piperidines and Tibial-Fractures

Tibia fracture followed by cast immobilization in rats evokes nociceptive, vascular, epidermal, and bone changes resembling complex regional pain syndrome (CRPS). In most cases, CRPS has three stages. Over time, this acute picture, allodynia, warmth, and edema observed at 4 weeks, gives way to a cold, dystrophic but still painful limb. In the acute phase (at 4 weeks post fracture), cutaneous immunological and NK1-receptor signaling mechanisms underlying CRPS have been discovered; however, the mechanisms responsible for the chronic phase are still unknown. The purpose of this study is to understand the mechanisms responsible for the chronic phases of CRPS (at 16 weeks post fracture) at both the peripheral and central levels.. We used rat tibial fracture/cast immobilization model of CRPS to study molecular, vascular, and nociceptive changes at 4 and 16 weeks post fracture. Immunoassays and Western blotting were carried out to monitor changes in inflammatory response and NK1-receptor signaling in the skin and spinal cord. Skin temperature and thickness were measured to elucidate vascular changes, whereas von Frey testing and unweighting were carried out to study nociceptive changes. All data were analyzed by one-way analysis of variance (ANOVA) followed by Neuman-Keuls multiple comparison test to compare among all cohorts.. In the acute phase (at 4 weeks post fracture), hindpaw allodynia, unweighting, warmth, edema, and/or epidermal thickening were observed among 90 % fracture rats, though by 16 weeks (chronic phase), only the nociceptive changes persisted. The expression of the neuropeptide signaling molecule substance P (SP), NK1 receptor, inflammatory mediators TNFα, IL-1β, and IL-6 and nerve growth factor (NGF) were elevated at 4 weeks in sciatic nerve and/or skin, returning to normal levels by 16 weeks post fracture. The systemic administration of a peripherally restricted IL-1 receptor antagonist (anakinra) or of anti-NGF inhibited nociceptive behaviors at 4 weeks but not 16 weeks. However, spinal levels of NK1 receptor, TNFα, IL-1β, and NGF were elevated at 4 and 16 weeks, and intrathecal injection of an NK1-receptor antagonist (LY303870), anakinra, or anti-NGF each reduced nociceptive behaviors at both 4 and 16 weeks.. These results demonstrate that tibia fracture and immobilization cause peripheral changes in neuropeptide signaling and inflammatory mediator production acutely, but central spinal changes may be more important for the persistent nociceptive changes in this CRPS model.

Topics: Animals; Antibodies; Antirheumatic Agents; Body Temperature; Complex Regional Pain Syndromes; Cytokines; Disease Models, Animal; Hindlimb; Indoles; Interleukin 1 Receptor Antagonist Protein; Male; Nerve Growth Factor; Neurokinin-1 Receptor Antagonists; Nociception; Piperidines; Rats; Rats, Sprague-Dawley; Receptors, Neurokinin-1; Sciatic Nerve; Substance P; Tibial Fractures; Time Factors

Patients with complex regional pain syndrome have increased tryptase in the skin of the affected extremity indicating mast cell (MC) accumulation and degranulation, processes known to be mediated by substance P (SP). The dysregulation of SP release from primary afferent neurons is characteristic of complex regional pain syndrome. The authors hypothesized that SP acting through the neurokinin-1 receptor results in mast cell accumulation, degranulation, and nociceptive sensitization in a rat model of complex regional pain syndrome.. Groups of 6-10 rats underwent tibia fracture and hind limb casting for 4 weeks, and the hind paw skin was harvested for histologic and immunohistochemical analysis. The effects of a selective neurokinin-1 receptor antagonist (LY303870) and of direct SP intraplantar injection were measured. Dermal MC degranulation induced by sciatic nerve stimulation and the effects of LY303870 on this process were investigated. Finally, the antinociceptive effects of acute and chronic treatment with a MC degranulator (48/80) were tested.. The authors observed that fracture caused MC accumulation, activation, and degranulation, which were inhibited by LY303870; the percentage of MCs in close proximity to peptidergic nerve fibers increased after fracture; electrical stimulation caused MC activation and degranulation, which was blocked by LY303870; intraplantar SP-induced MC degranulation and acute administration of 48/80 caused MC degranulation and enhanced postfracture nociception, but MC-depleted animals showed less sensitization.. These results indicate that facilitated peptidergic neuron-MC signaling after fracture can cause MC accumulation, activation, and degranulation in the injured limb, resulting in nociceptive sensitization.

