• S V Coutinho, P M Plotsky, M Sablad, J C Miller, H Zhou, A I Bayati, J A McRoberts, and E A Mayer.
• UCLA/CURE Neuroenteric Disease Program and Brain Research Institute, Department of Medicine, University of California at Los Angeles School of Medicine, 11301 Wilshire Blvd., Los Angeles, CA 90095, USA.
• Am. J. Physiol. Gastrointest. Liver Physiol. 2002 Feb 1; 282 (2): G307-16.

AbstractThis study investigated the combined effect of neonatal maternal separation and acute psychological stress on pain responses in adult rats. Long-Evans dams and their male pups were reared under two conditions: 1) 180 min daily maternal separation (MS180) on postnatal days 2-14 or 2) no handling or separation (NH). At 2 mo of age, visceromotor responses to graded intensities of phasic colorectal distension (10-80 mmHg) at baseline as well as following acute 60 min water avoidance stress (WA) were significantly higher in MS180 rats. Both groups showed similar stress-induced visceral hyperalgesia in the presence of naloxone (20 mg/kg ip). MS180 rats had smaller stress-induced cutaneous analgesia in the tail-flick test compared with NH rats, with a residual naloxone-resistant component. MS180 rats showed an enhanced fecal pellet output following WA or exposure to a novel environment. These data suggest that early life events predispose adult Long-Evans rats to develop visceral hyperalgesia, reduced somatic analgesia, and increased colonic motility in response to an acute psychological stressor, mimicking the cardinal features of irritable bowel syndrome.

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