Prenatal stress alters morphine- and stress-induced analgesia in male and female rats.
Prenatal stress affects the expression of many opioid-regulated behaviors in adulthood, e.g., aggressive, maternal, regulatory, and sexual. In the present report we examined two forms of analgesia, morphine-induced (opioid receptor-mediated), and stress-induced [cold-water swim (CWS), nonopioid] analgesia in adult prenatally-stressed (P-S) male and female rats to determine whether and to what extent these analgesic responses might be altered. Timed-mated Sprague-Dawley females were exposed to heat and restraint stress (three daily 1/2 hour sessions, 0830, 1230, and 1630 hr) from days 15-22 of gestation. Control animals remained undisturbed throughout pregnancy. Between 120-150 days of age, baseline pain sensitivities were determined using a tail-flick monitor. P-S and Control animals were then exposed to 3.5 min cold-water swims (2 degrees C) and pain thresholds were again determined at 30 min intervals for 120 min. P-S females exhibited significantly lower pain thresholds than Control females at the 30 and 60 min marks, whereas P-S and Control males did not differ. Six to eight days later, analgesia was measured for 180 min following morphine (5.0 mg/kg) administration. P-S females exhibited significantly greater analgesia at each time-point after morphine treatment than Controls. Conversely, P-S males were significantly less analgesic than Control males from 60 to 180 min. These data suggest that prenatal stress alters the status of endogenous opiate systems. Such prenatal stress-induced alterations in opiate function may help account for some of the behavioral effects reported in P-S animals.
Kinsley
C H
CH
Harvard Medical School, Laboratory of Human Reproduction and Reproductive Biology, Boston, MA 02115.
Mann
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PE
Bridges
R S
RS
D000818:Animals; D001835:Body Weight; D003080:Cold Temperature; D005260:Female; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D010146:Pain / Q000503:physiopathology*; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects; D051381:Rats; D011919:Rats, Inbred Strains; D012737:Sex Factors; D013312:Stress, Physiological / Q000503:physiopathology*
D009020:Morphine