THE ROLE OF NUCLEUS RAPHE MAGNUS IN THE ANTINOCICEPTIVE EFFECT OF MUSCLE SPINDLE AFFERENTS IN THE RAT

Objective To investigate the role of NRM in the antinociceptive effect of muscle spindle afferents,the influence of NRM lesion on the inhibitory effect of muscle spindle afferents on the nociceptive responses of wide dynamic range (WDR) neurons and the effects of the muscle spindle afferents on the NRM neuronal activities were observed. Methods The single units of WDR neurons in the spinal dorsal horn were recorded extracellularly, and the inhibitory effects of activating muscle spindle afferents by intravenous administration of succinylcholine (SCH) on the C fibers evoked responses (C responses) of WDR neurons were tested before and after lesion of NRM.The effects of the muscle spindle afferents activated by administrating SCH on the single NRM neurons were also examined.Results ①It was found that the C responses of WDR neurons were significantly inhibited by intravenously administration of SCH, and the inhibitory effect was reduced after lesion of NRM;②The activities of most of the NRM neurons could be changed significantly by administrating SCH. According to their responses, NRM neurons could be classified into three types:excitatory, inhibitory and non responsive neurons, and the responses were dose dependent. Conclusion These results suggest that the muscle spindle afferents evoked by SCH may activate the NRM neurons, which plays an important role in the antinociception of muscle spindle afferents.

Acute toxicity of 3,4-methylenedioxymethamphetamine in the anxious mood of rats

BACKGROUND： The long-term neurotoxicity of 3,4-methylenedioxymethamphetamine （MDMA） mainly caused by repeated exposure to MDMA or a single big dose of MDMA, which results in degeneration of serotonin terminal of central nervous system, and someone believe that the great release of serotonin transmitter in central nervous system will lead to anxious mood. OBJECTIVE： To observe the changes of anxiety related behaviors in rats after single administration of different doses of MDMA. DESIGN： A randomized control study SETTING： Laboratory of Psychopharmacology of the Mental Health Center, West China Hospital of Sichuan University. MATERIALS： Thirty male adult Wistar rats, weighing （251.3＋18.34） g, were used, MDMA were obtained from the National Institute for the Control of Pharmaceutical and Biological Products, and dissolved in saline. All the doses of the drug were administered in a volume of 1 mg/kg. METHODS ： The experiment was carried out in the Laboratory of Psychopharmacology of the Mental Health Center, West China Hospital of Sichuan University in July 2003. ①The rats were randomly divided into control group （n=6） and experimental group （n=24）, and then those in the latter were randomly assigned into four subgroups of MDMA 3, 5, 10 and 20 mg/kg groups, with 6 rats in each, which were administrated by single intraperitoneal injection of MDMA 3, 5, 10 and 20 mg/kg respectively, and those in the control group were administrated by single intraperitoneal injection of saline of the same volume. ② The open field test, elevated plus-maze test and social interaction test were performed immediately after administration. For the open field test, the apparatus was situated in a darkened room, illuminated by a single 60 W white light bulb located approximately 60 cm above the center of the open field. Before administration, all the rats were placed into the open field to be familiar with the open field for 5 minutes. They were observed for 45 minutes after administration. The locomotion （number of squares the rat passes）, rearing response, time spent in central squares and defecation were observed, 1 minute for each time for a total of 9 times. For the elevated plus-maze test, the maze was situated in a quiet darkened room, illuminated by a single 60 W white light bulb located approximately 50 cm above the center of the maze. Arm entries were only counted when all the four paws had entered either a closed or an open arm within 5 minutes, and the time spent in the arms were observed. For the social interaction test, the matched rats were put into the arena head-to-head in opposite direction, and aggressive-type behaviors, avoidance, passive and exploration were observed. ③ The one-way analysis of variance was performed with the SPSS 10.0 software. MAIN OUTCOME MEASURES： The results of open field test, elevated plus-maze test and social interaction test were observed. RESULTS： All the 30 rats were involved in the analysis of results. ① Results of open field test： After single administration of MDMA of 5, 10 and 20 mg/kg, the dose-dependent Iocomotors （number of squares the rat passes） in the experimental groups were obviously higher than those in the control group [（21.67±17,55）, （34.44±19.47）, （33.48±23.34）, （7.31 ±6,02） s; P 〈 0.05], and the rearing responses were markedly lower than those in the control group [（0.70±1.71）, （0.96±1.68）, （0.39±0.88）, （1.37±1.59） s, P 〈 0.05]. ② Results of the elevated plus-maze test： After acute administration of MDMA, there were no differences between the MDMA subgroups and saline group in the number of open-arms entries, the open-arms time, the percent of number of open arm entries/total arm entries, and the percent of time spent on the open arms/total time （P 〉 0.05）.③ Results of the social international test： After acute administration of MDMA, there were no differences between the MDMA subgroups and saline group in the aggressive-type behaviors, avoidance, passive, exploration and total time of interaction （P 〉 0.05） CONCLUSION： The acute administration of MDMA has no obvious influence on the anxiety-related behaviors of rats.

