Submitted to: International Society of Applied Ethology
Publication Type: Abstract Only
Publication Acceptance Date: 6/12/2010
Publication Date: 8/4/2010
Citation: Dennis, R.L., Lay Jr, D.C., Cheng, H. 2010. Effects of Early Serotonin Programming on Fear Response, Memory and Aggression. International Society of Applied Ethology. Proceedings No. Am. Regional Meeting ISAE.
Technical Abstract: The neurotransmitter serotonin (5-HT) also acts as a neurogenic compound in the developing brain. Early administration of a 5-HT agonist could alter development of serotonergic circuitry, altering behaviors mediated by 5-HT signaling, including memory, fear and aggression. The present study was designed to investigate the effects of early serotonin agonism on later behaviors. White leghorn chicks were injected with 5-MT (serotonin agonist) at 2.5mg/kg (low dose), 10mg/kg (high dose) or saline (control) on the day of hatch and a second dose 24 h later. Chicks were tested for fear response and memory at 2 weeks of age, and aggressiveness at 10 weeks. Chicks were subjected to a social isolation fear test for 20 minutes, time to first vocalization and numbers of vocalizations were recorded. High and low dose chicks had shorter latency to first vocalization and a greater number of vocalizations compared with control chicks (P<0.10 and P<0.05, respectively). In a memory test, chicks were placed in a running wheel and presented with an imprinted object (white box with a red light) and a similar shaped novel object (blue box with a white light), respectively. The distance traveled in the wheel toward each object was measured. Chicks from all groups traveled a similar distance toward a familiar object. However, control chicks walked the least toward a novel object, low dose chicks tended to walk further (P<0.10), and high dose chicks walked significantly further for a novel object (P<0.05). In aggression tests both high and low dose roosters exhibited greater frequency of aggressive behaviors (P<0.05) compared to controls. No difference was found between treatments in a tonic immobility test of fearfulness (P>0.05). Our data show that later behaviors including fear, memory and aggression can be altered by early alteration of the 5-HT system.