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| Question | Answer |
| What are social drugs | Social drugs are drugs taken by choice linked to the pleasurable effects they produce. A Pharmacologically heterogenerous (different) group |
| How social drugs evoke pleasure | Social drugs activate dopaminergic reward pathways in the brain that run from the ventral tegmental area to the nucleus accumbens. |
| Activation of the reward pathways | - Firing of reward pathways can be increased by direct or indirect mechanisms. |
| Direct activation of reward pathways | - Dopamine released at the VTA (ventral tegmental area), which travels down the nerve directly to increase the amount of dopamine in the nucleus accumbens |
| Indirect action (by disinhibition) | GABA is released, which disinhibits the VTA, which goes on to increase levels of dopamine in the nucleus accumbens. |
| Problems with social drugs | - Dependence is often an issue. This can be: Physical addiction- where withdrawal from the drug has an adverse physical effect. Psychological addiction- including cravings, as a result of positive reinforcement - Toxicity- when the habit causes harm to the individual |
| Legal drugs: Cigarette smoking | Desired effect: - Psychoactive stimulant and relaxant - Euphoria, increase alertness, relaxation Drug type: Nicotinic acetylcholine receptor agonist Pharmacology: - Agonist at Nach receptors - Excites autonomic ganglia in the periphery, causing adrenaline release from the adrenal medulla. This results in tachycardia, vasoconstriction and increased blood pressure. - In the CNS it causes neural excitation, resulting in the release of transmitters inc dopamine (euphoria), Ach (concentration), serotonin (relaxation). - Neuronal nicotinic Ach receptors are mar more sensitive than muscle nicotinic receptors. Toxicity of cigarette smoking: - Carbon monoxide displaces O2 from haemoglobin to form carboxyhaemaglobin, decreasing O2 carriage, increasing incidence of ischemic heart disease. - Nicotine is an vasoconstricyor taht increases platelet aggregation. Results in an increased risk of coronary thrombosis. - Tar and irritants- Increased incidence of lung cancer - Effects on unborn child- reduced birth weight, increased risk of spontaneous abortion, prematurity. |
| Legal drugs: cigarette smoking continued... | Possible neuroprotective effects of smoking due to increased expression of nicotinic Ach receptors. Those with parkinson's disease were able to quit smoking more easily than those who did not. Morbidity related to smoking: Causes 80% of deaths related to lung cancer, bronchitis and emphysemas, 14% of deaths from heart disease, 25% of cancer deaths. |
| Illegal drugs: Heroin | Desired effect: 2x as potent as morphine, which it is synthesised from, as its chemical structure allows it to enter the brain more quickly than morphine itself. In the brain it is converted back into morphine. -Euphoria, reward, addiction (tolerance develops rapidly). Pharmacology: Binds to opiate receptors in the reward/pleasure areas of the brain to induce euphoria, and in the periphery of the brain and spinal cord to reduce pain sensation. Toxicity: Acute toxicity- mild respiritory depression Chronic toxicity- severe respiritory depression, extreme sedation, respiritory failiure. Pysiological dependence- can be countered by methadone treatment |
| Illegal drugs: Ecstasy | Effect: Ecstasy is a psychoactive stimulant that causes euphoria, arousal, empathy, perceptual disturbances, endurance and increased self-confidence. Sources: Synthetically made Pharmacology: Displaces 5-HT from vesicles so it leaks out into the neuronal junction Blocks 5-HT reuptake pump to prolong 5-HT action, resulting in elevated 5-HT levels, causing a secondary rise in NA and DA, which is what causes empathy, arousal and euphoria. Toxicity: - Short-term acute toxicity; hypothermia, hyponatremia (low blood sodium conc.) - Chronic toxicity; depression, damage to 5-HT terminals |
| The legal vs illegal debate | Legality does not relate to toxicology, rather social/historical reasons |
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