesis that the anti-inflammatory action of gold involves a neurotoxic effect on peptidergic afferents.
Animals↗
An ultrastructural study of the projections from the midbrain periaqueductal gray to spinally projecting, serotonin-immunoreactive neurons of the medullary nucleus raphe magnus in the rat.
In this triple-label, electron microscopic study in the rat, a lesion of the midbrain periaqueductal gray (PAG) was made so that the distribution and targets of degenerating PAG terminals could be identified in the medullary nucleus raphe magnus (NRM). Spinally projecting NRM neurons were identified by the retrograde transport of wheat germ agglutinin-horseradish peroxidase from the cervical cord. We also used immunocytochemistry to define the subpopulation of NRM neurons which were serotonin-immunoreactive. We report that both serotonergic and non-serotonergic neurons of the medulla, which project to the spinal cord, receive monosynaptic inputs from the PAG.
Animals↗
Increased staining of immunoreactive dynorphin cell bodies in the deafferented spinal cord of the rat.
This study examined the distribution of immunoreactive dynorphin neurons in the lumbar dorsal horn of unilaterally deafferented, colchicine-treated rats. Ipsilateral to a multiple dorsal rhizotomy there was a significant increase both in the number and intensity of staining of dynorphin-immunoreactive cells in laminae I, outer II and V. A comparable change was seen in animals that were deafferented by sciatic nerve section. Enkephalin immunoreactivity was not altered under these conditions. These results indicate that many forms of injury, not all of which result in increased nociceptive input, can increase the level of dynorphin in spinal cord neurons.
Afferent Pathways↗