Central cholinergic involvement in the mediation of spontaneous motor activity in rats

ABSTRACT

Spontaneous motor activity of preweanling rats (14-day-old) was examined in an activity cage following the administration of atropine at 1.0, 2.5, 5.0, and 10.0 mg/kg respectively. Compared with saline-control animals, atropine at these dosages, did not significantly affect the activity level of the 14-day-old rat. The motor activity of 14-20-day-old rats was also measured following the administration of atropine (10mg/kg) in the Y-maze and the activity cage. The activity level was significantly decreased in (a) all ages in Y-maze and (b) the 18-day-old animals only in the activity cage. In contrast, amphetamine (2.0, 4.0, and 10.0 mg/kg) induced significant increments in spontaneous motor activity. It is suggested that a cholinergic mechanism concerned with the modulation of central nervous system arousability becomes functional at 18 days of age, that is, subsequent to a more caudal arousal inducing mechanism, which seems to be mediated by a catecholaminergic system (AU)