Document Type

Thesis

Degree Name

Master of Arts (MA)

Department

Psychology

Faculty/School

Faculty of Science

First Advisor

Hymie Anisman

Advisor Role

Thesis Supervisor

Abstract

Highly inbred mice of three strains (A/J, DBA/2J and C57BL/6J) were tested in an acitivity task at 14, 21, or 28 days of age. Ten minutes prior to testing, mice received treatment of either saline, scopolamine (0.1 or 1.0 mg/kg) or d-amphetamine (0.5, 1.0 or 5.0 mg/kg). At 14 days of age DBA mice exhibited higher levels of activity than either A or C57 mice. However, the increase in activity in C57 was such that at 21 and 28 days no difference was observed relative to DBA mice, and activity was higher than that of A mice. With respect to the drug treatments, d-amphetamine (5.0 mg/kg) increased activity in all strains at 14 days and 28 days of age. At 21 days, only C57 exhibited lack of a significant increase in activity. Clearly, the system responsible for responsivity to d-amphetamine (dopamine and norepinephrine) is mature at 14 days of age. In contrast to d-amphetamine, a response to scopolamine was evident in DBA at 21 days of age, and in C57 and A at 28 days of age. These data were taken to support a caudal-rostral gradient of brain development, with the inhibitory cholinergic system developing more slowly than the excitatory catecholamine system. Moreover, there also appears to be strain-specific differences in neuronal development. The differential development of the cholinergic system, together with potential differences in the ontogeny of the catecholamine system, were suggested as being responsible for age dependent variations in activity, as well as differential responsivity to pharmacological agents which increase catecholamine activity.

Convocation Year

1974

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