Dopamine basics - central nervous system (CNS) - neuroinflammation and neurodegeneration

By SWA

Highly pathogenic H5N1 influenza virus can enter the central nervous system (CNS) and induce neuroinflammation and neurodegeneration https://pubmed.ncbi.nlm.nih.gov/19667183/

A significant loss of dopaminergic neurons in the substantia nigra pars compacta 60 days after infection. Our results suggest that a pandemic H5N1 pathogen, or other neurotropic influenza virus, could initiate CNS disorders of protein aggregation including Parkinson's and Alzheimer's diseases.

Dopaminergic neurons are nerve cells in the brain and nervous system that produce and release dopamine, a neurotransmitter involved in several critical functions, including movement control, reward and pleasure, motivation, and cognition. These neurons play a major role in how we experience rewards, make decisions, and regulate our movements. Here's a breakdown of their function:

1. Production and Release of Dopamine

  • Dopaminergic neurons produce dopamine and release it at their synaptic terminals (the junctions between neurons).
  • When dopamine is released, it binds to dopamine receptors on nearby neurons, transmitting a signal that can either excite or inhibit those neurons, depending on the receptor type and the target region in the brain.

2. Movement and Motor Control

  • A major role of dopaminergic neurons is in motor control, which is managed primarily by dopaminergic neurons in the substantia nigra, a region of the brain in the basal ganglia.
  • These neurons project to the striatum, a region involved in initiating and controlling movement.
  • In disorders like Parkinson’s disease, dopaminergic neurons in the substantia nigra degenerate, leading to reduced dopamine in the striatum. This results in the motor symptoms associated with Parkinson’s, such as tremors, rigidity, and bradykinesia (slowness of movement).

3. Reward and Pleasure (Mesolimbic Pathway)

  • Dopaminergic neurons are key players in the brain’s reward system, particularly in the mesolimbic pathway, which links the ventral tegmental area (VTA) to areas like the nucleus accumbens.
  • When we experience something pleasurable (like eating, socializing, or achieving a goal), dopaminergic neurons in the VTA release dopamine in the nucleus accumbens, creating feelings of pleasure and reinforcing behavior.
  • This mechanism underlies reward-based learning and motivation—dopamine release essentially "rewards" behaviors that lead to positive outcomes, encouraging us to repeat them.

4. Cognition and Decision-Making (Mesocortical Pathway)

  • Dopaminergic neurons also play a role in cognitive functions, particularly in the prefrontal cortex, through the mesocortical pathway.
  • This pathway is involved in attention, working memory, and executive functions—the abilities that allow us to plan, focus, and make complex decisions.
  • Dysfunction in this pathway is associated with disorders like ADHD and schizophrenia, which involve impairments in attention, motivation, and cognitive processes.

5. Regulation of Mood

  • Dopamine also has a role in mood regulation and is associated with feelings of well-being and drive.
  • Imbalances in dopaminergic systems are implicated in depression and anxiety. While dopamine is not the only neurotransmitter involved in mood, its role in motivation and pleasure can influence overall mood states.

Summary of Dopaminergic Pathways

To sum up, dopaminergic neurons and their associated pathways are integral to a range of brain functions:

  • Nigrostriatal Pathway: Movement control (substantia nigra to striatum).
  • Mesolimbic Pathway: Reward, pleasure, and reinforcement (VTA to nucleus accumbens).
  • Mesocortical Pathway: Cognition, decision-making, and executive function (VTA to prefrontal cortex).
  • Tuberoinfundibular Pathway: Hormonal regulation (influences prolactin release in the hypothalamus).

Clinical Relevance

Because dopaminergic neurons play a key role in these systems, dysfunction in dopaminergic signaling can lead to various neurological and psychiatric disorders:

  • Parkinson’s Disease: Due to degeneration of dopaminergic neurons in the substantia nigra.
  • Addiction: Dopamine release in the reward system can reinforce addictive behaviors.
  • Schizophrenia: Thought to involve dysregulation in dopamine pathways, particularly the mesolimbic and mesocortical pathways.
  • ADHD: Often associated with dopamine dysregulation, affecting attention and executive function.

In summary, dopaminergic neurons are critical for enabling a range of behaviors and functions, from physical movement to complex cognitive and emotional experiences, by producing and releasing dopamine in specific pathways in the brain.

 © 2000-2025 Sieglinde W. Alexander. All writings by Sieglinde W. Alexander have a fife year copy right.
Library of Congress Card Number: LCN 00-192742
ISBN: 0-9703195-0-9

 

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