Neurotransmitters 101

This is just a brief review of the key neurotransmitters most frequently targeted by psychotropics, just as a foundation from which you can build your knowledge.

Neurotransmitters are chemical messengers produced within the body, such as the brainstem and gut, that either excite or inhibit the receptor’s response.  Some neurotransmitters can actually do both at different times.

Psychotropics are designed to mediate those responses—to either quiet excitation where there is too much or increase excitation where there is not enough. 

Serotonin, Norepinephrine and Dopamine, all key players in mental health, are Monoamines.  So for instance, when we talk about the antidepressants that are monoamine oxidase inhibitors, we’re talking about drugs that help keep these neurotransmitters available at the synapse. 

Serotonin is involved in mood, sleep regulation, hunger, pain perception, aggression, libido, body temperature, and hormonal activity.  Too much serotonin can cause agitation, anxiety, and serotonin syndrome (the symptoms of which include shivering, restlessness, diarrhea, muscle rigidity, fever, and seizures).  Too little serotonin can cause depression. 

Norepinephrine is involved in mood, attention, arousal, and the fight or flight stress response. Too much can cause mania, schizophrenia, and anxiety. And like serotonin, too little can cause depression.  As an aside, the blood pressure drug prazosin blocks hyperactivity of NE at the receptor, which may be why it helps quiet nightmare activity in those with severe PTSD. 

Dopamine is involved in fine motor movement, cognition, motivation, decision-making , reward and pleasure.  It also stimulates the heart, increases blood flow to organs, integrates emotions and thoughts, and is involved with hypothalamic activity.  Too much dopamine, and you see symptoms of schizophrenia or mania;  Too little can contribute to depression and Parkinson’s.  Haloperidol and other antipsychotics block dopamine receptors,  which prompts many to believe that psychosis is caused by overactivity of dopamine at the synapse.

Acetylcholine balances norepinephrine and dopamine. It is involved in skeletal muscle movement, arousal, memory, and sleep wake cycle.  Too little, and we see signs of  Alzheimers.  Drugs such as donepezil (Aricept) work by slowing down the degredation of acetylcoline, leaving more at the synapse.

GABA modulates neuronal excitability, and therefore helps manage anxiety levels;  Anxiolytics are designed to bolster the effectiveness of GABA by increasing the receptor’s sensitivity to it.