Measurement of Dopamine Uptake in Neuronal Cells and Tissues - Drugs of Abuse: Neurological Reviews and Protocols - page 453

32

Measurement of Dopamine Uptake
in Neuronal Cells and Tissues

Yuen-Sum Lau

1. Introduction
Biogenic amines such as dopamine (DA), norepinephrine, and serotonin
(5-hydroxytryptamine) are key neurotransmitters found in the central nervous
system (CNS). Major DA containing cells, nuclei, and neurons are located in
retina, olfactory bulb, hypothalamic-pituitary, nigrostriatal, mesolimbic, and
mesocortical areas. Stimulation of DA containing neurons releases DA from
storage vesicles at the nerve terminals into the synaptic region. Binding and
activation of the high-affi nity postsynaptic receptors by DA or DA agonists
within the tissue will manifest changes in physiological and behavioral
responses. Central DA receptors are known target sites for typical antipsychotic
drugs as well as dopaminomimetic anti-Parkinson's drugs. Therefore, the
amount and duration that DA accumulates at the synaptic region will determine
the intensity of DA receptor responses.
Following transmitter release, central DA action is terminated mainly by
an active reuptake process into the presynaptic nerve terminals, in addition to
some amount being diffused away or subject to metabolic degradation. The
uptake of DA at nerve terminals is a saturable, temperature-sensitive, and
energy-dependent process occurring against a concentration gradient. The
uptake system involves a high-affi nity (with low K m between 0.1 and 1

M ),
Na + -dependent, and carrier-mediated transporter (1 , 2) . The DA uptake trans-
porter has been molecularly cloned and its functional expression characterized
(3-7) . The structure and function of the DA transporter have been reviewed
further more recently (8) .

µ