High-affinity uptake of [3H]norepinephrine by primary astrocyte cultures and its inhibition by tricyclic antidepressants

Abstract

Primary astrocyte cultures from neonatal rat brains show uptake of [3H]norepinephrine ([3H]NE). This uptake has a high-affinity component with an apparent Km of approximately 3 X 10(-7) M. At 10(-7) M [3H]NE both the initial rate of uptake and steady-state content of [3H]NE is inhibited by up to 95% by omission of external Na+. The Na+-dependent component of this uptake is totally inhibited by the tricyclic antidepressants desipramine (DMI) and amitryptyline with IC50 values of 2 X 10(-9) and 4 X 10(-8) M, respectively. Inhibition of [3H]NE uptake by DMI shows competitive kinetics. These characteristics are essentially identical to those found for high-affinity uptake of NE in total membrane or synaptosome fractions from rodent brains and suggests that such uptake in neural tissue is not exclusively neuronal.