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Analysis of muscle strength and mechanical allodynia in Wistar rats after painful stimulation during neonatal period
Abstracts (236) Anti-hypernociceptive properties of extract from the Bulbils of Dioscorea bulbifera L. var sativa (Dioscoreaceae) in persistent inflammatory and neuropathic models of pain in mice M Mbiantcha; University of Dschang , Dschang, Ouest Region, Cameroon Here we evaluated the antinociceptive effects of the extract from the bulbils of Dioscorea bulbifera L. var sativa (Dioscoreaceae) in persistent inflammatory and neuropathic models of pain in mice, in order to assess some of the mechanisms involved in its actions. This plant is used in Cameroonian traditional medicine in the treatment of many pathologies including pain. The analgesic effects were evaluated on three models of acute pain induced by LPS, PGE2 and capsaicin, one model of chronic inflammatory pain induced by CFA and two models of neuropathic pain induced after avulsion of the brachial nerve and sciatic nerve ligature. Oral administration of the methanol extract inhibited significantly and in a dose-dependent manner the different models of pain used. The methanol extract of D. bulbifera significantly inhibited acute pain induced by LPS and prostaglandin E2, the inflammatory pain induced by CFA and the neuropathic pains induced by avulsion of the brachial nerve and sciatic nerve ligature; in addition, on the other hand this extract did not have an effect on the capsaicin induced pain. The analgesic activity of the methanol extract of D. bulbifera was inhibited by L-NAME and glibenclamide on the prostaglandin E2 induced pain. These results suggest that, the analgesic effect of the extract of D. bulbifera could result from an activation of the NO/GMPc/ ATP dependent potassium channel. These results show that the bulbils of D. bulbifera possess analgesic properties. In conclusion, Dioscorea bulbifera L. var sativa have therapeutic virtues, which justify its use in traditional medicine. The results of this study show that this plant is equipped with pharmacological analgesics properties and probably anti-inflammatory.
The Journal of Pain
P35
(238) Analysis of muscle strength and mechanical allodynia in Wistar rats after painful stimulation during neonatal period E Carmo, L Sanada, N Machado, and V Fazan; School of Medicine of Ribeir~ao Preto , S~ao Paulo, Brazil The childhood of rats is marked by countless changes in the skeletal muscle system, thus an increased functional demand. Although the literature has shown similarities between humans and rats pain pathways, little is known about the painful effects on neonatal development in relation to muscle strength and mechanical allodynia. The aim of the present study was to analyze if the pain on neonate period were capable to alter the sensitivity and the strength of the hindpaw, and if there is any difference between genders. Forty Wistar rats were separated in 4 groups: I) Male control group (N=10); II) Female control group (N=10); III) Male pain group (N=10); IV) Female pain group (N=10). All animals were followed since they were born until 90 days of life. The pain group was stimulated with a needle on the right hindpaw, twice a day for 15 days. The control group was stimulated with a swab on the right hindpaw, twice a day for 15 days. All animals were evaluated with 15, 30, 60 and 90 days of life. For the assessment, we applied Von Frey Monofilament and the assessment of muscle strength of hindpaw in both groups was conducted through Grip Strength Meter. This device measures the grip strength of the hindpaw of rats. Specific static tests were applied, and p value was considered significant when it was lower than 0.05. We observed that the pain group, male and female, had lower scores of grip test when they were compared with the control group. No difference was observed when gender was analyzed. Furthermore, there was no difference on the sensibility of the hindpaw, when the pain and control group were compared. Therefore, the pain in neonate period was capable to alter the strength in male and female. Financial Support: CNPq, CAPES, FAEPA and FAPESP.
