Neurochemistry II

2025-10-07

Rick Gilmore

Department of Psychology

Prelude

– Dancer (2016)

Monoamine Song

Monoamines, do-do do do-do
Monoamines, do do do-do
Monoamines, do do do do-do do do-do do do-do do do do do-do do

Monoamine Song

Monoamines, do-pa-mine is one
Monoamines, norepi, too
Monoamines, sero-tonin e-pinephrine, dop-a-mine, nor-epinephrine, melatonin, whoo!

Monoamine Song

Monoamines, mod-u-late neurons
Monoamines, throughout the brain
Monoamines, keep people happy, brains snappy, not sleepy, not sappy, do-do do-do do-do do

Today’s topics

  • Neurotransmitters

Warm-up

More on neurotransmitters

Monoamines

Family Neurotansmitter
Monoamines Dopamine (DA)
Norepinephrine (NE)/Noradrenaline (NAd)
Epinephrine (Epi)/Adrenaline (Ad)
Serotonin (5-HT)
Melatonin
Histamine

Dopamine (DA)

  • Released by two pathways
  • Both originate in the midbrain tegmentum

Dopamine (DA)

  • Substantia nigra -> striatum, meso-striatal projection
  • Ventral tegmental area (VTA) -> nucleus accumbens, ventral striatum, hippocampus, amygdala, cortex; meso-limbo-cortical projection

Dopamine (DA)

  • Disruption linked to
    • Parkinson’s Disease (mesostriatal)
      • DA agonists treat (agonists facilitate/increase transmission)
    • Schizophrenia (mesolimbocortical)
      • DA antagonists treat
    • Addiction (mesolimbocortical)
    • ADHD (mesolimbocortical)

Dopamine (DA)

McHugh & Buckley (2015)

Dopamine (DA)

Type Receptor Comments
Metabotropic D1-like (D1 and D5) more prevalent
D2-like (D2, D3, D4) target of many antipsychotics (drugs that treat schizophrenia symptoms)

Dopamine (DA)

  • Not the pleasure or motivation NT
  • One function: signals differences between predicted and actual outcomes

Bell (2013)

Norepinephrine (NE)

  • Role in arousal, mood, eating, sexual behavior
  • Released by

Wikipedia

Norepinephrine (NE)

  • Released by Sympathetic branch of Autonomic Nervous System (ANS) onto targets in PNS

Norepinephrine (NE)

  • Monoamine oxidase (MAO) inactivates monoamines in neurons, glial cells
  • Monoamine oxidase inhibitors (MAOIs) increase NE, DA
    • Inhibiting inactivation ~ -(-1) = + 1
  • Early treatment for depression, but side effects (dry mouth, nausea, headache, dizziness)

Youdim, Edmondson, & Tipton (2006)

Norepinephrine (NE)

Type Receptor Comments
Metabotropic \(\alpha\) (1,2) antagonists treat anxiety, panic
\(\beta\) (1,2,3) ‘beta blockers’ in cardiac disease

Serotonin (5-HT)

  • Released by raphe nuclei in brainstem
  • Role in mood, sleep, eating, pain, nausea, cognition, memory
  • Modulates release of other NTs

Wikipedia

Serotonin (5-HT)

  • Most of body’s 5-HT neurons regulate digestion
    • via Enteric Nervous System (in PNS)

Furness (2012)

Serotonin (5-HT)

  • 5-HT receptors
    • Seven families (5-HT 1-7) with 14 types
    • All but one metabotropic

Serotonin (5-HT)

  • Ecstasy (MDMA) disturbs serotonin
  • So does LSD
  • Fluoxetine (Prozac)
    • Selective Serotonin Reuptake Inhibitor (SSRI)
    • Inhibits reuptake -> increases extracellular concentration
    • Treats depression, panic, eating disorders, others
  • 5-HT3 receptor antagonists are anti-mimetics used in treating nausea

Melatonin

  • Hormone released by pineal gland into bloodstream
  • Concentrations vary over the day, peak near bedtime
  • Release regulated by inputs from hypothalamus

