Kerman University of Medical Sciences

Document Type: Original Article

Authors

1 Department of Neuroscience and Basic Sciences, School of Medicine, AJA University of Medical Sciences, Tehran, Iran

2 Department of Neuroscience AND Neuroscience Research Center, Neuropharmacology Institute, Kerman University of Medical Sciences, Kerman, Iran

Abstract

Background: Empathy is defined as the ability to simulate the mental states of others. Recent studies have
demonstrated empathy-like behaviors in other animals including rats and mice. The objective of the current
study was to evaluate the effect of acute administration of morphine and naloxone on cognition and
nociception changes following observing conspecifics undergoing nociceptive stimulus.
Methods: Adult male Wistar rats were used (n = 8 for each group). One cagemate received formalin injection
into the hindpaw five times within a nine-day period and the other cagemate observed the pain while being
pretreated with saline, morphine, or naloxone [10 mg/kg, intraperitoneal (i.p.)]. Pain behaviors, anxiety-like
behaviour, locomotion, balance and muscle strength were evaluated in the observer animals.
Findings: Observing a cagemate in pain increased anxiety-like behavior and reduced thermal pain threshold in the
observer animals. Administration of morphine reversed these effects and naloxone did not affect the responses.
Conclusion: Results of the current study reveal an important role for opioid receptors (ORs) in empathy for
pain, so that activation of this system dampens the empathy-like responses.


Keywords

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