Sign up ×  If a dopamine is released at T=0 and binds to
receptor D2, what determines the time when the concentration of
this neurotransmitter bound to the receptor reaches half of the
original concentration? In other words, when will the effect of
neurotransmitter on the intercell signalling fall in half?  Is
there any time estimate of how quickly the brain thinks that
neurotransmitter has "fulfilled its purpose" and is to be re-
uptaken? Or is this process completely random?  Thank you for
your input!  share|improve this question All processes involving
reuptake or metabolism of biological molecules are completely
random. However, when you look at a large number of molecules
over time, the random events combine into a stable, predictable
rate of decay. This rate is usually either exponential decay (a
half-life) or, more rarely, a constant amount per second. – 
octern Nov 18 '12 at 19:10 I don't know what the answer is for
dopamine, and individuals probably vary in how zealous their
brains are about dopamine