Drugs of Dependence, Addiction and Overdose Flashcards
define physical dependence
occurs when pharmacological adaptation and physiological changes in brain lead to tolerance in which more drug is needed to achieve same effect, withdrawal symptoms will ocurr if use ceased
define psychological dependence
emotional-motivational withdrawal symptoms, many daily drug users show both dependences
What variables work simultaneously to influence probability that user will develop physical/psychological dependence and/or addiction
agent, host and environment in which use occurs
Describe the physical reward pathway in the brain
natural systems reward actions that promote propagation of species producing slight mood elevation
what brain structures are involved in the reward pathways
VTA, nucleus accumbens and frontal cortex
describe the connection between the brain structures in the reward pathways and DA
DA is released in the VTA and is sent to many structures including the nucleus accumbens and frontal cortex
How does the brain cope with change?
CNS has plasticity where it can modify its hardware to best function in changing environments specifically change in receptor numbers
describe the reasons for an increase and decrease in receptor numbers on post-synaptic membranes
increase caused by up regulation due to the presence of an antagonist drug/molecule for a long period of time which significantly reduces the amount of NT released by the pre-synaptic membrane as well as blocking the post-synaptic receptors = more receptors present to try and collect as much of the NT as possible
decrease caused by presence of agonist for a long period of time resulting in down-regulation which blocks the reuptake of NTs causing too many available to post-synaptic membrane = less receptors present
What factors affect likelihood for drug abuse?
availability, cost, purity and potency, mode of administration, time of onset, level of addictiveness
What host factors affect likelihood for abuse?
heredity, metabolism, psychiatric symptoms, prior experiences, propensity for risk taking behaviour
Describe the relationship between morphine and heroin
morphine is synthetically acetylated to produce heroin, once heroin is injected it crosses the BBB and converts to morphine
Describe heroins effect on DA in the brain
heroin binds to and activates the mu opioid receptor inhibiting the release of GABA from the nerve terminal. This reduces GABAs inhibitory effect on DA neurons causing an increase in DA release in the nucleus accumbens. This causes sustained activation of the post-synaptic membrane lasting around 3-5 hours
List the effects of heroin
dry mouth, slurred speech, droopy eyelids, bradycardia, respiratory depression
Why is OD more common in long term drug users?
long term use of the drug causes down regulation of receptors when users tolerance increases and they can’t be sure which concentration they are receiving until its too late
describe cocaine’s effect on DA in the brain
cocaine binds to and blocks DA reuptake transporters on pre-synaptic membranes inhibiting clearance of DA from the synaptic cleft and degradation by the MAO in the nerve terminal, the DA then remains in the synaptic cleft and is free to bind to its receptors on post-synaptic membrane
why do cocaine and heroin together produce an even more intense DA activation?
because they work on different mechanisms on DA neurons of the reward pathway
