Ligustrazine inhibits high voltage-gated Ca~(2+) and TTX-resistant Na~+ channels of primary sensory neuron and thermal nociception in the rat:a study on peripheral mechanism

Objective Ligustrazine, also named as tetramethylpyrazine, is a compound purified from Ligusticum chuanxiong hort and has ever been testified to be a calcium antagonist. The present investigation was to determine the antinoci-ceptive effect of ligustrazine and, if any, the peripheral ionic mechanism involved. Methods Paw withdrawal Latency ( PWL) to noxious heating was measured in vivo and whole-cell patch recording was performed on small dorsal root ganglion (DRG) neurons. Results Intraplantar injection of ligustrazine (0.5 mg in 25μl) significantly prolonged the withdrawal latency of ipsilateral hindpaw to noxious heating in the rat. Ligustrazine not only reversibly inhibited high-voltage gated calcium current of dorsal root ganglion (DRG) neuron in dose-dependent manner with IC50 of 1.89 mmol/L, but also decreased tetrodotoxin (TTX) -resistant sodium current in relatively selective and dose-dependent manner with IC50 of 2.49 mmol/L. Conclusion The results suggested that ligustrazine could elevate the threshold of thermal nociception through inhibiting the high-voltage gated calcium current and TTX-resistant sodium current of DRG neuron in the rat.     

刺激强度对黑质DA能神经元伤害性反应的影响

本研究用细胞外记录方法研究大鼠黑质多巴胺能神经元伤害性反应的特点。共记录了194个多巴胺能神经元。其中,大多数神经元(78％)可被尾部强电刺激(15mA,1.0ms)所抑制,15％被兴奋。兴奋和抑制反应均依赖于刺激强度。当刺激强度变化于0～20mA时,伤害性反应强度与刺激强度的对数显著相关。来自不同部位的刺激可会聚于同一神经元。反应潜伏期和阈值提示Aδ纤维参与伤害性信息传入黑质的过程。本文还讨论了多巴胺能神经元系统在痛觉机制中的作用。     

Mechanisms by which the putative serotonin receptor antagonist metitepin alters nociception in mice

Summary The putative serotonin (5-HT) receptor antagonist metitepin (0.5 mg/ kg, intraperitoneally) produced hypoalgesia in the increasing temperature hot-plate test and hyperalgesia in the tail-flick test in mice. The effects of metitepin were not altered after depletion of 5-HT by the neurotoxin 5,7-dihydroxytryptamine (5, 7-DHT, 80 g free base, intracerebroventricularly) or the serotonin synthesis inhibitor p-chlorophenylalanine (PCPA, 400 mg/kg for 10 consecutive days). After chronic administration (2 or 5 mg/kg for 18 consecutive days) tolerance to the effect of metitepin (0.5 mg/kg) and cross-tolerance to the antinociceptive effect of the 5-HT agonist 5-methoxy-N,N-dimethyltryptamine (5-MeODMT, 3 mg/kg) was found in the hot-plate test but not in the tail-flick test. It is suggested that metitepin may block descending 5-HT transmission while more complex mechanisms of action are involved at supraspinal level. One possibility is that metitepin exhibits partial agonist properties or, alternatively, that the drug may block 5-HT subsystems which tonically enhance nociception.     

Modulation of acute visceral nociception and bladder inflammation by plant triterpene, α, β-amyrin in a mouse model of cystitis: role of tachykinin NK<Subscript>1</Subscript>-receptors,and K<Superscript>+</Superscript><Subscript>ATP</Subscript> channels

Objective and design: We previously described the visceral antinociceptive property of α, β-amyrin in a mouse model of cystitis induced by cyclophosphamide (CPM). This study examined the contribution of vanilloid-1 (TRPV1), peripheral NK1 receptors to CPM-evoked nociceptive behaviors and bladder edema, and its possible modulation by α, β-amyrin. Methods: The effect of α, β-amyrin (10, 30, and 100 mg/kg, p. o.) and N-acetylcysteine (NAC) on CPM (400 mg/kg, i. p.)-induced cystitis was studied in mice. Sensory deafferentation was done by a high dose capsaicin. The parameters analysed were: CPM-evoked noxious behaviors, bladder edema, vascular permeability, and NK₁ immunoreactivity. To assess the role of K⁺ _ATP channels in α, β-amyrin effect, animals were pretreated with glibenclamide. Results: α, β-amyrin (30 and 100 mg/kg) and NAC significantly (p < 0.01) suppressed the visceral pain-related behaviors and NK₁ immunoreactivity, but bladder edema was reduced weakly. Glibenclamide reversed the effects of α, β-amyrin. Sensory deafferentation by capsaicin significantly reduced the nociceptive responses and the NK₁ immunoreactivity to noxious stimulation by CPM. Conclusions: α, β-amyrin attenuates CPM-induced visceral pain and bladder edema by mechanisms that involve, at least in part, a block either of Substance P release or its receptor function, and partly by opening K⁺ _ATP channels. Received 13 February 2007; returned for revision 13 April 2007; accepted by G. Geisslinger 14 May 2007     

