Assessment of somatosensory development in Wistar rats after pain stimulus during neonate period: gender and age differences

Abstract

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. 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.