E02 Animal Pain Models - Other (237) The effects of modulating stimulation parameters of spinal cord stimulation (SCS) and glial activity in animals with neuropathic pain K Sato, E King, L Johanek, and K Sluka; University of Iowa, Iowa City, IA Spinal cord stimulation is (SCS) is an effective treatment for the management of chronic intractable neuropathic pain. We therefore used an animal model of SCS to modulate frequency (4Hz vs. 60Hz), duration (30m vs. 6h), or intensity (50%, 75%, or 90% MT) in animals with neuropathic pain. To elucidate potential mechanisms modulated by SCS we examined immunoreactivity for glial markers in the spinal cord in animals with SCS compared to those with sham SCS. Neuropathic pain was induced in Sprague-Dawley rats using the spared nerve injury model (SNI). An epidural SCS lead was implanted in the upper lumbar spinal cord. Animals were tested for mechanical withdrawal threshold (MWT) of the paw before and 2 weeks after SCS, before and after SCS daily for 4 days, and 1, 4 and 9 days after SCS. Group of animals was transcardially perfused after 4 days of 6 h SCS and glial immunoreactivity examined. All rats showed a decrease in MWT 2 weeks after nerve injury and an increase on glial activation. For frequency, 4Hz or 60Hz SCS reversed the MWT when compared to sham SCS. For duration, 6h of SCS showed a greater reduction in MWT when compared to 30 min; both durations were greater than sham SCS. For intensity, 90% MT was greater than 75% MT and both were greater than sham SCS; 50% MT SCS had no effect and was no different from sham. SCS decreased glial activation in the spinal cord dorsal horn when compared to sham. In conclusion, 4Hz and 60 Hz SCS for 6h duration and 90% MT intensity were the most effective parameters for reducing hyperalgesia suggesting parameters of stimulation are important for clinical effectiveness of SCS. One potential mechanisms of effect for SCS may be to reduce glial activation at the level of the spinal cord.
(239) Assessment of somatosensory development in Wistar rats after pain stimulus during neonate period: gender and age differences L Sanada, N Machado, E Carmo, and V Fazan; School of Medicine of Ribeir~ao Preto, S~ao Paulo, Brazil Premature infants are often exposed to repetitive invasive procedures causing acute pain during the course of neonatal intensive care. A series of anatomic, neurochemical, and electrophysiological experiments in neonatal rats have revealed that repetitive painful experiences or prolonged tissue or nerve damage can lead to long-lasting neurobehavioral sequel. Nevertheless, there are few investigations on the long term effects of pain during neonatal period, assessing the somatosensory development. Therefore the aim of the present study were to evaluate the somatosensory development of Wistar rats which suffered pain or sensitive stimuli during the neonatal period, comparing different ages and gender. Wistar rats (n=40) were followed since they were born until 90 days of life, and they were separated in 4 groups: 1) Male control group (10 animals stimulated with swab twice a day for 15 days, since they were born); 2) Female control group (10 animals stimulated with swab twice a day for 15 days, since they were born); 3) Male pain group (10 animals stimulated with needle twice a day for 15 days, since they were born); 4) Female pain group (10 animals stimulated with needle twice a day for 15 days, since they were born). Animals were evaluated with 15, 30, 60 and 90 days of life. Functional assessment was performed by the Von Frey Monofilament, Calibrated Forceps and Gait analysis. Specific statistic tests were applied, and differences were considered significant when p<0.05. There was a significant difference between control and pain groups, in different ages, when we compared calibrated forceps and gait analysis. Furthermore, there was a significant difference between genders, in pain group, when we compared the calibrated forceps. Therefore, pain stimuli in neonate period were capable to alter the somatossensory development in young rats. Financial Support: FAPESP, CNPq, CAPES and FAPEPA.
The Journal of Pain
P35
(238) Analysis of muscle strength and mechanical allodynia in Wistar rats after painful stimulation during neonatal period E Carmo, L Sanada, N Machado, and V Fazan; School of Medicine of Ribeir~ao Preto , S~ao Paulo, Brazil The childhood of rats is marked by countless changes in the skeletal muscle system, thus an increased functional demand. Although the literature has shown similarities between humans and rats pain pathways, little is known about the painful effects on neonatal development in relation to muscle strength and mechanical allodynia. The aim of the present study was to analyze if the pain on neonate period were capable to alter the sensitivity and the strength of the hindpaw, and if there is any difference between genders. Forty Wistar rats were separated in 4 groups: I) Male control group (N=10); II) Female control group (N=10); III) Male pain group (N=10); IV) Female pain group (N=10). All animals were followed since they were born until 90 days of life. The pain group was stimulated with a needle on the right hindpaw, twice a day for 15 days. The control group was stimulated with a swab on the right hindpaw, twice a day for 15 days. All animals were evaluated with 15, 30, 60 and 90 days of life. For the assessment, we applied Von Frey Monofilament and the assessment of muscle strength of hindpaw in both groups was conducted through Grip Strength Meter. This device measures the grip strength of the hindpaw of rats. Specific static tests were applied, and p value was considered significant when it was lower than 0.05. We observed that the pain group, male and female, had lower scores of grip test when they were compared with the control group. No difference was observed when gender was analyzed. Furthermore, there was no difference on the sensibility of the hindpaw, when the pain and control group were compared. Therefore, the pain in neonate period was capable to alter the strength in male and female. Financial Support: CNPq, CAPES, FAEPA and FAPESP.
