After Release into the Synaptic Cleft, the Neurotransmitter Dopamine Is

question 26

Multiple Choice

After release into the synaptic cleft, the neurotransmitter dopamine is actively taken up by the cells via specific dopamine transporters. The drug cocaine interferes with this process and is therefore called a reuptake inhibitor. The inhibition of the transporter at a certain cocaine concentration is qualitatively represented in the following graph. Based on this graph, which of the following describes the effect of cocaine on the kinetics of dopamine reuptake by the transporter?

• A) In the presence of cocaine, the maximal rate of transport (Vmₐₓ) is unaffected, but the apparent affinity of the transporter for dopamine is reduced.
• B) In the presence of cocaine, the maximal rate of transport (Vmₐₓ) is reduced, but the apparent affinity of the transporter for dopamine is unaffected.
• C) In the presence of cocaine, the maximal rate of transport (Vmₐₓ) is enhanced, but the apparent affinity of the transporter for dopamine is unaffected.
• D) In the presence of cocaine, both the maximal rate of transport (Vmₐₓ) and the apparent affinity of the transporter for dopamine are enhanced.
• E) In the presence of cocaine, both the maximal rate of transport (Vmₐₓ) and the apparent affinity of the transporter for dopamine are unaffected, but the transporter is nevertheless inhibited.