BACKGROUND: Pain during labor is a common and severe phenomenon, but its clinical management remains haphazard because its neurophysiology is poorly understood. In the current study, the authors evaluate the parturient rat as a relevant model to study the pharmacology of labor pain. METHODS: Control of birth timing in term pregnant rats was achieved by gavage with RU 486 (5 mg/kg) the day before the expected day of parturition. The behavioral events preceding the expulsion of the first pup were analyzed, and immunodetection of the c-Fos protein was used to evaluate the spinal neuronal activity at the lumbosacral level where genital and perineal inputs terminate. RESULTS: Hind limb and abdominal stretches occurred during labor (mean number, 57 +/- 10), arbitrarily defined as the time elapsed between the first stretch and the expulsion of the first pup (mean duration, 62 +/- 5 min). Subcutaneous oxytocin increased the frequency of stretches, accounting for the fact that these manifestations are linked to uterine contractions. Finally, epidural morphine (30 microg/10 microl) in oxytocin-treated rats, although resulting in no change of labor duration, significantly decreased the number of stretches (8 +/- 2 vs. 57 +/- 12 for epidural saline) and the number of c-Fos-positive neurons in the lumbosacral spinal segments (80 +/- 25 vs. 165 +/- 17 for epidural saline). CONCLUSIONS: These results indicate that stretches during labor in the rat correspond to a behavioral response to nociception associated with uterine contractions and suggest that parturition in the rat could be a relevant model to investigate nociceptive mechanisms associated with parturition in women.
BACKGROUND:Pain during labor is a common and severe phenomenon, but its clinical management remains haphazard because its neurophysiology is poorly understood. In the current study, the authors evaluate the parturient rat as a relevant model to study the pharmacology of labor pain. METHODS: Control of birth timing in term pregnant rats was achieved by gavage with RU 486 (5 mg/kg) the day before the expected day of parturition. The behavioral events preceding the expulsion of the first pup were analyzed, and immunodetection of the c-Fos protein was used to evaluate the spinal neuronal activity at the lumbosacral level where genital and perineal inputs terminate. RESULTS: Hind limb and abdominal stretches occurred during labor (mean number, 57 +/- 10), arbitrarily defined as the time elapsed between the first stretch and the expulsion of the first pup (mean duration, 62 +/- 5 min). Subcutaneous oxytocin increased the frequency of stretches, accounting for the fact that these manifestations are linked to uterine contractions. Finally, epidural morphine (30 microg/10 microl) in oxytocin-treated rats, although resulting in no change of labor duration, significantly decreased the number of stretches (8 +/- 2 vs. 57 +/- 12 for epidural saline) and the number of c-Fos-positive neurons in the lumbosacral spinal segments (80 +/- 25 vs. 165 +/- 17 for epidural saline). CONCLUSIONS: These results indicate that stretches during labor in the rat correspond to a behavioral response to nociception associated with uterine contractions and suggest that parturition in the rat could be a relevant model to investigate nociceptive mechanisms associated with parturition in women.
Authors: Ting Yang; Lei Zhuang; António M Rei Fidalgo; Evgenia Petrides; Niccolo Terrando; Xinmin Wu; Robert D Sanders; Nicola J Robertson; Mark R Johnson; Mervyn Maze; Daqing Ma Journal: PLoS One Date: 2012-05-17 Impact factor: 3.240
Authors: Tusar Giri; Jia Jiang; Zhiqiang Xu; Ronald McCarthy; Carmen M Halabi; Eric Tycksen; Alison G Cahill; Sarah K England; Arvind Palanisamy Journal: Sci Rep Date: 2022-02-24 Impact factor: 4.379