E02 Animal Pain Models - Other (237) The effects of modulating stimulation parameters of spinal cord stimulation (SCS) and glial activity in animals with neuropathic pain K Sato, E King, L Johanek, and K Sluka; University of Iowa, Iowa City, IA Spinal cord stimulation is (SCS) is an effective treatment for the management of chronic intractable neuropathic pain. We therefore used an animal model of SCS to modulate frequency (4Hz vs. 60Hz), duration (30m vs. 6h), or intensity (50%, 75%, or 90% MT) in animals with neuropathic pain. To elucidate potential mechanisms modulated by SCS we examined immunoreactivity for glial markers in the spinal cord in animals with SCS compared to those with sham SCS. Neuropathic pain was induced in Sprague-Dawley rats using the spared nerve injury model (SNI). An epidural SCS lead was implanted in the upper lumbar spinal cord. Animals were tested for mechanical withdrawal threshold (MWT) of the paw before and 2 weeks after SCS, before and after SCS daily for 4 days, and 1, 4 and 9 days after SCS. Group of animals was transcardially perfused after 4 days of 6 h SCS and glial immunoreactivity examined. All rats showed a decrease in MWT 2 weeks after nerve injury and an increase on glial activation. For frequency, 4Hz or 60Hz SCS reversed the MWT when compared to sham SCS. For duration, 6h of SCS showed a greater reduction in MWT when compared to 30 min; both durations were greater than sham SCS. For intensity, 90% MT was greater than 75% MT and both were greater than sham SCS; 50% MT SCS had no effect and was no different from sham. SCS decreased glial activation in the spinal cord dorsal horn when compared to sham. In conclusion, 4Hz and 60 Hz SCS for 6h duration and 90% MT intensity were the most effective parameters for reducing hyperalgesia suggesting parameters of stimulation are important for clinical effectiveness of SCS. One potential mechanisms of effect for SCS may be to reduce glial activation at the level of the spinal cord.
(239) Assessment of somatosensory development in Wistar rats after pain stimulus during neonate period: gender and age differences L Sanada, N Machado, E Carmo, and V Fazan; School of Medicine of Ribeir~ao Preto, S~ao Paulo, Brazil Premature infants are often exposed to repetitive invasive procedures causing acute pain during the course of neonatal intensive care. A series of anatomic, neurochemical, and electrophysiological experiments in neonatal rats have revealed that repetitive painful experiences or prolonged tissue or nerve damage can lead to long-lasting neurobehavioral sequel. Nevertheless, there are few investigations on the long term effects of pain during neonatal period, assessing the somatosensory development. Therefore the aim of the present study were to evaluate the somatosensory development of Wistar rats which suffered pain or sensitive stimuli during the neonatal period, comparing different ages and gender. Wistar rats (n=40) were followed since they were born until 90 days of life, and they were separated in 4 groups: 1) Male control group (10 animals stimulated with swab twice a day for 15 days, since they were born); 2) Female control group (10 animals stimulated with swab twice a day for 15 days, since they were born); 3) Male pain group (10 animals stimulated with needle twice a day for 15 days, since they were born); 4) Female pain group (10 animals stimulated with needle twice a day for 15 days, since they were born). Animals were evaluated with 15, 30, 60 and 90 days of life. Functional assessment was performed by the Von Frey Monofilament, Calibrated Forceps and Gait analysis. Specific statistic tests were applied, and differences were considered significant when p<0.05. There was a significant difference between control and pain groups, in different ages, when we compared calibrated forceps and gait analysis. Furthermore, there was a significant difference between genders, in pain group, when we compared the calibrated forceps. Therefore, pain stimuli in neonate period were capable to alter the somatossensory development in young rats. Financial Support: FAPESP, CNPq, CAPES and FAPEPA.