title: Tickling during adolescence alters fear-related and cognitive behaviors in rats after prolonged isolation.
abstract: 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.
authors.affiliation: Foundation for Advancement of International Science, Tsukuba, Ibaraki 305-0821, Japan; Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, 305-8577 Japan.
authors.forename: Miyo
authors.initials: M
authors.lastname: Hori
authors.affiliation: Institute of Psychology and Behavioral Neuroscience, University of Tsukuba, Tsukuba, 305-8577, Japan.
authors.forename: Kazuo
authors.initials: K
authors.lastname: Yamada
authors.affiliation: Foundation for Advancement of International Science, Tsukuba, Ibaraki 305-0821, Japan; Department of Food and Nutrition, Tokyo Kasei University, Itabashi, Tokyo 173-0003, Japan.
authors.forename: Junji
authors.initials: J
authors.lastname: Ohnishi
authors.affiliation: Foundation for Advancement of International Science, Tsukuba, Ibaraki 305-0821, Japan.
authors.forename: Shigeko
authors.initials: S
authors.lastname: Sakamoto
authors.affiliation: Institute of Psychology and Behavioral Neuroscience, University of Tsukuba, Tsukuba, 305-8577, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Furuie
authors.affiliation: Foundation for Advancement of International Science, Tsukuba, Ibaraki 305-0821, Japan.
authors.forename: Kazuo
authors.initials: K
authors.lastname: Murakami
authors.affiliation: Institute of Psychology and Behavioral Neuroscience, University of Tsukuba, Tsukuba, 305-8577, Japan. Electronic address: y-ichit@human.tsukuba.ac.jp.
authors.forename: Yukio
authors.initials: Y
authors.lastname: Ichitani
mesh_terms: D000818:Animals; D001307:Auditory Perception / Q000502:physiology; D003071:Cognition / Q000502:physiology*; D003213:Conditioning, Psychological / Q000502:physiology; D004644:Emotions / Q000502:physiology; D005239:Fear / Q000502:physiology*; D046352:Freezing Reaction, Cataleptic; D006799:Housing, Animal; D008297:Male; D018782:Maze Learning / Q000502:physiology; D010812:Physical Stimulation; D010988:Play and Playthings; D011916:Rats, Inbred F344; D012934:Social Isolation; D065852:Spatial Memory / Q000502:physiology; D014110:Touch / Q000502:physiology*; D014828:Vocalization, Animal / Q000502:physiology
keywords: 50-kHz ultrasonic vocalization; Adolescence; Fear conditioning; Morris water maze; Rats; Social isolation; Tickling