Influence of sex and experimental protocol on the effect of maternal deprivation on rectal sensitivity to distension in the adult rat

Abstract

Neonatal maternal separation induces visceral hyperalgesia before and after stress in male rats. This study compares the effects on sensitivity to rectal distension in adult male and female rats, using two protocols of deprivation. Between postnatal days 1 and 14, maternal deprivation was performed for 2 h per day according to a protocol of type M (removal of all pups from home cage) or type P (separation of half of littermates). Visceral sensitivity was assessed at 12 weeks of age by the number of abdominal contractions induced by rectal distension before and after restraint stress. Calcitonin gene-related peptide (CGRP) was identified in the rectal wall by immunohistochemistry. In basal conditions, both separation protocols induced hyperalgesia, that was greater after type M than type P, and in females than in males for type P separation. Acute restraint stress induced hyperalgesia in control females only, and this effect was similarly enhanced by both type P and M separation. No difference was found between controls and deprived rats in rectal CGRP immunoreactivity which was greater in females and increased after rectal distension. These results indicate that long-term visceral hyperalgesia depends upon the type of maternal deprivation and that females are more sensitive than males.

Neonatal Maternal Separation Causes Colonic Dysfunction in Rat Pups Including Impaired Host Resistance

“…During the stress-hyporesponsive period (d 4 -14), the corticosterone response is almost entirely inhibited (29). Following this period, there is a concomitant rise in corticosterone levels (d [12][13][14] that tapers off by approximately d 22-24, coinciding with spontaneous weaning (26). The timing of these changes is thought to serve as a cue for changes in digestive enzymes that occur in the intestine in the third postnatal week (26).…”

“…MS is associated with gut inflammation in adult rats (10), which is thought to be maintained by nerve growth factor (9). In addition, exposure to early life stress affects colonic motility and induces visceral hyperalgesia both basally (12) and in response to an acute stressor in adulthood (11). Previous studies from our group (8) indicate that adult rats exposed to MS as neonates become susceptible to intestinal mucosal pathophysiology when exposed to mild acute stress.…”

Neonatal maternal separation of rat pups results in abnormal cholinergic regulation of epithelial permeability

“…stress; colonic; barrier THE NEONATAL PERIOD is an important developmental period in humans and rodents, and stress during this time can have long-lasting effects on behavior and physiology. Maternal separation (MS) is a well-characterized model of early life stress used in the study of anxiety and depression (17, 31) as well as intestinal dysfunction (1,2,7,28,37). The physiological response to stress is controlled by the hypothalamicpituitary adrenal (HPA) axis, which develops during the neonatal period.…”

“…Maternal separation (MS) is a well-characterized model of early life stress used in the study of anxiety and depression (17,31) as well as intestinal dysfunction (1,2,7,28,37). The physiological response to stress is controlled by the hypothalamicpituitary adrenal (HPA) axis, which develops during the neonatal period.…”

“…Adult rats of a stress susceptible strain that are subjected to daily separation from the dam during the neonatal period demonstrate increased colonic permeability (2) and visceral hyperalgesia (28). Adult rats that are not genetically susceptible to stress can also develop similar abnormalities following exposure to a mild acute stressor if they have been subjected to neonatal MS (7,37).…”