Circuits in psychopharmacology

• Cerebral cortex
• Brodmann areas
• Functional brain areas
• Areas within prefrontal cortex
• Beyond prefrontal cortex to hippocampus and amygdala
• The planes of the brain
• Neurotransmitter nodes
• Dopamine
• Norepinephrine
• Serotonin
• Acetylcholine
• Histamine
• Linking it all together into functional loops
• Corticocortical circuits
• Cortico-striatal-thalamic-cortical circuits
• Pyramidal cells as drivers of cortical circuits
• Pyramidal cell excitatory outputs
• Pyramidal cell inhibitory inputs
• Pyramidal cell excitatory inputs
• Fine tuning pyramidal cells with monoamine, acetylcholine, and histamine input
• Regulating the monoamine “tuners”
• Summary

Circuits in psychopharmacology

Psychopharmacology is moving beyond receptors, enzymes, and other molecules as the targets of drugs as well as mental illnesses. The issue now is where in the brain are drugs and illnesses targeting specific molecules, and specifically within which circuits? Circuits can now be imaged in patients in research settings, and this may soon be possible in clinical settings as well.

The good news is that brain imaging is transforming the fields of psychiatry and psychopharmacology, with the promise that this technology may allow much more precise assessments of psychiatric risk, of malfunctioning brain circuits, and of the effects of treatments not just on symptoms but on brain functioning. The bad news is that the modern psychopharmacologist who wishes to follow the current research literature and be prepared to utilize these techniques in clinical practice must now become at least an amateur neuroanatomist.

Here we will review those aspects of brain anatomy most robustly linked to psychiatric symptoms and to the actions of psychotropic drugs. In general, this means an emphasis on the prefrontal cortex. This part of the journey into contemporary psychopharmacology may be a bit painful to some and may require reading of this chapter more than once. However, the reward that comes from a working knowledge of neuroanatomy is to open an entirely new paradigm of understanding psychiatric disorders and their treatments: namely, to know where in the brain psychiatric symptoms are hypothetically mediated and thus how best to select and combine drugs to reduce symptoms of psychiatric disorders in individual patients.

The various pathways and brain regions introduced here will be discussed repeatedly throughout this book and will be adapted to specific psychiatric disorders and drugs in the chapters on individual psychiatric disorders.