The Brain & the Actions of Cocaine, Opiates, and Marijuana

Show how opiates activiate the reward system using the nucleus accumbens as an example. Explain that the action is a little more complicated than cocaine's because more than two neurons are involved. Point out that three neurons participate in opiate action: the dopamine terminal, another terminal (on the right) containing a different neurotransmitter (probably GABA for those that would like to know), and the post-synaptic cell containing dopamine receptors. Show that opiates bind to opiate receptors (green) on the neighboring terminal and this sends a signal to the dopamine terminal to release more dopamine. [In case an inquisitive student asks how, one theory is that opiate receptor activation decreases GABA release, which normally inhibits dopamine release, so dopamine release is increased.]