Psychomotor stimulants

Psychomotor stimulants are drugs that stimulate the central nervous system to increase motor activity and to produce euphoria, excitement, and a feeling of having lots of energy.

Unfortunately, some drugs of abuse, like methamphetamine or cocaine, belong to this class of substances.

However, there are a few medications in this class that do have clinical applications so let’s go over those.

To understand how psychomotor stimulants work, let’s zoom in on one of the synapses of the brain.

Normally electrical signals, or action potentials, travel down the axon to the axon terminal, where they trigger the release of chemical messengers, called neurotransmitters, from synaptic vesicles into the synapse.

The neurotransmitters travel across the synapse and bind to receptors on the postsynaptic neuron, where they give the cell a message.

After the neurotransmitters have done their job, they unbind from the receptors, and can: diffuse away, get degraded by enzymes, or get picked up by proteins and returned to their original release site in a process called reuptake.

Psychomotor stimulants, in general, increase the release of certain neurotransmitters, but their biggest effect is blocking reuptake receptors on presynaptic axon terminals.

Both actions keep neurotransmitters - like dopamine, norepinephrine, and serotonin - in the synapse longer, and increases their effects.

For example, increased concentrations of dopamine in the brain’s reward pathway, which includes the nucleus accumbens, ventral tegmentum, and prefrontal cortex, produce intense feelings of euphoria, pleasure, and the emotional “high” associated with psychomotor stimulants.

The physical “high” or feeling of hyper-stimulation is caused by increased norepinephrine concentrations throughout the brain, which produces a variety of effects throughout the body like increased energy, constricted blood vessels, dilated pupils, increased body temperature, increased heart rate, and increased blood pressure.