Behavioral phenotyping of mice in pharmacological and toxicological research

The evaluation of behavioral effects is an important component for the in vivo screening of drugs or potentially toxic compounds in mice. Ideally, such screening should be composed of monitoring general health, sensory functions, and motor abilities, right before specific behavioral domains are tested. A rational strategy in the design and procedure of testing as well as an effective composition of different well-established and reproducible behavioral tests can minimize the risk of false positive and false negative results in drug screening. In the present review we describe such basic considerations in planning experiments, selecting strains of mice, and propose groups of behavioral tasks suitable for a reliable detection of differences in specific behavioral domains in mice. Screening of general health and neurophysiologic functions (reflexes, sensory abilities) and motor function (pole test, wire hang test, beam walking, rotarod, accelerod, and footprint) as well as specific hypothesis-guided testing in the behavioral domains of learning and memory (water maze, radial maze, conditioned fear, and avoidance tasks), emotionality (open field, hole board, elevated plus maze, and object exploration), nociception (tail flick, hot plate), psychiatric-like conditions (porsolt swim test, acoustic startle response, and prepulse inhibition), and aggression (isolation-induced aggression, spontaneous aggression, and territorial aggression) are described in further detail. This review is designed to describe a general approach, which increases reliability of behavioral screening. Furthermore, it provides an overview on a selection of specific procedures suitable for but not limited to behavioral screening in pharmacology and toxicology.     

Potent anti-inflammatory/analgesic effects of lornoxicam in comparison to other nsaids: A c-fos study in the rat

This study evaluates the anti-inflammatory/analgesic effects of lornoxicam, a new non-steroidal anti-inflammatory drug, using the method of c-Fos protein immunoreactivity in the carrageenan model of inflammatory nociception in the rat. The immunohistochemical revelation of inflammatory/nociceptive stimulation evoked c-Fos expression in spinal neurons was used as an indirect marker of neurons involved in spinal nociceptive transmission. Lornoxicam (0.1, 0.3, 1, 3 and 9 mg/kg; n=10 rats for each group) was preadministered intravenously 25 min before an intraplantar injection of carrageenan (6 mg/150 ml of saline). Three hours after carrageenan, the peripheral oedema (paw and ankle diameters) and the number of c-Fos-protein-like immunoreactive (c-Fos-LI) neurons in the lumbar spinal cord, were assessed. Preadministered lornoxicam dose relatedly reduced the total number of c-Fos-LI neurons (regression coefficient r=0.79; p<0.001) with the strongest effect corresponding to the 75±2% reduction (p<0.001) for the highest dose of 9 mg/kg, and the 45±3% reduction (p<0.001) for the low dose of 0.3 mg/kg. Lornoxicam (0.1, 0.3, 1, 3 and 9 mg/kg iv) significantly reduced the number of c-Fos-LI neurons in both superficial (24±6, 33±5, 53±4, 54±4, and 63±4% reduction, respectively, p<0.001 for all doses) and deep (28±4, 48±4, 62±2, 69±3 and 79±2% reduction, respectively, p<0.001 for all doses) laminae of the dorsal horn of the spinal cord. These reducing effects were dose related in both superficial and deep laminae (regression coefficient r=0.66 and r=0.08, respectively; p<0.001 for both). The lowes dose of lornoxicam (0.1 mg/kg iv) had a similar effect in both superficial and deep laminae, whereas the four higher doses (0.3, 1, 3 and 9 mg/kg iv) had a significantly stronger effect on the number of c-Fos-LI neurons in deep laminae as compared to that in superficial laminae. Lornoxicam (0.1, 0.3, 1, 3 and 9 mg/kg iv) dose relatedly reduced the carrageenan induced oedema at both the paw and ankle levels (regression coefficient r=0.63 and r=0.53, respectively, p<0.001 for both), with a stronger effect on the ankle diameter (34±8, 61±9, 66±8, 80±6 and 83±5% reduction, respectively p<0.001 for all doses). Furthermore reductions of the carrageenan evoked peripheral oedema and spinal c-Fos expression were positively correlated (correlation coefficient r=0.74 and r=0.57 for the paw and ankle diameter respectively, p<0.001 for both). These correlations suggest a predominant peripheral site, without excluding central site of action of lornoxicam in the carrageenan-induced inflammation. Our results provide clear evidence for a potent anti-inflammatory/analgesic effects of low doses of lornoxicam which have a reduced risk of sideeffects. Taken together, the results of the present study revealed the effects of lornoxicam in the same range as those of other previously studied NSAIDs, more precisely, closely comparable to the effects of ketoprofen.     

