Highly inbred mice of 3 strains (A/J, DBA/2J, and C57BL/6J) were tested in an open field at 14, 21, or 28 days of age. Ten minutes prior to testing, mice received treatment of saline, scopolamine (.5 or 1.0 mg/kg of body weight), or d amphetamine (.5, 1.0, or 5.0 mg/kg). The d amphetamine (5.0 mg/kg) increased activity in all strains at 14 days and 28 days of age, and at 21 days significantly increased activity in all except the C57BL/6. In contrast, increased activity with the scopolamine treatment was seen in DBA/2 at 21 days, but not in A and C57BL/6 until 28 days postnatally. The data support a caudal rostral gradient of brain development with the inhibitory cholinergic system developing more slowly than the excitatory catecholamine system. In addition, strain specific differences in activity levels are discussed in relation to the differential rates of cholinergic maturation.

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Journal Developmental Psychobiology
Remington, G., & Anisman, H. (1976). Genetic and ontogenetic variations in locomotor activity following treatment with scopolamine or d amphetamine. Developmental Psychobiology, 9(6), 579–585.