Alcohol's toxicity impacts neural circuits and the body's

 Alcohol's toxicity impacts neural circuits and the body's stress response through several distinct biochemical and physiological mechanisms.

Alcohol Toxicity and Neural Circuit Disruption

The substance consumed in alcoholic beverages, ethyl alcohol or ethanol, is known to be a toxin that produces substantial stress and damage to cells.

1. Metabolic Conversion to Toxin: When ingested, ethanol is converted in the body, primarily in the liver, into acetaldehyde. Acetaldehyde is considered a poison that damages and kills cells indiscriminately. The state of being drunk or inebriated is essentially a poison-induced disruption in the way neural circuits function.

2. Access to the Brain: Because alcohol is both water-soluble and fat-soluble, it can easily pass into all cells and tissues of the body, including cruising right across the blood-brain barrier and into the brain environment.

3. Short-Term Effects on Neural Circuits: Alcohol's toxic effects disrupt specific brain areas:

    ◦ Prefrontal Cortex (PFC): Alcohol causes a slight suppression of neuronal activity in the PFC, the area of the brain responsible for thinking, planning, and suppression of impulsive behavior (known as top-down inhibition).

    ◦ Impulse Control: Shutting down the PFC removes GABAergic (inhibitory) suppression of impulses. This leads to increased volume of speech, more gesticulation, spontaneous dancing, and people saying or doing things without much forethought. Brain areas involved in flexible behavior (considering different options) may shut down entirely.

    ◦ Memory: Alcohol strongly suppresses the neural networks involved in memory formation and storage in the hippocampus, which is the basis of forgetting the events of a night out, or "blacking out".

    ◦ Mood: The toxic effects of acetaldehyde disrupt mood circuitries that use serotonin. This initially makes them hyperactive, leading to feelings of well-being and talkativeness. However, as more alcohol is ingested or wears off, serotonin levels and circuit activity drop, causing individuals to feel less good.

4. Chronic Effects on Neural Circuits: Regular chronic drinking, even at low to moderate levels (e.g., one or two drinks per night, or focused use on weekends), causes well-recognized changes in neural circuits that persist long after the feeling of being drunk has worn off.

    ◦ Habit and Impulsivity: Regular drinking leads to changes in neural circuits controlling habitual and impulsive behavior, modifying and strengthening them. This occurs through a literal growth in the number of synapses (connections) in the neural circuits that control habitual behavior.

    ◦ Behavioral Outcome: These changes make people more impulsive and habitual even when they are not drinking.

    ◦ Reversibility: Fortunately, these neural circuits can return to their original state after a period of abstinence, ranging from two to six months or longer, unless heavy alcohol usage has been maintained for many years.

Impact on the Body's Stress Response

Alcohol consumption significantly disrupts the body's stress response system, leading to higher baseline anxiety when sober.

1. HPA Axis Alteration: Alcohol changes the relationship between the hypothalamus, the pituitary gland, and the adrenals, collectively known as the hypothalamic-pituitary-adrenal (HPA) axis. The HPA axis maintains physiological balance regarding what is perceived as stressful.

2. Increased Baseline Cortisol: Regular drinkers experience changes in the HPA axis that result in more cortisol (a stress hormone) being released at baseline when they are not drinking.

3. Increased Stress and Anxiety: As a consequence of this increased baseline cortisol, drinkers feel more stressed and anxious when they are not consuming alcohol. This feeling is often referred to as "hangxiety".

4. Vicious Cycle: This leads to a detrimental pattern where people drink to diminish immediate stress, but the chronic effect of this consumption causes increased feelings of stress and diminished mood when sober, leading them to crave alcohol just to return to their prior baseline.

5. Genetic Predisposition: The genes involved in alcohol use disorder tend to fall in the pathways related to the HPA axis, as well as GABA and serotonin synthesis/receptors, indicating that the stress system is a core component of alcohol susceptibility