Ontogenesis of rearing and stereotypy responses to apomorphine in the rat.

Abstract
The ontogenesis of rearing and stereotypy behavior in response to apomorphine was investigated in the developing rat. The rearing was rarely observed in 15-day-old rats but was distinctly observed in 18-day-old ones. A s.c. injection of apomorphine in dose of 1 mg/kg or 2 mg/kg decreased the frequency of rearing in animals older than 20 days. The 15-day-old rats were responsive to apomorphine in stereotypy behavior. There was a reciprocal relationship between rearing and stereotypy responses to apomorphine in rats older than 18 days. Functional relationships between rearing and stereotypy in response to apomorphine were discussed in view of the central dopaminergic mechanisms in developing rats.