Calbindin-D28K (CaBP28k)-like Immunoreactivity in Ascending Projections

This study concerns the involvement of calbindin-D28K (CaBP28k)-containing neurons in ascending spinal projections to the brainstem (nucleus of the solitary tract, lateral reticular nucleus area), pontine (parabrachial area) and mesencephalic (periaqueductal grey) structures. All these central structures are important in the processing of visceroception and visceronociception and all are targets for spinal efferents from similar areas. CaBP28k controls the excitability of cells by acting on intrinsic calcium metabolism. Results refer to the caudal spinal areas where the visceroceptive regions are concentrated. Experiments were performed through a double labelling approach that combined the retrograde transport of a protein - gold complex to identify the projection cells and immunohistochemistry to identify the CaBP28k-positive cells. The caudal spinal cord is rich in both CaBP28k-containing and projection cells. Cells colocalizing the protein and the retrograde tracer were quite numerous, with a particularly high concentration in the superficial layers of the dorsal horn (laminae I and outer II) and the lateral spinal nucleus. The other spinal areas containing immunoreactive projection cells were the reticular part of the neck of the dorsal horn, the medial laminae VII and VIII, lamina X and the sacral parasympathetic nucleus. The superficial layers and the neck of the dorsal horn are targets for nociceptive, visceroceptive and thermal inputs; the sacral parasympathetic column and lamina X are involved in visceroceptive integration. A functional role for the lateral spinal nucleus has not yet been established. Quite similar results were obtained for each of the ascending pathways under study. The high incidence of CaBP28k in spinal pathways suggests that calbindin has a major role in controlling the excitability of spinal cells subserving the processing of visceroception and/or visceronociception information to supraspinal levels. The participation of CaBP28k-immunoreactive cells in spinal ascending tract cells largely outnumbers those previously reported for various neuropeptides (Leah et al., Neuroscience, 24, 195 - 207, 1988)     

酸敏感离子通道的研究进展

酸敏感通道广泛表达于中枢与外周神经系统,在疼痛、伤害感觉中发挥了重要的作用。其分子结构与分布特点、调控机制以及在某些病理生理过程中的作用已经得到了部分阐明。未来对其研究将是离子通道研究领域的热门课题。     

A Novel Diagnostic Test for End-Stage Sensory Failure Associated With Diabetic Foot Ulceration: Proof-of-Principle Study

Background:Diabetic foot ulceration (DFU) affects only a subgroup of patients with diabetic neuropathy, that is, those with pain-insensitivity due to end-stage sensory failure. Pain perception failure develops insidiously and remains asymptomatic until first DFU. As loss of pain perception is clinically significant, timely detection is mandatory.Objectives:A novel suprathreshold pinprick pain stimulus of 512 mN force made from optical glass-fiber was explored in a prospective cross-sectional diagnostic accuracy study to detect DFU-related end-stage sensory failure.Methods:A total of 116 participants were studied (25 healthy people, 22 patients with diabetes without relevant complications, 19 patients with previous painful foot or leg injuries, and 50 patients with previous or active painless DFU [reference standard]). Palmar and plantar surfaces were stimulated in a standardized fashion. At the feet, the second and third toe skinfolds and the middle of the plantar arch were stimulated. Participants scored stimulated pricking discomfort or pain intensity 0 to 10 on a numerical rating scale.Results:At hands, intensity was rated on average 5 (1-10) [median (range)] by 114/116 participants. Per foot, participants without DFU scored 5 (1-10), while those with DFU scored 0 (0-3) (P < .0001). At plantar toe skinfolds, the absence of pinprick pain perception detected DFU-associated sensory failure with an accuracy of 99.5% (sensitivity 99.5%, specificity 99.4%, positive likelihood ratio 248, and negative likelihood ratio 0.005).Conclusion:In this pilot study, nociceptive stimulation of a plantar toe skinfold with a 512 mN optical glass-fiber pinprick accurately identified DFU-associated end-stage sensory failure.     

Nociceptive and sympathetic innervations in the abaxial part of the cranial horn of the equine medial meniscus: an immunohistochemical approach

In athletic horses, diseases leading to lameness are of great importance due to the loss of performance and the resultant economic concerns. Although stifle lesions are frequent in the hindlimb, due to the large size and complexity of the joint, and although meniscal tears have been identified as the most common soft tissue injuries in this joint, little is known about the mechanism that causes the painful sensation and thus the lameness. The aim of our study was to highlight any peripheral fibres involved in meniscal nociception in five macroscopically sound cranial horns of the equine medial meniscus, which has been one of the most common sites reported for equine meniscal injuries. Immunohistochemical stainings were performed using antibodies against Substance P in order to identify nociceptive fibres; against tyrosine hydroxylase for detecting postganglionic sympathetic fibres; and against glial fibrillary acidic proteins in order to identify Schwann cells. Our work highlights for the first time the presence of nociceptive and sympathetic fibres in equine menisci. They were found in the abaxial part of the cranial horn of the equine medial meniscus. This study suggests that when the abaxial part is injured, the meniscus itself could be the source of pain. These findings could provide a better understanding of the clinical presentation of horses with meniscal injury and contribute towards improving therapeutic strategies to alleviate pain in cases of equine meniscal injury.