PSYB65H3 Lecture Notes - Lecture 8: Methanol, Barbiturate, Circadian Rhythm

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18 Nov 2012
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Lecture 8
Depressants
- also known as sedative hypnotics
- causes cortex to go into a relaxed state
- 3 types:
1. Barbiturates
2. Non-barbiturates
3. Alcohol
Barbiturates:
Mechanism: work through GABA => primary inhibitory amino acid transmitter
=> bind to GABA receptors and lowers brain excitability
- most depressants are synergistic w each other – work w similar mechanisms and enhance each other or cancel each
other’s withdrawal’s effect
- eg barbiturates w alcohol
- prescribed for sleep induction, most commonly in elderly due to disturbance of circadian rhythms and inability to sleep
in elderly
Withdrawal: brain becomes hyper-excitable after coming off depressants; if person has been taking barbiturates for a
long time there is a chance of seizures/convulsions
=> alcohol will stop the withdrawal symptoms
Alcohol:
- made by yeast digesting sugar and excreting alcohol
- accounts for largest number of admissions to mental hospitals => 20-40% of all admissions
- 55% of all arrests => one of the parties was drinking
- 50-75% of all homicides => a person was drinking
- 50% of driver deaths => one of the parties was drinking
- 20-30% of all suicides => the person had been drinking
- experiment of prohibition in the US => Jan 1920 - Dec 1933, until law was re-appealed making alcohol legal again
=> all the statistics dropped for alcohol problems, but didn’t last long
- by 1930 (10 years in) all the statistics had moved up back to where they were before prohibition
=> ppl were drinking illegally, finding ways around the law
- illegal products result in impurities and no inspection
=> drinking alcohol is ethyl alcohol; if accidentally ingest methyl alcohol it causes blindness
- better to educate ppl rather then completely banning alcohol
Chemistry and metabolism of alcohol:
- absorbed directly through the stomach wall without breaking down
=> one of the fastest sources of energy available
- contains a lot of energy => 200 calories/ounce, but cannot be stored as fat
=> body uses the energy from the alcohol preferentially, but everything else consumed gets stored as fat
- causes a decrease in ADH, resulting in higher excretion of fluids
=> excrete more than intake, resulting in dehydration
Central nervous system effects of alcohol:
- in part works on the GABAergic system, may affect metabolism, alter membrane excitability
=> not clear what is responsible for CNS depressant effects – may be combination
- low levels of alcohol cause a disinhibition/excitation in cortical EEG
=> inhibits inhibitory centres, depressing centres => the rest of the brain allowed to become active
- as person consumes more and more alcohol, the whole brain becomes inhibited
=> ppl slow down, become unstable
- at low levels of alcohol ppl are able to function better – reflexes faster
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