Stereotyped behavior in the ontogeny of rats.

The ontogenetic development of stereotyped behavior induced by activation of dopamine D1 and D2 receptors with apomorphine was studied in rat pups (1st month of life) and adult rats (2nd-12th months of life). Stereotyped sniffing and licking movements developed not simultaneously under the influence of apomorphine. Apomorphine-induced sniffing hyperactivity was observed in newborn animals, but disappeared after eye opening (day 18 of life). Stereotyped licking movements (long-term intense licking of the wall of the actograph) induced by activation of dopamine D2 receptors with apomorphine were revealed in rat pups on the 4th week of life. The duration of these movements in rats was maximum by the 9th month of life. The dynamics of stereotyped behavior probably reflects the non-simultaneous formation and development of dopamine D1 and D2 receptors in the ventrolateral striatum during the ontogeny of rats.