Kirk B

“Cannabinoids relax the rules of cortical crowd control, but 300 micrograms of d-lysergic acid diethylamide break them completely. This is a clean sweep. This is the Renaissance after the Dark Ages. Dopamine—the fuel of desire—is only one of four major neuro modulators. Each of the neuromodulators fuels brain operations in its own particular way. But all four of them share two properties. First, they get released and used up all over the brain, not at specific locales. Second, each is produced by one specialized organ, a brain part designed to manufacture that one potent chemical (see Figure 3). Instead of watering the flowers one by one, neuromodulator release is like a sprinkler system. That’s why neuromodulators initiate changes that are global, not local. Dopamine fuels attraction, focus, approach, and especially wanting and doing. Norepinephrine fuels perceptual alertness, arousal, excitement, and attention to sensory detail. Acetylcholine energizes all mental operations, consciousness, and thought itself. But the final neuromodulator, serotonin, is more complicated in its action. Serotonin does a lot of different things in a lot of different places, because there are many kinds of serotonin receptors, and they inhabit a great variety of neural nooks, staking out an intricate network. One of serotonin’s most important jobs is to regulate information flow throughout the brain by inhibiting the firing of neurons in many places. And it’s the serotonin system that gets dynamited by LSD. Serotonin dampens, it paces, it soothes. It raises the threshold of neurons to the voltage changes induced by glutamate. Remember glutamate? That’s the main excitatory neurotransmitter that carries information from synapse to synapse throughout the brain. Serotonin cools this excitation, putting off the next axonal burst, making the receptive neuron less sensitive to the messages it receives from other neurons. Slow down! Take it easy! Don’t get carried away by every little molecule of glutamate. Serotonin soothes neurons that might otherwise fire too often, too quickly. If you want to know how it feels to get a serotonin boost, ask a depressive several days into antidepressant therapy. Paxil, Zoloft, Prozac, and all their cousins leave more serotonin in the synapses, hanging around, waiting to help out when the brain becomes too active. Which is most of the time if you feel the world is dark and threatening. Extra serotonin makes the thinking process more relaxed—a nice change for depressives, who get a chance to wallow in relative normality.”
― Marc Lewis, Memoirs of an Addicted Brain: A Neuroscientist Examines his Former Life on Drugs