Time as a reward: role of dopamine and melatonin in the circadian modulation of interval timing

BUSSI I.L.; GOLOMBEK D.A.; LEVÍN, G; AGOSTINO P.V.

Huerta Grande, Córdoba

Congreso; XXVII Congreso Anual de la Sociedad Argentina de Investigación en Neurociencia.; 2012

Temporal perception is fundamental to environmental adaptation. Most organisms have developed a system to perceive time over a wide range of magnitudes, being most important interval timing -in the seconds-to-minutes range? and circadian timing ?in the 24h range. We have previously reported that circadian disruption impaired performance of mice in a peak-interval timing task. Additionally, our results showed significant differences in time estimation along the day (Agostino et al., 2011, Brain Res. 1370:154). In this work we studied the involvement of melatonin and dopamine signaling in the interaction between circadian and interval timing. Striatal dopamine levels measured by HLPC-ED indicated a daily rhythm under light/dark (LD) conditions. This variation, however, was eliminated under constant light (LL) conditions. On the other hand, daily injections of L-DOPA improved timing performance in mice with circadian disruptions, suggesting that a daily increase of dopamine is necessary for a correct performance. Melatonin has been reported to affect dopamine signaling in nocturnal rodents. Pinealectomized (melatonin depleted) Wistar rats showed less learning ability compared to controls, indicating that melatonin could be of importance to modulate interval timing on a circadian base. Our findings add further support to the notion that circadian and interval timing share some common processes, interacting to some extent at the level of the dopaminergic system.