Pharmacological mechanisms of time estimation: Dopaminergic and serotonerglc agonist effect

Abstract

It has been shown that the serotonergic and dopaminergic neurotransmitter systems play a major role in timing behavior. Previous reports showed that the administration of dopamine agonists for the D2 receptor subtype increase the velocity of an "hypothetical clock", while the administration of antagonists decrease its velocity. The participation of the serotonergic system in timing behavior was included after the observation that the destruction of ascendant serotonergic pathways produced a shift in the bisection point towards short durations. On the basis of the findings reviewed it can be suggested that the serotonergic system participates in the regulation of the hypothetical clock, because the 5-HT, agonist 8-OH-DPAT was able to produce a shift in the bisection point of a retrospective timing task. However, a limited number of drugs had been explored and in some cases the effects observed are specific to the immediate but not the retrospective task. Also, although there is evidence for the participation of the dopaminergic system it has not been possible to determine the differential participation of the various receptor subtypes; therefore the research in this area must continue.