Tickling during adolescence alters fear-related and cognitive behaviors in rats after prolonged isolation

Physiol Behav. 2014 May 28;131:62-7. doi: 10.1016/j.physbeh.2014.04.008. Epub 2014 Apr 13.


Social interactions during adolescence are important especially for neuronal development and behavior. We recently showed that positive emotions induced by repeated tickling could modulate fear-related behaviors and sympatho-adrenal stress responses. In the present study, we examined whether tickling during early to late adolescence stage could reverse stress vulnerability induced by socially isolated rearing. Ninety-five male Fischer rats were reared under different conditions from postnatal day (PND) 21 to 53: group-housed (three rats/cage), isolated-nontickled (one rat/cage) and isolated-tickled (received tickling stimulation for 5min a day). Auditory fear conditioning was then performed on the rats at PND 54. Isolated-tickled rats exhibited significantly lower freezing compared with group-housed rats in the first retention test performed 48h after conditioning and compared with isolated-nontickled rats in the second retention test performed 96h after conditioning. Moreover, group-housed and isolated-tickled rats tended to show a significant decrease in freezing responses in the second retention test; however, isolated-nontickled rats did not. In the Morris water maze task that was trained in adulthood (PND 88), but not in adolescence (PND 56), isolated-nontickled rats showed slower decrease of escape latency compared to group-housed rats; however, tickling treatment significantly improved this deficit. These results suggest that tickling stimulation can alleviate the detrimental effects of isolated rearing during adolescence on fear responses and spatial learning.

Keywords: 50-kHz ultrasonic vocalization; Adolescence; Fear conditioning; Morris water maze; Rats; Social isolation; Tickling.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Auditory Perception / physiology
  • Cognition / physiology*
  • Conditioning, Psychological / physiology
  • Emotions / physiology
  • Fear / physiology*
  • Freezing Reaction, Cataleptic
  • Housing, Animal
  • Male
  • Maze Learning / physiology
  • Physical Stimulation
  • Play and Playthings
  • Rats, Inbred F344
  • Social Isolation*
  • Spatial Memory / physiology
  • Touch / physiology*
  • Vocalization, Animal / physiology