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Published on: July 29, 2014
Interactions of inflammatory pain and morphine in infant rats: long-term behavioral effects
A T Bhutta1, C Rovnaghi, P M Simpson
1University of Arkansas for Medical Sciences, Little Rock, AR 72202, USA.
Insights
Neonatal pain in rats can alter adult behavior and pain sensitivity. Combining inflammatory pain and morphine treatments in neonates shows specific long-term behavioral effects in adulthood.
Area of Science:
- Neuroscience
- Developmental Biology
- Behavioral Science
Background:
- Neonatal pain exposure can lead to long-term behavioral changes.
- Prolonged inflammatory pain models in neonates may better reflect clinical relevance for ex-preterm infants.
- Understanding these effects is crucial for infant care and developmental outcomes.
Purpose of the Study:
- To investigate the long-term behavioral consequences of neonatal inflammatory pain.
- To examine the effects of morphine pretreatment on pain and behavior.
- To establish a rat model for studying neonatal pain's impact on adult behavior.
Main Methods:
- Neonatal rat pups (postnatal days 1-7) received repeated formalin injections (inflammatory pain) with or without morphine.
- Adult behavioral testing included hot-plate (HP) and tail-flick (TF) tests for pain thresholds.
- Assessed alcohol preference and locomotor activity (baseline and post-amphetamine).
Main Results:
- Neonatal inflammatory pain increased adult HP latencies; males showed higher thresholds than females.
- Morphine alone prolonged adult TF latencies.
- Both pain and morphine reduced ethanol preference, but effects were not additive.
- Adult males exposed to neonatal pain showed reduced locomotor activity.
Conclusions:
- Neonatal formalin and morphine induce distinct long-term behavioral effects in adult rats.
- Combined neonatal treatments show some attenuated long-term effects compared to individual treatments.
- This study provides insights into the lasting impact of early-life pain experiences.
Abstract:
Neonatal rat pups exposed to repetitive acute pain show decreases in pain threshold and altered behavior during adulthood. A model using prolonged inflammatory pain in neonatal rats may have greater clinical relevance for investigating the long-term behavioral effects of neonatal pain in ex-preterm neonates. Neonatal rat pups were exposed to repeated formalin injections on postnatal (P) days 1-7 (P1-P7), with or without morphine pretreatment, and were compared with untreated controls. Behavioral testing during adulthood assessed pain thresholds using hot-plate (HP) and tail-flick (TF) tests, alcohol preference, and locomotor activity (baseline and postamphetamine). Adult rats exposed to neonatal inflammatory pain exhibited longer HP latencies than controls and male rats had longer HP thresholds compared to females. Male rats exposed to neonatal morphine alone exhibited longer TF latencies than controls. Both neonatal morphine treatment and neonatal inflammatory pain decreased ethanol preference, but their effects were not additive. During adulthood, male rats exposed to neonatal inflammatory pain exhibited less locomotor activity than untreated controls. We conclude that neonatal formalin and morphine treatment have specific patterns of long-term behavioral effects in adulthood, some of which are attenuated when the two treatments are combined.
