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4. PSYCHOPHARMACOLOGY OF DEPENDENCE FOR DIFFERENT DRUG CLASSES

Effects of prolonged use Altered brain function and morphology Cognitive impairments Decreased brain volume Memory impairment Health effects due to smoking are well-documented. Difficult to dissociate effects of nicotine from other components of tobacco Long-term changes in opioid receptors and peptides Adaptations in reward, learning, stress responses

Shaking, perspiration, weakness, agitation, headache, nausea, Delirium tremens Anxiety, arousal, insomnia, excitability, Irritability, hostility, anxiety, dysphoria, depressed mood, decreased heart rate, increased appetite Watering eyes, runny nose, yawning, sweating, restlessness, chills, cramps, muscle aches

Withdrawal vomiting Seizures restlessness, seizures

Summary of characteristics of selected psychoactive substances
Metabolic tolerance occurs due to enzyme Behavioural tolerance develops through Tolerance also develops through changes to GABA-A receptor Develops rapidly to most effects (except anticonvulsant) due to changes in GABA-A Tolerance develops through metabolic factors, as well as receptor changes Short-term and long- desensitization intracellular signalling

Tolerance induction learning receptor term receptor Adaptations in mechanisms

Behavioural effects Sedation Impaired memory Motor incoordination Anxiolysis Sedation Anaesthesia Motor incoordination Cognitive impairments Memory impairment Arousal, increased attention, concentration and memory; decreased anxiety and appetite; stimulant-like effects Euphoria, analgesia, sedation, respiratory depression

Primary mechanism of action Increases activity of GABA-A receptors Benzodiazepines: facilitate GABA’s opening of GABA-A chloride channel Barbiturates: bind to a specific site on the GABA ionophore and increase chloride conductance Nicotinic cholinergic receptor agonist Increases sodium inflow through the channel, causing depolarization Mu and delta opioid receptor

Table 4.1 Substance Ethanol Hypnotics and sedatives Nicotine Opioids

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