Wikipedia

Histamine

  • In brain, released by hypothalamus, projects to whole brain
    • Metabotropic receptors
    • Role in arousal/sleep regulation
  • In body, part of immune response

Haas & Panula (2003)

Other NTs

  • Gases
    • Nitric Oxide (NO), carbon monoxide (CO)
  • Neuropeptides
    • Substance P and endorphins (endogenous morphine-like compounds) have role in pain
    • Orexin/hypocretin, project from lateral hypothalamus across brain, regulate appetite, arousal

Other NTs

  • Neuropeptides (continued)
    • Cholecystokinin (CCK) stimulates digestion
    • Oxytocin and vasopressin released by posterior hypothalamus onto posterior pituitary, regulate social behavior

Non-chemical communication between neurons

  • Gap junctions
  • Electrical coupling
  • Connect cytoplasm directly

Wikipedia

Non-chemical communication between neurons

  • Fast, but fixed, hard to modulate
  • Examples: retina, cardiac muscle

Wikipedia

Ways to think about synaptic communication

  • Specificity: point-to-point vs. broadcast
  • Direct (immediate) action vs. (delayed, prolonged) modulatory
  • Agonists vs. antagonists

Agonists vs. Antagonists

  • Agonists
    • bind to receptor
    • mimic action of endogenous chemical
  • Antagonists
    • bind to receptor
    • block/impede action of endogenous chemical

Valium is a GABA-A receptor agonist. This means:

  • A. It decreases inhibition
  • B. It activates a metabotropic Cl- channel
  • C. It facilitates/increases Cl- flux
  • D. It blocks an ionotropic channel

Valium is a GABA-A receptor agonist. This means:

  • A. It decreases inhibition
  • B. It activates a metabotropic Cl- channel
  • C. It facilitates/increases Cl- flux
  • D. It blocks an ionotropic channel

Main points

  • Monoamine neurotransmitters–DA, NE, 5-HT–modulate activity of other neurons
  • Released from specific areas in midbrain and hindbrain
  • Monamines inactivated chemically and via transporters
  • Many drugs that treat psychiatric illness affect monoamines
  • Most monoamines activate metabotropic receptors

Next time

Resources

About

This talk was produced using Quarto, using the RStudio Integrated Development Environment (IDE), version 2025.5.1.513.

The source files are in R and R Markdown, then rendered to HTML using the revealJS framework. The HTML slides are hosted in a GitHub repo and served by GitHub pages: https://psu-psychology.github.io/psych-260-2025-fall/

References

Bell, V. (2013, February 3). The unsexy truth about dopamine. The Guardian. The Guardian. Retrieved from https://www.theguardian.com/science/2013/feb/03/dopamine-the-unsexy-truth
Dancer, T. (2016). Sesame street - mahna mahna (1969). Youtube. Retrieved from https://www.youtube.com/watch?v=y5W60VwDkas&list=RDy5W60VwDkas&start_radio=1
Furness, J. B. (2012). The enteric nervous system and neurogastroenterology. Nature Reviews. Gastroenterology & Hepatology, 9(5), 286–294. https://doi.org/10.1038/nrgastro.2012.32
Haas, H., & Panula, P. (2003). The role of histamine and the tuberomamillary nucleus in the nervous system. Nature Reviews. Neuroscience, 4(2), 121–130. https://doi.org/10.1038/nrn1034
McHugh, P. C., & Buckley, D. A. (2015). Chapter eleven - the structure and function of the dopamine transporter and its role in CNS diseases. In G. Litwack (Ed.), Vitamins & hormones (Vol. 98, pp. 339–369). Academic Press. https://doi.org/10.1016/bs.vh.2014.12.009
Youdim, M. B. H., Edmondson, D., & Tipton, K. F. (2006). The therapeutic potential of monoamine oxidase inhibitors. Nature Reviews. Neuroscience, 7(4), 295–309. https://doi.org/10.1038/nrn1883