Sensory and Affective Dimensions of Pain and Anxiety Like Behaviors Are Altered in an Animal Model of Pain Empathy.

Pain is a unique and subjective experience that has a prominent function in animals' survival. Observation of pain in others leads to alterations in pain sensation and affection, termed "Empathy for pain". The present study aimed to evaluate the effect of empathy on sensory and affective dimensions of pain and its effect on anxiety-like behaviors. In this study, male Wistar rats were used. Two cage mates were selected, one of which underwent administration of a noxious stimuli for 10 days and the other observed the conspecific in pain. Hot plate, tail flick, and conditioned place aversion were used to evaluate sensory and affective dimensions of pain, respectively. Anxiety-like behavior was assayed using elevated plus maze paradigm and time spent in open and close arms and number of entrance into each arm was recorded as the anxiety indicator within a 5-minute framework. Rats observing the cage mate in pain had a lower threshold to noxious stimuli in comparison to controls. They also had an increased aversion from painful stimuli, demonstrating heightened affective response to pain. Anxiety-like behavior was also enhanced in the observers. Results of this study demonstrate that both sensory and affective dimensions of pain are altered following observation of pain in a conspecific. Further studies evaluating the underlying mechanisms are encouraged to elucidate the role of different neurotransmitters in this phenomenon.