Neurotransmitters and Associated Conditions

Neurotransmitters are chemical messengers that facilitate communication between neurons. Imbalances in their levels can contribute to various neurological and psychological conditions. Below is an overview of key neurotransmitters and conditions linked to their dysregulation.

Function: Regulates mood, appetite, sleep, and cognitive processing.

1. Low Levels:
   • Depression
   • Anxiety disorders
   • Obsessive-Compulsive Disorder (OCD)
   • Insomnia
2. High Levels:
   • Serotonin syndrome (agitation, hyperthermia)
   • May contribute to mania in bipolar disorder

Function: Controls reward, motivation, movement, and emotional responses.

1. Low Levels:
   • Parkinson’s disease (motor symptoms)
   • Depression
   • ADHD (dysregulation)
2. High Levels:
   • Schizophrenia (excess in mesolimbic pathway)
   • Addiction
   • Mania

Function: Modulates alertness, arousal, and the “fight-or-flight” response.

1. Low Levels:
   • Depression
   • ADHD
   • Fatigue
2. High Levels:
   • Anxiety disorders
   • Hypertension
   • PTSD (hyperarousal)

Function: Primary inhibitory neurotransmitter; reduces neuronal excitability.

1. Low Levels:
   • Anxiety disorders
   • Epilepsy
   • Insomnia
2. High Levels:
   • Sedation (e.g., from benzodiazepines)
   • Respiratory depression (overdose)

Function: Primary excitatory neurotransmitter; involved in learning and memory.

1. Low Levels:
   • Rare; may impair cognition
2. High Levels:
   • Excitotoxicity (stroke, traumatic brain injury)
   • Neurodegenerative diseases (Alzheimer’s, ALS)

Function: Regulates muscle activation, memory, and attention.

1. Low Levels:
   • Alzheimer’s disease
   • Myasthenia gravis (receptor dysfunction)
2. High Levels:
   • Organophosphate poisoning (muscle spasms, seizures)
   • Parkinson’s tremors (in specific pathways)

Function: Natural painkillers; promote pleasure and stress relief.

1. Low Levels:
   • Chronic pain syndromes
   • Depression
   • Opioid withdrawal
2. High Levels:
   • “Runner’s high” (exercise-induced)
   • Euphoria (opioid use)

Function: Regulates wakefulness, immune response, and allergic reactions.

1. Low Levels:
   • Sedation (antihistamine side effect)
   • Narcolepsy (possible link)
2. High Levels:
   • Allergic reactions (hives, anaphylaxis)
   • Insomnia (overactivation)

• Neurotransmitter systems are highly interconnected, and imbalances often involve multiple chemicals.
• Conditions listed are simplified associations; actual aetiology may involve receptors, reuptake, or genetic factors.
• Always consult a healthcare professional for diagnosis and treatment.

Neurotransmitters are primarily known for their role in neuronal communication within the central nervous system (CNS). However, when they are released into the bloodstream or act outside the blood-brain barrier, they can function as hormones, influencing various physiological processes throughout the body.

Norepinephrine:

• In the CNS, norepinephrine acts as a neurotransmitter, regulating attention and arousal.
• Outside the CNS, it is released by the adrenal medulla as a hormone, contributing to the “fight-or-flight” response by increasing heart rate, blood pressure, and blood flow to muscles.

Dopamine:

• In the brain, dopamine regulates reward, motivation, and movement.
• In the periphery, dopamine acts as a hormone in the kidneys, where it helps regulate sodium excretion and blood pressure.

Serotonin:

• In the CNS, serotonin modulates mood, appetite, and sleep.
• In the gut (where 90% of serotonin is produced), it acts as a hormone to regulate intestinal motility and blood flow.

Acetylcholine:

• In the CNS, acetylcholine is involved in memory and learning.
• Outside the CNS, it acts as a hormone in the autonomic nervous system, controlling heart rate, digestion, and muscle contraction.

Histamine:

• In the brain, histamine regulates wakefulness and appetite.
• In the body, it acts as a hormone in immune responses, triggering inflammation and allergic reactions.

Glutamate and GABA:

• These are primarily CNS neurotransmitters, but small amounts in the periphery may influence hormone release (e.g., glutamate stimulates insulin secretion in the pancreas).

• Neurotransmitters can have dual roles: as chemical messengers in the brain and as hormones in the body.
• Their effects depend on location: CNS (neuronal signaling) vs. periphery (hormonal action).
• The blood-brain barrier restricts their movement, but peripheral production allows them to act systemically.