Stimulants and alcohol

Cocaine

• typically snorted (mucus membrane) in powder form or smoked (quick at entering bloodstream) in its free-base form (crack)

• Reaches peak in blood at 30-60 minutes

• Easily penetrates the blood brain barrier (lipophilic)

• Biological half life = 30-90 minutes - leaves body relatively quickly but depends on how much fat you have, tolerance etc

Cocaine short term effects

• is a stimulant so increases:

  • euphoria

  • Energy

  • Confidence

  • Talkativeness

  • Activity

  • Alertness

  • Attention

Action of cocaine at mono-aminergic synapses

• mono-amines: serotonin, dopamine, noradrenaline/ norepinephrine (suppresses arousal and plateau) and Adrenalin/ epinephrine

• Cocaine blocks reuptake (recycle neurotransmitters back into presynaptic neuron so there’s less in the synapse) from occurring so neurotransmitters stay for longer in the synapse → longer affect

Autoreceptor

Signal to presynaptic terminal to not release anymore neurotransmitters if there are too many in the synapse

Cocaine long term effects

• lack of reuptake/ recycling → depletion of monoamines as recycling tends to be a faster process than making neurotransmitters → lower levels in the presynaptic terminal → crash into depression after several hours (lack of serotonin)

• Remedied by taking more cocaine → 2-3 day cocaine binges

• Destruction of the nasal septum due to restricted blood flow

• Schizophrenia type symptoms due to too much dopamine e.g. hallucinations, delusions of persecution, mood disturbances and repetitive behaviours

• Sexual dysfunction

• Tolerance to the desired effects (from noradrenaline and serotonin) so need higher dose

• Sensitisation (low dose required) to achieve negative effects e.g. convulsiveness, stereotyped behaviour and addictiveness (from dopamine)

Cocaine addictiveness

• direct effect on dopamine released in the nucleus accumbens and PFC → direct activation of seeking and reward pathways

• Strong psychological (dopamine) addictiveness but much less physical addictiveness (withdrawal)

Action of amphetamines at mono-aminergic synapses

• same as cocaine

• Reverse reuptake channels so they’re pushing the neurotransmitters back into the synapse (reverse effect)

Ritalin (methylphenidate)

• acts similarly to cocaine by blocking the mono-amine re-uptake transporter → gradual releases so doesn’t have the same immediate effect as cocaine

• Effective treatment for attention deficit hyperactivity disorder (ADHD)

Caffeine

• typically ingested in coffee/ soft drinks

• Concentration peaks after ~40 mins

• Easily passes through the blood brain barrier

• Biological half life = 3.5-5 hours (longer in children)

• Lethal dose = 100 cups of coffee (10g of caffeine)

Caffeine short term effects

• psychostimulant

• Increases alertness and wakefulness

• Clear thinking

• Restlessness

• Difficulty with fine movements (shaky hands)

• Increases cardiac contractions

• Constricts blood vessels

Caffeine side effects

• anxiety

• Insomnia

• Change in mood

• Hypertension

Caffeine physiological action

• blocks adenosine receptors which is involved in sleep and vasodilation (blood vessels)

• Stimulates adrenaline release from adrenal medulla

Caffeine long term effects

• sleep deprivation (especially slow wave)

• Can be countered by using more caffeine to wake up in the morning → dependence

Caffeine addictiveness

• physical dependence/ withdrawals symptoms include:

  • headaches (vasodilation)

  • Sleepiness

  • Irritability

  • Difficulty concentrating

• Psychological dependence: increases dopamine released in nucleus accumbens

Nicotine

• from the tobacco leaf

• Typically smoked/ vaped (quick way of entering the bloodstream) or sometimes chewed

• Within 7 seconds of a puff, 25% nicotine in the smoke has crossed the blood brain barrier

• Biological half life of 2 hours in a chronic smoker → regular intakes to avoid withdrawal

Nicotine short term effects

• induces vomiting - affects brain stem area involved in vomiting - regular smokers will get tolerance to this

• Reduces muscle tone (relaxes) so withdrawal → tense muscles

• Reduces weight gain so withdrawal → weight gain

• Increases heart rate and blood pressure

Nicotine physiological action

• Binds to nicotine acetylcholine receptors found in the brain which are involves in stimulation of the sympathetic nervous system including release of adrenaline from the adrenal gland

• Also acts on parasympathetic nervous system but influences the sympathetic

• Agonist

Nicotine long term effects

• tolerance

• Wears out the heart more quickly

• The major problems come from other components of tobacco/ cigarette smoke (cancer, cardiovascular disease etc) but nicotine causes addiction

Nicotine addictiveness

• physical dependence/ withdrawals include:

  • craving

  • Irritability

  • Increased appetite

  • Insomnia

• Argued to be the most addictive drug psychologically due to its effect on dopamine in nucleus accumbens being so high

• 70% smokers become addicted (Compared to 30% heroin users)

• 20% who quit stay quit after 2 years - perhaps due to how addictive it is and how easy it is to access

Alcohol

• usually ingested (drink)

• Reaches max blood concentration in 30-90 minutes = quick but depends on how full you are (more food = slower)

• Easily crosses blood brain barrier (soluble in both water and lipids)

• Mostly eliminated by the liver which breaks it down at a steady rate

Alcohol short term effects

• low dose = mild euphoria and anxiolytic (lowers anxiety) = easier to interact with others

• Higher dose = intoxication:

  • slower reflexes

  • In coordination

  • Sedation

  • Memory problems

• Dilation of blood vessels as skin is warm due to more blood → felling less cold but causes core temperature to lower → heat loss

Alcohol physiological action

• agonist (mimics affect) of GABA-A receptors which increases inhibitory processes → more sleepy

• Antagonist (block effects) of NMDA (involved in memory) receptors e.g. glutamate which suppresses excitatory processes → inability to form new memories

Alcohol long term affects

• cirrhosis/ failure of the liver

• Brain damage, especially to the hippocampus → Korsakoff’s syndrome = permanent inability to make new memories

Alcohol addictiveness

• physical dependence/ withdrawal:

  • tolerance induced even from one night of drinking → mild withdrawal symptoms (hangover)

  • Chronic use → strong withdrawal symptoms which can be fatal e.g. delirium tremens which is where there is not enough inhibition due to raised GABA during alcohol intake naturally lowers levels over time → seizures due to overactive cells. Can be stabilised over time if no alcohol is consumed

• Psychological dependence:

  • increases dopamine release in the nucleus accumbens

  • Strong heritable component to alcoholism