Behavioural and pharmacological effects of fluvoxamine on decision-making in food patches and the inter-temporal choices of domestic chicks.

Behavioural effects of fluvoxamine (FLV, selective serotonin reuptake inhibitor) were examined in 1-2 week old domestic chicks. Chicks were tested in an I-shaped maze equipped with a feeder (ON feeder) that served 1 or 2 grains of millet at gradually increasing intervals, so that a depleting food patch was mimicked. By leaving the feeder, the food delivery program was reset, and chicks gained food at short intervals only after a travel to a dummy feeder (OFF feeder) placed on the opposite side of the maze. Chicks quickly learned to actively shuttle between the ON and the OFF feeders. FLV (intra-peritoneal injection, 20 mg/kg BW) acutely caused chicks to stay longer at the gradually depleting ON feeder. Inter-temporal choices were also tested, whereby two coloured beads were simultaneously presented, each associated with a small/short-delay reward or a large/long-delay alternative. FLV suppressed the choice of the short-delay option. It is suggested that an enhanced level of serotonin (5-HT) makes chicks more tolerant of the delayed food item in both behavioural paradigms. Furthermore, the decision to leave a depleting patch cannot be equated to choosing the long-delay option of the choice paradigm. Furthermore, FLV suppressed work efforts (velocity and running distance) in uncued shuttle and number of distress calls. In vivo microdialysis experiments revealed that FLV enhanced the extracellular concentration of 5-HT as well as dopamine (DA) locally in the medial striatum/nucleus accumbens. Underlying neuromodulatory mechanisms of behavioural control are examined in relation to locomotion, behavioural tolerance and interval timing.