[The role of the epiphysis in forming a conditioned reaction to time in rats].

Pinealectomy impeded formation of time-conditioned reflex in the mode of fixed intervals. This was accompanied by a shortening of reaction latency and runs as well as by an increase in the number of intertrial responses. On the contrary, melatonin injection (0.1 mg/kg) facilitated conditioning by restricting the locomotion. It is suggested that pineal compounds have specific chronotropic properties.