Neurotransmitters and Propranolol Overview

Voluntary Movement

• Motivation, learning, and arousal levels can all play a role in voluntary movement, influencing our behaviour and cognitive function

Norepinephrine (NE)

• NE is a neurotransmitter that originates in the locus coeruleus of the brainstem
• NE has widespread projections throughout the brain, influencing areas like the cortex and cerebellum
• NE has 2 main metabotropic receptor types with subtypes and sub-subtypes, which have modulatory effects
• NE and epinephrine act similarly on the same receptors
• NE facilitates wakefulness and arousal
• NE plays a key role in stress and emotional responses, enhancing memory formation.
• Elevated NE levels are associated with traumatic memories and PTSD.
• Propranolol, a beta blocker, can be used to reduce NE activity, potentially helping to treat PTSD.

Propranolol

• Propranolol is a beta-blocker which can be used to reduce stress arousal
• Propranolol can be used in therapeutic settings to help people re-experience traumatic events without the same intensity, reducing the impact of those memories

Serotonin

• Serotonin is a neurotransmitter that originates from the raphe nuclei in the brainstem
• Serotonin has widespread projections throughout the brain, including the cortex, thalamus, and cerebellum
• Serotonin has 15 different receptor types, with most being metabotropic
• Serotonin synthesis is dependent on the amino acid precursor tryptophan
• Serotonin depletion can lead to cognitive inflexibility, increased aggression, and poorer performance on tasks like the Stroop test

Selective Serotonin Reuptake Inhibitors (SSRIs)

• SSRIs like Prozac are commonly used to treat depression, anxiety, and OCD
• SSRIs work by blocking the reuptake of serotonin from the synapse
• SSRIs can have a quick onset of action, but improvements in symptoms take several weeks
• Evidence suggests SSRIs may only be effective for a subset of patients, particularly those with severe depression

Hallucinogens

• Hallucinogens like LSD, DMT, and psilocybin are serotonin receptor agonists
• Hallucinogens cause radical changes in consciousness and perception, but have minimal effects on mood.
• Research suggests that psychedelics may have therapeutic potential for conditions like end-of-life care, PTSD, and addiction

Acetylcholine

• Acetylcholine is a small-molecule neurotransmitter
• Acetylcholine plays a critical role at the neuromuscular junction and in the basal forebrain, influencing wakefulness, attention, and other cognitive functions
• Nicotine is an acetylcholine agonist, which explains some of its stimulating effects

Endocannabinoids

• Endocannabinoids are small-molecule neurotransmitters
• Endocannabinoids are involved in retrograde transmission, traveling from the dendrite to the axon
• Endocannabinoids can weaken the connection between neurons at a synapse.
• THC is a cannabinoid agonist

Adenosine

• Adenosine is a byproduct of ATP, the cellular energy molecule
• Adenosine can act as a neurotransmitter, binding to metabotropic receptors that are generally inhibitory
• Accumulating adenosine levels may contribute to sleepiness.
• Caffeine is an adenosine antagonist, blocking adenosine receptors and preventing the build-up of sleepiness

Endogenous Opioids

• Endogenous opioids are peptide neurotransmitters that play a role in pain relief and pleasure
• They act through metabotropic GPCRs and primarily have inhibitory effects.
• These neurotransmitters are highly addictive and contribute to feelings of euphoria and increased baseline pleasure.
• Exogenous opioids, including heroin, morphine, and fentanyl, mimic the effects of endogenous opioids
• Naloxone is an opioid antagonist, used to counteract opioid overdose.
• Opioid receptors are found in various brain regions, including the spinal cord, periaqueductal grey area, and nucleus accumbens

Neuroimaging

• Structural Neuroimaging provides static images of the brain, allowing researchers to examine brain structure and anatomy, including:
  • X-rays
  • Computed Tomography (CT) scans
  • Magnetic Resonance Imaging (MRI) scans
  • Diffusion Tensor Imaging (DTI) scans
• Functional Neuroimaging allows researchers to investigate brain activity and function, including:
  • Electroencephalography (EEG)
  • Positron Emission Tomography (PET)
  • Functional Magnetic Resonance Imaging (fMRI)

This quiz explores the roles of norepinephrine in voluntary movement, arousal, and emotional responses. It also delves into the use of propranolol as a beta-blocker in therapeutic contexts, specifically for managing stress and PTSD. Test your knowledge of these critical concepts in neuroscience.