Papers of the Week

: Empathy is defined as the capability to comprehend and simulate the feelings of others. Though it has been considered as a human feature, recent studies have demonstrated empathy-like behaviors in other animals including rats. The objective of the current study was to evaluate the role of nitric oxide system in cognition and nociception changes following observation of cagemates in pain. Adult male Wistar rats were used (n = 8 for each group). One sibling received formalin injection into the hindpaw five times within a nine-day period and the other sibling observed the pain while being pretreated with saline, L-NAME or L-arginine (10 mg/kg, i.p.). Nociception, anxiety-like behavior and locomotion, balance, muscle strength, spatial and fear learning were evaluated.: Observing a family member (sibling) in pain increased anxiety-like behavior, led to a hyperalgesia in the observer and disruption of spatial memory. Nitric oxide system modulated these changes, so that in some paradigms the activation of NO and in some others inhibition of NO dampened the effect of observing pain in a cagemate on the evaluated features.: Results in the current study demonstrated a modulating effect of NO on empathy induced changes in nociception, motor function and spatial memory. Further studies addressing the specific brain regions and other neurotransmitters involved are recommended. Highlights:Observing a cagemate in pain leads to impairments in locomotion and spatial memoryAnimals observing a cage-mate in pain had an increased anxiety-like behaviorAffective component of pain increased following observation of pain in a cage mateNociceptive response was significantly reduced in in the pain-observing groupNO has a modulating effect on empathy induced changes in nociception and memory.