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NEUROSCIENCE OF PSYCHOACTIVE SUBSTANCE USE AND DEPENDENCE

Effects of prolonged use Cognitive impairments, risk of relapse and exacerbation of mental illness Cognitive deficits, abnormalities on PET with orbitofrontal cortex Impaired motor function Decreased reaction times, EEG abnormalities,cerebral ischaemia, infarcts, haemorrhages Sleep disturbances, anxiety, decreased appetite, increased blood pressure; decreased brain dopamine, precurs

Summary of characteristics of selected psychoactive substances (continued)
Withdrawal Rare, perhaps due to long half-life of cannabinoids Not much, except “post-high down” Fatigue, increased appetite, irritability, emotional depression, anxiety Nausea, muscle stiffness, headache, loss of appetite, blurred vision, dry mouth, insomnia, depression, anxiety, fatigue, difficulty concentrating

Develops rapidly to Perhaps short-term acute tolerance Develops rapidly to behavioural and physiological effects May develop in some

Tolerance most effects individuals

Behavioural effects Relaxation, increased sensory awareness, decreased short-term memory, motor incoordi- nation, analgesia, antiemetic and antiepi- leptic effects, increased appetite Increased alertness, energy, motor activity, feelings of competence; euphoria, anxiety, restlessness, paranoia Increased alertness, arousal, energy, motor activity, speech, self- confidence, co

Primary mechanism of action CB1 receptor agonists Monoamine (dopamine, norepinephrine, seroto- nin) transporter blocker (increases monoamines in synaptic cleft) Increased release of dopamine from nerve terminals via dopamine transporter Not dependent upon action potentials Inhibits monoamine oxidase (MAO) Blocks serotonin reuptake

Table 4.1 Substance Cannabinoids Cocaine Amphetamines Ecstasy

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