Related Experiment Video
Updated: May 28, 2026
A Preterm Rat Model for Pain Studies
Published on: February 9, 2024
Fentanyl administration in infant rats produces long-term behavioral responses
Liciane Fernandes Medeiros1, Ana Cláudia de Souza, Andressa de Souza
1Laboratory of Pharmacology of Pain, Department of Pharmacology, Institute of Basic Health Sciences (ICBS), Federal University of Rio Grande do Sul (UFRGS), 90050-170 Porto Alegre, RS, Brazil.
Insights
Early exposure to fentanyl or S(+)-ketamine in young rats alters long-term behavior and pain responses. This study emphasizes the lasting impact of neonatal drug administration on neurodevelopment and behavior.
Area of Science:
- Neuroscience
- Pharmacology
- Animal Models
Background:
- Pain mechanisms are crucial in animal model studies.
- Investigating early-life drug effects on behavior is important.
Purpose of the Study:
- To assess the long-term behavioral and nociceptive effects of acute fentanyl (FEN) and S(+)-ketamine (KET) administration in young rats.
- To evaluate these effects at postnatal day 14 (P14), P30, and P60.
Main Methods:
- Young Wistar rats (P14) received acute doses of FEN or KET.
- Behavioral responses were assessed using open field (OF), elevated plus-maze (EPM), formalin test (FT), and tail-flick latency.
- Statistical analysis involved two-way ANOVA followed by Bonferroni.
Main Results:
- Significant long-term behavioral differences were observed across groups in OF and EPM tests.
- FEN and KET altered behaviors like arm entries, time spent in arms, and head-dipping in the EPM test.
- FEN group showed reduced nociception in the first phase of the FT.
Conclusions:
- Single early-life administration of FEN or KET can induce lasting changes in behavioral responses.
- These findings underscore the necessity of studying the long-term consequences of drug administration in young animals into adulthood.
Abstract:
Considering the importance of studies in animal models that are focused on systems involved in pain mechanisms, this investigation aimed to evaluate the effects of pharmacological treatments on the behavioral responses of younger animals. To this end, we evaluated the effect of an acute dose of fentanyl (FEN) or S(+)-ketamine (KET) at postnatal day 14 (P14) upon behavioral responses in the short- (P14), medium- (P30) and long-term (P60) using the open field (OF), elevated plus-maze (EPM) and formalin tests (FT) and tail-flick latency. Fourteen-day-old male Wistar rats were divided into three groups: control (CT), fentanyl (FEN) and S(+)ketamine (KET) groups for statistical analysis, it was performed two-way ANOVA followed by Bonferroni. We found that, regardless of the test performed (OF or EPM), between-group differences occurred over time in all behaviors analyzed, including in the second phase of FT. In addition, EPM showed significant differences in behavioral responses related to acute administration (at P14) of fentanyl or S(+)-ketamine, in behaviors such as number of entries in open and closed arms, time spent in open and closed arms, and number of head-dipping. In relation to nociceptive response, the FEN group exhibited a decrease in the first phase of FT. These results indicate that unique administration of fentanyl or S(+)ketamine in an early period of life (P14) can promote changes in behavioral responses. In addition, our findings highlight the importance of extending the investigation of the effect of drug administration in young rats into adulthood.
