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Long term muscle involvement after neonatal pain
Author(s) -
Alves Júlia Aparecida,
Simões Ana Leda B,
Dias Fernando José,
Carmo Elisabete C,
Machado Nathalia B,
Sanada Luciana S,
Fazan Valeria Paula Sassoli
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.30.1_supplement.1043.10
Subject(s) - grip strength , medicine , nociception , gastrocnemius muscle , anesthesia , anatomy , physiology , skeletal muscle , receptor
Nociceptive stimuli applied soon after birth play an important role in the development of pain in adult life. Previous studies in our laboratory have shown that pain in the neonatal period can cause a number of changes both in the central nervous system and the musculoskeletal [1], but experimental substrates for these changes still need investigation. We designed an experimental study to explore whether pain in the neonatal period can cause long term changes in the locomotor system. The pain groups (male and female Wistar rats, N = 10 per group) were stimulated with a needle on the right hind paw, twice a day, since birth, for 15 consecutive days. The control groups (male and female Wistar rats, N = 10 per group) were stimulated with a cotton swab. Final experiments were performed 180 days after birth. In order to evaluate the motor function of the hind paws, grip strength tests were conducted. Maximum and average (mean of three consecutive measures) grip strength were studied. Afterwards, rats were anesthetized and the medial gastrocnemius (MG) muscles were obtained by surgical biopsy. The muscle fragments were frozen and stained with the techniques for nictotinamide adenine dinucleotide (NADH) and mitochondrial succinate dehydrogenase (SDH). For muscle morphometry, the number of fibers was counted and their area and diameter were measured. Specific statistic tests were applied and differences were considered significant when p<0.05. The grip strength was higher in males compared to females in both, control and pain groups, but smaller on pain groups, in both genders, compared to controls. Preliminary morphometric results showed that the female pain group had a higher average area of the MG fibers than the control group, while no differences between pain and control groups were found on males. The comparison between genders showed that male controls have larger average number of fibers compared to the females. On the pain groups, females showed larger fiber area compared to males. Our results are suggestive that pain in the neonatal period caused a reduced grip ability that was maintained in the long term after the painful stimulus was ceased, with a slightly better performance on older females. Neonatal pain was also responsible for increasing the average size of muscular fibers in the MG in females, with no apparent effect in males. Increasing the number of animals for the histological studies will help the identification of the type of muscle fibers that are being related to the grip ability alterations observed in this model of pain. Support or Funding Information FAPESP, CNPq, CAPES and FAEPA