Topics: Animals; Complex Regional Pain Syndromes; Disease Models, Animal; Indoles; Male; Mast Cells; Neurokinin-1 Receptor Antagonists; Nociception; Pain Measurement; Piperidines; Rats; Rats, Sprague-Dawley; Receptors, Neurokinin-1; Substance P; Tibial Fractures

A 63-year-old woman with amyotrophic lateral sclerosis (ALS) was scheduled for open reduction and internal fixation of the right tibia. Total intravenous anesthesia using propofol and remifentanil without muscle relaxant was selected as the anesthetic method, in order to avoid the possible occurrence of ventilatory depression due to abnormal responses to muscle relaxants and exacerbation of the motor neuron disease. After standard and neuromuscular monitoring devices were applied, anesthesia was induced and maintained with target controlled infusion of propofol and remifentanil in the range of 2.5-5.0 microg x ml(-1) and 2.5-5.0 ng x ml(-1), respectively. To avoid delayed neuromuscular recovery, we did not use any muscle relaxant at all. Intubation was successful and there were no remarkable events during anesthesia, except for three brief hypotensive events; there was no exacerbation of ALS itself during or after the anesthesia. She was discharged on postoperative day 3, without any discomfort.

Topics: Amyotrophic Lateral Sclerosis; Anesthesia, Intravenous; Anesthetics, Intravenous; Female; Fracture Fixation; Humans; Intubation, Intratracheal; Middle Aged; Muscle Relaxants, Central; Piperidines; Propofol; Remifentanil; Tibial Fractures

Wrist and ankle fractures are the most frequent causes of complex regional pain syndrome (CRPS type I). The current study examined the temporal development of vascular, nociceptive and bony changes after distal tibial fracture in rats and compared these changes to those observed after cast immobilization in intact normal rats. After baseline testing the right distal tibial was fractured and the hindlimb casted. A control group was simply casted without fracturing the tibia. After 4 weeks the casts were removed and the rats retested. Subsequent testing was performed at 6, 8, 10, 16, and 20 weeks after onset of treatment. Distal tibial fracture or cast immobilization alone generated chronic hindlimb warmth, edema, spontaneous protein extravasation, allodynia, and periarticular osteoporosis, changes resembling those observed in CRPS. Hindlimb warmth and allodynia resolved much more quickly after cast immobilization than after fracture. Previously we observed that the substance P receptor (NK(1)) antagonist LY303870 reversed vascular and nociceptive changes in a sciatic section rat model of CRPS type II. Postulating that facilitated substance P signaling may also contribute to the vascular and nociceptive abnormalities observed after tibial fracture or cast immobilization, we attempted to reverse these changes with LY303870. Hindpaw warmth, spontaneous extravasation, edema, and allodynia were inhibited by LY303870. Collectively, these data support the hypotheses that the distal tibial fracture model simulates CRPS, immobilization alone can generate a syndrome resembling CRPS, and substance P signaling contributes to the vascular and nociceptive changes observed in these models.

Topics: Animals; Body Temperature; Bone Diseases, Metabolic; Casts, Surgical; Disease Models, Animal; Edema; Hindlimb; Indoles; Male; Nociceptors; Piperidines; Rats; Rats, Sprague-Dawley; Reflex Sympathetic Dystrophy; Signal Transduction; Substance P; Tibial Fractures