ABSTRACT
Objective To investigate the effects of skin/muscle incision and retraction(SMIR)on mechanical paw withdrawal threshold and the ability of spatial learning and memory in immature rats after adulthood. Methods 27 male SD rats aged 3 weeks and weighing 60 ~ 80 g were randomly divided into 3 groups(n = 9):control group(group C),sham operation group(group Sham)and skin/muscle incision and retraction group (group SMIR). Group SMIR received operation for skin/muscle incision and retraction. Sham group received skin/muscle incision but no retraction.No surgery was operated on C group. Pain behavior was assessed by mechanical paw withdrawal threshold(MWT)to von Frey filament stimulation before and 1,3,7,12,22 and 32 days after operation.The effects of spatial learning and memory function were assessed by Morris water-maze test at 33 days after operation. Results Mechanical paw withdrawal threshold of group SMIR decreased 1 day after operation (P<0.05)and showed no significant difference before and 3,7,12,22,32 days after operation in 3 groups(P >0.05). In Morris water-maze test,compared with Sham and C group,the average escape latency in SMIR was sig-nificantly longer in the water maze navigation experiment(P < 0.01);the ratios of time and path in the quadrant of the platform were obviously lower in SMIR(P < 0.01). There was no statistical difference between sham and C group(P>0.05).Conclusion SMIR did not cause chronic pain but may cause a decrease in the ability of spatial learning and memory in immature rats.
ABSTRACT
AIM: To observe the expression change of growth and differentiation factor 10 ( GDF10 ) in the spinal cord of the rats with neuropathic pain .METHODS:Male SD rats (n=60) were used.The neuropathic pain was induced by ligation of left L 5 spinal nerves of the animals .The paw withdrawal threshold was detected 1 d before surgery , and 0 d, 1 d, 3 d, 10 d and 21 d after surgery.The changes of GDF10 in the dorsal horn of L5 spinal cord were detected by immunofluorescence staining and Western blot .RESULTS:The paw withdrawal threshold of the rats with spinal nerve ligation was decreased from 1 d after surgery until 3 d with obvious difference compared with the na ve rats ( P<0.05 ) , continuously decreased until 10 d, and then stabilized at 21 d.The GDF10 was located in the cytoplasm of the neurons in the dorsal horn of L5 spinal cord detected by immunofluorescence staining .The expression of GDF10 in L5 dorsal horn de-tected by immunofluorescence staining was reduced after surgery , significantly decreased from 10 d ( P<0.05) until more than 21 d after surgery in spinal nerve ligation group compared with na ve group.GDF10 in L5 spinal cord detected at 10 d after surgery by Western blot was significantly down-regulated in spinal nerve ligation group compared with na ve group (P<0.05).CONCLUSION:Spinal nerve ligation induces the decrease in GDF 10 expression in spinal dorsal horn .The down-regulation of GDF10 may contribute to the regulation of hyperpathia caused by mechanical stimulation after the injury of spinal nerve .
ABSTRACT
Whole bee venom (WBV) and its major component, melittin, have been reported to induce long-lasting spontaneous flinchings and hyperalgesia. The current study was designed to elucidate the peripheral and spinal mechanisms of N-methyl-D-aspartate (NMDA) and non-NMDA receptors by which intraplantar (i.pl.) injection of WBV and melittin induced nociceptive responses. Changes in mechanical threshold and flinching behaviors were measured after the injection of WBV (0.04 mg or 0.1 mg/paw) and melittin (0.02 mg or 0.05 mg/paw) into the mid-plantar area of a rat hindpaw. MK-801 and CNQX (6-cyano-7-nitroquinoxaline-2, 3-dione disodium) were administered intrathecally (i.t. 10microgram) or i.pl. (15microgram) 15 min before or i.t. 60 min after i.pl. WBV and melittin injection. Intrathecal pre- and post- administration of MK-801 and CNQX significantly attenuated the ability of high dose WBV and melittin to reduce paw withdrawal threshold (PWT). In the rat injected with low dose, but not high dose, of WBV and melittin, i.pl. injection of MK-801 effectively suppressed the decrease of PWTs only at the later time-points, but the inhibitory effect of CNQX (i.pl.) was significant at all time-point after the injection of low dose melittin. High dose WBV- and melittin-induced spontaneous flinchings were significantly suppressed by i.t. administration of MK-801 and CNQX, and low dose WBV- and melittin-induced flinchings were significantly reduced only by intraplantarly administered CNQX, but not by MK-801. These experimental flinchings suggest that spinal, and partial peripheral mechanisms of NMDA and non-NMDA receptors are involved in the development and maintenance of WBV- and melittin-induced nociceptive responses.