Ontogeny of adrenergic arousal and cholinergic inhibitory mechanisms in the rat.

With spontaneous activity as a measure of arousal, dose response curves were established for scopolamine and amphetamine administered to 10-, 15-, 20-, 25-, and 100-day-old rats. Amphetamine always increased activity, but scopolamine had no efect on younger rats, which suggests that adrenergic excitatory areas in the brainstem mature more rapidly than cholinergic inhibitory areas in the forebrain.