Recording of spared motor evoked potentials and its augmentation by 4-aminopyridine in chronic spinal cord-injured rats

Objective To research the direct electrophysiological evidence of discomplete spinal cord injury (SCI) and the effect of 4-aminopyridine on it.Methods Motor evoked potentials (MEPs), both spinal cord recorded MEPs (scMEPs) and extracellularly recorded MEPs (exMEPs) were recorded and characterized on a T13 epidural electrode (scMEPs) and an extracellular microelectrode (exMEPs) for 10 normal rats and 40 rats with lesions of various severity (sham, 35?g*cm force (gcf), 70?gcf, 100?gcf impact injury) at the T8-T9 cord using the Allen's drop model. The incline plane and Tarlov techniques were used to assess clinical neurological function. Results MEPs in the normal rats were elicited by applying transcortical suprathreshold stimulation consisting of 3-4 early negative peaks (N1, N2, N3 and N4) followed by several late waves. The N1 and N2 peaks were largest in the anterior and ventrolateral funiculus, respectively, which was indicative of extrapyramidal pathways. The 100?gcf impact injuries and the cord transection abolished the MEP distal to the lesion, whereas the 35?gcf injuries resulted in a latency shift and amplitude decrement of the MEP peaks. Eighteen of the 20 rats with 70?gcf injuries showed clinical paraplegia. Among them, 7 rats had neurophysiological evidence of residual conduction pathways through the lesioned cord segment, such as the presence of N1 and N2 peaks in the scMEPs or exMEPs. After 4-aminopyridine (4-AP) administrations (1?mg/kg), the amplitude of the spared exMEP increased significantly and spread more widely. Conclusions MEPs evoked by transcortical stimulation travel mostly in the extrapyramidal tract. MEP monitoring could provide an excellent method of detecting the functional integrity of the motor tracts after SCI, and could even detect spared motor fibers after discomplete SCI. Furthermore, the use of 4-AP or other K+ channel blocking agents may be a potential treatment for patients with chronic moderate to severe SCI.

Blockade of 4-1BB/4-1BB ligand interactions prevents acute rejection in rat liver transplantation

Background Blocking the 4-1BB/4-1BB ligand （4-1BBL） signal may modulate the secretion of Th1/Th2 cytokines and prolong the survival of the grafts, which play a key role in organ transplantation tolerance. The aim of this study was to investigate the role of blockade of the 4-1BB/4-1BBL co-stimulatory pathway with 4-1BBL monoclonal antibody （mAB） in acute rejection of rat orthotopic liver transplantation. Methods The orthotopic liver transplantation model was set up, while male Lewis rats were used as liver donors and Brown-Norway rats as recipients. The recipient rats were intravenously injected with anti 4-1BBL mAB or isotype control antibody. Groups were monitored for graft survival after transplantation. Plasma chemistry, including aspartate transaminase （AST）, alanine aminotransferase （ALT）, and bilirubin （BIL）, was assayed. The concentrations of interleukin （IL）-2, IL-10 and interferon （IFN）-γ in plasma were also measured by enzyme-linked immunosorbent assay. Allograft histology images were collected under light microscope and electron microscope. Results Isotype antibody treated recipients exhibited elevated plasma levels of liver injury markers including AST, ALT and BIL, progressive portal and venous inflammation and cellular infiltration of the liver ailografts, and a mean graft survival time （MST） of 10.9 days. Administration of anti 4-1BBL mAB resulted in a decrease in plasma levels of liver injury markers and the concentrations of IL-2, IL-10 and IFN-γ. The histological grade of rejection on day 7 decreased and MST （17.3 days） increased substantially. Conclusions These results demonstrate that attenuation of acute rejection follows the blockade of the 4-1BB/4-1BBL co-stimulatory pathway with 4-1BBL monoclonal antibody and strongly suggest it is a promising strategy to prevent progression of graft rejection by suppressing T cell-mediated immunity.