addiction day Flashcards
Neurobiology of Addiction
- Addiction is a chronic, progressive behavioral disorder whose central feature is compulsive drug use despite adverse consequences
- Addiction pathophysiology involves the brain reward system and the alterations that reward enhancing drugs effect on this system
Ventral Tegmental Area (VTA)
Location of dopamine cell bodies that projects to nucleus accumbens (reward center) and prefrontal cortex (executive control)
Nucleus Accumbens (NA)
- The “reward center” of the brain.
- Integrates VTA (dopamine) and PFC (glutamate) inputs to determine motivational output.
- Incentive (appetitive)
- Reward (consummatory)
Prefrontal Cortex (PFC)
- Exerts executive control over midbrain structures
- Judgment
- Cost-benefit analysis
- Consider Further PFC delineation next
With increasing addiction, frontal lobe structures can become
less active (less glutamate) and even atrophy allowing increasing, maladaptive addictive (more DA) behaviors to occur. (risk calculations are in error, emotional valence is put onto the addictive substance and response prevention falters
DLPFC-=
statistical analysis, prioritizing, top down control center:(failure to assess the risks of a behavior ie drunk driving)
VMPFC=
assigns emotional valience (drinking feels good, less stress, more social)
OFC-
impulse prevention ( I can beat up that football player, grope that model, drive my car)
ACC=
vigilance(Scanning environment for next beer, vodka, bar…)
Decision Making is
Glutamate Driven via PFC structures
Limbic Drive is
Dopamine Driven
D3 receptors govern
static levels of DA neuronal activity to allow homeostatic wakefulness, alertness, etc
D2 receptors are
pulsatile depending on motivation, drive, reward expectations
Effects of Drugs and ‘Addictive Behavior’ on the Brain Reward Pathways
1. All act in brain limbic reward pathways to either: enhance dopamine (DA) release enhance DA effects in the Nucleus Accumbens (Nac) or related structures or produce effects similar to DA 2. Drug-induced states are important motivators/reinforces of initial drug use 3. Chronic use leads to reward circuitry changes that promote more future drug use - Increased limbic function - Decreased PFC function
The VTA barn supplies DA to
the nucleus accumbens (NAc)
The Amygdala assigns a
pleasure, threat, or an emotional value to the linkage between 1 and 2 (perhaps this is the terrain of the ranch or how much the horses are to be fed?)
1-3 are the Limbic Addiction Pathways that are excessive in addictive behaviors
With increasing addiction, frontal lobe structures can become
less active (less glutamate) and even atrophy allowing increasing, maladaptive addictive (more DA) behaviors to occur. (risk calculations are in error, emotional valence is put onto the addictive substance and response prevention falters
Summary
- Must know the neurotransmitters involved in normal reward and addiction (DA/GLU)
- Must know functional brain areas
- Must know if areas become more or less active with addiction
alcohol binds to
GABA-A receptor
Intoxication/Withdrawal Alcohol
- Anxiolysis
- Disinhibition
- Slurred Speech
- Ataxia
- Sedation/Stupor
- Respiratory Supression
- Coma
- Death
Rx with support, restraint, protect airway, ventilate
alcohol withdrawal
- Agitation, Insomnia
- Tremor
- GI upset
- Inc Pulse, HR, BP
- Seizures
- Hallucinations
- Delirium
- Death
Rx with benzodiazepines (cross reactive) until vital signs and withdrawal symptoms normalize
Intoxication/Withdrawal Sedatives (Benzodiazepines, Barbiturates)
- Anxiolysis
- Slurred Speech
- Ataxia
- Sedation/Stupor
- Respiratory Supression
- Coma
- Death
Rx with support, restraint, protect airway, ventilate
Reverse with flumazenil
For benzodiazepines
Will not work for alcohol or barbiturates
withdrawal symptoms with benzo and barbs
- Agitation, Insomnia
- Tremor
- GI cramps
- Hypereflexia
- Inc HR
- Seizures
- Hallucinations
- Delirium
- Death
Rx with benzodiazepine replacement until vital signs and withdrawal symptoms normalize
Stimulants and the D2 ReceptorCocaine, Amphetamine
- Stimulants block dopamine reuptake, may reverse it
2. The net effect is more DA availability in the mesolimbic system which allows increased CNS arousal and excitability
Intoxication of Stimulants
- Elevated mood and esteem
- irritability
- Insomnia
- Appetite loss
- Dilated pupils
- Racing heart
- Inc BP, elevated temp
- Hyperreflexia
- Psychosis
- Cardiac arrest
- seizure
Rx with support, and use meds to reverse specific intoxication symptoms
withdrawal of stimulants
- Fatigue
- Anhedonia
- Depression
- Increased sleep
- Increased appetite
Opiates and the Opioid System
- affect mu, delta, kappa receptors
2. many prescription narcotic pain meds are naturally occurring alkaloids (poppy), some are synthetic
Mu (OP3,MOP) reduces
pain, increases positive emotion,
Rx opiates are often
full agonists and very effective at activating endogenious opioid receptors
Kappa(OP2, KOP)/delta(OP1, DOP) allows
mild analgesia
They are g protein linked and cause neuronal hyperpolarization via
cAMP reduction and increased K+ influx and decrease Ca++ efflux –> Increases descending midbrain pain inhibitory paths
Next increasing serotonin and enkephalin firing
Many prescription narcotic pain meds are naturally occurring alkaloids (poppy), some are synthetic
- Morphine, codeine,oxycodone, hydrocodone, tramadol
- They tend to activate the Mu, OP3, MOP receptors to control pain and improve the emotional state associated with said pain
Intoxication of Opiates
- Elevated mood
- Pupil constriction
- Respiratory suppression
- Gag reflex loss
- Low HR, BP
- Constipation
Rx with support, protect airway and use naloxone to reverse
dopamine lives in
ventral tegmental area (VTA) –> location of dopamine cell bodies that project to nucleus accumbens (reward center)